Science.gov

Sample records for state phase equilibria

  1. State-of-the-art review of phase equilibria

    SciTech Connect

    Prausnitz, J.M.

    1980-03-01

    High-pressure phase-equilibrium calculations using an equation of state are more sensitive to the mixing rules than to details in the effect of density or temperature on pressure. Attention must be given to the problem of how to extend equations of state to mixtures. One possible technique is provided by perturbation theory; another by superposition of chemical equilibria. At low or moderate pressures, vapor-phase corrections are often important. When specific intermolecular forces produce formation of molecular aggregates, strong deviations from ideal-gas behavior can be significant even at pressures well below 1 bar. When vapor-liquid equilibrium data are reduced using conventional expressions for the excess Gibbs energy, the resulting binary parameters tend to be partially correlated, it difficult, but no impossible, to calculate ternary liquid-liquid equilibria using binary parameters only. New models for calculating properties of liquid-phase mixtures mist allow for changes in free volume to give consideration to the effect of mixing on changes in rotational and vibrational degrees of freedom. Liquid-phase volumetric effects are also important in describing the solubilities of gases in solvent mixtures. Therefore, future liquid-phase models should incorporate a liquid-phase equation of state, either of the van der Waals type or, perhaps, as given by the direct-correlation function theory of liquids.

  2. Solid-State Phase Equilibria in the ZnS-Ga2S3 System

    DTIC Science & Technology

    1989-10-01

    S!PC FE.Wpy OFFICE OF NAVAL RESEARCH Contract N00014-87-K-0531 R&TCode 431a016 " ITECHNICAL REPORT NO. 4SSolid-State Phase Equilibria in the ZnS...FUNDING NUMBERS PROGRAM IPROJECT ITASK WORK UNIT ELEMENT NO. I(NO. (NO. (NO. 11. TITLE (include Security Classification) Soltd-State Phase Equilibria in...pure components. The identification of the phases was determined by x-ray diffraction methods. Ile principal feature of the phase equilibria is the

  3. Solid-State Phase Equilibria in the ZnS-CdS System

    DTIC Science & Technology

    1988-09-01

    OFFICE OF NAVAL RESEARCH !iTIB - K Contract N00014-87-K-0531 R&TCode 431a016 TECHNICAL REPORT NO. I Solid-State Phase Equilibria in the ZnS-CdS...PROGRAM PROJECT TASK VVORK j*JT ELEMENT NO NO NO % Q I rTi (Incluc e Security Classitication) Solid-State Phase Equilibria in the ZnS-CdS System 12 PERSONAL...are obsolete Accesslon For NTI& GRA&1 SOLD-STATE PHASE EQUILIBRIA IN THE ZnS-CdS SYSTEM DTIC TAB 3 W. W. Chen, J. M. Zhang, A. J. Ardell, and B. Dunn

  4. Phase Equilibria Diagrams Database

    National Institute of Standards and Technology Data Gateway

    SRD 31 NIST/ACerS Phase Equilibria Diagrams Database (PC database for purchase)   The Phase Equilibria Diagrams Database contains commentaries and more than 21,000 diagrams for non-organic systems, including those published in all 21 hard-copy volumes produced as part of the ACerS-NIST Phase Equilibria Diagrams Program (formerly titled Phase Diagrams for Ceramists): Volumes I through XIV (blue books); Annuals 91, 92, 93; High Tc Superconductors I & II; Zirconium & Zirconia Systems; and Electronic Ceramics I. Materials covered include oxides as well as non-oxide systems such as chalcogenides and pnictides, phosphates, salt systems, and mixed systems of these classes.

  5. Solid state phase equilibria and intermetallic compounds of the Al-Cr-Ho system

    SciTech Connect

    Pang, Mingjun; Zhan, Yongzhong; Du, Yong

    2013-02-15

    The solid state phase equilibria of the Al-Cr-Ho ternary system at 500 Degree-Sign C were experimentally investigated. The phase relations at 500 Degree-Sign C are governed by 14 three-phase regions, 29 two-phase regions and 15 single-phase regions. The existences of 10 binary compounds and 2 ternary phases have been confirmed. Al{sub 11}Cr{sub 2}, Al{sub 11}Cr{sub 4} and Al{sub 17}Ho{sub 2} were not found at 500 Degree-Sign C. Crystal structures of Al{sub 9}Cr{sub 4} and Al{sub 8}Cr{sub 4}Ho were determined by the Rietveld X-ray powder data refinement. Al{sub 9}Cr{sub 4} was found to exhibit cubic structure with space group I4-bar 3m (no. 217) and lattice parameters a=0.9107(5) nm. Al{sub 8}Cr{sub 4}Ho crystallizes in ThMn{sub 12} structure type with space group I4/mmm (no. 139) and lattice parameters a=0.8909(4) nm, c=0.5120(5) nm. It is concluded that the obtained Al{sub 4}Cr phase in this work should be {mu}-Al{sub 4}Cr by comparing with XRD pattern of the hexagonal {mu}-Al{sub 4}Mn compound. - Graphical abstract: The solid state phase equilibria of the Al-Cr-Ho ternary system at 500 Degree-Sign C. Highlights: Black-Right-Pointing-Pointer Al-Cr-Ho system has been investigated. Black-Right-Pointing-Pointer Al{sub 9}Cr{sub 4} has cubic structure with space group I4-bar 3m. Black-Right-Pointing-Pointer Al{sub 8}Cr{sub 4}Ho crystallizes in ThMn{sub 12} type with space group I4/mmm. Black-Right-Pointing-Pointer Al{sub 4}Cr phase is {mu}-type at 500 Degree-Sign C.

  6. Melt-gas phase equilibria and state diagrams of the selenium-tellurium system

    NASA Astrophysics Data System (ADS)

    Volodin, V. N.; Trebukhov, S. A.; Burabaeva, N. M.; Nitsenko, A. V.

    2017-05-01

    The partial pressures of saturated vapor of the components in the Se-Te system are determined and presented in the form of temperature-concentration dependences from which the boundaries of the melt-gas phase transition are calculated at atmospheric pressure and vacuums of 2000 and 100 Pa. The existence of azeotropic mixtures is revealed. It is found that the points of inseparably boiling melts correspond to 7.5 at % of Se and 995°C at 101325 Pa, 10.9 at % at 673°C and 19.5 at % at 522°C in vacuums of 2000 and 100 Pa, respectively. A complete state diagram is constructed, including the fields of gas-liquid equilibria at atmospheric and low pressures, the boundaries of which allow us to assess the behavior of selenium and tellurium upon distillation fractionation.

  7. Putting Phase Equilibria into Geodynamic Models: An Equation of State Approach (Invited)

    NASA Astrophysics Data System (ADS)

    Connolly, J.

    2009-12-01

    temperature and pressure. Although this formulation is straightforward, the computation of phase equilibria as a function of entropy and volume is challenging because the equations of state for individual phases are usually expressed as a function of temperature and pressure. This challenge can be met by an algorithm in which continuous equations of state are approximated by a series of discrete states; a representation that reduces the phase equilibrium problem to a linear optimization problem that is independent of the functional form used for the equations of state of individual phases and readily solved by successive linear programming. Regardless of the way free energy minimization is implemented and the choice of independent variables, a consistent definition of pressure, and the coupling of equilibrium kinetics to deformation, is only possible if the continuity equation accounts for dilational strain.

  8. Mussel bed boundaries as dynamic equilibria: thresholds, phase shifts, and alternative states.

    PubMed

    Donahue, Megan J; Desharnais, Robert A; Robles, Carlos D; Arriola, Patricia

    2011-11-01

    Ecological thresholds are manifested as a sudden shift in state of community composition. Recent reviews emphasize the distinction between thresholds due to phase shifts-a shift in the location of an equilibrium-and those due to alternative states-a switch between two equilibria. Here, we consider the boundary of intertidal mussel beds as an ecological threshold and demonstrate that both types of thresholds may exist simultaneously and in close proximity on the landscape. The discrete lower boundary of intertidal mussel beds was long considered a fixed spatial refuge from sea star predators; that is, the upper limit of sea star predation, determined by desiccation tolerance, fixed the lower boundary of the mussel bed. However, recent field experiments have revealed the operation of equilibrium processes that maintain the vertical position of these boundaries. Here, we cast analytical and simulation models in a landscape framework to show how the discrete lower boundary of the mussel bed is a dynamic predator-prey equilibrium, how the character of that boundary depends on its location in the landscape, and how boundary formation is robust to the scale of local interactions.

  9. Cubical equations of state for predicting the phase equilibria of poorly studied substances

    NASA Astrophysics Data System (ADS)

    Shestova, T. D.; Markvart, A. S.; Lozovskii, T. L.; Zheleznyi, V. P.

    2013-06-01

    A new procedure for determining the coefficients of the Peng-Robinson equation of state is proposed, for which a minimum of information is required. It is shown that using the Morachevskii complexity factor of molecular interaction in the algorithm for calculating the saturation vapor pressure of substances enables us to study the parameters of the vapor-liquid equilibria of substances with various polarities. Based on our validation of the procedure for determining the coefficients of the Ping-Robinson equation, it is concluded that the values for the saturation vapor pressure of halide derivatives of hydrocarbons calculated from tabular reference data agree satisfactorily in practice.

  10. Phase equilibria for complex fluid mixtures

    SciTech Connect

    Prausnitz, J.M.

    1983-04-01

    After defining complex mixtures, attention is given to the canonical procedure used for the thermodynamics of fluid mixtures: first, we establish a suitable, idealized reference system and then we establish a perturbation (or excess function) which corrects the idealized system for real behavior. For complex mixtures containing identified components (e.g. alcohols, ketones, water) discussion is directed at possible techniques for extending to complex mixtures our conventional experience with reference systems and perturbations for simple mixtures. Possible extensions include generalization of the quasi-chemical approximation (local compositions) and superposition of chemical equilibria (association and solvation) on a physical equation of state. For complex mixtures containing unidentified components (e.g. coal-derived fluids), a possible experimental method is suggested for characterization; conventional procedures can then be used to calculate phase equilibria using the concept of pseudocomponents whose properties are given by the characterization data. Finally, as an alternative to the pseudocomponent method, a brief introduction is given to phase-equilibrium calculations using continuous thermodynamics.

  11. Standard state Gibbs energies of hydration of hydrocarbons at elevated temperatures as evaluated from experimental phase equilibria studies

    NASA Astrophysics Data System (ADS)

    Plyasunov, Andrey V.; Shock, Everett L.

    2000-08-01

    Experimental results of phase equilibria studies at elevated temperatures for more than twenty hydrocarbon-water systems were uniformly correlated within the framework of the Peng-Robinson-Stryjek-Vera equation of state in combination with simple mixing rules. This treatment allows evaluation of the Gibbs energy of hydration for many alkanes, 1-alkenes, cycloalkanes (derivatives of cyclohexane) and alkylbenzenes up to 623 K at saturated water vapor pressure and up to 573 K at 50 MPa. Results for homologous series show regular changes with increasing carbon number, and confirm the applicability of the group contribution approach to the Gibbs energy of hydration of hydrocarbons at elevated temperatures. The temperature dependence of group contributions to the Gibbs energy of hydration were determined for CH 3, CH 2, and CH in aliphatic hydrocarbons; C=C and H for alkenes; c-CH 2 and c-CH in cycloalkanes; and CH ar and C ar in alkylbenzenes (or aromatic hydrocarbons). Close agreement between calculated and experimental results suggests that this approach provides reasonable estimates of Gibbs energy of hydration for many alkanes, 1-alkenes, alkyl cyclohexanes and alkylbenzenes at temperatures up to 623 K and pressures up to 50 MPa.

  12. Solid-State Phase Equilibria and Intermetallic Compounds of the Si-V-Zr Ternary System

    NASA Astrophysics Data System (ADS)

    Pan, Yanfang; Ye, Haimei; Chen, Xiaoxian; Jiang, Wenping; Yang, Wenchao; Zhan, Yongzhong

    2016-12-01

    Phase relations in the Si-V-Zr ternary system at 973 K (700 °C) were experimentally investigated using X-ray powder diffraction and scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy. The isothermal section at 973 K (700 °C) is governed by seventeen three-phase regions, thirty-two two-phase regions, and sixteen single-phase regions. Ten binary compounds and one ternary compound (SiVZr) were confirmed. There are two new ternary compounds found in this work for the first time. One of them (Si4V3Zr2) was found in the stoichiometric composition around V 38 pct, Si 50 pct, and Zr 12 pct. The existence of another one (V17Si12Zr3) was observed while analyzing the XRD results of large quantities of equilibrated samples in the region around 54 at. pct V, 33 at. pct Si, and 13 at. pct Zr.

  13. Binary Solid-Liquid Phase Equilibria

    ERIC Educational Resources Information Center

    Ellison, Herbert R.

    1978-01-01

    Indicates some of the information that may be obtained from a binary solid-liquid phase equilibria experiment and a method to write a computer program that will plot an ideal phase diagram to which the experimental results may be compared. (Author/CP)

  14. Phase Equilibria and Crystallography of Ceramic Oxides

    PubMed Central

    Wong-Ng, W.; Roth, R. S.; Vanderah, T. A.; McMurdie, H. F.

    2001-01-01

    Research in phase equilibria and crystallography has been a tradition in the Ceramics Division at National Bureau of Standards/National Institute of Standatrds and Technology (NBS/NIST) since the early thirties. In the early years, effort was concentrated in areas of Portland cement, ceramic glazes and glasses, instrument bearings, and battery materials. In the past 40 years, a large portion of the work was related to electronic materials, including ferroelectrics, piezoelectrics, ionic conductors, dielectrics, microwave dielectrics, and high-temperature superconductors. As a result of the phase equilibria studies, many new compounds have been discovered. Some of these discoveries have had a significant impact on US industry. Structure determinations of these new phases have often been carried out as a joint effort among NBS/NIST colleagues and also with outside collaborators using both single crystal and neutron and x-ray powder diffraction techniques. All phase equilibria diagrams were included in Phase Diagrams for Ceramists, which are collaborative publications between The American Ceramic Society (ACerS) and NBS/NIST. All x-ray powder diffraction patterns have been included in the Powder Diffraction File (PDF). This article gives a brief account of the history of the development of the phase equilibria and crystallographic research on ceramic oxides in the Ceramics Division. Represented systems, particularly electronic materials, are highlighted. PMID:27500068

  15. Phase Equilibria and Crystallography of Ceramic Oxides.

    PubMed

    Wong-Ng, W; Roth, R S; Vanderah, T A; McMurdie, H F

    2001-01-01

    Research in phase equilibria and crystallography has been a tradition in the Ceramics Division at National Bureau of Standards/National Institute of Standatrds and Technology (NBS/NIST) since the early thirties. In the early years, effort was concentrated in areas of Portland cement, ceramic glazes and glasses, instrument bearings, and battery materials. In the past 40 years, a large portion of the work was related to electronic materials, including ferroelectrics, piezoelectrics, ionic conductors, dielectrics, microwave dielectrics, and high-temperature superconductors. As a result of the phase equilibria studies, many new compounds have been discovered. Some of these discoveries have had a significant impact on US industry. Structure determinations of these new phases have often been carried out as a joint effort among NBS/NIST colleagues and also with outside collaborators using both single crystal and neutron and x-ray powder diffraction techniques. All phase equilibria diagrams were included in Phase Diagrams for Ceramists, which are collaborative publications between The American Ceramic Society (ACerS) and NBS/NIST. All x-ray powder diffraction patterns have been included in the Powder Diffraction File (PDF). This article gives a brief account of the history of the development of the phase equilibria and crystallographic research on ceramic oxides in the Ceramics Division. Represented systems, particularly electronic materials, are highlighted.

  16. Phase Equilibria, Phase Diagrams and Phase Transformations - 2nd Edition

    NASA Astrophysics Data System (ADS)

    Hillert, Mats

    2006-03-01

    Computational tools allow material scientists to model and analyze increasingly complicated systems to appreciate material behavior. Accurate use and interpretation however, requires a strong understanding of the thermodynamic principles that underpin phase equilibrium, transformation and state. This fully revised and updated edition covers the fundamentals of thermodynamics, with a view to modern computer applications. The theoretical basis of chemical equilibria and chemical changes is covered with an emphasis on the properties of phase diagrams. Starting with the basic principles, discussion moves to systems involving multiple phases. New chapters cover irreversible thermodynamics, extremum principles, and the thermodynamics of surfaces and interfaces. Theoretical descriptions of equilibrium conditions, the state of systems at equilibrium and the changes as equilibrium is reached, are all demonstrated graphically. With illustrative examples - many computer calculated - and worked examples, this textbook is an valuable resource for advanced undergraduates and graduate students in materials science and engineering. Fully revised and updated edition covering the fundamentals of thermodynamics with a view to modern computer applications such as Thermo-Calc Emphasis is placed on phase diagrams, the key application of thermodynamics Contains numerous illustrative examples, many computer-calculated and some for real systems, and worked examples to help demonstrate the principles

  17. The application of the Deiters equation of state to the calculations of the vapour-liquid phase equilibria in systems containing halogenhydrocarbons

    NASA Astrophysics Data System (ADS)

    Dąbrowska, Barbara

    2000-03-01

    The Deiters equation of state and the Redlich-Kwong equation of state were used for calculations of low-temperature vapour-liquid phase equilibria and related thermodynamic properties in binary systems containing halogenhydrocarbons. In all calculations, standard mixing rules for the Deiters equation of state as well as the modified mixing rules (including the repulsion function and density-dependent weight factors or the repulsion function and modified mean density approximation with density-dependent weight factors) were used. The calculations were done for the following systems: CF 4/CHF 3, CF 3Cl/CF 2Cl 2, CH 4/CHF 2Cl, CH 4/CF 2Cl 2, CHF 3/CFCl 3, N 2/CF 2Cl 2. The best results were achieved with the Deiters equation of state, especially with modified mixing rules. For higher pressures and lower temperatures the Redlich-Kwong equation of state is not able to predict the phase equilibria in halogenhydrocarbon systems accurately. It fails too in the case of strongly polar substances. The best parameter sets for the Redlich-Kwong equation of state and the Deiters equation of state for the systems investigated were collected.

  18. Computation of Phase Equilibria, State Diagrams and Gas/Particle Partitioning of Mixed Organic-Inorganic Aerosols

    NASA Astrophysics Data System (ADS)

    Zuend, A.; Marcolli, C.; Peter, T.

    2009-04-01

    The chemical composition of organic-inorganic aerosols is linked to several processes and specific topics in the field of atmospheric aerosol science. Photochemical oxidation of organics in the gas phase lowers the volatility of semi-volatile compounds and contributes to the particulate matter by gas/particle partitioning. Heterogeneous chemistry and changes in the ambient relative humidity influence the aerosol composition as well. Molecular interactions between condensed phase species show typically non-ideal thermodynamic behavior. Liquid-liquid phase separations into a mainly polar, aqueous and a less polar, organic phase may considerably influence the gas/particle partitioning of semi-volatile organics and inorganics (Erdakos and Pankow, 2004; Chang and Pankow, 2006). Moreover, the phases present in the aerosol particles feed back on the heterogeneous, multi-phase chemistry, influence the scattering and absorption of radiation and affect the CCN ability of the particles. Non-ideal thermodynamic behavior in mixtures is usually described by an expression for the excess Gibbs energy, enabling the calculation of activity coefficients. We use the group-contribution model AIOMFAC (Zuend et al., 2008) to calculate activity coefficients, chemical potentials and the total Gibbs energy of mixed organic-inorganic systems. This thermodynamic model was combined with a robust global optimization module to compute potential liquid-liquid (LLE) and vapor-liquid-liquid equilibria (VLLE) as a function of particle composition at room temperature. And related to that, the gas/particle partitioning of semi-volatile components. Furthermore, we compute the thermodynamic stability (spinodal limits) of single-phase solutions, which provides information on the process type and kinetics of a phase separation. References Chang, E. I. and Pankow, J. F.: Prediction of activity coefficients in liquid aerosol particles containing organic compounds, dissolved inorganic salts, and water - Part

  19. Thermodynamics and Phase Equilibria in the Vandium-Silicon System.

    DTIC Science & Technology

    1984-09-01

    and Phase Equilibria in July 1, 1982-June 30, 1985 the Vandium-Silicon System 6. PERFORMING ORG. REPORT NUMBER 7. AUTHOR(a) S. CONTRACT OR GRANT...e) Effusion, Mass Spectrometry, Vanadium Silicides, Phase Equilibria , Range of Homogeneity, Thermodynamics Activities, Free Energies of Formation...DD Form 1473. Copies of form available from cognizant contract administrator. THERMODYNAMICS AND PHASE EQUILIBRIA IN THE VANDIUM-SILICON SYSTEM

  20. An analytical equation of state for describing isotropic-nematic phase equilibria of Lennard-Jones chain fluids with variable degree of molecular flexibility.

    PubMed

    van Westen, Thijs; Oyarzún, Bernardo; Vlugt, Thijs J H; Gross, Joachim

    2015-06-28

    We develop an equation of state (EoS) for describing isotropic-nematic (IN) phase equilibria of Lennard-Jones (LJ) chain fluids. The EoS is developed by applying a second order Barker-Henderson perturbation theory to a reference fluid of hard chain molecules. The chain molecules consist of tangentially bonded spherical segments and are allowed to be fully flexible, partially flexible (rod-coil), or rigid linear. The hard-chain reference contribution to the EoS is obtained from a Vega-Lago rescaled Onsager theory. For the description of the (attractive) dispersion interactions between molecules, we adopt a segment-segment approach. We show that the perturbation contribution for describing these interactions can be divided into an "isotropic" part, which depends only implicitly on orientational ordering of molecules (through density), and an "anisotropic" part, for which an explicit dependence on orientational ordering is included (through an expansion in the nematic order parameter). The perturbation theory is used to study the effect of chain length, molecular flexibility, and attractive interactions on IN phase equilibria of pure LJ chain fluids. Theoretical results for the IN phase equilibrium of rigid linear LJ 10-mers are compared to results obtained from Monte Carlo simulations in the isobaric-isothermal (NPT) ensemble, and an expanded formulation of the Gibbs-ensemble. Our results show that the anisotropic contribution to the dispersion attractions is irrelevant for LJ chain fluids. Using the isotropic (density-dependent) contribution only (i.e., using a zeroth order expansion of the attractive Helmholtz energy contribution in the nematic order parameter), excellent agreement between theory and simulations is observed. These results suggest that an EoS contribution for describing the attractive part of the dispersion interactions in real LCs can be obtained from conventional theoretical approaches designed for isotropic fluids, such as a Perturbed

  1. Phase equilibria in model surfactants forming Langmuir monolayers.

    PubMed

    Ramírez, E; Santana, A; Cruz, A; López, G E

    2007-12-14

    The study of Langmuir monolayers has generated the attention of researchers because of their unique properties and their not well understood phase equilibrium. These monolayers exhibit interesting phase diagrams where the unusual liquid-liquid equilibrium can be observed for a single component monolayer. Monte Carlo computer simulations in the virtual Gibbs ensemble were used to obtain the phase diagram of Langmuir monolayers. The liquid-vapor and liquid-liquid phase equilibria were considered by constructing the Cailletet-Mathias phase diagrams. By using the Ising model and the rectilinear approximations the identification of the critical properties for both equilibria was determined. These critical parameters were calculated as a function of the strength of the interaction between the surfactant molecules and the aqueous subphase. As a result, we have identified the coexistence between a liquid expanded state (LES)-vapor and the liquid condensed state-LES, in agreement with experimental and theoretical evidence in the literature. We obtained a clear separation of phases and a strong dependence on the strength of the solvent used. Namely, as the interaction between the solvent and the head of the surfactant increases, the critical properties also increase. Equilibrium states were characterized by computing thermodynamic quantities as a function of temperature and solvent strength.

  2. Phase equilibria in polydisperse nonadditive hard-sphere systems.

    PubMed

    Paricaud, Patrice

    2008-08-01

    Colloidal particles naturally exhibit a size polydispersity that can greatly influence their phase behavior in solution. Nonadditive hard-sphere (NAHS) mixtures are simple and well-suited model systems to represent phase transitions in colloid systems. Here, we propose an analytical equation of state (EOS) for NAHS fluid mixtures, which can be straightforwardly applied to polydisperse systems. For positive values of the nonadditivity parameter Delta the model gives accurate predictions of the simulated fluid-fluid coexistence curves and compressibility factors. NPT Monte Carlo simulations of the mixing properties of the NAHS symmetric binary mixture with Delta>0 are reported. It is shown that the enthalpy of mixing is largely positive and overcomes the positive entropy of mixing when the pressure is increased, leading to a fluid-fluid phase transition with a lower critical solution pressure. Phase equilibria in polydisperse systems are predicted with the model by using the density moment formalism [P. Sollich, Adv. Chem. Phys. 116, 265 (2001)]. We present predictions of the cloud and shadow curves for polydisperse NAHS systems composed of monodisperse spheres and polydisperse colloid particles. A fixed nonadditivity parameter Delta > 0 is assumed between the monodisperse and polydisperse spheres, and a Schulz distribution is used to represent the size polydispersity. Polydispersity is found to increase the extent of the immiscibility region. The predicted cloud and shadow curves depend dramatically on the upper cutoff diameter sigmac of the Schulz distribution, and three-phase equilibria can occur for large values of sigmac.

  3. Electronic structure and phase equilibria in ternary substitutional alloys

    SciTech Connect

    Traiber, A.J.S.; Allen, S.M.; Turchi, P.E.A.; Waterstrat, R.M.

    1996-04-26

    A reliable, consistent scheme to study phase equilibria in ternary substitutional alloys based on the tight-binding approximation is presented. With electronic parameters from linear muffin-tin orbital calculations, the computed density of states and band structures compare well with those from more accurate {ital ab}{ital initio} calculations. Disordered alloys are studied within the tight-binding coherent-potential approximation extended to alloys; energetics of ordered systems are obtained through effective pair interactions computed with the general perturbation method; and partially ordered alloys are studied with a novel simplification of the molecular coherent-potential approximation combined with the general perturbation method. The formalism is applied to bcc-based Zr-Ru-Pd alloys which are promising candidates for medical implant devices. Using energetics obtained from the above scheme, we apply the cluster- variation method to study phase equilibria for particular pseudo- binary alloys and show that results are consistent with observed behavior of electronic specific heat coefficient with composition for Zr{sub 0.5}(Ru, Pd){sub 0.5}.

  4. Equation of state modeling of the phase equilibria of ionic liquid mixtures at low and high pressure.

    PubMed

    Karakatsani, Eirini K; Economou, Ioannis G; Kroon, Maaike C; Bermejo, Maria D; Peters, Cor J; Witkamp, Geert-Jan

    2008-10-28

    Accurate design of processes based on ionic liquids (ILs) requires knowledge of the phase behavior of the systems involved. In this work, the truncated perturbed chain polar statistical associating fluid theory (tPC-PSAFT) is used to correlate the phase behavior of binary and ternary IL mixtures. Both non-polar and polar solvents are examined, while methyl imidazolium ILs are used in all cases. tPC-PSAFT accounts explicitly for weak dispersion interactions, highly directive polar interactions between permanent dipolar and quadrupolar molecules and association between hydrogen bonding molecules. For mixtures of non-polar solvents, tPC-PSAFT predicts accurately the binary mixture data. For the case of polar solvents, a binary interaction parameter is fitted to the experimental data and the agreement between experiment and correlation is very good in all cases.

  5. Nanoscale effects on thermodynamics and phase equilibria in oxide systems.

    PubMed

    Navrotsky, Alexandra

    2011-08-22

    Because different solid materials (phases) have different surface energies, equilibria among them will be significantly affected by particle size. This Minireview summarizes experimental (calorimetric) data for the surface energies of oxides and discusses shifts in the stability of polymorphs, the thermodynamics of hydration, and oxidation-reduction reactions in nanoscale oxide systems.

  6. Phase equilibria of a low S and C lunar core: Implications for an early lunar dynamo and physical state of the current core

    NASA Astrophysics Data System (ADS)

    Righter, K.; Go, B. M.; Pando, K. A.; Danielson, L.; Ross, D. K.; Rahman, Z.; Keller, L. P.

    2017-04-01

    Multiple lines of geochemical and geophysical evidence suggest the Moon has a small metallic core, yet the composition of the core is poorly constrained. The physical state of the core (now or in the past) depends on detailed knowledge of its composition, and unfortunately, there is little available data on relevant multicomponent systems (i.e., Fe-Ni-S-C) at lunar interior conditions. In particular, there is a dearth of phase equilibrium data to elucidate whether a specific core composition could help to explain an early lunar geodynamo and magnetic field intensities, or current solid inner core/liquid outer core states. We utilize geochemical information to estimate the Ni, S and C contents of the lunar core, and then carry out phase equilibria experiments on several possible core compositions at the pressure and temperature conditions relevant to the lunar interior. The first composition is 0.5 wt% S and 0.375 wt% C, based on S and C contents of Apollo glasses. A second composition contains 1 wt% each of S and C, and assumes that the lunar mantle experienced degassing of up to 50% of its S and C. Finally a third composition contains C as the dominant light element. Phase equilibrium experiments were completed at 1, 3 and 5 GPa, using piston cylinder and multi-anvil techniques. The first composition has a liquidus near 1550 °C and solidus near 1250 °C. The second composition has a narrower liquidus and solidus temperatures of 1400 and 1270 °C, respectively, while the third composition is molten down to 1150 °C. As the composition crystallizes, the residual liquid becomes enriched in S and C, but S enrichment is greater due to the incorporation of C (but not S) into solid metallic FeNi. Comparison of these results to thermal models for the Moon allow an evaluation of which composition is consistent with the geophysical data of an early dynamo and a currently solid inner and liquid outer core. Composition 1 has a high enough liquidus to start crystallizing

  7. EXPERIMENTAL PHASE EQUILIBRIA OF SELECTED BINARY, TERNARY, AND HIGHER ORDER SYSTEMS. PART 4. THE PHASE DIAGRAM W-B-C

    DTIC Science & Technology

    system and the mutual solubilities between carbide and boride phases are small. The solid state sections (򒾐C) are characterized by two- phase ... equilibria existing between the phase pairs W2B + W2C, W2B + WC, WC + WB, WB + C, W2B5 + C, W2B5 + B4C, and WB approximately 4 + B4C. The two-phase

  8. Experimental methods for phase equilibria at high pressures.

    PubMed

    Dohrn, Ralf; Fonseca, José M S; Peper, Stephanie

    2012-01-01

    Knowledge of high-pressure phase equilibria is crucial in many fields, e.g., for the design and optimization of high-pressure chemical and separation processes, carbon capture and storage, hydrate formation, applications of ionic liquids, and geological processes. This review presents the variety of methods to measure phase equilibria at high pressures and, following a classification, discusses the measurement principles, advantages, challenges, and error sources. Examples of application areas are given. A detailed knowledge and understanding of the different methods is fundamental not only for choosing the most suitable method for a certain task but also for the evaluation of experimental data. The discrepancy between the (sometimes low) true accuracy of published experimental data and the (high) accuracy claimed by authors is addressed. Some essential requirements for the generation of valuable experimental results are summarized.

  9. Phase Equilibria and Mutual Diffusion in Polymer - Polymer Systems with Chlorine-containing Components

    NASA Astrophysics Data System (ADS)

    Chalykh, Anatolii E.; Sapozhnikova, I. N.

    1984-11-01

    The experimental studies of the phase equilibria and mutual diffusion in polymer mixtures are examined. A thermodynamic analysis of the phase equilibria in the poly(vinyl chloride) - poly(methyl methacrylate) and chloropolyethylene - poly(methyl methacrylate) systems is presented within the framework of classical and new theories; the influence of the previous history of the specimens and of the chemical structure and stereoregularity of the polymer chains on the phase composition of the mixtures is demonstrated. The translational mobility of the macromolecules in the highly elastic and highly fluid states and its role in the formation of the phase structure of the mixtures and also the irreversible changes in the phase structure on thermal decomposition of chlorine-containing polymers are considered. The bibliography includes 95 references.

  10. Phase equilibria study of pseudobrookite type minerals

    NASA Technical Reports Server (NTRS)

    Friel, J. J.

    1974-01-01

    Pseudobrookite, is found in volcanic rocks, and the mineral armalcolite ((Fe,Mg)Ti2O5) found in the Apollo 11 and subsequent lunar samples seems to be unique to the moon. In plutonic rocks on the earth, ilmenite and rutile were found with what appears to be an equilibrium liquidus texture, while on the moon armalcolite often appears to be the primary liquidus phase among Ti-oxides. This suggests that total pressure may be a factor in the formation of these minerals, and a knowledge of the phase relations in this system yields information about the pressure under which a given magma crystallized.

  11. Phase Equilibria in Thin Polymer Films

    NASA Astrophysics Data System (ADS)

    Müller, M.; Binder, K.; Albano, E. V.

    Within self-consistent field theory and Monte Carlo simulations the phase behavior of a symmetrical binary AB polymer blend confined into a thin film is studied. The film surfaces interact with the monomers via short ranged potentials. One surface attracts the A component and the corresponding semi-infinite system exhibits a first order wetting transition. The surface interaction of the opposite surface is varied as to study the crossover from capillary condensation for symmetric surface fields to interface localization/delocalization transition for antisymmetric surface fields. In the former case the phase diagram has a single critical point close to the bulk critical point. In the latter case the phase diagram exhibits two critical points which correspond to the prewetting critical points of the semi-infinite system. Only below a triple point there is a single two-phase coexistence region. The crossover between these qualitatively different limiting behaviors occurs gradually, however, the critical temperature and the critical composition exhibit a non-monotonic dependence on the surface field. The dependence of the phase behavior for antisymmetric boundaries is studied as a function of the film thickness and the strength of the surface interactions. Upon reducing the film thickness or decreasing the strength of the surface interactions we can change the order of the interface localization/delocalization transition from first to second. The role of fluctuations is explored via Monte Carlo simulations of a coarse grained lattice model. Close to the (prewetting) critical points we observe 2D Ising critical behavior. Also, there is a rich crossover behavior between Ising critical, tricritical and mean field behavior. At lower temperatures capillary waves of the AB interface lead to a pronounced dependence of the effective interface potential on the lateral system size.

  12. Silicate-Sulfide-Oxide Phase Equilibria in Subduction Zones

    NASA Astrophysics Data System (ADS)

    Brown, J. L.; Ellis, D. J.; Christy, A. G.; Arculus, R. J.

    2008-12-01

    Classical O2- and S2-dependent equilibria have been extrapolated to high P, showing that fO2 and fS2 in a wide variety of geological environments can be gauged by comparison to fluid buffering reactions. Many of these equilibria involve magnetite, which in intermediate to mafic rock types is eliminated with increasing P during the gabbro to eclogite transition (Green and Ringwood, 1967). It is not generally recognized that traditional buffers, such as QFM (quartz-fayalite-magnetite), are not appropriate for evaluating fluid conditions in subduction zones. This paper will present new fS2 and fO2 equilibria that are consistent with silicate, oxide, and sulfide petrography of the blueschist-eclogite belt in northern New Caledonia (Brown, 2007), and are therefore appropriate for evaluating fluid conditions consistent with subduction zone metamorphism. We evaluate reactions, which are supported by textural evidence in natural specimens, between silicates, oxides, and sulfides (stable at low P) to form garnet (at higher P). Several analogues that eliminate plagioclase +/- magnetite to produce garnet are proposed. A consequence of reacting Fe in sulfide to produce garnet is the concentration of chalcophile elements in the remaining sulfide phase. This is consistent with petrographic observations in the New Caledonian high P belt. Implications of new equilibiria demonstrate that phase relations proposed with garnet cannot be related to classical fS2-fO2 phase diagrams involving QFM. The only reactions involving mineral phases commonly present throughout the range of PT conditions in subducted crust involve ilmenite-rutile-sulfide equilibria. These equilibria can be widely applied to evaluating fluid conditions in the crust and mantle, not just subduction zones. References Brown, J.L. (2007) The Deep Sulfur Cycle: Insights from sulfide metamorphism in blueschist and eclogite, NE New Caledonia. PhD Thesis, The Australian National University. Green, D.H. and Ringwood, A

  13. Phase Equilibria of Stored Chemical Energy Reactants.

    DTIC Science & Technology

    1984-07-25

    and Westrum, Jr .,E. F., J. Chem. Thermo. 7, [8] 693 (1975). 33. Hastie, J. W. and Bonnell, D. W., A Predictive Phase Equilibrium Model for...aluminate and lithium ferrite: Diss. Abstr. Int. B, V. 37, No. 7, p. 1277-8. Venero, A. F. and Westrum, E. F., Jr ., 1975, Heat capacities and...Energy Comm., Report No. Y-1601, 22 p. Dixon, S., Jr ., 1975, Nonlinear properties of aluminum-substituted lithium ferrite: AlP Conf. Proc., V. 211, p

  14. Phase equilibria modification by electric fields. 1997 annual progress report

    SciTech Connect

    Tsouris, C.; Shah, V.M.

    1997-09-01

    'In this research program, Oak Ridge National Laboratory is investigating the modification of phase equilibria and interface transport enhancement-caused by electric fields. The majority of environmental and waste treatment processes involve complex chemical separations and reactions. The treatment efficiency in such processes is governed by thermodynamic equilibria and transport. The objective of this project is to use electric fields to favorably manipulate the thermodynamic and transport properties of mixtures so that higher separation efficiencies can be achieved. An understanding of the mechanisms of the underlying phenomena of molecular and fluid interactions with electric fields will lead to the development of efficient remediation methods for contaminated natural environments and wastes. Research Statement The main focus of this project is to understand and quantify the influence of electric fields on thermodynamic equilibria and transport properties of fluid mixtures and to determine the conditions and properties of the systems for which this influence is of practical significance. The specific objectives of the project are discussed.'

  15. Phase equilibria of chlorofluorocarbon alternative refrigerant mixtures

    SciTech Connect

    Lee, B.G.; Park, J.Y.; Lim, J.S.; Cho, S.Y.; Park, K.Y.

    1999-03-01

    Isothermal vapor-liquid equilibrium data were determined for binary systems of difluoromethane/1,1,1,2-tetrafluoroethane (HFC-32/HFC-134a), difluoromethane/pentafluoroethane (HFC-32/HFC-125), difluoromethane/1,1,1-trifluoroethane (HFC-32/HFC-143A), and difluoromethane/1,1-difluoroethane (HFC-32/HFC-152a). The vapor and liquid compositions and pressures were measured in a circulation-type apparatus at 303.15 K and 323.15 K. The experimental data were compared with literature results and correlated with the Canahan-Starling-De Santis equation of state within the uncertainty of {+-}1.0%.

  16. Phosphorus Equilibria Among Mafic Silicate Phases

    NASA Technical Reports Server (NTRS)

    Berlin, Jana; Xirouchakis, Dimitris

    2002-01-01

    Phosphorus incorporation in major rock-forming silicate minerals has the following implications: (1) Reactions between phosphorus-hosting major silicates and accessory phosphates, which are also major trace element carriers, may control the stability of the latter and thus may affect the amount of phosphorus and other trace elements released to the coexisting melt or fluid phase. (2) Less of a phosphate mineral is needed to account for the bulk phosphorus of planetaty mantles. (3) During partial melting of mantle mineral assemblages or equilibrium fractional crystallization of basaltic magmas, and in the absence or prior to saturation with a phosphate mineral, silicate melts may become enriched in phosphorus, especially in the geochemically important low melt fraction regime, Although the small differences in the ionic radii of IVp5+, IVSi4+, and IV Al3+ makes phosphoms incorporation into crystalline silicates perhaps unsurprising, isostructural silicate and phosphate crystalline solids do not readily form solutions, e.g., (Fe, Mg)2SiO4 vs. LiMgPO4, SiO)2 VS. AlPO4. Nonetheless, there are reports of, poorly characterized silico-phosphate phases in angrites , 2-4 wt% P2O5 in olivine and pyroxene grains in pallasites and reduced terestrial basalts which are little understood but potentially useful, and up to 17 wt% P2O5 in olivine from ancient slags. However, such enrichments are rare and only underscore the likelihood of phosphoms incorporation in silicate minerals. The mechanisms that allow phosphorus to enter major rock-forming silicate minerals (e.g., Oliv, Px, Gt) remain little understood and the relevant data base is limited. Nonetheless, old and new high-pressure (5-10 GPa) experimental data suggest that P2O5 wt% decreases from silica-poor to silica-rich compositions or from orthosilicate to chain silicate structures (garnet > olivine > orthopyroxene) which implies that phosphorus incorporation in silicates is perhaps more structure-than site-specific. The

  17. Refractory and Hard Materials in the Ti-Si-B-C-N System - Phase Equilibria, Phase Reactions and Thermal Stabilities

    DTIC Science & Technology

    2004-12-01

    1 REFRACTORY AND HARD MATERIALS IN THE Ti-Si-B-C-N SYSTEM – PHASE EQUILIBRIA , PHASE REACTIONS AND THERMAL STABILITIES Hans Jürgen Seifert...the underlying phase equilibria and reactions have to be known in detail. The main goal of this work was to study the thermal stability with...respect to the phase equilibria and the phase reactions of ceramics and refractory and hard materials in the Ti-Si-B-C-N system by means of CALPHAD

  18. PHASE EQUILIBRIA INVESTIGATIONS OF BINARY, TERNARY, AND HIGHER ORDER SYSTEMS. PART 2. EFFECT OF RHENIUM AND ALUMINUM ADDITIONS ON THE METAL-RICH EQUILIBRIA IN THE TITANIUM-MOLYBDENIUM-CARBON AND TITANIUM-NIOBIUM-CARBON SYSTEMS

    DTIC Science & Technology

    The solid state phase equilibria of the metal-rich regions of the Titanium-Molybdenum-Carbon and Titanium-Niobium-Carbon systems with up to 12 At...Rhenium and 10 At.% Aluminum additions, respectively, have been determined on hot pressed, heat treated, and in part arc melted alloys. The phase ... equilibria in the metal-rich regions, with these additions, is practically unchanged over that of the ternary Titanium-Molybdenum-Carbon and Titanium

  19. PHASE EQUILIBRIA INVESTIGATION OF BINARY, TERNARY, AND HIGHER ORDER SYSTEMS. PART 9. CALCULATION OF THERMODYNAMIC QUANTITIES FROM PHASE DIAGRAMS

    DTIC Science & Technology

    The thermodynamic fundamentals relating phase equilibria in binary and ternary systems to the thermodynamic properties of the phases are reviewed and...system demonstrate the application of the equations for extracting thermodynamic data from phase diagrams and also for the prediction of phase equilibria .

  20. Phase equilibria and plate-fluid interfacial tensions for associating hard sphere fluids confined in slit pores.

    PubMed

    Fu, Dong; Li, Xiao-Sen

    2006-08-28

    The excess Helmholtz free energy functional for associating hard sphere fluid is formulated by using a modified fundamental measure theory [Y. X. Yu and J. Z. Wu, J. Chem. Phys. 117, 10156 (2002)]. Within the framework of density functional theory, the thermodynamic properties including phase equilibria for both molecules and monomers, equilibrium plate-fluid interfacial tensions and isotherms of excess adsorption, average molecule density, average monomer density, and plate-fluid interfacial tension for four-site associating hard sphere fluids confined in slit pores are investigated. The phase equilibria inside the hard slit pores and attractive slit pores are determined according to the requirement that temperature, chemical potential, and grand potential in coexistence phases should be equal and the plate-fluid interfacial tensions at equilibrium states are predicted consequently. The influences of association energy, fluid-solid interaction, and pore width on phase equilibria and equilibrium plate-fluid interfacial tensions are discussed.

  1. Nematogenic Aromatic Block Copolymers of Rigid and Flexible Units. II. Phase Equilibria.

    DTIC Science & Technology

    1986-11-06

    Phase Equilibria 12 PERSONAL AUTHOR(S) -W_ R_ Krinhaum- 7- Shuf~in-. Prpdnn- A (’ifiarri anri r. rnnin 13a 1,TAPOF -EPORT 113b TIME COVERED 14. DATE...and Flexible Units. II. Phase Equilibria by W. R. Krigbaum, Z. Shufan, Jack Preston, A. Ciferri and G. Conio q Prepared for Publication in the

  2. Phase equilibria in carbon dioxide expanded solvents: Experiments and molecular simulations.

    PubMed

    Houndonougbo, Yao; Jin, Hong; Rajagopalan, Bhuma; Wong, Kean; Kuczera, Krzysztof; Subramaniam, Bala; Laird, Brian

    2006-07-06

    We present complementary molecular simulations and experimental results of phase equilibria for carbon dioxide expanded acetonitrile, methanol, ethanol, acetone, acetic acid, toluene, and 1-octene. The volume expansion measurements were done using a high-pressure Jerguson view cell. Molecular simulations were performed using the Gibbs ensemble Monte Carlo method. Calculations in the canonical ensemble (NVT) were performed to determine the coexistence curve of the pure solvent systems. Binary mixtures were simulated in the isobaric-isothermal distribution (NPT). Predictions of vapor-liquid equilibria of the pure components agree well with experimental data. The simulations accurately reproduced experimental data on saturated liquid and vapor densities for carbon dioxide, methanol, ethanol, acetone, acetic acid, toluene, and 1-octene. In all carbon dioxide expanded liquids (CXL's) studied, the molecular simulation results for the volume expansion of these binary mixtures were found to be as good as, and in many cases superior to, predictions based on the Peng-Robinson equation of state, demonstrating the utility of molecular simulation in the prediction of CXL phase equilibria.

  3. Phase Equilibria and Transition in Mixtures of a Homopolymer and a Block Copolymer. II.

    DTIC Science & Technology

    1983-01-26

    AD-A124 929 PHASE EQUILIBRIA AND TRANSITION IN MIXTURES OF A In- NOMOPOLYMER AND’A BLOCK..(U) CINCINNATI UNJY ON DEPT OF MATERIALS SCIENCE AND...REPORT NO. 7 v2 L Phase Equilibria and Transition in Mixtures of a Homopolymer and a Block Copolymer II. The Phase Diagram by R. J. Roe and W. C. Zin...homopolymers as in our systems. The phase equilibria at temperatures above the "pseudo-triple point" BCD can be interpreted in terms of the free energy of

  4. A new equation of state of a flexible-chain polyelectrolyte solution: Phase equilibria and osmotic pressure in the salt-free case.

    PubMed

    Budkov, Yu A; Kolesnikov, A L; Georgi, N; Nogovitsyn, E A; Kiselev, M G

    2015-05-07

    We develop a first-principle equation of state of salt-free polyelectrolyte solution in the limit of infinitely long flexible polymer chains in the framework of a field-theoretical formalism beyond the linear Debye-Hueckel theory and predict a liquid-liquid phase separation induced by a strong correlation attraction. As a reference system, we choose a set of two subsystems-charged macromolecules immersed in a structureless oppositely charged background created by counterions (polymer one component plasma) and counterions immersed in oppositely charged background created by polymer chains (hard-core one component plasma). We calculate the excess free energy of polymer one component plasma in the framework of modified random phase approximation, whereas a contribution of charge densities' fluctuations of neutralizing backgrounds we evaluate at the level of Gaussian approximation. We show that our theory is in a very good agreement with the results of Monte Carlo and MD simulations for critical parameters of liquid-liquid phase separation and osmotic pressure in a wide range of monomer concentration above the critical point, respectively.

  5. Metamorphism and partial melting of ordinary chondrites: Calculated phase equilibria

    NASA Astrophysics Data System (ADS)

    Johnson, T. E.; Benedix, G. K.; Bland, P. A.

    2016-01-01

    Constraining the metamorphic pressures (P) and temperatures (T) recorded by meteorites is key to understanding the size and thermal history of their asteroid parent bodies. New thermodynamic models calibrated to very low P for minerals and melt in terrestrial mantle peridotite permit quantitative investigation of high-T metamorphism in ordinary chondrites using phase equilibria modelling. Isochemical P-T phase diagrams based on the average composition of H, L and LL chondrite falls and contoured for the composition and abundance of olivine, ortho- and clinopyroxene, plagioclase and chromite provide a good match with values measured in so-called equilibrated (petrologic type 4-6) samples. Some compositional variables, in particular Al in orthopyroxene and Na in clinopyroxene, exhibit a strong pressure dependence when considered over a range of several kilobars, providing a means of recognising meteorites derived from the cores of asteroids with radii of several hundred kilometres, if such bodies existed at that time. At the low pressures (<1 kbar) that typify thermal metamorphism, several compositional variables are good thermometers. Although those based on Fe-Mg exchange are likely to have been reset during slow cooling, those based on coupled substitution, in particular Ca and Al in orthopyroxene and Na in clinopyroxene, are less susceptible to retrograde diffusion and are potentially more faithful recorders of peak conditions. The intersection of isopleths of these variables may allow pressures to be quantified, even at low P, permitting constraints on the minimum size of parent asteroid bodies. The phase diagrams predict the onset of partial melting at 1050-1100 °C by incongruent reactions consuming plagioclase, clinopyroxene and orthopyroxene, whose compositions change abruptly as melting proceeds. These predictions match natural observations well and support the view that type 7 chondrites represent a suprasolidus continuation of the established petrologic

  6. Model for phase equilibria in micellar solutions of nonionic surfactants

    NASA Astrophysics Data System (ADS)

    Goldstein, Raymond E.

    1986-03-01

    The formation of spherical micelles in aqueous solutions of nonionic surfactants and the equilibria between two such micellar phases are studied with a phenomenological model incorporating hydrophobic interactions and the configurational entropy of the amphiphiles. The distribution of micelle sizes is determined over the entire temperature-composition phase diagram, and moments of that distribution function determine the consolute point parameters. In a generalization of an analysis given by Stillinger and Ben-Naim, the mathematical properties of various thermodynamic functions in the neighborhood of the critical micelle concentration are related to the location of branch points of the osmotic pressure in the complex concentration plane. The model attributes the experimentally observed lower critical solution points in these systems to surfactant-water hydrogen bonding, whose temperature dependence is described with a mean field approximation. Calculated phase diagrams are in qualitative agreement with those from experiments, in particular, exhibiting closed solubility loops with quite distinct upper and lower critical compositions, and values for the lower critical composition on the order of several percent volume fraction. The relevance of certain aspects of the model to the understanding of microemulsions is discussed.

  7. Solid-Phase Equilibria for Metal-Silicon-Oxygen Ternary Systems. II. Sc, Y, and La

    DTIC Science & Technology

    1991-02-28

    Organization: Regents of the University of California TECHNICAL REPORT No. 9 SOLID- PHASE EQUILIBRIA FOR METAL-SILICON-OXYGEN TERNARY SYSTEMS: 11: Sc, Y, AND La...34’ SOLID- PHASE EQUILIBRIA FOR METAL-SILICON-OXYGEN TERNARY SYSTEMS: 11: Sc, Y, AND 1a 13 0911OtiA AUTHORCS) Haojie Yuan and R. Stanley Williams lI" TV...0660te tCLhSSWI=) Solid phase equilibria for metal-silicon-oxygen ternary systems I1: Sc, Y and La Haojie Yuan and R. Stanley Williams Department of

  8. Eutectic, monotectic and immiscibility systems of nimesulide with water-soluble carriers: phase equilibria, solid-state characterisation and in-vivo/pharmacodynamic evaluation.

    PubMed

    Abdelkader, Hamdy; Abdallah, Ossama Y; Salem, Hesham; Alani, Adam W G; Alany, Raid G

    2014-10-01

    The solid-state interactions of fused mixtures nimesulide (ND) with polyethylene glycol (PEG) 4000, urea or mannitol were studied through constructing thaw-melt phase equilibrium diagrams. The solid-state characteristics were investigated using differential scanning calorimetry (DSC) and X-ray diffraction (XRD). Various types of interactions were identified such as the formation of a eutectic system of ND-PEG 4000, monotectic system of ND-urea and complete solid immiscibility of ND with mannitol. The effects of carrier concentrations on the equilibrium solubility and in-vitro dissolution characteristics were studied. Linear increases (R(2)  > 0.99) in the aqueous solubility of ND in various concentrations of PEG 4000 and urea were obtained, whereas mannitol did not exhibit any effect on the solubility of ND. Similar trends were obtained with the dissolution efficiency of the fused mixtures of ND with PEG 4000 and urea compared with the corresponding physical mixtures and untreated drug. The analgesic effects of untreated ND and the selected formulations were investigated by evaluating the drug's ability to inhibit the acetic acid-induced writhing response. The analgesic effect of ND in a eutectic mixture with PEG 4000 and a monotectic mixture with urea was potentiated by 3.2 and 2.7-fold respectively compared with the untreated drug. © 2014 Royal Pharmaceutical Society.

  9. Solid Phase Equilibria in the Pi-Ga-As and Pt-Ga-Sb Systems

    DTIC Science & Technology

    1988-07-22

    OFFICE OF NAVAL RESEARCH Research Contract N00014-87-K-0014 R&T Code 413E026---01 AD-A 198 654 TECHNICAL REPORT No. 9 SOLID PHASE EQUILIBRIA IN THE...Classtcation) UNCLASSLFIED: Tech.Rept.#9 SOLID PHASE EQUILIBRIA IN T11: Pt-Ga-As AND Pt-Ga-Sb SYST’IS 12 PERSONAL AuTiOR(S) C.T. Tsai and R.S. Williats 13a TYPE

  10. Correlation of three-liquid-phase equilibria involving ionic liquids.

    PubMed

    Rodríguez-Escontrela, I; Arce, A; Soto, A; Marcilla, A; Olaya, M M; Reyes-Labarta, J A

    2016-08-03

    The difficulty in achieving a good thermodynamic description of phase equilibria is finding a model that can be extended to a large variety of chemical families and conditions. This problem worsens in the case of systems containing more than two phases or involving complex compounds such as ionic liquids. However, there are interesting applications that involve multiphasic systems, and the promising features of ionic liquids suggest that they will play an important role in many future processes. In this work, for the first time, the simultaneous correlation of liquid-liquid and liquid-liquid-liquid equilibrium data for ternary systems involving ionic liquids has been carried out. To that end, the phase diagram of the water + [P6 6 6 14][DCA] + hexane system has been determined at 298.15 K and 323.15 K and atmospheric pressure. The importance of this system lies in the possibility of using the surface active ionic liquid to improve surfactant enhanced oil recovery methods. With those and previous measurements, thirteen sets of equilibrium data for water + ionic liquid + oil ternary systems have been correlated. The isoactivity equilibrium condition, using the NRTL model, and some pivotal strategies are proposed to correlate these complex systems. Good agreement has been found between experimental and calculated data in all the regions (one triphasic and two biphasic) of the diagrams. The geometric aspects related to the Gibbs energy of mixing function obtained using the model, together with the minor common tangent plane equilibrium condition, are valuable tools to check the consistency of the obtained correlation results.

  11. Phase equilibria of the system methane-ethane from temperature scaling Gibbs Ensemble Monte Carlo simulation

    NASA Astrophysics Data System (ADS)

    Zhang, Zhigang; Duan, Zhenhao

    2002-10-01

    A new technique of temperature scaling method combined with the conventional Gibbs Ensemble Monte Carlo simulation was used to study liquid-vapor phase equilibria of the methane-ethane (CH 4-C 2H 6) system. With this efficient method, a new set of united-atom Lennard-Jones potential parameters for pure C 2H 6 was found to be more accurate than those of previous models in the prediction of phase equilibria. Using the optimized potentials for liquid simulations (OPLS) potential for CH 4 and the potential of this study for C 2H 6, together with a simple mixing rule, we simulated the equilibrium compositions and densities of the CH 4-C 2H 6 mixtures with accuracy close to experiments. The simulated data are supplements to experiments, and may cover a larger temperature-pressure-composition space than experiments. Compared with some well-established equations of state such as Peng-Robinson equation of state (PR-EQS), the simulated results are found to be closer to experiments, at least in some temperature and pressure ranges.

  12. Solid-liquid phase equilibria of the Gaussian core model fluid.

    PubMed

    Mausbach, Peter; Ahmed, Alauddin; Sadus, Richard J

    2009-11-14

    The solid-liquid phase equilibria of the Gaussian core model are determined using the GWTS [J. Ge, G.-W. Wu, B. D. Todd, and R. J. Sadus, J. Chem. Phys. 119, 11017 (2003)] algorithm, which combines equilibrium and nonequilibrium molecular dynamics simulations. This is the first reported use of the GWTS algorithm for a fluid system displaying a reentrant melting scenario. Using the GWTS algorithm, the phase envelope of the Gaussian core model can be calculated more precisely than previously possible. The results for the low-density and the high-density (reentrant melting) sides of the solid state are in good agreement with those obtained by Monte Carlo simulations in conjunction with calculations of the solid free energies. The common point on the Gaussian core envelope, where equal-density solid and liquid phases are in coexistence, could be determined with high precision.

  13. Transferable potentials for phase equilibria-coarse-grain description for linear alkanes.

    PubMed

    Maerzke, Katie A; Siepmann, J Ilja

    2011-04-07

    Coarse-grain potentials allow one to extend molecular simulations to length and time scales beyond those accesssible to atomistic representations of the interacting system. Since the coarse-grain potentials remove a large number of interaction sites and, hence, a large number of degrees of freedom, it is generally assumed that coarse-grain potentials are not transferable to different systems or state points (temperature and pressure). Here we apply lessons learned from the parametrization of transferable atomistic potentials to develop a systematic procedure for the parametrization of transferable coarse-grain potentials. In particular, we apply an iterative Boltzmann optimization for the determination of the bonded interactions for coarse-grain beads belonging to the same molecule and separated by one or two coarse-grain bonds and parametrize the nonbonded interactions by fitting to the vapor-liquid coexistence curves computed for selected molecules represented by the TraPPE-UA (transferable potentials for phase equilibria-united atom) force field. This approach is tested here for linear alkanes where parameters for C(3)H(7) end segments and for C(3)H(6) middle segments of the TraPPE-CG (transferable potentials for phase equilibria-coarse grain) force field are determined and it is shown that these parameters yield quite accurate vapor-liquid equilibria for neat n-hexane to n-triacontane and for the binary mixture of n-hexane and n-hexatriacontane. In addition, the position of the first peak in various radial distribution functions and the coordination number for the first solvation shell are well reproduced by the TraPPE-CG force field, but the first peaks are too high and narrow.

  14. Phase equilibria in potential Pb-free solder alloy systems

    NASA Astrophysics Data System (ADS)

    Loomans, Michael Eugene

    1999-11-01

    Worldwide concern over the toxicity of Pb, voiced in an assortment of ways, has forced the electronics industry to seek Pb-free replacements for the Pb-containing solders that are extensively employed in the industry. The main purpose of this research was to re-examine various claims made concerning eutectic behavior in certain low-melting-point, Sn-based alloy systems that were considered to be potential sources of useful Pb-free solders. Some basic phase equilibrium data has also been produced in this research. Four alloy systems were examined: Sn-Ag-Cu, Sn-Zn, Sn-Zn-Cu, and Sn-Ag-Zn. The alloy systems were examined using differential scanning calorimetry, annealing studies, and microscopy. Phase identification was conducted in a scanning electron microscope using semi-quantitative energy dispersive spectroscopy. In the Sn-Ag-Cu system a careful eutectic composition determination placed the ternary eutectic composition at Sn-3.5Ag-(0.8 to 0.9)wt% Cu. An alloy having the composition Sn47Ag-1.7wt% Cu, a eutectic composition proposed in the literature, was found to have a melting range of approximately 50°C. In the Sn-Zn system, careful eutectic composition determination placed the Sn-Zn eutectic composition at Sn-7.9wt% Zn. This composition differs from the accepted Sn-Zn eutectic composition (Sn-8.8wt% Zn), but is not inconsistent with the data from the study that produced the accepted composition. The present study assigns a melting range of 8°C to the accepted eutectic composition. Only one experimental investigation of the Sn-corner of the Sn-Zn-Cu system was found in the literature. The present study did not observe the ternary eutectic reaction proposed by that investigation. Also, phase equilibria observed in the present study differ significantly from those predicted by the other investigation. Three different Sn-Zn-Cu alloys (Sn-7.8Zn-0.5wt% Cu, Sn-7.5Zn-1.5wt% Cu, and Sn7.4Zn-1.5wt% Cu) were examined in the present study. The present study demonstrated

  15. Densities, Electrical Conductivities, Viscosities and Phase Equilibria of 1,3-Dialkylimidazolium Chloride - Aluminum Chloride Binary and Ternary Melts.

    DTIC Science & Technology

    1982-07-01

    FRANK J. SELLER RESEARCH LABORATORY FJSRL-TR-82-0006 JULY 1982 DENSITIES, ELEC’TRICAL CONDUCTIVITIES, VISCOSITIES AND PHASE EQUILIBRIA OF 1,3...Conductivities, Viscosities and Phase Equilibria of 1,3- Interim 6/81-7/82 Dialkylimidazolium Chloride-Aluminum Chloride 6. PERFORMING ORG. REPORT NUMBER...Entered) FJSRL-TR-82-0006 DENSITIES, ELECTRICAL CONDUCTIVITIES, VISCOSITIES AND PHASE EQUILIBRIA OF 1,3-DIALKYLIMIDAZOLIUM CHLORIDE- ALUMINUM CHLORIDE

  16. Phase equilibria and physical properties of core materials

    NASA Astrophysics Data System (ADS)

    Seagle, Christopher T.

    The physical properties and phase equilibria of materials suspected to be important for Earth's core have been investigated at high pressures using the diamond anvil cell. The optical properties of iron have been derived from reflectance measurements at room temperature up to 50 GPa. There are strong changes in the optical properties associated with the bcc to hcp phase transition in iron at ˜13 GPa. The spectral emissivity of iron is a particularly important property because it appears in the equations used to measure temperature in the laser heated diamond anvil cell, and shock wave experiments. The emissivity of iron in the near infrared is a strong function of wavelength below the bcc to hcp phase transition. Above this phase transition, the infrared emissivity of iron does not have wavelength dependence, it behaves as a greybody. Temperature measurements utilizing spectroradiometry on iron samples below ˜13 GPa need to take into account the wavelength dependent emissivity of iron, or accept errors on the measured temperature as large at ˜25% or more. Investigations into the high pressure binary Fe-FeO and Fe-Fe3S phase diagrams using the laser heated diamond anvil cell in conjunction with synchrotron x-ray diffraction have been used to place constraints on the temperature and composition of Earth's core. The data suggests that oxygen is likely to preferentially partition into the liquid at the inner core boundary, while sulfur does not have a strong preference for the liquid or solid. This is an important result because it suggests that oxygen may be required in the core in order to explain the different abundances of light elements in the inner and outer cores. The melting temperatures in these systems were also measured up to ˜100 GPa for the Fe-FeO system and up to ˜150 GPa for the Fe-Fe3S system. The melting point depression with respect to pure iron is negligible in the case of adding oxygen, but a depression of 100-800 K was observed for the sulfur

  17. Phase transformations and phase equilibria in the Co-Sn-Ti system in the crystallization interval

    NASA Astrophysics Data System (ADS)

    Fartushna, Iu.; Bulanova, M.; Ayral, R. M.; Tedenac, J. C.; Meleshevich, K.

    2016-12-01

    The Co-Sn-Ti system was studied in the crystallization interval (below 50 at% Sn) by the methods of Scanning Electron Microscopy, microprobe analysis, Differential Thermal Analysis, X-ray diffraction. The liquidus and solidus projections and the melting diagram were constructed. Only Co2TiSn(τ1) ternary compound (Heusler phase-L12) was found in equilibria with the liquid in the concentration interval studied. Taking into account our recent data, the liquidus projection is characterized by the fields of primary crystallization of (βTi), (Co), binary-based phases Ti3Sn, Ti2Sn, Ti5Sn3, Ti6Sn5, Ti2Co, TiCo, TiCo2 (c), TiCo2 (h), TiCo3, βCo3Sn2, CoSn and ternary τ1. The solidus projection is characterized by thirteen three-phase fields, which result from invariant four-phase equilibria, five are of eutectic type (E) and eight of transition type (U) and the existence of one more region Ti2Sn3+βCoSn3+(Sn) in the solidus projection is discussed.

  18. New investigation of phase equilibria in the system Al-Cu-Si.

    PubMed

    Ponweiser, Norbert; Richter, Klaus W

    2012-01-25

    The phase equilibria and invariant reactions in the system Al-Cu-Si were investigated by a combination of optical microscopy, powder X-ray diffraction (XRD), differential thermal analysis (DTA) and electron probe micro analysis (EPMA). Isothermal phase equilibria were investigated within two isothermal sections. The isothermal section at 500 °C covers the whole ternary composition range and largely confirms the findings of previous phase diagram investigations. The isothermal section at 700 °C describes phase equilibria only in the complex Cu-rich part of the phase diagram. A new ternary compound τ was found in the region between (Al,Cu)-γ(1) and (Cu,Si)-γ and its solubility range was determined. The solubility of Al in κ-CuSi was found to be extremely high at 700 °C. In contrast, no ternary solubility in the β-phase of Cu-Al was found, although this phase is supposed to form a complete solid solution according to previous phase diagram assessments. Two isopleths, at 10 and 40 at.% Si, were investigated by means of DTA and a partial ternary reaction scheme (Scheil diagram) was constructed, based on the current work and the latest findings in the binary systems Al-Cu and Cu-Si. The current study shows that the high temperature equilibria in the Cu-rich corner are still poorly understood and additional studies in this area would be favorable.

  19. New investigation of phase equilibria in the system Al–Cu–Si

    PubMed Central

    Ponweiser, Norbert; Richter, Klaus W.

    2012-01-01

    The phase equilibria and invariant reactions in the system Al–Cu–Si were investigated by a combination of optical microscopy, powder X-ray diffraction (XRD), differential thermal analysis (DTA) and electron probe micro analysis (EPMA). Isothermal phase equilibria were investigated within two isothermal sections. The isothermal section at 500 °C covers the whole ternary composition range and largely confirms the findings of previous phase diagram investigations. The isothermal section at 700 °C describes phase equilibria only in the complex Cu-rich part of the phase diagram. A new ternary compound τ was found in the region between (Al,Cu)-γ1 and (Cu,Si)-γ and its solubility range was determined. The solubility of Al in κ-CuSi was found to be extremely high at 700 °C. In contrast, no ternary solubility in the β-phase of Cu–Al was found, although this phase is supposed to form a complete solid solution according to previous phase diagram assessments. Two isopleths, at 10 and 40 at.% Si, were investigated by means of DTA and a partial ternary reaction scheme (Scheil diagram) was constructed, based on the current work and the latest findings in the binary systems Al–Cu and Cu–Si. The current study shows that the high temperature equilibria in the Cu-rich corner are still poorly understood and additional studies in this area would be favorable. PMID:22287828

  20. The Representation of Highly Non-Ideal Phase Equilibria Using Computer Graphics.

    ERIC Educational Resources Information Center

    Charos, Georgios N.; And Others

    1986-01-01

    Previous work focused on use of computer graphics in teaching thermodynamic phase equilibria for classes I and II. Extends this work to include the considerably more non-ideal phase behavior shown by classes III, IV, and V. Student and instructor response has been overwhelmingly positive about the approach. (JN)

  1. Transport and phase equilibria of benzene in FAU type zeolites

    NASA Astrophysics Data System (ADS)

    Saravanan, Chandra

    We have studied lattice models for self-diffusion of benzene in FAU type zeolites, to explore the effect of the thermodynamics of confined fluids on the transport properties of molecules in zeolites. Our model assumes that benzene molecules are located near Na+ ions in supercages, and in 12-ring windows separating adjacent supercages, respectively. The study was performed in three stages. First, to disentangle the effect of a vapor-liquid phase equilibria on diffusion in zeolites, the transport of benzene in Na-Y is modeled in the absence of attractive guest-guest interactions. The loading dependence of diffusion coefficient, Dtheta, at a constant temperature, referred to as a diffusion isotherm, is modeled with site-blocking effects using a mean field theory (MFT) that yields, Dq=16kq a2q, where atheta ≅ 11 A is the mean intercage jump length and 1/ktheta is the mean supercage residence time. A completely analytical expression is derived to calculate ktheta. The MFT is tested using a mean field approximation (MFA) where ktheta and atheta are calculated from kinetic Monte Carlo simulations yielding excellent qualitative agreement. Further calculations are performed to test MFA by calculating "exact" diffusion coefficients from mean square displacement (MSD) calculations also yielding excellent qualitative agreement. Next, by including guest-guest attractive interactions, we have performed lattice grand canonical Monte Carlo simulations of benzene adsorption in Na-X zeolite to determine whether strongly confined benzene molecules exhibit subcritical properties. We observe a phase transition from low to high density of adsorbed benzene, analogous to vapor-liquid equilibrium, at temperatures as high as 300 K and above. By performing thermodynamic integration to construct the coexistence curve, we obtain a critical point for benzene in Na-X at Tc = 370 +/- 20 K, thetac = 0.45 +/- 0.05 fractional coverage. We suggest that careful adsorption experiments should be

  2. Investigation of Phase Equilibria and Some Properties of Alloys of Ti-Al-Fe and Ti-Al-V Systems,

    DTIC Science & Technology

    Some data on the structure and properties of Ti-Al-Fe alloys are presented. The phase equilibria in alloys in the system Ti-Al-V were studies...However, the data available in the literature on phase equilibria in the systems Ti-Al-Fe and Ti-Al-V require refinement, as they are insufficiently

  3. The nucleation rate surfaces design over diagram of phase equilibria and their applications for computational chemistry

    NASA Astrophysics Data System (ADS)

    Anisimov, M. P.

    2016-12-01

    One can find in scientific literature a pretty fresh idea of the nucleation rate surfaces design over the diagrams of phase equilibria. That idea looks like profitable for the nucleation theory development and for various practical applications where predictions of theory have no high enough accuracy for today. The common thermodynamics has no real ability to predict parameters of the first order phase transition. Nucleation experiment can be provided in very local nucleation conditions even the nucleation takes place from the critical line (in two-component case) down to the absolute zero temperature limit and from zero nucleation rates at phase equilibria up to the spinodal conditions. Theory predictions have low reliability as a rule. The computational chemistry has chance to make solution of that problem easier when a set of the used axiomatic statements will adapt enough progressive assumptions [1]. Semiempirical design of the nucleation rate surfaces over diagrams of phase equilibria have a potential ability to provide a reasonable quality information on nucleation rate for each channel of nucleation. Consideration and using of the nucleation rate surface topologies to optimize synthesis of a given phase of the target material can be available when data base on nucleation rates over diagrams of phase equilibria will be created.

  4. TERNARY PHASE EQUILIBRIA IN TRANSITION METAL-BORON-CARBON-SILICON SYSTEMS. PART 4. THERMOCHEMICAL CALCULATIONS, VOLUME 3. COMPUTATIONAL APPROACH TO THE CALCULATION OF TERNARY PHASE DIAGRAMS

    DTIC Science & Technology

    The general conditional equations which govern the phase equilibria in three-component systems are presented. Using the general conditional equations...a general method has been developed to precalculate the phase equilibria in three-component systems from first principle using computer technique...The method developed has been applied to several model examples and the system Ta-Hf-C. The phase equilibria in three-component systems calculated

  5. Pressure and phase equilibria in interacting active brownian spheres.

    PubMed

    Solon, Alexandre P; Stenhammar, Joakim; Wittkowski, Raphael; Kardar, Mehran; Kafri, Yariv; Cates, Michael E; Tailleur, Julien

    2015-05-15

    We derive a microscopic expression for the mechanical pressure P in a system of spherical active Brownian particles at density ρ. Our exact result relates P, defined as the force per unit area on a bounding wall, to bulk correlation functions evaluated far away from the wall. It shows that (i) P(ρ) is a state function, independent of the particle-wall interaction; (ii) interactions contribute two terms to P, one encoding the slow-down that drives motility-induced phase separation, and the other a direct contribution well known for passive systems; and (iii) P is equal in coexisting phases. We discuss the consequences of these results for the motility-induced phase separation of active Brownian particles and show that the densities at coexistence do not satisfy a Maxwell construction on P.

  6. Phase and chemical equilibria in the transesterification reaction of vegetable oils with supercritical lower alcohols

    NASA Astrophysics Data System (ADS)

    Anikeev, V. I.; Stepanov, D. A.; Ermakova, A.

    2011-08-01

    Calculations of thermodynamic data are performed for fatty acid triglycerides, free fatty acids, and fatty acid methyl esters, participants of the transesterification reaction of vegetable oils that occurs in methanol. Using the obtained thermodynamic parameters, the phase diagrams for the reaction mixture are constructed, and the chemical equilibria of the esterification reaction of free fatty acids and the transesterification reaction of fatty acid triglycerides attained upon treatment with supercritical methanol are determined. Relying on our analysis of the obtained equilibria for the esterification reaction of fatty acids and the transesterification reaction of triglycerides attained upon treatment with lower alcohols, we select the optimum conditions for performing the reaction in practice.

  7. Phase equilibria in the Ag-Au-In system at 500°C

    NASA Astrophysics Data System (ADS)

    Ptashkina, E. A.; Romanova, A. G.; Pavlenko, A. S.; Kabanova, E. G.; Kuznetsov, V. N.

    2017-02-01

    Phase equilibria in Ag-Au-In system at 500°C are investigated by means of electron microscopy, electron probe microanalysis, and X-ray powder diffraction. The part of the system's isothermal cross section with an indium content of up to 50 at % is constructed.

  8. Calculation of liquid water-hydrate-methane vapor phase equilibria from molecular simulations.

    PubMed

    Jensen, Lars; Thomsen, Kaj; von Solms, Nicolas; Wierzchowski, Scott; Walsh, Matthew R; Koh, Carolyn A; Sloan, E Dendy; Wu, David T; Sum, Amadeu K

    2010-05-06

    Monte Carlo simulation methods for determining fluid- and crystal-phase chemical potentials are used for the first time to calculate liquid water-methane hydrate-methane vapor phase equilibria from knowledge of atomistic interaction potentials alone. The water and methane molecules are modeled using the TIP4P/ice potential and a united-atom Lennard-Jones potential, respectively. The equilibrium calculation method for this system has three components, (i) thermodynamic integration from a supercritical ideal gas to obtain the fluid-phase chemical potentials, (ii) calculation of the chemical potential of the zero-occupancy hydrate system using thermodynamic integration from an Einstein crystal reference state, and (iii) thermodynamic integration to obtain the water and guest molecules' chemical potentials as a function of the hydrate occupancy. The three-phase equilibrium curve is calculated for pressures ranging from 20 to 500 bar and is shown to follow the Clapeyron behavior, in agreement with experiment; coexistence temperatures differ from the latter by 4-16 K in the pressure range studied. The enthalpy of dissociation extracted from the calculated P-T curve is within 2% of the experimental value at corresponding conditions. While computationally intensive, simulations such as these are essential to map the thermodynamically stable conditions for hydrate systems.

  9. Ab Initio Study of Phase Equilibria in TiCx

    NASA Astrophysics Data System (ADS)

    Korzhavyi, P. A.; Pourovskii, L. V.; Hugosson, H. W.; Ruban, A. V.; Johansson, B.

    2002-01-01

    The phase diagram for the vacancy-ordered structures in the substoichiometric TiCx ( x = 0.5-1.0) has been established from Monte Carlo simulations with the long-range pair and multisite effective interactions obtained from ab initio calculations. Three ordered superstructures of vacancies ( Ti2C, Ti3C2, and Ti6C5) are found to be ground state configurations. Their stability has been verified by full-potential total energy calculations of the fully relaxed structures.

  10. Electronic Structure and Phase Equilibria in Ternary Substitutional Alloys: a Tight-Binding Approach

    NASA Astrophysics Data System (ADS)

    Traiber, Ariel Javier Sebastian

    1995-01-01

    The goal of this thesis is to develop and apply alloy theory methods to transition metals and alloys (particularly ternary systems) based on the tight-binding (TB) model of atomic cohesion in studies of stability and phase equilibria. At least two factors make this kind of formalism desirable: it can bring a clear understanding of the underlying physical mechanisms that many times get obscured in first-principles calculations, and it is easily adapted to complex problems and multicomponent solutions, at low computational cost. The original physical insight given by the TB method is demonstrated by the study of the relation between the atomic local environment and the relative stability of simple phases, through the calculation of the moments of the electronic density of states. We show that the relative stability of phases related to the Bain transformation is mainly controlled by the moment of order five, and we have identified the main contributions to this moment. We present a model for cohesive energy based on the assumption that it can be written as the sum of a band -structure contribution and a repulsive short-range contribution. We have calculated the band contribution using a TB Hamiltonian with d states and applied the linearized Green's function method based on the recursion technique. For the repulsive part of the energy we employ a Born-Mayer potential. The model was used to study total energies for Mo. We show that a six-moment approximation to the band energy is sufficient to reproduce more accurate results, using the standard recursion method, for the energetics of this transition metal. We describe a reliable and consistent scheme to study phase equilibria in ternary substitutional alloys based on the TB approximation. The TB electronic parameters are obtained from linear muffin-tin orbital calculations. The transfer integrals are scaled in distance with an orbital -dependent exponential decay parametrization, while the on-site energies are scaled

  11. Determination of phase equilibria in confined systems by open pore cell Monte Carlo method.

    PubMed

    Miyahara, Minoru T; Tanaka, Hideki

    2013-02-28

    We present a modification of the molecular dynamics simulation method with a unit pore cell with imaginary gas phase [M. Miyahara, T. Yoshioka, and M. Okazaki, J. Chem. Phys. 106, 8124 (1997)] designed for determination of phase equilibria in nanopores. This new method is based on a Monte Carlo technique and it combines the pore cell, opened to the imaginary gas phase (open pore cell), with a gas cell to measure the equilibrium chemical potential of the confined system. The most striking feature of our new method is that the confined system is steadily led to a thermodynamically stable state by forming concave menisci in the open pore cell. This feature of the open pore cell makes it possible to obtain the equilibrium chemical potential with only a single simulation run, unlike existing simulation methods, which need a number of additional runs. We apply the method to evaluate the equilibrium chemical potentials of confined nitrogen in carbon slit pores and silica cylindrical pores at 77 K, and show that the results are in good agreement with those obtained by two conventional thermodynamic integration methods. Moreover, we also show that the proposed method can be particularly useful for determining vapor-liquid and vapor-solid coexistence curves and the triple point of the confined system.

  12. Two-component system CCl4 + (CH3)3CBr: extrema in equilibria involving orientationally disordered phases.

    PubMed

    Barrio, M; Pardo, L C; Tamarit, J Ll; Negrier, Ph; Salud, J; López, D O; Mondieig, D

    2006-06-22

    Phase equilibria involving orientationally disordered (OD) and liquid phases of the two-component system between carbon tetrachloride (CCl4) and 2-methyl-2-bromomethane ((CH3)3CBr) have been determined by means of X-ray powder diffraction and thermal analysis techniques from 210 K up to the liquid state. The isomorphism relation between the OD stable face-centered cubic (FCC) phase of (CH3)3CBr and the metastable FCC phase of CCl4 has been demonstrated throughout the continuous evolution of the lattice parameters and the existence of the two-phase equilibrium [FCC + L] for the whole range of composition, despite the monotropy of the FCC phase for the CCl4 component with respect to its OD rhombohedral (R) stable phase. A continuous series of OD R mixed crystals is found, which confirms the R lattice symmetry of the OD phase II of (CH3)3CBr, for which the crystallographic results have been long-time misinterpreted. X-ray patterns of such a phase were indexed according to the recent single-crystal results obtained by Rudman (Rudman, R. J. Mol. Struct. 2001, 569, 157). In addition, some experimental evidences are given to confirm the number of molecules per unit cell (Z = 21). The thermodynamic assessment reproduces coherently the phase diagram for the stable [R + L] and [R + FCC] two-phase equilibria as well as for the partially metastable [FCC + L] two-phase equilibrium and provides a set of data for the thermodynamic properties of nonexperimentally available phase transitions of pure components. Surprisingly, the phase equilibrium involving R and FCC OD phases appears as one of the very few showing a solid-solid equilibrium with two extremes.

  13. Olivine-wadsleyite-ringwoodite phase equilibria in (Mg,Fe)2SiO4 from first-principles calculations

    NASA Astrophysics Data System (ADS)

    Yu, Y. G.; Vinograd, V. L.; Winkler, B.; Wentzcovitch, R. M.

    2012-12-01

    Phase equilibria of α , β , and γ (Mg,Fe)2SiO4 are important to understanding the mineralogy of the Earth's upper mantle. Here using the first principles approach, we studied thermodynamic properties and phase stability fields of Fe2SiO4. We show that the correct phase transition sequence in Fe2SiO4 (α -> γ ) can be obtained with the DFT + self-consistent Hubbard U method, while standard DFT methods (LSDA and σ -GGA) as well as the DFT + constant U method fail the task. The vibrational virtual crystal approximation was used to derive the phonon density of state of the Fe2SiO4 polymorphs. High-pressures thermodynamic properties of Fe2SiO4 are then derived with the aid of the quasi-harmonic approximation. They are in very good agreement with experiments. The phase diagram of (Mg,Fe)2SiO4 system is calculated under the assumption of ideal mixing within α , β , and γ solid solutions. The model permits the investigation of the temperature and pressure effects on the phase boundaries. The widths of the divariant α -β and β -γ loops are barely sensitive to the temperature changes within the range of 1473--1873 K. This study shows the promise of applying the DFT + self-consistent Hubbard U method to study phase equilibria of iron-bearing Earth minerals.

  14. Adiabatic invariants and phase equilibria for first-order orbital resonances. [solar mass change effect on asteroid orbits

    NASA Technical Reports Server (NTRS)

    Heppenheimer, T. A.

    1975-01-01

    In the planar circular restricted three-body problem, the evolution of near-commensurable orbits is studied under change in the mass ratio, mu. The evolution involves preservation of two adiabatic invariants. Transition from circulation to libration may occur; such transitions are of two types. Type I transition occurs when the evolutionary track in phase space passes through near-zero eccentricity; as in the ordinary case (no transition), pre- and post-evolutionary states are linked by solution of a two-point boundary-value problem. Type II transition occurs when the evolutionary track encounters an unstable phase equilibrium or periodic orbit. There is then a discontinuous change in one adiabatic invariant, and pre- and post-evolutionary states are linked by solution of a three-point boundary-value problem. No evolutionary track can encounter a stable phase equilibrium, but the class of all stable phase equilibria is mapped into itself under mu change.

  15. Fast Method for Computing Chemical Potentials and Liquid-Liquid Phase Equilibria of Macromolecular Solutions.

    PubMed

    Qin, Sanbo; Zhou, Huan-Xiang

    2016-08-25

    Chemical potential is a fundamental property for determining thermodynamic equilibria involving exchange of molecules, such as between two phases of molecular systems. Previously, we developed the fast Fourier transform (FFT)-based method for Modeling Atomistic Protein-crowder interactions (FMAP) to calculate excess chemical potentials according to the Widom insertion. Intermolecular interaction energies were expressed as correlation functions and evaluated via FFT. Here, we extend this method to calculate liquid-liquid phase equilibria of macromolecular solutions. Chemical potentials are calculated by FMAP over a wide range of molecular densities, and the condition for coexistence of low- and high-density phases is determined by the Maxwell equal-area rule. When benchmarked on Lennard-Jones fluids, our method produces an accurate phase diagram at 18% of the computational cost of the current best method. Importantly, the gain in computational speed increases dramatically as the molecules become more complex, leading to many orders of magnitude in speed up for atomistically represented proteins. We demonstrate the power of FMAP by reporting the first results for the liquid-liquid coexistence curve of γII-crystallin represented at the all-atom level. Our method may thus open the door to accurate determination of phase equilibria for macromolecular mixtures such as protein-protein mixtures and protein-RNA mixtures, that are known to undergo liquid-liquid phase separation, both in vitro and in vivo.

  16. Thermodynamic calculations in the system CH4-H2O and methane hydrate phase equilibria

    USGS Publications Warehouse

    Circone, S.; Kirby, S.H.; Stern, L.A.

    2006-01-01

    Using the Gibbs function of reaction, equilibrium pressure, temperature conditions for the formation of methane clathrate hydrate have been calculated from the thermodynamic properties of phases in the system CH4-H 2O. The thermodynamic model accurately reproduces the published phase-equilibria data to within ??2 K of the observed equilibrium boundaries in the range 0.08-117 MPa and 190-307 K. The model also provides an estimate of the third-law entropy of methane hydrate at 273.15 K, 0.1 MPa of 56.2 J mol-1 K-1 for 1/n CH4??H 2O, where n is the hydrate number. Agreement between the calculated and published phase-equilibria data is optimized when the hydrate composition is fixed and independent of the pressure and temperature for the conditions modeled. ?? 2006 American Chemical Society.

  17. Thermodynamic calculations in the system CH4-H2O and methane hydrate phase equilibria.

    PubMed

    Circone, Susan; Kirby, Stephen H; Stern, Laura A

    2006-04-27

    Using the Gibbs function of reaction, equilibrium pressure, temperature conditions for the formation of methane clathrate hydrate have been calculated from the thermodynamic properties of phases in the system CH4-H2O. The thermodynamic model accurately reproduces the published phase-equilibria data to within +/-2 K of the observed equilibrium boundaries in the range 0.08-117 MPa and 190-307 K. The model also provides an estimate of the third-law entropy of methane hydrate at 273.15 K, 0.1 MPa of 56.2 J mol(-1) K(-1) for 1/nCH4.H2O, where n is the hydrate number. Agreement between the calculated and published phase-equilibria data is optimized when the hydrate composition is fixed and independent of the pressure and temperature for the conditions modeled.

  18. Development of the Transferable Potentials for Phase Equilibria Model for Hydrogen Sulfide.

    PubMed

    Shah, Mansi S; Tsapatsis, Michael; Siepmann, J Ilja

    2015-06-11

    The transferable potentials for phase equilibria force field is extended to hydrogen sulfide. The pure-component and binary vapor-liquid equilibria with methane and carbon dioxide and the liquid-phase relative permittivity are used for the parametrization of the Lennard-Jones (LJ) and Coulomb interactions, and models with three and four interaction sites are considered. For the three-site models, partial point charges are placed on the sites representing the three atoms, while the negative partial charge is moved to an off-atom site for the four-site models. The effect of molecular shape is probed using either only a single LJ interaction site on the sulfur atom or adding sites also on the hydrogen atoms. This procedure results in four distinct models, but only those with three LJ sites can accurately reproduce all properties considered for the parametrization. These two are further assessed for predictions of the liquid-phase structure, the lattice parameters and relative permittivity for the face-centered-cubic solid, and the triple point. An effective balance between LJ interactions and the dipolar and quadrupolar terms of the first-order electrostatic interactions is struck in order to obtain a four-site model that describes the condensed-phase properties and the phase equilibria with high accuracy.

  19. Spin State Equilibria of Asteroids due to YORP Effects

    NASA Astrophysics Data System (ADS)

    Golubov, Oleksiy; Scheeres, Daniel J.; Lipatova, Veronika

    2016-05-01

    Spins of small asteroids are controlled by the Yarkovsky--O'Keefe--Radzievskii--Paddack (YORP) effect. The normal version of this effect has two components: the axial component alters the rotation rate, while the obliquity component alters the obliquity. Under this model the rotation state of an asteroid can be described in a phase plane with the rotation rate along the polar radius and the obliquity as the polar angle. The YORP effect induces a phase flow in this plane, which determines the distribution of asteroid rotation rates and obliquities.We study the properties of this phase flow for several typical cases. Some phase flows have stable attractors, while in others all trajectories go to very small or large rotation rates. In the simplest case of zero thermal inertia approximate analytical solutions to dynamics equations are possible. Including thermal inertia and the Tangential YORP effect makes the possible evolutionary scenarios much more diverse. We study possible evolution paths and classify the most general trends. Also we discuss possible implications for the distribution of asteroid rotation rates and obliquities.A special emphasis is put on asteroid (25143) Itokawa, whose shape model is well determined, but who's measured YORP acceleration does not agree with the predictions of normal YORP. We show that Itokawa's rotational state can be explained by the presence of tangential YORP and that it may be in or close to a stable spin state equilibrium. The implications of such states will be discussed.

  20. Theory of phase equilibria for model mixtures of n-alkanes, perfluoroalkanes and perfluoroalkylalkane diblock surfactants

    NASA Astrophysics Data System (ADS)

    Dos Ramos, María Carolina; Blas, Felipe J.

    2007-05-01

    An extension of the SAFT-VR equation of state, the so-called hetero-SAFT approach [Y. Peng, H. Zhao, and C. McCabe, Molec. Phys. 104, 571 (2006)], is used to examine the phase equilibria exhibited by a number of model binary mixtures of n-alkanes, perfluoroalkanes and perfluoroalkylalkane diblock surfactants. Despite the increasing recent interest in semifluorinated alkanes (or perfluoroalkylalkane diblock molecules), the phase behaviour of mixtures involving these molecules with n-alkanes or perfluoroalkanes is practically unknown from the experimental point of view. In this work, we use simple molecular models for n-alkanes, perfluoroalkanes and perfluoroalkylalkane diblock molecules to predict, from a molecular perspective, the phase behaviour of selected model mixtures of perfluoroalkylalkanes with n-alkanes and perfluoroalkanes. In particular, we focus our interest on the understanding of the microscopic conditions that control the liquid-liquid separation and the stabilization of these mixtures. n-Alkanes and perfluoroalkanes are modelled as tangentially bonded monomer segments with molecular parameters taken from the literature. The perfluoroalkylalkane diblock molecules are modelled as heterosegmented diblock chains, with parameters for the alkyl and perfluoroalkyl segments developed in earlier work. This simple approach, which was proposed in previous work [P. Morgado, H. Zhao, F. J. Blas, C. McCabe, L. P. N. Rebelo, and E. J. M. Filipe, J. Phys. Chem. B, 111, 2856], is now extended to describe model n-alkane (or perfluoroalkane) + perfluroalkylalkane binary mixtures. We have obtained the phase behaviour of different mixtures and studied the effect of the molecular weight of n-alkanes and perfluoroalkanes on the type of phase behaviour observed in these mixtures. We have also analysed the effect of the number of alkyl and perfluoroalkyl chemical groups in the surfactant molecule on the phase behaviour. In addition to the usual vapour-liquid phase

  1. Phase Equilibria and Magnetic Phases in the Ce-Fe-Co-B System

    PubMed Central

    Wang, Tian; Kevorkov, Dmytro; Medraj, Mamoun

    2016-01-01

    Ce-Fe-Co-B is a promising system for permanent magnets. A high-throughput screening method combining diffusion couples, key alloys, Scanning Electron Microscope/Wavelength Dispersive X-ray Spectroscope (SEM/WDS), and Magnetic Force Microscope (MFM) is used in this research to understand the phase equilibria and to explore promising magnetic phases in this system. Three magnetic phases were detected and their homogeneity ranges were determined at 900 °C, which were presented by the formulae: Ce2Fe14−xCoxB (0 ≤ x ≤ 4.76), CeCo4−xFexB (0 ≤ x ≤ 3.18), and Ce3Co11−x FexB4 (0 ≤ x ≤ 6.66). The phase relations among the magnetic phases in this system have been studied. Ce2(Fe, Co)14B appears to have stronger magnetization than Ce(Co, Fe)4B and Ce3(Co, Fe)11B4 from MFM analysis when comparing the magnetic interactions of selected key alloys. Also, a non-magnetic CeCo12−xFexB6 (0 ≤ x ≤ 8.74) phase was detected in this system. A boron-rich solid solution with Ce13FexCoyB45 (32 ≤ x ≤ 39, 3 ≤ y ≤ 10) chemical composition was also observed. However, the crystal structure of this phase could not be found in the literature. Moreover, ternary solid solutions ε1 (Ce2Fe17−xCox (0 ≤ x ≤ 12.35)) and ε2 (Ce2Co17−xFex (0 ≤ x ≤ 3.57)) were found to form between Ce2Fe17 and Ce2Co17 in the Ce-Fe-Co ternary system at 900 °C. PMID:28772374

  2. Phase Equilibria and Magnetic Phases in the Ce-Fe-Co-B System.

    PubMed

    Wang, Tian; Kevorkov, Dmytro; Medraj, Mamoun

    2016-12-28

    Ce-Fe-Co-B is a promising system for permanent magnets. A high-throughput screening method combining diffusion couples, key alloys, Scanning Electron Microscope/Wavelength Dispersive X-ray Spectroscope (SEM/WDS), and Magnetic Force Microscope (MFM) is used in this research to understand the phase equilibria and to explore promising magnetic phases in this system. Three magnetic phases were detected and their homogeneity ranges were determined at 900 °C, which were presented by the formulae: Ce₂Fe14-xCoxB (0 ≤ x ≤ 4.76), CeCo4-xFexB (0 ≤ x ≤ 3.18), and Ce₃Co11-x FexB₄ (0 ≤ x ≤ 6.66). The phase relations among the magnetic phases in this system have been studied. Ce₂(Fe, Co)14B appears to have stronger magnetization than Ce(Co, Fe)₄B and Ce₃(Co, Fe)11B₄ from MFM analysis when comparing the magnetic interactions of selected key alloys. Also, a non-magnetic CeCo12-xFexB₆ (0 ≤ x ≤ 8.74) phase was detected in this system. A boron-rich solid solution with Ce13FexCoyB45 (32 ≤ x ≤ 39, 3 ≤ y ≤ 10) chemical composition was also observed. However, the crystal structure of this phase could not be found in the literature. Moreover, ternary solid solutions ε₁ (Ce₂Fe17-xCox (0 ≤ x ≤ 12.35)) and ε₂ (Ce₂Co17-xFex (0 ≤ x ≤ 3.57)) were found to form between Ce₂Fe17 and Ce₂Co17 in the Ce-Fe-Co ternary system at 900 °C.

  3. Phase and chemical equilibria in multicomponent fluid systems with a chemical reaction

    NASA Astrophysics Data System (ADS)

    Toikka, A. M.; Samarov, A. A.; Toikka, M. A.

    2015-04-01

    Studies of the phase and chemical equilibria in the systems with chemical reaction cover a wide range of problems related to both experimental determination of physicochemical characteristics of these systems and various aspects of thermodynamic analysis of the phase and chemical processes occurring there. The main goal of this review consists in systematization and analysis of available experimental data concerning the vapour-liquid and liquid-liquid equilibria in multicomponent systems where chemical reactions occur. The studies considered here have been mainly published in recent years, and they include rather detailed data on physicochemical properties, phase transitions and chemical processes in fluid systems, i.e., the data which are essential for thermodynamic analysis. Available approaches to the thermodynamic analysis of heterogeneous systems with chemical reactions are also discussed. Particular attention is paid to the studies of the simultaneous phase and chemical equilibria. We hope that this review could be useful both for fundamental studies of heterogeneous reactive systems and for solving applied problems on the design of combined reactive and mass-transfer processes. The bibliography includes 79 references.

  4. Effects of gravity reduction on phase equilibria. Part 1: Unary and binary isostructural solids

    NASA Technical Reports Server (NTRS)

    Larson, D. J., Jr.

    1975-01-01

    Analysis of the Skylab II M553 Experiment samples resulted in the hypothesis that the reduced gravity environment was altering the melting and solidification reactions. A theoretical study was conducted to define the conditions under which such alteration of phase relations is feasible, determine whether it is restricted to space processing, and, if so, ascertain which alloy systems or phase reactions are most likely to demonstrate such effects. Phase equilibria of unary and binary systems with a single solid phase (unary and isomorphous) were considered.

  5. Phase equilibria constraints on the chemical and physical evolution of the campanian ignimbrite

    USGS Publications Warehouse

    Fowler, S.J.; Spera, F.J.; Bohrson, W.A.; Belkin, H.E.; de Vivo, B.

    2007-01-01

    The Campanian Ignimbrite is a > 200 km3 trachyte-phonolite pyroclastic deposit that erupted at 39.3 ?? 0.1 ka within the Campi Flegrei west of Naples, Italy. Here we test the hypothesis that Campanian Ignimbrite magma was derived by isobaric crystal fractionation of a parental basaltic trachyandesitic melt that reacted and came into local equilibrium with small amounts (5-10 wt%) of crustal rock (skarns and foid-syenites) during crystallization. Comparison of observed crystal and magma compositions with results of phase equilibria assimilation-fractionation simulations (MELTS) is generally very good. Oxygen fugacity was approximately buffered along QFM+1 (where QFM is the quartz-fayalite-magnetite buffer) during isobaric fractionation at 0.15 GPa (???6 km depth). The parental melt, reconstructed from melt inclusion and host clinopyroxene compositions, is found to be basaltic trachyandesite liquid (51.1 wt% SiO2, 9.3 wt% MgO, 3 wt% H2O). A significant feature of phase equilibria simulations is the existence of a pseudo-invariant temperature, ???883??C, at which the fraction of melt remaining in the system decreases abruptly from ???0.5 to < 0.1. Crystallization at the pseudo-invariant point leads to abrupt changes in the composition, properties (density, dissolved water content), and physical state (viscosity, volume fraction fluid) of melt and magma. A dramatic decrease in melt viscosity (from 1700 Pa s to ???200 Pa s), coupled with a change in the volume fraction of water in magma (from ??? 0.1 to 0.8) and a dramatic decrease in melt and magma density acted as a destabilizing eruption trigger. Thermal models suggest a timescale of ??? 200 kyr from the beginning of fractionation until eruption, leading to an apparent rate of evolved magma generation of about 10-3 km3/year. In situ crystallization and crystal settling in density-stratified regions, as well as in convectively mixed, less evolved subjacent magma, operate rapidly enough to match this apparent

  6. Phase transitions and connectivity in three-dimensional vortex equilibria

    SciTech Connect

    Akao, J.H.

    1994-05-01

    The statistical mechanics of collections of closed self avoiding vortex loops on a lattice are studied. The system is related to the vortex form of the three dimensional XY model and to lattice vortex equilibrium models of turbulence. The system exhibits vortex connectivity and screening effects, and models in vorticity variables the superfluid transition. The equilibrium states of the system are simulated by a grand canonical Monte Carlo method. A set of geometric transformations for self-avoiding loops is developed. The numerical method employs histogram sampling techniques and utilizes a modification to the Metropolis flow which enhances efficiency. Results are given for a region in the temperature-chemical potential plane, where the chemical potential is related to the vortex fugacity. A line of second order transitions is identified at low temperature. The transition is shown to be a percolation threshold at which connected vortex loops of infinite size appear in the system. The nature of the transition supports the assumption that the lambda transition in bulk superfluid helium is driven by vortices. An asymptotic analysis is performed for the energy and entropy scaling of the system as functions of the system size and the lattice spacing. These estimates indicate that the infinite temperature line is a phase boundary between small scale fractal vortices and large scale smooth vortices. A suggestion is made that quantum vortices have uniform structure on the scale of the lattice spacing and lie in the positive temperature regime, while classical vortices have uniform structure on the scale of the domain and lie in the negative temperature regime.

  7. Phase equilibria in DOPC/DPPC-d62/cholesterol mixtures.

    PubMed

    Davis, James H; Clair, Jesse James; Juhasz, Janos

    2009-01-01

    There is broad interest in the question of fluid-fluid phase coexistence in membranes, in particular, whether evidence for liquid-disordered (l(d))-liquid-ordered (l(o)) two-phase regions or membrane "rafts" can be found in natural membranes. In model membrane systems, such phase behavior is observed, and we have used deuterium nuclear magnetic resonance spectroscopy to map the phase boundaries of ternary mixtures containing 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC), chain-perdeuterated 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC-d(62)), and cholesterol. For both this ternary model system and the binary DPPC-d(62)/cholesterol system, we present clear evidence for l(d)-l(o) two-phase coexistence. We have selected sample compositions to focus on this region of fluid-fluid phase coexistence and to determine its temperature and composition ranges. The deuterium nuclear magnetic resonance spectra for compositions near the l(d)-l(o) phase boundary at high cholesterol concentrations show evidence of exchange broadening or critical fluctuations in composition, similar to that reported by Vist and Davis. There appears to be a line of critical compositions ranging from 48 degrees C for a DOPC/DPPC-d(62)/cholesterol composition of 0:75:25, to approximately -8 degrees C for the composition 57:14:29. At temperatures below this two-phase region, there is a region of three-phase coexistence (l(d)-l(o)-gel). These results are collected and presented in terms of a partial ternary phase diagram that is consistent with previously reported results of Vist and Davis.

  8. Phase equilibria in fluid mixtures at high pressures: The He-CH4 system

    NASA Technical Reports Server (NTRS)

    Streett, W. B.; Erickson, A. L.; Hill, J. L. E.

    1972-01-01

    An experimental study of phase equilibria in the He-CH4 system was carried out over the temperature range 95 to 290 K and at pressures to 10,000 atm. The experimental results consist of equilibrium phase composition for twenty-eight isotherms in the region of coexistence of two fluid phases, together with the pressure-temperature trace of the three-phase boundary at which a CH4-rich solid phase is in equilibrium with the two fluid phases. The system exhibits a fluid-fluid phase separation which persists to temperatures and pressures beyond the range of this experiment. These results, together with those recently obtained for other binary systems, provide information about the form of phase diagrams for binary gas mixtures in the region of pressure induced phase transitions at high pressures. These findings are relevant to problems of deep atmosphere and interior structures in the outer planets.

  9. Phase equilibria in a system of 'breathing' molecules

    SciTech Connect

    Wu, Jianzhong; Prausnitz, John

    2001-09-30

    It is now well known that details in the intermolecular potential can significantly affect the qualitative features of a phase diagram where temperature is plotted against density for the coexistence curves among fluid and solid phases. While previous calculations of phase diagrams have assumed a time-invariant potential function, this report concerns the phase diagram for ''breathing'' molecules, i.e., molecules whose strength of intermolecular attraction fluctuates in time. Such fluctuations can occur in biomacromolecules where an active site can switch between ''on'' and ''off'' positions. Phase-equilibrium calculations were performed for molecules that have a periodic (breathing) attractive force in addition to the conventional intermolecular forces. The phase diagram for such molecules is as expected when the ''breathing'' properties are independent of density. However, when (more realistically), the ''breathing'' properties are density dependent, the phase diagram exhibits dramatic changes. These calculations may be useful for interpreting experimental data for protein precipitation, for plaque formation in blood vessels and for scaffold-supported tissue formation.

  10. Partitioning and phase equilibria of PEGylated excipients in fluorinated liquids.

    PubMed

    Paul, Alison; Talbot, Gemma L; Bowles, James W; James, Jennifer; Griffiths, Peter C; Rogueda, Philippe G

    2010-03-15

    Mixtures of common polymeric excipients and hydrofluoroalkane (HFA) liquids show rich and complex phase behaviour. Phase diagrams and phase compositions are reported for poly(ethylene glycol)s with varying levels of end-group methylation in mixed solvent systems consisting of the model propellant 2H,3H-perfluoropentane (HPFP) and the fully fluorinated analogue perfluoropentane (PFP). Studies have been performed as a function of molecular weight as well as end group chemistry (monomethyl, MM; dimethyl, DM; and dihydroxyl, DH), and for binary polymer mixtures in HPFP/PFP solvent systems. The solvent composition required to induce phase separation by addition of the non-hydrogen bonding PFP is strongly dependent on end-group concentrations. It shows a linear increase with increasing methylation, whilst remaining insensitive to OH group concentration in dihydroxylated PEG systems. For single polymer systems it is observed that strong partitioning of the polymer is observed, and changes in polymer concentration occurring across the phase diagram are a result of changing solvent partitioning between upper and lower phases. These solvent effects are dependent on the composition (wt% PFP) in the solvent mixture. The linear dependence of solvent composition required to induce phase separation at fixed polymer concentration on end group concentrations can be used to predict the phase behaviour for mixtures of monomethylated PEG with either dimethyl or dihydroxyl PEGs, whereas mixtures of dihydroxyl with dimethyl end-capped PEGs show a deviation from linear behaviour with dominance of the dihydroxyl end groups, which is reflected in the obtained phase diagrams. This study hence progresses understanding of factors that influence solubility of PEG-type polymers in HFAs and will facilitate the identification of predictive methodologies for formulation.

  11. Phase equilibria and crystal chemistry of rubidium niobates and rubidium tantalates

    NASA Technical Reports Server (NTRS)

    Minor, D. B.; Roth, R. S.; Parker, H. S.; Brower, W. S.

    1977-01-01

    The phase equilibria relations and crystal chemistry of portions of the Rb2O-Nb2O5 and Rb2O-Ta2O5 systems were investigated for structures potentially useful as ionic conductors. A hexagonal tungsten bronze-type (HTB) structure was found in both systems as well as three hexagonal phases with mixed HTB-pyrochlore type structures. Ion exchange experiments between various alkali ions are described for several phases. Unit cell dimensions and X-ray diffraction powder patterns are reported.

  12. Phase equilibria and crystal chemistry of rubidium niobates and rubidium tantalates

    NASA Technical Reports Server (NTRS)

    Minor, D. B.; Roth, R. S.; Parker, H. S.; Brower, W. S.

    1977-01-01

    The phase equilibria relations and crystal chemistry of portions of the Rb2O-Nb2O5 and Rb2O-Ta2O5 systems were investigated for structures potentially useful as ionic conductors. A hexagonal tungsten bronze-type (HTB) structure was found in both systems as well as three hexagonal phases with mixed HTB-pyrochlore type structures. Ion exchange experiments between various alkali ions are described for several phases. Unit cell dimensions and X-ray diffraction powder patterns are reported.

  13. Petrogenesis of Mt. Baker basalts (Cascade arc): Constraints from thermobarometry, phase equilibria, trace elements and isotopes

    NASA Astrophysics Data System (ADS)

    Mullen, E. K.; McCallum, I. S.

    2010-12-01

    Primitive arc basalts provide information on sub-arc mantle compositions and processes. The relative abundance of basalts in the Cascade arc decreases northward, and basalts are rare in the most northerly segment of the arc (Garibaldi belt) where the Mt. Baker volcanic field (MBVF) is located. Following reconstruction of the compositions of the primary basalts at MBVF (olivine addition ± plag subtraction), we have applied phase equilibria and forward-modeled trace element abundances and isotope ratios to obtain petrogenetic constraints. The most primitive lavas are the Sulphur Cr, Lk Shannon, and Park Butte basalts and the Hogback, Tarn Plateau, and Cathedral Crag basaltic andesites, ranging from 716 to 10 ka. Most erupted peripheral to the major centers. Spinel/olivine and Fe-Ti oxide oxybarometry indicate redox states of ~QFM + 1 corresponding to Fe3+/ΣFe = 0.20. Mg# ranges from 51 to 71. The lavas are medium-K and similar to calc-alkaline basalts and high-Mg basaltic andesites from the High Cascades. MBVF basalts have higher MgO and lower CaO and Al2O3 than typical CAB and HAOT, grading to alkalic compositions with TiO2 and Na2O of up to 1.65 and 5.4 wt%, respectively (Sulphur Cr). Phenocryst contents are 5 to 33% (plag + olivine ± cpx) and the lavas are holo- or hypocrystalline with glass contents of up to 15%. The whole rocks are close to equilibrium with olivine cores (range Fo 87-68). Plagioclase cores range from An 88-68. Reconstructed primary basalt compositions give liquidus T and P values (from olivine-liquid equilibria and silica activities) ranging from 1280°C and 1 GPa (Tarn Plateau) to 1350°C and 1.4 GPa (Sulphur Cr), corresponding to the upper mantle above the core of the mantle wedge. These estimates take into account the 1 to 3 wt% initial H2O contents of the basalts calculated using plagioclase cores. Phase equilibria of the primary basalts indicate a similar pressure range of 1-2 GPa and indicate a residual mantle assemblage of harzburgite

  14. Phase equilibria for highly unsymmetrical plasmas and electrolytes

    PubMed Central

    Pitzer, Kenneth S.

    1980-01-01

    The conclusion of classical Debye-Hückel theory that a phase separation may occur in highly unsymmetrical plasmas or electrolytes is shown to be false and to arise from a serious error in the treatment of the interaction of pairs of the most highly charged ions. After an approximate correction for this error, no phase separation is predicted. Specific application to iron in the solar plasmas is discussed. PMID:16592831

  15. A Continuous Family of Equilibria in Ferromagnetic Media are Ground States

    NASA Astrophysics Data System (ADS)

    Su, Xifeng; de la Llave, Rafael

    2017-09-01

    We show that a foliation of equilibria (a continuous family of equilibria whose graph covers all the configuration space) in ferromagnetic transitive models are ground states. The result we prove is very general, and it applies to models with long range and many-body interactions. As an application, we consider several models of networks of interacting particles including models of Frenkel-Kontorova type on Z^d and one-dimensional quasi-periodic media. The result above is an analogue of several results in the calculus of variations (fields of extremals) and in PDE's. Since the models we consider are discrete and long range, new proofs need to be given. We also note that the main hypothesis of our result (the existence of foliations of equilibria) is the conclusion (using KAM theory) of several recent papers. Hence, we obtain that the KAM solutions recently established are minimizers when the interaction is ferromagnetic and transitive (these concepts are defined later).

  16. Phase equilibria and modeling of pyridinium-based ionic liquid solutions.

    PubMed

    Domańska, Urszula; Królikowski, Marek; Ramjugernath, Deresh; Letcher, Trevor M; Tumba, Kaniki

    2010-11-25

    The phase diagrams of the ionic liquid (IL) N-butyl-4-methylpyridinium bis{(trifluoromethyl)sulfonyl}imide ([BM(4)Py][NTf(2)]) with water, an alcohol (1-butanol, 1-hexanol, 1-octanol, 1-decanol), an aromatic hydrocarbon (benzene, toluene, ethylbenzene, n-propylbenzene), an alkane (n-hexane, n-heptane, n-octane), or cyclohexane have been measured at atmospheric pressure using a dynamic method. This work includes the characterization of the synthesized compound by water content and also by differential scanning calorimetry. Phase diagrams for the binary systems of [BM(4)Py][NTf(2)] with all solvents reveal eutectic systems with regards to (solid-liquid) phase equilibria and show immiscibility in the liquid phase region with an upper critical solution temperature (UCST) in most of the mixtures. The phase equilibria (solid, or liquid-liquid) for the binary systems containing aliphatic hydrocarbons reported here exhibit the lowest solubility and the highest immiscibility gap, a trend which has been observed for all ILs. The reduction of experimental data has been carried out using the nonrandom two-liquid (NRTL) correlation equation. The phase diagrams reported here have been compared with analogous phase diagrams reported previously for systems containing the IL N-butyl-4-methylpyridinium tosylate and other pyridinium-based ILs. The influence of the anion of the IL on the phase behavior has been discussed.

  17. Thermodynamic modeling of phase equilibria in magmatic systems: Progress and future directions (Robert Wilhelm Bunsen Medal Lecture)

    NASA Astrophysics Data System (ADS)

    Ghiorso, Mark S.

    2010-05-01

    Research over the past thirty years has established that thermodynamic modeling is extremely useful for illuminating the production, transport, chemical differentiation, and eruptive potential of magmas. The key to successful modeling of this kind is the formulation of an internally consistent thermodynamic database that includes properties of liquid and solid endmember components, and - most importantly - a cohesive set of models that describe the thermodynamics of mixing of both liquid (± fluid) and mineral solid solutions. Despite numerous successes in the application of thermodynamic modeling to liquid-solid phase equilibria under crustal and upper mantle pressure-temperature conditions, there are critical and relevant areas of application where the models fail to generate useful results. Importantly, these applications include phase equilibria in hornblende- and biotite-bearing magmas and the melting relations of silicate mantle-like bulk compositions at pressures above 3 GPa. Research is underway to address many of these modeling deficiencies. Approaches include (1) the development of new solution models for igneous pyroxenes and garnets, including majoritic garnet components, (2) the reformulation of thermodynamic models for liquid solution properties in order to implement non-deal associative solutions and a more robust equation of state that allows extrapolation of liquid density and free energy to high-pressures, (3) the creation of an experimental program to generate data necessary for the calibration of solution theory for igneous hornblendes and mica, and (4) the use of molecular dynamics simulations to facilitate the creation of a data base of liquid thermochemical properties at high-pressures that will serve as a basis for the calibration of phase equilibria models under Earth-like lower mantle conditions. All of these approaches give hope that in the future it will be possible to compute melting and melt-rock reaction over a much broader range of

  18. Predicting vapor-liquid phase equilibria with augmented ab initio interatomic potentials

    NASA Astrophysics Data System (ADS)

    Vlasiuk, Maryna; Sadus, Richard J.

    2017-06-01

    The ability of ab initio interatomic potentials to accurately predict vapor-liquid phase equilibria is investigated. Monte Carlo simulations are reported for the vapor-liquid equilibria of argon and krypton using recently developed accurate ab initio interatomic potentials. Seventeen interatomic potentials are studied, formulated from different combinations of two-body plus three-body terms. The simulation results are compared to either experimental or reference data for conditions ranging from the triple point to the critical point. It is demonstrated that the use of ab initio potentials enables systematic improvements to the accuracy of predictions via the addition of theoretically based terms. The contribution of three-body interactions is accounted for using the Axilrod-Teller-Muto plus other multipole contributions and the effective Marcelli-Wang-Sadus potentials. The results indicate that the predictive ability of recent interatomic potentials, obtained from quantum chemical calculations, is comparable to that of accurate empirical models. It is demonstrated that the Marcelli-Wang-Sadus potential can be used in combination with accurate two-body ab initio models for the computationally inexpensive and accurate estimation of vapor-liquid phase equilibria.

  19. Effect of CTAB and SDS micelles on the excited state equilibria of some indole probes

    NASA Astrophysics Data System (ADS)

    Sharma, Neera; Jain, Sapan K.; Rastogi, Ramesh C.

    2007-11-01

    The absorption and fluorescence spectral characteristics of some biologically active indoles have been studied as a function of acidity and basicity (H_/pH/H o) in cationic (cetyltrimethylammonium bromide, CTAB), anionic (sodium dodecylsulphate, SDS) and aqueous phases at a given surfactant concentration. The prototropic equilibrium reactions of these probes have been studied in aqueous and micellar phases and apparent excited state acidity constant (pKa*) values are calculated. The probes show formation of different species on changing pH. Various species present in water, CTAB and SDS have been identified and the equilibrium constants have been determined by Fluorimetric Titration method. The fluorescence spectral data suggest the formation of oxonium ion through the excited state proton transfer reaction in highly acidic media and formation of photoproducts due to the base catalyzed auto-oxidative reaction in basic aqueous solutions. Variations in the apparent pKa* value have been observed in different media. The change in the apparent p Ka values depends upon the solubilising power of the micelles, as well as on the location of the protonating site in the molecule. The observation about increase in pKa* values in SDS and decrease in CTAB compared to pure water for various equilibria is consistent with the pseudophase ion-exchange (PIE) model.

  20. Phase equilibria in polymer blend thin films: a Hamiltonian approach.

    PubMed

    Souche, M; Clarke, N

    2009-12-28

    We propose a Hamiltonian formulation of the Flory-Huggins-de Gennes theory describing a polymer blend thin film. We then focus on the case of 50:50 polymer blends confined between antisymmetric walls. The different phases of the system and the transitions between them, including finite-size effects, are systematically studied through their relation with the geometry of the Hamiltonian flow in phase space. This method provides an easy and efficient way, with strong graphical insight, to infer the qualitative physical behavior of polymer blend thin films.

  1. Phase equilibria in fluid mixtures at high pressures - The He-CH4 system.

    NASA Technical Reports Server (NTRS)

    Streett, W. B.; Erickson, A. L.; Hill, J. L. E.

    1972-01-01

    An experimental study of phase equilibria in the He-CH4 system has been carried out over the temperature range 95 to 290 K and at pressures to 10,000 atm. The experimental results consist of equilibrium phase composition for twenty-eight isotherms in the region of coexistence of two fluid phases, together with the pressure-temperature trace of the three-phase boundary at which a CH4-rich solid phase is in equilibrium with the two fluid phases. The system exhibits a fluid-fluid phase separation which persists to temperatures and pressures beyond the range of this experiment. These findings are relevant to problems of deep atmosphere and interior structures in the outer planets.-

  2. Phase equilibria of H2SO4, HNO3, and HCl hydrates and the composition of polar stratospheric clouds

    NASA Technical Reports Server (NTRS)

    Wooldridge, Paul J.; Zhang, Renyi; Molina, Mario J.

    1995-01-01

    Thermodynamic properties and phase equilibria behavior for the hydrates and coexisting pairs of hydrates of common acids which exist in the stratosphere are assembled from new laboratory measurements and standard literature data. The analysis focuses upon solid-vapor and solid-solid-vapor equilibria at temperatures around 200 K and includes new calorimetric and vapor pressure data. Calculated partial pressures versus 1/T slopes for the hydrates and coexisting hydrates agree well with experimental data where available.

  3. Phase equilibria of H2SO4, HNO3, and HCl hydrates and the composition of polar stratospheric clouds

    NASA Technical Reports Server (NTRS)

    Wooldridge, Paul J.; Zhang, Renyi; Molina, Mario J.

    1995-01-01

    Thermodynamic properties and phase equilibria behavior for the hydrates and coexisting pairs of hydrates of common acids which exist in the stratosphere are assembled from new laboratory measurements and standard literature data. The analysis focuses upon solid-vapor and solid-solid-vapor equilibria at temperatures around 200 K and includes new calorimetric and vapor pressure data. Calculated partial pressures versus 1/T slopes for the hydrates and coexisting hydrates agree well with experimental data where available.

  4. Phase Equilibria of H2SO4, HNO3, and HCl Hydrates and the Composition of Polar Stratospheric Clouds

    NASA Technical Reports Server (NTRS)

    Wooldridge, Paul J.; Zhang, Renyi; Molina, Mario J.

    1995-01-01

    Thermodynamic properties and phase equilibria behavior for the hydrates and coexisting pairs of hydrates of common acids which exist in the stratosphere are assembled from new laboratory measurements and standard literature data. The analysis focuses upon solid-vapor and solid-solid-vapor equilibria at temperatures around 200 K and includes new calorimetric and vapor pressure data. Calculated partial pressures versus 1/T slopes for the hydrates and coexisting hydrates agree well with experimental data where available.

  5. Phase equilibria in the neodymium–cadmium binary system

    PubMed Central

    Skołyszewska-Kühberger, Barbara; Reichmann, Thomas L.; Ipser, Herbert

    2014-01-01

    The equilibrium phase diagram of the neodymium–cadmium system has been established by thermal, metallographic and X-ray analysis based on a study of 70 alloys. The system contains three congruently melting intermetallic compounds, i.e. NdCd (1040 °C), NdCd2 (995 °C), Nd11Cd45 (855 °C), and four incongruently melting compounds NdCd3 (860 °C), Nd13Cd58 (740 °C), NdCd6 (655 °C) and NdCd11 (520 °C). Four eutectic reactions are found in this binary system, i.e. at ∼25 at.% Cd and 770 °C, at 58 at.% Cd and 955 °C, at 79 at.% Cd and 850 °C, and very close to pure Cd at 318 °C, as well as one eutectoid reaction at ∼15 at.% Cd and 500 °C. The solid solubility of Nd in Cd is negligible. Dilatometric curves were recorded for three Nd–Cd compositions up to 4 at.% Cd, to accurately determine phase transitions between the solid solutions of Cd in the low- and high-temperature modification of Nd. PMID:25197164

  6. Phase equilibria in the neodymium-cadmium binary system.

    PubMed

    Skołyszewska-Kühberger, Barbara; Reichmann, Thomas L; Ipser, Herbert

    2014-09-05

    The equilibrium phase diagram of the neodymium-cadmium system has been established by thermal, metallographic and X-ray analysis based on a study of 70 alloys. The system contains three congruently melting intermetallic compounds, i.e. NdCd (1040 °C), NdCd2 (995 °C), Nd11Cd45 (855 °C), and four incongruently melting compounds NdCd3 (860 °C), Nd13Cd58 (740 °C), NdCd6 (655 °C) and NdCd11 (520 °C). Four eutectic reactions are found in this binary system, i.e. at ∼25 at.% Cd and 770 °C, at 58 at.% Cd and 955 °C, at 79 at.% Cd and 850 °C, and very close to pure Cd at 318 °C, as well as one eutectoid reaction at ∼15 at.% Cd and 500 °C. The solid solubility of Nd in Cd is negligible. Dilatometric curves were recorded for three Nd-Cd compositions up to 4 at.% Cd, to accurately determine phase transitions between the solid solutions of Cd in the low- and high-temperature modification of Nd.

  7. Simulating fluid-phase equilibria of water from first principles.

    PubMed

    McGrath, Matthew J; Siepmann, J Ilja; Kuo, I-Feng W; Mundy, Christopher J; Vandevondele, Joost; Hutter, Jürg; Mohamed, Fawzi; Krack, Matthias

    2006-01-19

    Efficient Monte Carlo algorithms and a mixed-basis set electronic structure program were used to compute from first principles the vapor-liquid coexistence curve of water. A water representation based on the Becke-Lee-Yang-Parr exchange and correlation functionals yields a saturated liquid density of 900 kg/m3 at 323 K and normal boiling and critical temperatures of 350 and 550 K, respectively. An analysis of the structural and electronic properties of the saturated liquid phase shows an increase of the asymmetry of the local hydrogen-bonded structure despite the persistence of a 4-fold coordination and decreases of the molecular dipole moment and of the spread of the lowest unoccupied molecular orbital with increasing temperature.

  8. TERNARY PHASE EQUILIBRIA IN TRANSITION METAL-BORON-CARBON-SILICON SYSTEMS. PART II. TERNARY SYSTEMS. VOLUME XVI. V-NB-C SYSTEM,

    DTIC Science & Technology

    Phase equilibria in the ternary system vanadium-niobium-carbon from 800C through the melting ranges of the cubic monocarbide solid solutions were...established on the basis of X-ray, melting point and metallographic studies. The phase equilibria above 1400C are presented in a three-dimensional...temperature-composition constitutional diagram, since the phase equilibria below 1400C were not thoroughly investigated due to kinetic problems. Vanadium

  9. Diffusion, phase equilibria and partitioning experiments in the Ni-Fe-Ru system

    NASA Astrophysics Data System (ADS)

    Blum, Joel D.; Wasserburg, G. J.; Hutcheon, I. D.; Beckett, J. R.; Stolper, E. M.

    1989-02-01

    Results are presented on thin-film diffusion experiments designed to investigate phase equilibria in systems containing high concentrations of Pt-group elements, such as Ni-Fe-Ru-rich systems containing Pt, at temperatures of 1273, 1073, and 873 K. The rate of Ru diffusion in Ni was determined as a function of temperature, and, in addition, the degree of Pt and Ir partitioning between phases in a Ni-Fe-Ru-rich system and of V between phases in a Ni-Fe-O-rich system at 873 were determined. It was found that Pt preferentially partitions into the (gamma)Ni-Fe phase, whereas Ir prefers the (epsilon)Ru-Fe phase. V partitions strongly into Fe oxides relative to (gamma)Ni-Fe. These results have direct application to the origin and thermal history of the alloys rich in Pt-group elements in meteorites.

  10. Diffusion, phase equilibria and partitioning experiments in the Ni-Fe-Ru system

    NASA Technical Reports Server (NTRS)

    Blum, Joel D.; Wasserburg, G. J.; Hutcheon, I. D.; Beckett, J. R.; Stolper, E. M.

    1989-01-01

    Results are presented on thin-film diffusion experiments designed to investigate phase equilibria in systems containing high concentrations of Pt-group elements, such as Ni-Fe-Ru-rich systems containing Pt, at temperatures of 1273, 1073, and 873 K. The rate of Ru diffusion in Ni was determined as a function of temperature, and, in addition, the degree of Pt and Ir partitioning between phases in a Ni-Fe-Ru-rich system and of V between phases in a Ni-Fe-O-rich system at 873 were determined. It was found that Pt preferentially partitions into the (gamma)Ni-Fe phase, whereas Ir prefers the (epsilon)Ru-Fe phase. V partitions strongly into Fe oxides relative to (gamma)Ni-Fe. These results have direct application to the origin and thermal history of the alloys rich in Pt-group elements in meteorites.

  11. Solid-liquid phase equilibria of Fe-Cr-Al alloys and spinels

    NASA Astrophysics Data System (ADS)

    McMurray, J. W.; Hu, R.; Ushakov, S. V.; Shin, D.; Pint, B. A.; Terrani, K. A.; Navrotsky, A.

    2017-08-01

    Ferritic FeCrAl alloys are candidate accident tolerant cladding materials. There is a paucity of data concerning the melting behavior for FeCrAl and its oxides. Analysis tools have therefore had to utilize assumptions for simulations using FeCrAl cladding. The focus of this study is to examine in some detail the solid-liquid phase equilibria of FeCrAl alloys and spinels with the aim of improving the accuracy of severe accident scenario computational studies.

  12. Theory of nematic systems of semiflexible polymers. III. Phase equilibria in solutions

    NASA Astrophysics Data System (ADS)

    Ronca, G.; Yoon, D. Y.

    1985-07-01

    Biphasic equilibria of lyotropic solutions of semiflexible polymers are calculated using the worm-like chain model with limiting curvature. The threshold concentration at incipient phase separation varies gradually with molecular weight to reach a finite value at infinite chain length. This limiting concentration is found to depend on the axial ratio of the persistence length and on the temperature. The theory is then applied specifically to poly(n-hexyl isocyanate) (PHIC) solutions. Deriving the configurational parameters from measurements on chain dimensions in dilute solutions, theoretical calculations are found to satisfactorily match recent experimental results on the molecular weight dependence of the threshold concentration of PHIC in toluene.

  13. Phases, phase equilibria, and phase rules in low-dimensional systems.

    PubMed

    Frolov, T; Mishin, Y

    2015-07-28

    We present a unified approach to thermodynamic description of one, two, and three dimensional phases and phase transformations among them. The approach is based on a rigorous definition of a phase applicable to thermodynamic systems of any dimensionality. Within this approach, the same thermodynamic formalism can be applied for the description of phase transformations in bulk systems, interfaces, and line defects separating interface phases. For both lines and interfaces, we rigorously derive an adsorption equation, the phase coexistence equations, and other thermodynamic relations expressed in terms of generalized line and interface excess quantities. As a generalization of the Gibbs phase rule for bulk phases, we derive phase rules for lines and interfaces and predict the maximum number of phases than may coexist in systems of the respective dimensionality.

  14. Phases, phase equilibria, and phase rules in low-dimensional systems

    SciTech Connect

    Frolov, T.; Mishin, Y.

    2015-07-28

    We present a unified approach to thermodynamic description of one, two, and three dimensional phases and phase transformations among them. The approach is based on a rigorous definition of a phase applicable to thermodynamic systems of any dimensionality. Within this approach, the same thermodynamic formalism can be applied for the description of phase transformations in bulk systems, interfaces, and line defects separating interface phases. For both lines and interfaces, we rigorously derive an adsorption equation, the phase coexistence equations, and other thermodynamic relations expressed in terms of generalized line and interface excess quantities. As a generalization of the Gibbs phase rule for bulk phases, we derive phase rules for lines and interfaces and predict the maximum number of phases than may coexist in systems of the respective dimensionality.

  15. Electrical Conductivity and Phase Equilibria of Niobium Doped Cerium (iv) Dioxide.

    NASA Astrophysics Data System (ADS)

    Shingler, Martin Joseph

    Niobium-doped cerium (IV) oxide is being considered as an alternative cathode material for molten carbonate fuel cells. Design criteria state that the electrical conductivity of an acceptable cathode material should be at least 0.1 (ohm-cm)^{-1} at 650^circC. The conductivity of CeO_2 doped with 0.82 and 1.28 mol% Nb was found to exceed this value at temperatures greater than 750^circC. However, as the temperature is lowered and the oxygen pressure is increased, this material exhibits a very sharp decrease in the conductivity below this target value and the conductivity at typical MCFC cathode operating conditions is 0.05 (ohm -cm)^{-1}. This sharp decrease in the conductivity is caused by the formation of the second phase, CeNbO_4 . The niobium precipitates out of solution under these conditions and the electrical conductivity decreases as the concentration of the dopant, Nb decreases. In addition, the complex point defect equilibria of donor-doped CeO_2 has been mathematically modeled. This modeling has introduced several new concepts to the analysis of Kroger-Vink/Brouwer diagrams, where these diagrams show how the conductivity varies as a function of oxygen pressure at a constant temperature. The slopes of theoretically predicted conductivity curves have been derived and several observations were made from these curves. Most of these observations concern the transition region between two defect regimes where this transition region has been ignored in previous point defect studies. By examining this transition region, the point defect behavior of an electronic material can be described with more certainty compared to the traditional Kroger-Vink/Brouwer approaches.

  16. Electrical conductivity and phase equilibria of niobium doped cerium (IV) dioxide

    SciTech Connect

    Shingler, M.J.

    1989-01-01

    Niobium-doped cerium (IV) oxide is being considered as an alternative cathode material for molten carbonate fuel cells. Design criteria state that the electrical conductivity of an acceptable cathode material should be at least 0.1 (ohm-cm){sup {minus}1} at 650{degree}C. The conductivity of CeO{sub 2} doped with 0.82 and 1.28 mol% Nb was found to exceed this value at temperatures greater than 750{degree}C. However, as the temperature is lowered and the oxygen pressure is increased, this material exhibits a very sharp decrease in the conductivity below this target value and the conductivity at typical MCFC cathode operating conditions is 0.05 (ohm-cm){sup {minus}1}. This sharp decrease in the conductivity is caused by the formation of the second phase, CeNbO{sub 4}. The niobium precipitates out of solution under these conditions and the electrical conductivity decreases as the concentration of the dopant, Nb decreases. In addition, the complex point defect equilibria of donor-doped CeO{sub 2} has been mathematically modeled. This modeling has introduced several new concepts to the analysis of Kroger-Vink/Brouwer diagrams, where these diagrams show how the conductivity varies as a function of oxygen pressure at a constant temperature. The slopes of theoretically predicted conductivity curves have been derived and several observations were made from these curves. Most of these observations concern the transition region between two defect regimes where this transition region has been ignored in previous point defect studies. By examining this transition region, the point defect behavior of an electronic material can be described with more certainty compared to the traditional Kroger-Vink/Brouwer approaches.

  17. Modeling the Thermodynamics of Mixed Organic-Inorganic Aerosols to Predict Water Activities and Phase Equilibria

    NASA Astrophysics Data System (ADS)

    Zuend, A.; Marcolli, C.; Luo, B.; Peter, T.

    2008-12-01

    Tropospheric aerosol particles contain mixtures of inorganic salts, acids, water, and a large variety of organic compounds. Interactions between these substances in liquid mixtures lead to discrepancies from ideal thermodynamic behavior. While the thermodynamics of aqueous inorganic systems at atmospheric temperatures are well established, little is known about the physicochemistry of mixed organic-inorganic particles. Salting-out and salting-in effects result from organic-inorganic interactions and are used to improve industrial separation processes. In the atmosphere, they may influence the aerosol phases. Liquid-liquid phase separations into a mainly polar (aqueous) and a less polar organic phase may considerably influence the gas/particle partitioning of semi-volatile substances compared to a single phase estimation. Moreover, the phases present in the aerosol define the reaction medium for heterogeneous and multiphase chemistry occurring in aerosol particles. A correct description of these phases is needed when gas- or cloud-phase reaction schemes are adapted to aerosols. Non-ideal thermodynamic behavior in mixtures is usually described by an expression for the excess Gibbs energy. We present the group-contribution model AIOMFAC (Aerosol Inorganic-Organic Mixtures Functional groups Activity Coefficients), which explicitly accounts for molecular interactions between solution constituents, both organic and inorganic, to calculate activities, chemical potentials and the total Gibbs energy of mixed systems. This model allows to compute vapor-liquid (VLE), liquid-liquid (LLE) and solid-liquid (SLE) equilibria within one framework. Focusing on atmospheric applications we considered eight different cations, five anions and a wide range of alcohols/polyols as organic compounds. With AIOMFAC, the activities of the components within an aqueous electrolyte solution are very well represented up to high ionic strength. We show that the semiempirical middle

  18. Phase Equilibria of Water/CO2 and Water/n-Alkane Mixtures from Polarizable Models.

    PubMed

    Jiang, Hao; Economou, Ioannis G; Panagiotopoulos, Athanassios Z

    2017-02-16

    Phase equilibria of water/CO2 and water/n-alkane mixtures over a range of temperatures and pressures were obtained from Monte Carlo simulations in the Gibbs ensemble. Three sets of Drude-type polarizable models for water, namely the BK3, GCP, and HBP models, were combined with a polarizable Gaussian charge CO2 (PGC) model to represent the water/CO2 mixture. The HBP water model describes hydrogen bonds between water and CO2 explicitly. All models underestimate CO2 solubility in water if standard combining rules are used for the dispersion interactions between water and CO2. With the dispersion parameters optimized to phase compositions, the BK3 and GCP models were able to represent the CO2 solubility in water, however, the water composition in CO2-rich phase is systematically underestimated. Accurate representation of compositions for both water- and CO2-rich phases cannot be achieved even after optimizing the cross interaction parameters. By contrast, accurate compositions for both water- and CO2-rich phases were obtained with hydrogen bonding parameters determined from the second virial coefficient for water/CO2. Phase equilibria of water/n-alkane mixtures were also studied using the HBP water and an exponenial-6 united-atom n-alkanes model. The dispersion interactions between water and n-alkanes were optimized to Henry's constants of methane and ethane in water. The HBP water and united-atom n-alkane models underestimate water content in the n-alkane-rich phase; this underestimation is likely due to the neglect of electrostatic and induction energies in the united-atom model.

  19. Three-body interactions and solid-liquid phase equilibria: application of a molecular dynamics algorithm.

    PubMed

    Wang, Liping; Sadus, Richard J

    2006-09-01

    The effect of three-body interactions on the solid-liquid phase boundaries of argon, krypton, and xenon is investigated via a novel technique that combines both nonequilibrium and equilibrium molecular dynamics. The simulations involve the evaluation of two- and three-body forces using accurate two-body and three-body intermolecular potentials. The effect of three-body interactions is to substantially increase the coexistence pressure and to lower the densities of liquid and solid phases. Comparison with experiment indicates that three-body interactions are required to accurately determine the total pressure. In contrast to vapor-liquid phase equilibria, the relative contribution of three-body interactions to the freezing pressure exceeds the contribution of two-body interactions at all temperatures.

  20. Phase equilibria in metal-indium-arsenic, nickel-gallium-antimony, nickel-indium systems and interfacial reactions between nickel and indium arsenide

    SciTech Connect

    Sutopo

    1993-12-31

    Phase equilibrium studies were carried out in the Rh-In-As, Ir-In-As, Co-In-As, Ni-Ga-Sb, and Ni-In-Sb systems at various temperatures. The experimental techniques used to establish the phase equilibria were X-ray diffraction, optical microscopy, electron probe microanalysis, scanning electron microscopy. An isothermal section of the Rh-In-As phase diagram was determined at 600{degrees}C. One ternary phase was identified and the composition of ternary phase was Rh{sub 3}In{sub 5}As{sub 2}. Three binary phases and one ternary phase were confirmed to be in equilibrium with InAs; RhIn{sub 3}, RhAs{sub 2}, RhAs{sub 3} and Rh{sub 3}In{sub 5}As{sub 2}. Phase equilibria were established in the Ir-In-As system at 600{degrees}C. No ternary phases were detected in the system and the ternary solubilities of the binary phases were found to be negligible. InAs was shown to be in thermodynamic equilibrium with liquid indium metal, IrAs{sub 2}, and IrAs{sub 3}. Solid state phase equilibria at 475{degrees}C in the system Co-In-As were determined. InAs formed equilibria with liquid indium, CoAs{sub 2} and CoAs. The presence of ternary phase with the composition CO{sub 19}In{sub 15}As{sub 6} was identified. From the Ni-Ga-Sb and Ni-In-Sb ternary phase diagrams were found that NiSb phase exhibited an extensive ternary solubilities deep into the Ga-Ni and In-Ni binaries respectively. There were no true ternary phases to be existence, but rather represented a specific composition of extensive solid solutions of constituent binary phases. NiSb{sub 2}, NiSb and Ni{sub 2}Ga{sub 3} were in thermodynamic equilibrium with GaSb and NiSb{sub 2}, NiSb and Ni{sub 2}In{sub 3} were also in thermodynamic stable with InSb. The Kinetics of bulk Ni/InAs diffusion couples were investigated using electron probe microanalysis and scanning electron microscopy. Intrinsic diffusivities and interdiffusion coefficients of the Ni{sub 3}InAs phase in Ni/InAs were determined using ternary multi-phase models.

  1. Phase equilibria and thermodynamic modeling of ethane and propane hydrates in porous silica gels.

    PubMed

    Seo, Yongwon; Lee, Seungmin; Cha, Inuk; Lee, Ju Dong; Lee, Huen

    2009-04-23

    In the present study, we examined the active role of porous silica gels when used as natural gas storage and transportation media. We adopted the dispersed water in silica gel pores to substantially enhance active surface for contacting and encaging gas molecules. We measured the three-phase hydrate (H)-water-rich liquid (L(W))-vapor (V) equilibria of C(2)H(6) and C(3)H(8) hydrates in 6.0, 15.0, 30.0, and 100.0 nm silica gel pores to investigate the effect of geometrical constraints on gas hydrate phase equilibria. At specified temperatures, the hydrate stability region is shifted to a higher pressure region depending on pore size when compared with those of bulk hydrates. Through application of the Gibbs-Thomson relationship to the experimental data, we determined the values for the C(2)H(6) hydrate-water and C(3)H(8) hydrate-water interfacial tensions to be 39 +/- 2 and 45 +/- 1 mJ/m(2), respectively. By using these values, the calculation values were in good agreement with the experimental ones. The overall results given in this study could also be quite useful in various fields, such as exploitation of natural gas hydrate in marine sediments and sequestration of carbon dioxide into the deep ocean.

  2. Advantages of ion-based mole fractions for describing phase equilibria in ionic liquids: application to gas solubility.

    PubMed

    Longinotti, María Paula; Alvarez, Jorge L; Japas, M Laura

    2009-03-19

    Despite the obvious ionic character of ionic liquids (ILs), previous studies of phase equilibria in these media were formulated implicitly assuming a "molecular" behavior of the ionic solvent. In this work, a more appropriate thermodynamic treatment is applied to describe the solubility of gases in ILs. According to our results, if the concentration is expressed on an ionic basis, solutions of simple gases in ILs display rather small deviations from ideal behavior in wide composition ranges, whereas deviations are larger when the solvent is considered as an anion-cation pair. The present thermodynamic formulation also accounts for the observed solid-liquid phase equilibria of molecular and IL binary mixtures.

  3. Liquid-vapor phase equilibria and the thermodynamic properties of 2-methylpropanol- n-alkyl propanoate solutions

    NASA Astrophysics Data System (ADS)

    Suntsov, Yu. K.; Goryunov, V. A.; Chuikov, A. M.; Meshcheryakov, A. V.

    2016-08-01

    The boiling points of solutions of five binary systems are measured via ebulliometry in the pressure range of 2.05-103.3 kPa. Equilibrium vapor phase compositions, the values of the excess Gibbs energies, enthalpies, and entropies of solution of these systems are calculated. Patterns in the changes of phase equilibria and thermodynamic properties of solutions are established, depending on the compositions and temperatures of the systems. Liquid-vapor equilibria in the systems are described using the equations of Wilson and the NRTL (Non-Random Two-Liquid Model).

  4. Phase Equilibria and Transition in Mixtures of a Homopolymer and a Block Copolymer. I. Small-Angle X-Ray Scattering Study.

    DTIC Science & Technology

    1983-03-08

    AA2588 PHASE EQUILIBRIA AND TRANSITION IN MIXTURES OF A I HOMOPOLYMER AND A BLOCK..(U) CINCINNATI UNIV OH DEPT OF SMATERIALS SCIENCE AND.METALLURGICA...OFFICE OF NAVAL RESEARCH Contract N00014-77-C-0376 Task No. NR 356-655 TECHNICAL REPORT NO. 8 Phase Equilibria and Transition in Mixtures of a

  5. MTDATA and the Prediction of Phase Equilibria in Oxide Systems: 30 Years of Industrial Collaboration

    NASA Astrophysics Data System (ADS)

    Gisby, John; Taskinen, Pekka; Pihlasalo, Jouni; Li, Zushu; Tyrer, Mark; Pearce, Jonathan; Avarmaa, Katri; Björklund, Peter; Davies, Hugh; Korpi, Mikko; Martin, Susan; Pesonen, Lauri; Robinson, Jim

    2017-02-01

    This paper gives an introduction to MTDATA, Phase Equilibrium Software from the National Physical Laboratory (NPL), and describes the latest advances in the development of a comprehensive database of thermodynamic parameters to underpin calculations of phase equilibria in large oxide, sulfide, and fluoride systems of industrial interest. The database, MTOX, has been developed over a period of thirty years based upon modeling work at NPL and funded by industrial partners in a project co-ordinated by Mineral Industry Research Organisation. Applications drawn from the fields of modern copper scrap smelting, high-temperature behavior of basic oxygen steelmaking slags, flash smelting of nickel, electric furnace smelting of ilmenite, and production of pure TiO2 via a low-temperature molten salt route are discussed along with calculations to assess the impact of impurities on the uncertainty of fixed points used to realize the SI unit of temperature, the kelvin.

  6. Planetary phase equilibria - Application to formation of earth, Venus and Mercury

    NASA Technical Reports Server (NTRS)

    Saxena, S. K.

    1981-01-01

    Calculations of phase equilibria in a solar mixture with variable hydrogen abundance show that the major element chemical composition of the earth and Venus can be simply explained by their formation in equilibrium at 800 and 1000 K, respectively, at a pressure of 0.001 atm, provided that there is an iron loss from the region of proto-Venus relative to the solar nebula. The calculated mineralogical chemical compositions of the two planets are in excellent agreement with the available chemical and physical data. Phase equilibrium calculations at 1500 K and 0.001 atm show that nearly 96% of the silicates and 81% of metal must have been lost from the region of proto-Mercury.

  7. Hydration energies of deprotonated amino acids from gas phase equilibria measurements.

    PubMed

    Wincel, Henryk

    2008-08-01

    Singly hydrated clusters of deprotonated amino acids were studied using an electrospray high-pressure mass spectrometer equipped with a pulsed ion-beam reaction chamber. Thermochemical data, DeltaH(o), DeltaS(o), and DeltaG(o), for the hydration reaction [AA - H](-) + H(2)O = [AA - H](-).(H(2)O) were obtained from gas-phase equilibria determinations for AA = Gly, Ala, Val, Pro, Phe, Lys, Met, Trp, Gln, Arg, and Asp. The hydration free-energy changes are found to depend significantly on the side-chain substituents. The water binding energy in [AA - H](-).(H(2)O) increases with the gas-phase acidity of AA. The anionic hydrogen bond strengths in [AA - H](-).(H(2)O) are compared with those of the cationic bonds in the corresponding AAH(+).(H(2)O) systems.

  8. Phase equilibria of the magnesium sulfate-water system to 4 kbars

    NASA Technical Reports Server (NTRS)

    Hogenboom, D. L.; Kargel, J. S.; Ganasan, J. P.; Lee, L.

    1993-01-01

    Magnesium sulfate is the most abundant salt in carbonaceous chondrites, and it may be important in the low-temperature igneous evolution and aqueous differentiation of icy satellites and large chondritic asteroids. Accordingly, we are investigating high-pressure phase equilibria in MgSO4-H2O solutions under pressures up to four kbars. An initial report was presented two years ago. This abstract summarizes our results to date including studies of solutions containing 15.3 percent, 17 percent, and 22 percent MgSO4. Briefly, these results demonstrate that increasing pressure causes the eutectic and peritectic compositions to shift to much lower concentrations of magnesium sulfate, and the existence of a new low-density phase of magnesium sulfate hydrate.

  9. Exact calculations of phase and membrane equilibria for complex fluids by Monte Carlo simulation

    SciTech Connect

    Panagiotopoulos, A.Z.

    1990-08-28

    The general objective of this project is the investigation of phase equilibria for complex fluids using a novel methodology, Monte Carlo simulation in the Gibbs ensemble. The methodology enables the direct determination of the properties of two coexisting fluid phases (e.g. a liquid at equilibrium with its vapor) from a single computer experiment, and is applicable to multicomponent systems with arbitrary equilibrium constraints imposed. The specific goals of this work are to adapt the Gibbs technique to (a) highly asymmetric mixtures with large differences in size and potential energies of interaction (b) chain molecules and (c) ionic systems. Significant progress has been made in all three areas. In this paper, we will briefly describe the progress made in each area, using the same numbering scheme for the tasks as in the original proposal.

  10. Planetary phase equilibria - Application to formation of earth, Venus and Mercury

    NASA Technical Reports Server (NTRS)

    Saxena, S. K.

    1981-01-01

    Calculations of phase equilibria in a solar mixture with variable hydrogen abundance show that the major element chemical composition of the earth and Venus can be simply explained by their formation in equilibrium at 800 and 1000 K, respectively, at a pressure of 0.001 atm, provided that there is an iron loss from the region of proto-Venus relative to the solar nebula. The calculated mineralogical chemical compositions of the two planets are in excellent agreement with the available chemical and physical data. Phase equilibrium calculations at 1500 K and 0.001 atm show that nearly 96% of the silicates and 81% of metal must have been lost from the region of proto-Mercury.

  11. Bayesian Nash equilibria using extended Werner-like states

    NASA Astrophysics Data System (ADS)

    Alid-Vaccarezza, M.; Soto, M. E.

    2016-10-01

    We study quantum strategies in games of incomplete information using a formalism of game theory based on multi-sector probability matrix. We analyze an extension of the well-known game of Battle of Sexes using an extended Werner-like state focusing in how its mixedness and entanglement affect the Bayesian Nash payoffs of the player. It is shown that entanglement is needed to outperform classical payoffs but not all entangled states are useful due to the presence of mixedness. A threshold for the mixedness parameter and the minimum entanglement value were found.

  12. A novel approach to phase equilibria predictions using ab initio methods

    SciTech Connect

    Sum, A.K.; Sandler, S.I.

    1999-07-01

    Molecular orbital ab initio calculations have been used to compute interaction energies between pairs of molecules in a large molecular cluster. These energies are then used as the interaction energy parameters in the widely used Wilson and UNIQUAC activity coefficient models. Low-pressure vapor-liquid equilibria predictions based on the calculated parameters have been computed for binary systems of water with methanol, ethanol, 1-propanol, 2-propanol, formic acid, acetic acid, acetone, acetonitrile, acetaldehyde, and m-methylformamide. Excellent predictions are obtained with the UNIQUAC model, whereas poor results are found with the Wilson model. In several cases, the authors` predictions are also superior to those obtained from UNIFAC. In addition, using the same parameters and the UNIQUAC model, high-pressure-vapor-liquid equilibria predictions were made using the Peng-Robinson-Stryjek-Vera equation of state and the Wong-Sandler mixing rule for methanol, ethanol, 2-propanol, and acetone separately with water. The low- and high-pressure results demonstrate that this unique approach can lead to accurate vapor-liquid equilibrium predictions for hydrogen-bonding mixtures based only on pure-component properties and the structure of the molecules.

  13. The systems Sr-Zn-{l_brace}Si,Ge{r_brace}: Phase equilibria and crystal structure of ternary phases

    SciTech Connect

    Romaka, V.V.; Falmbigl, M.; Grytsiv, A.; Rogl, P.

    2012-02-15

    Phase relations have been established by electron probe microanalysis (EPMA) and X-ray powder diffraction (XPD) for the Sr-poor part of the ternary systems Sr-Zn-Si at 800 Degree-Sign C and Sr-Zn-Ge at 700 Degree-Sign C. In the Sr-Zn-Si system one new ternary compound SrZn{sub 2+x}Si{sub 2-x} (0{<=}x{<=}0.45) with CeAl{sub 2}Ga{sub 2} structure and a statistical mixture of Zn/Si in the 4e site was found. Neither a type-I nor a type-IX clathrate phase was encountered. This system is characterized by formation of two further phases, i.e. SrZn{sub 1-x}Si{sub 1+x} with ZrBeSi-type (0.16{<=}x{<=}0.22) and SrZn{sub 1-x}Si{sub 1+x} with AlB{sub 2}-type (0.35{<=}x{<=}0.65) with a random distribution of Zn/Si atoms in the 2c site. For the Sr-Zn-Ge system, the homogeneity regions of the isotypic phases SrZn{sub 1-x}Ge{sub 1+x} with ZrBeSi-type (0{<=}x{<=}0.17) and AlB{sub 2}-type (0.32{<=}x{<=}0.56), respectively, have been determined. Whereas the germanide SrZn{sub 2+x}Ge{sub 2-x} (CeAl{sub 2}Ga{sub 2}-type) is characterized by a homogeneity region (0{<=}x{<=}0.5), the clathrate type-I phase Sr{sub 8}Zn{sub 8}Ge{sub 38} shows a point composition. - Graphical abstract: Phase equilibria of ternary compounds in the Sr-Zn-Si-system at 800 Degree-Sign C. Highlights: Black-Right-Pointing-Pointer Phase equilibria in the Sr-Zn-Si-system are established at 800 Degree-Sign C. Black-Right-Pointing-Pointer Phase equilibria in the Sr-Zn-Ge-system are established at 700 Degree-Sign C. Black-Right-Pointing-Pointer Crystal structures of the ternary compounds were confirmed by X-ray powder diffraction. Black-Right-Pointing-Pointer All ternary compounds except the clathrate-I in the Ge-system are characterized by a homogeneity region.

  14. Exploring fluctuations and phase equilibria in fluid mixtures via Monte Carlo simulation

    NASA Astrophysics Data System (ADS)

    Denton, Alan R.; Schmidt, Michael P.

    2013-03-01

    Monte Carlo simulation provides a powerful tool for understanding and exploring thermodynamic phase equilibria in many-particle interacting systems. Among the most physically intuitive simulation methods is Gibbs ensemble Monte Carlo (GEMC), which allows direct computation of phase coexistence curves of model fluids by assigning each phase to its own simulation cell. When one or both of the phases can be modelled virtually via an analytic free energy function (Mehta and Kofke 1993 Mol. Phys. 79 39), the GEMC method takes on new pedagogical significance as an efficient means of analysing fluctuations and illuminating the statistical foundation of phase behaviour in finite systems. Here we extend this virtual GEMC method to binary fluid mixtures and demonstrate its implementation and instructional value with two applications: (1) a lattice model of simple mixtures and polymer blends and (2) a free-volume model of a complex mixture of colloids and polymers. We present algorithms for performing Monte Carlo trial moves in the virtual Gibbs ensemble, validate the method by computing fluid demixing phase diagrams, and analyse the dependence of fluctuations on system size. Our open-source simulation programs, coded in the platform-independent Java language, are suitable for use in classroom, tutorial, or computational laboratory settings.

  15. Phase and extraction equilibria in water-polyethyleneglycol ethers of monoethanolamides of synthetic fatty acid-ammonium chloride systems

    NASA Astrophysics Data System (ADS)

    Lesnov, A. E.; Golovkina, A. V.; Kudryashova, O. S.; Denisova, S. A.

    2016-08-01

    Phase equilibria in layering systems of water, polyethyleneglycol ethers of monoethanolamides of synthetic fatty acids (SFAs) (synthamide-5), and ammonium chloride are studied. The possibility of using such systems for the liquid extraction of metal ions is evaluated. The effect the nature of salting-out agents has on the processes of segregation of the systems has been considered.

  16. Planet Alsioff - A problem set for students of phase equilibria or metamorphic petrology

    NASA Technical Reports Server (NTRS)

    Burt, Donald M.

    1988-01-01

    This paper presents a problem set that contains questions for students of phase equilibria or metamorphic petrology concerning a hypothetical planet Alsioff, for which incomplete data are given. On this panet, the SiF4 is the major volatile and Al, Si, O, and F are the only elements present. Progressive metamorphism on Alsioff mainly involves devolatilization of fluid SiF4. The problem set includes ten questions. Some of these are concerned with possible chemical reactions that should affect water, wollastonite, or Ca-SiO3 exposed to the atmosphere of Alsioff; the mechanism of controls of the O2 and F2 contents of the Alsioffian atmosphere; and the devolatilization reactions involving SiF4 with progressive thermal metamorphism.

  17. Extension of the transferable potentials for phase equilibria force field to dimethylmethyl phosphonate, sarin, and soman.

    PubMed

    Sokkalingam, Nandhini; Kamath, Ganesh; Coscione, Maria; Potoff, Jeffrey J

    2009-07-30

    The transferable potentials for phase equilibria force field is extended to dimethylmethylphosphonate (DMMP), sarin, and soman by introducing a new interaction site representing the phosphorus atom. Parameters for the phosphorus atom are optimized to reproduce the liquid densities at 303 and 373 K and the normal boiling point of DMMP. Calculations for sarin and soman are performed in predictive mode, without further parameter optimization. Vapor-liquid coexistence curves, critical properties, vapor pressures and heats of vaporization are predicted over a wide range of temperatures with histogram reweighting Monte Carlo simulations in the grand canonical ensemble. Excellent agreement with experiment is achieved for all compounds, with unsigned errors of less than 1% for vapor pressures and normal boiling points and under 5% for heats of vaporization and liquid densities at ambient conditions.

  18. Biomolecular simulations with the transferable potentials for phase equilibria: extension to phospholipids.

    PubMed

    Bhatnagar, Navendu; Kamath, Ganesh; Potoff, Jeffrey J

    2013-08-29

    The Transferable Potentials for Phase Equilibria (TraPPE) is extended to zwitterionic and charged lipids including phosphatidylcholine (PC), phosphatidylethanolamine (PE), phosphatidylserine (PS), and phosphatidylglycerol (PG). The performance of the force field is validated through isothermal-isobaric ensemble (NPT) molecular dynamics simulations of hydrated lipid bilayers performed with the aforementioned head groups combined with saturated and unsaturated alkyl tails containing 12-18 carbon atoms. The effects of water model and sodium ion parameters on the performance of the lipid force field are determined. The predictions of the TraPPE force field for the area per lipid, bilayer thickness, and volume per lipid are within 1-5% of experimental values. Key structural properties of the bilayer, such as order parameter splitting in the sn-2 chain and X-ray form factors, are found to be in close agreement with experimental data.

  19. Planet Alsioff - A problem set for students of phase equilibria or metamorphic petrology

    NASA Technical Reports Server (NTRS)

    Burt, Donald M.

    1988-01-01

    This paper presents a problem set that contains questions for students of phase equilibria or metamorphic petrology concerning a hypothetical planet Alsioff, for which incomplete data are given. On this panet, the SiF4 is the major volatile and Al, Si, O, and F are the only elements present. Progressive metamorphism on Alsioff mainly involves devolatilization of fluid SiF4. The problem set includes ten questions. Some of these are concerned with possible chemical reactions that should affect water, wollastonite, or Ca-SiO3 exposed to the atmosphere of Alsioff; the mechanism of controls of the O2 and F2 contents of the Alsioffian atmosphere; and the devolatilization reactions involving SiF4 with progressive thermal metamorphism.

  20. Phase equilibria in the iron oxide-cobalt oxide-phosphorus oxide system

    NASA Technical Reports Server (NTRS)

    De Guire, Mark R.; Prasanna, T. R. S.; Kalonji, Gretchen; O'Handley, Robert C.

    1987-01-01

    Two novel ternary compounds are noted in the present study of 1000 C solid-state equilibria in the Fe-Co-P-O system's Fe2O3-FePO4-Co3(Po4)2-CoO region: CoFe(PO4)O, which undergoes incongruent melting at 1130 C, and Co3Fe4(PO4)6, whose incongruent melting occurs at 1080 C. The liquidus behavior-related consequences of rapidly solidified cobalt ferrite formation from cobalt ferrite-phosphate melts are discussed with a view to spinel formation. It is suggested that quenching from within the spinel-plus-liquid region may furnish an alternative to quenching a homogeneous melt.

  1. Phase equilibria in the iron oxide-cobalt oxide-phosphorus oxide system

    NASA Technical Reports Server (NTRS)

    De Guire, Mark R.; Prasanna, T. R. S.; Kalonji, Gretchen; O'Handley, Robert C.

    1987-01-01

    Two novel ternary compounds are noted in the present study of 1000 C solid-state equilibria in the Fe-Co-P-O system's Fe2O3-FePO4-Co3(Po4)2-CoO region: CoFe(PO4)O, which undergoes incongruent melting at 1130 C, and Co3Fe4(PO4)6, whose incongruent melting occurs at 1080 C. The liquidus behavior-related consequences of rapidly solidified cobalt ferrite formation from cobalt ferrite-phosphate melts are discussed with a view to spinel formation. It is suggested that quenching from within the spinel-plus-liquid region may furnish an alternative to quenching a homogeneous melt.

  2. The heat-capacity of ilmenite and phase equilibria in the system Fe-T-O

    USGS Publications Warehouse

    Anovitz, Lawrence M.; Treiman, A.H.; Essene, E.J.; Hemingway, B.S.; Westrum, E.F.; Wall, V.J.; Burriel, R.; Bohlen, S.R.

    1985-01-01

    Low temperature adiabatic calorimetry and high temperature differential scanning calorimetry have been used to measure the heat-capacity of ilmenite (FeTiO3) from 5 to 1000 K. These measurements yield S2980 = 108.9 J/(mol ?? K). Calculations from published experimental data on the reduction of ilmenite yield ??2980(I1) = -1153.9 kJ/(mol ?? K). These new data, combined with available experimental and thermodynamic data for other phases, have been used to calculate phase equilibria in the system Fe-Ti-O. Calculations for the subsystem Ti-O show that extremely low values of f{hook}O2 are necessary to stabilize TiO, the mineral hongquiite reported from the Tao district in China. This mineral may not be TiO, and it should be re-examined for substitution of other elements such as N or C. Consideration of solid-solution models for phases in the system Fe-Ti-O allows derivation of a new thermometer/oxybarometer for assemblages of ferropseudobrookite-pseudobrookitess and hematite-ilmenitess. Preliminary application of this new thermometer/oxybarometer to lunar and terrestrial lavas gives reasonable estimates of oxygen fugacities, but generally yields subsolidus temperatures, suggesting re-equilibration of one or more phases during cooling. ?? 1985.

  3. Phase equilibria in the ternary In–Ni–Sn system at 700 °C

    PubMed Central

    Schmetterer, C.; Zemanova, A.; Flandorfer, H.; Kroupa, A.; Ipser, H.

    2013-01-01

    The phase equilibria of the ternary system In–Ni–Sn were investigated experimentally at 700 °C using X-ray diffraction (XRD) and scanning electron microscopy (SEM) including electron micro probe analysis (EMPA) and energy dispersive X-ray spectroscopy (EDX). A corresponding isothermal section was established based on these results. This particular temperature was chosen because it allowed obtaining reliable results within reasonable time. The existence of the ternary phase InNi6Sn5 was confirmed whereas the ternary compound In2NiSn, reported earlier in literature, was found to be part of a large solid solution field based on binary InNi. The ternary solubility of the binary phases was established, and continuous solid solutions were found between the isostructural phases Ni3Sn LT and InNi3 as well as between Ni3Sn2 HT and InNi2. In addition, this isothermal section could be well reproduced by CALPHAD modelling. The resulting calculated isotherm at 700 °C is presented, too, and compared with the experimental results. PMID:27087756

  4. Monte Carlo calculation of phase equilibria for a bead-spring polymeric model

    SciTech Connect

    Sheng, Y.J.; Panagiotopoulos, A.Z. . School of Chemical Engineering); Kumar, S.K. . Dept. of Materials Science and Engineering); Szleifer, I. )

    1994-01-17

    Vapor-liquid phase diagrams for a bead-spring polymeric model have been calculated for chain lengths of 20, 50, and 100 from Monte Carlo simulations using the recently proposed chain increment method to determine the chain chemical potentials. Densities of both phases at coexistence and vapor pressures were obtained directly for a range of temperatures from highly subcritical to the vicinity of the critical point, and the critical temperature and density for each chain length were obtained by extrapolation. They also calculated the second virial coefficients for chain-chain interactions of the model and found that the temperature at which the second virial coefficients for chain-chain interactions of the model and found that the temperature at which the second virial coefficient vanishes for long chains coincides, within computational uncertainty, with the infinite chain length critical point from the phase equilibrium results. At the critical points of the finite length chains the second virial coefficient assume negative values, indicating attractive interchain interactions. The radius of gyration of chains of varying length was also determined and the [theta] temperature obtained from the radii of gyration found to coincide, within computational uncertainty, with the critical point for an infinite chain length polymer. The computational methodology they utilize can be extended to the calculation of phase equilibria in multicomponent polymer/solvent systems.

  5. Phase equilibria in the ternary In-Ni-Sn system at 700 °C.

    PubMed

    Schmetterer, C; Zemanova, A; Flandorfer, H; Kroupa, A; Ipser, H

    2013-04-01

    The phase equilibria of the ternary system In-Ni-Sn were investigated experimentally at 700 °C using X-ray diffraction (XRD) and scanning electron microscopy (SEM) including electron micro probe analysis (EMPA) and energy dispersive X-ray spectroscopy (EDX). A corresponding isothermal section was established based on these results. This particular temperature was chosen because it allowed obtaining reliable results within reasonable time. The existence of the ternary phase InNi6Sn5 was confirmed whereas the ternary compound In2NiSn, reported earlier in literature, was found to be part of a large solid solution field based on binary InNi. The ternary solubility of the binary phases was established, and continuous solid solutions were found between the isostructural phases Ni3Sn LT and InNi3 as well as between Ni3Sn2 HT and InNi2. In addition, this isothermal section could be well reproduced by CALPHAD modelling. The resulting calculated isotherm at 700 °C is presented, too, and compared with the experimental results.

  6. Phase Equilibria of the Fe-Ni-Sn Ternary System at 270°C

    NASA Astrophysics Data System (ADS)

    Huang, Tzu-Ting; Lin, Shih-Wei; Chen, Chih-Ming; Chen, Pei Yu; Yen, Yee-Wen

    2016-12-01

    The Fe-42 wt.% Ni alloy, also known as a 42 invar alloy (Alloy 42), is used as a lead-frame material because its thermal expansion coefficient is much closer to Si substrate than Cu or Ni substrates. In order to enhance the wettability between the substrate and solder, the Sn layer was commonly electroplated onto the Alloy 42 surface. A clear understanding of the phase equilibria of the Fe-Ni-Sn ternary system is necessary to ensure solder-joint reliability between Sn and Fe-Ni alloys. To determine the isothermal section of the Fe-Ni-Sn ternary system at 270°C, 26 Fe-Ni-Sn alloys with different compositions were prepared. The experimental results confirmed the presence of the Fe3Ni and FeNi phases at 270°C. Meanwhile, it observed that the isothermal section of the Fe-Ni-Sn ternary system was composed of 11 single-phase regions, 19 two-phase regions and nine tie-triangles. Moreover, no ternary compounds were found in the Fe-Ni-Sn system at 270°C.

  7. Solid-liquid Phase Equilibria of U(VI) in NaCl Solutions

    NASA Astrophysics Data System (ADS)

    Díaz Arocas, P.; Grambow, B.

    1998-01-01

    Solid-liquid phase equilibria and equilibrium phase relationships of U(VI) in up to 5 m NaCl solutions were studied by analyzing the precipitation process in initially oversaturated solutions at different pH values. Comparison to corresponding behavior in NaClO 4 media is made. Solid precipitates and solution concentrations of U were characterized as a function of time and pH. In NaClO 4 media schoepite (UO 3·2H 2O) was found to be the stable phase between pH 4 and 6. By contrast, in NaCl media, sodium polyuranates formed. For a given NaCl concentration and pH, differences in the solubility concentration of about 3 orders of magnitude were observed, as attributed to metastability with respect to crystallinity and Na/U ratio of the precipitates. Average solubility constants log K° soere calculated for schoepite (log K° so = 5.37 ± 0.25) and for Na 0.33UO 3.16·2H 2O (log K° so = 7.13 ± 0.15). Based on these data and together with a critical review of literature data on schoepite and polyuranates a solid solution model is developed, describing composition and phase transformation of Na-polyuranates as a function of the activity ratio Na/H in solution. Solid solution formation is rationalized within the structural context of uranyl mineral sheet structure topologies and interlayer water properties.

  8. Phase equilibria and transformations in the Ti-Al-Nb system

    NASA Astrophysics Data System (ADS)

    Mishurda, Joseph Constantine

    The phase equilibria and transformations in the Nb-Ti-Al system in the vicinity of the Sigma phase field have been examined with respect to the Liquidus Surface (Phase 1), the Phase Equilibria and Equilibrium Transformations (Phase II), and the Phase Transformations, Mechanisms and Kinetics (Phase III). Eight alloy compositions were produced by arc melting. The alloys were characterized by differential thermal analysis, metallography, X-ray diffraction, scanning electron microscopy (BSEI), electron probe microanalysis and transmission electron microscopy. The liquidus examination shed new light on previous microstructural interpretations, opening up new possibilities for microstructural development and control of multiphase alloys. Differential thermal analysis has identified the existence of a beta to sigma + gamma transformation in an alloy where it was not previously thought to exist. The results differed from the calculated diagram by higher titanium solubility in the sigma and delta phases than predicted at lower temperatures and a lower solubility of alpha2 and gamma. The high temperature betao transforms to gamma + sigma in a eutectoid fashion resulting in a desirable lamellar structure of sigma and gamma. The existence of a new body centered tetragonal crystal structure ao = 5.11A and co 28.12A with a point group symmetry of P4/mmm, at 700°C was discovered. A plethel section was found for the sigma + beta two phase alloys. A betao + O + sigma three phase field passes through the alloys between 981 and 1000°C. The plethel section at the transformation has an eutectoid characteristic, however, the nature of the transformation changes to a peritectoid. At temperatures below 970°C, the first transformation to occur is the decomposition of the metastable betao phase to an intermediate metastable phase O'. Reasonable values for Q were obtained, applicable to the diffusion limited region of the TTT-curve. The microstructure evolution of the sigma + beta

  9. High-Temperature Phase Equilibria of Duplex Stainless Steels Assessed with a Novel In-Situ Neutron Scattering Approach

    NASA Astrophysics Data System (ADS)

    Pettersson, Niklas; Wessman, Sten; Hertzman, Staffan; Studer, Andrew

    2017-04-01

    Duplex stainless steels are designed to solidify with ferrite as the parent phase, with subsequent austenite formation occurring in the solid state, implying that, thermodynamically, a fully ferritic range should exist at high temperatures. However, computational thermodynamic tools appear currently to overestimate the austenite stability of these systems, and contradictory data exist in the literature. In the present work, the high-temperature phase equilibria of four commercial duplex stainless steel grades, denoted 2304, 2101, 2507, and 3207, with varying alloying levels were assessed by measurements of the austenite-to-ferrite transformation at temperatures approaching 1673 K (1400 °C) using a novel in-situ neutron scattering approach. All grades became fully ferritic at some point during progressive heating. Higher austenite dissolution temperatures were measured for the higher alloyed grades, and for 3207, the temperature range for a single-phase ferritic structure approached zero. The influence of temperatures in the region of austenite dissolution was further evaluated by microstructural characterization using electron backscattered diffraction of isothermally heat-treated and quenched samples. The new experimental data are compared to thermodynamic calculations, and the precision of databases is discussed.

  10. High-Temperature Phase Equilibria of Duplex Stainless Steels Assessed with a Novel In-Situ Neutron Scattering Approach

    NASA Astrophysics Data System (ADS)

    Pettersson, Niklas; Wessman, Sten; Hertzman, Staffan; Studer, Andrew

    2017-01-01

    Duplex stainless steels are designed to solidify with ferrite as the parent phase, with subsequent austenite formation occurring in the solid state, implying that, thermodynamically, a fully ferritic range should exist at high temperatures. However, computational thermodynamic tools appear currently to overestimate the austenite stability of these systems, and contradictory data exist in the literature. In the present work, the high-temperature phase equilibria of four commercial duplex stainless steel grades, denoted 2304, 2101, 2507, and 3207, with varying alloying levels were assessed by measurements of the austenite-to-ferrite transformation at temperatures approaching 1673 K (1400 °C) using a novel in-situ neutron scattering approach. All grades became fully ferritic at some point during progressive heating. Higher austenite dissolution temperatures were measured for the higher alloyed grades, and for 3207, the temperature range for a single-phase ferritic structure approached zero. The influence of temperatures in the region of austenite dissolution was further evaluated by microstructural characterization using electron backscattered diffraction of isothermally heat-treated and quenched samples. The new experimental data are compared to thermodynamic calculations, and the precision of databases is discussed.

  11. Phase equilibria and liquid phase epitaxy growth of PbSnSeTe lattice matched to PbSe

    NASA Technical Reports Server (NTRS)

    Mccann, Patrick J.; Fonstad, Clifton G.; Fuchs, Jacob; Feit, Ze'ev

    1987-01-01

    The necessary phase diagram data for growing lattice-matched layers of PbSnSeTe on PbSe are presented. Solid compounds of Pb(1-x)Sn(x)Se(1-y)Te(y) lattice-matched to PbSe were grown from liquid melts consisting of (Pb/1-x/Sn/x/)(1-z)(Se/1-y/Te/y/)(z); phase equilibria data were determined together with liquidus data for values of x(liquid) from 0 to 40 percent and y(liquid) from 0 to 40 percent for temperatures between 450 and 540 C. It was found that relatively large amounts of Te must be added to the melt to achieve lattice matching because of its low segregation coefficient relative to Se. A significant lattice-pulling effect was discovered for the 5-percent Sn case, and a similar effect is expected for the 10- and 20-percent Sn cases.

  12. Phase equilibria and liquid phase epitaxy growth of PbSnSeTe lattice matched to PbSe

    NASA Technical Reports Server (NTRS)

    Mccann, Patrick J.; Fonstad, Clifton G.; Fuchs, Jacob; Feit, Ze'ev

    1987-01-01

    The necessary phase diagram data for growing lattice-matched layers of PbSnSeTe on PbSe are presented. Solid compounds of Pb(1-x)Sn(x)Se(1-y)Te(y) lattice-matched to PbSe were grown from liquid melts consisting of (Pb/1-x/Sn/x/)(1-z)(Se/1-y/Te/y/)(z); phase equilibria data were determined together with liquidus data for values of x(liquid) from 0 to 40 percent and y(liquid) from 0 to 40 percent for temperatures between 450 and 540 C. It was found that relatively large amounts of Te must be added to the melt to achieve lattice matching because of its low segregation coefficient relative to Se. A significant lattice-pulling effect was discovered for the 5-percent Sn case, and a similar effect is expected for the 10- and 20-percent Sn cases.

  13. Petrogenesis of Mt. Baker Basalts and Andesites: Constraints From Mineral Chemistry and Phase Equilibria

    NASA Astrophysics Data System (ADS)

    Mullen, E.; McCallum, I. S.

    2009-12-01

    Basalts in continental arcs are volumetrically subordinate to andesites and this is the case for Mt. Baker in the northern Cascade magmatic arc. However, basalts provide indirect evidence on mantle compositions and processes that produce magmas parental to the abundant andesites and dacites of the stratocones. Basalts at Mt. Baker erupted from monogenetic vents peripheral to the andesitic stratocone. Flows are variable in composition; some samples would more appropriately be classified as basaltic andesites. The “basalts” have relatively low Mg/(Mg+Fe) indicating that they have evolved from their original compositions. Samples studied are Park Butte, Tarn Plateau, Lk. Shannon, Sulphur Cr. basalts, and Cathedral Crag, Hogback, and Rankin Ridge basaltic andesites. Mt. Baker lavas belong to the calc-alkaline basalt suite (CAB) defined by Bacon et al. (1997) and preserve arc geochemical features. High alumina olivine tholeiite (HAOT) are absent. Equilibrium mineral pairs and whole rock compositions were used to calculate pre-eruptive temperatures, water contents, and redox states of the “basalts.” All samples have zoned olivine phenocrysts with Fo68 to Fo87 cores and chromite inclusions. Cpx and zoned plagioclase occur in all flows, but opx occurs only in Cathedral Crag, Rankin Ridge, and Tarn Plateau. Ti-magnetite and ilmenite coexist in all flows except for Sulphur Cr., Lk. Shannon and Hogback, which contain a single Fe-Ti oxide. Liquidus temperatures range from 1080 to 1232°C and are negatively correlated with water contents. Water contents estimated using liquidus depression due to H2O (0.8 to 5.4 wt.%) agree well with plag core-whole rock equilibria estimates (1.2 to 3.9 wt.%). Park Butte, Sulphur Cr. and Lk. Shannon had <1.5 wt.% H2O, and Cathedral Crag is most hydrous. Redox states from ol-chr pairs (QFM +0.1 to +2.8) and Fe-Ti oxide pairs (QFM -0.6 to +1.8) indicate that Park Butte and Sulphur Cr. are most oxidized and Cathedral Crag most reduced

  14. Phase equilibria of (Mg,Fe)2SiO4 at the Earth's upper mantle conditions from first-principles studies

    NASA Astrophysics Data System (ADS)

    Yu, Yonggang G.; Vinograd, Victor L.; Winkler, Björn; Wentzcovitch, Renata M.

    2013-04-01

    Phase equilibria of α, β, and γ (Mg,Fe)2SiO4 are important to understanding the mineralogy of the Earth's upper mantle. Using the first principles approach, we studied thermodynamic properties and phase stability fields of Fe2SiO4. We show that the correct phase transition sequence in Fe2SiO4 (α → γ) can be obtained with the DFT + self-consistent Hubbard U method, while standard DFT methods (LSDA and σ-GGA) as well as the DFT + constant U method fail the task. The vibrational virtual crystal approximation was used to derive the phonon density of state of the Fe2SiO4 polymorphs. High-pressure thermodynamic properties of Fe2SiO4 are then derived with the aid of the quasi-harmonic approximation. They are in very good agreement with experiments. The phase diagram of the (Mg,Fe)2SiO4 system is calculated under the assumption of ideal mixing within α, β, and γ solid solutions. The model permits the investigation of the temperature and pressure effects on the phase boundaries. The widths of the divariant α-β and β-γ loops are barely sensitive to temperature between 1473 and 1873 K. This study shows the promise of applying the DFT + self-consistent Hubbard U method to study phase equilibria of iron-bearing Earth minerals.

  15. Phase Equilibria of Sn-Sb-Ag Ternary System (II): Calculation

    NASA Astrophysics Data System (ADS)

    Gierlotka, Wojcieh; Huang, Yu-Chih; Chen, Sinn-Wen

    2008-12-01

    Knowledge of the phase equilibria of the Sn-Sb-Ag ternary system is of fundamental importance in Sn-Sb-based solder applications. Thermodynamic models of the ternary Sn-Sb-Ag system and the binary Sb-Ag and Sn-Ag systems are developed using the calculation of phase diagrams (CALPHAD) method. The calculated 250 °C isothermal section, liquidus projection, and thermodynamic properties are in good agreement with the experimental results. There are two continuous solid solutions formed between the ɛ-Ag3Sn and ɛ-Ag3Sb, and ζ-Ag17Sb3 and ζ-Ag5Sn phases, but there is no ternary compound. There are three class II ternary invariant reactions, L + Sb ↔ ɛ + β-SnSb, L + β-SnSb ↔ Sn3Sb2 + ɛ, and L + Sn3Sb2 ↔ Sn + ɛ. Their reaction temperatures are 379 °C, 313 °C, and 231 °C, respectively.

  16. Direct molecular dynamics simulation of liquid-solid phase equilibria for a three-component plasma.

    PubMed

    Hughto, J; Horowitz, C J; Schneider, A S; Medin, Zach; Cumming, Andrew; Berry, D K

    2012-12-01

    The neutron-rich isotope ²²Ne may be a significant impurity in carbon and oxygen white dwarfs and could impact how the stars freeze. We perform molecular dynamics simulations to determine the influence of ²²Ne in carbon-oxygen-neon systems on liquid-solid phase equilibria. Both liquid and solid phases are present simultaneously in our simulation volumes. We identify liquid, solid, and interface regions in our simulations using a bond angle metric. In general we find good agreement for the composition of liquid and solid phases between our MD simulations and the semianalytic model of Medin and Cumming. The trace presence of a third component, neon, does not appear to strongly impact the chemical separation found previously for two-component carbon and oxygen systems. This suggests that small amounts of ²²Ne may not qualitatively change how the material in white dwarf stars freezes. However, we do find systematically lower melting temperatures (higher Γ) in our MD simulations compared to the semianalytic model. This difference seems to grow with impurity parameter Q_{imp} and suggests a problem with simple corrections to the linear mixing rule for the free energy of multicomponent solid mixtures that is used in the semianalytic model.

  17. In y Co4Sb12 Skutterudite: Phase Equilibria and Crystal Structure

    NASA Astrophysics Data System (ADS)

    Grytsiv, A.; Rogl, P.; Michor, H.; Bauer, E.; Giester, G.

    2013-10-01

    Phase relations were investigated for the In-Co-Sb system in the temperature range from 375°C to 800°C using as-cast and annealed alloys. Phase equilibria in the CoSb-InSb-(Sb) composition triangle are presented by a series of isothermal sections and solidus and liquidus surfaces, accompanied by a Schulz-Scheil reaction scheme. The indium-filled skutterudite In y Co4Sb12 already forms an equilibrium with liquid at 484°C, which might limit high-temperature applications of In-Co-Sb-based skutterudites. The maximal solubility of indium in In y Co4Sb12 ( y = 0.22) remains almost constant in the temperature range from 475°C to 700°C and corresponds to the equilibrium with CoSb2 and InSb. The solubility of indium in the skutterudite phase is reduced to y = 0.09 when it coexists in equilibrium with InSb and (Sb), and this decrease of the solubility might be responsible for the formation of InSb precipitates. Temperature-dependent x-ray single-crystal and specific heat data for In y Co4Sb12 were employed to determine the rattling behavior of In atoms in the skutterudite lattice.

  18. Direct molecular dynamics simulation of liquid-solid phase equilibria for a three-component plasma

    NASA Astrophysics Data System (ADS)

    Hughto, J.; Horowitz, C. J.; Schneider, A. S.; Medin, Zach; Cumming, Andrew; Berry, D. K.

    2012-12-01

    The neutron-rich isotope 22Ne may be a significant impurity in carbon and oxygen white dwarfs and could impact how the stars freeze. We perform molecular dynamics simulations to determine the influence of 22Ne in carbon-oxygen-neon systems on liquid-solid phase equilibria. Both liquid and solid phases are present simultaneously in our simulation volumes. We identify liquid, solid, and interface regions in our simulations using a bond angle metric. In general we find good agreement for the composition of liquid and solid phases between our MD simulations and the semianalytic model of Medin and Cumming. The trace presence of a third component, neon, does not appear to strongly impact the chemical separation found previously for two-component carbon and oxygen systems. This suggests that small amounts of 22Ne may not qualitatively change how the material in white dwarf stars freezes. However, we do find systematically lower melting temperatures (higher Γ) in our MD simulations compared to the semianalytic model. This difference seems to grow with impurity parameter Qimp and suggests a problem with simple corrections to the linear mixing rule for the free energy of multicomponent solid mixtures that is used in the semianalytic model.

  19. Solid-Phase Equilibria in the Au-As, Au-Ga-Sb, Au-In-As, and Au-In-Sb Ternaries.

    DTIC Science & Technology

    1986-02-28

    AD6i5 469 SOLID- PHASE EQUILIBRIA IN THE Ru-As AU-GA-SB AU-IN-AS- 1/17 AND AU-IN-SB TERNAR (U) CALIFORNIA UNIV LOS ANGELES DEPT OF CHEMISTRY AND...REPORT & PERIOD COVERED SOLID- PHASE EQUILIBRIA IN THE Au-Ga-As, Au-Ga-Sb Thchnical Report Au-In-As, and Au-In-Sb TEARIEIS S. PERFORMING ORG. REPORT NUMBER...CLASSIFICATION OF THIS PAGEMI*n Does Entepd) 4./ lie- . .- - - - - -- -- Solid Phase Equilibria in the Au-Ga-As, Au-Ga-Sb, Au-In-As, and Au-In-Sb Ternaries C

  20. Grand canonical Monte Carlo simulations of vapor-liquid equilibria using a bias potential from an analytic equation of state.

    PubMed

    Castillo Sanchez, Juan Manuel; Danner, Timo; Gross, Joachim

    2013-06-21

    This article introduces an efficient technique for the calculation of vapor-liquid equilibria of fluids. Umbrella Sampling Monte Carlo simulations in the grand canonical ensemble were conducted for various types of molecules. In Umbrella Sampling, a weight function is used for allowing the simulation to reach unlikely states in the phase space. In the present case this weight function, that allows the system to overcome the energetic barrier between a vapor and liquid phase, was determined by a trivialized Density Functional Theory (DFT) using the PC-SAFT equation of state. The implementation presented here makes use of a multicanonical ensemble approach to divide the space of fluctuating particle number N into various subsystems. The a priori estimate of the weight function from the analytic DFT allows the parallelization of the calculation, which significantly reduces the computation time. In addition, it is shown that the analytic equation of state can be used to substitute sampling the dense liquid phase, where the sampling of insertion and deletion moves become demanding.

  1. Large-aperture variable-volume view cell for the determination of phase-equilibria in high pressure systems and supercritical fluids

    NASA Astrophysics Data System (ADS)

    Licence, Peter; Dellar, Martin P.; Wilson, Richard G. M.; Fields, Peter A.; Litchfield, David; Woods, Helen M.; Poliakoff, Martyn; Howdle, Steven M.

    2004-10-01

    A high-pressure, variable-volume view cell incorporating a custom engineered, optically transparent sapphire piston is described. The view cell has an unbroken field of vision that enables the entire sample volume to be observed at all times. When lit from the rear of the cell, a near perfect view of any physical transition or change in state is available to the experimenter. The system has been shown to be particularly suitable for the determination of phase equilibria and cloud point measurements in supercritical fluid systems and has been rated for experiments up to 400 bar, 200 °C.

  2. Processing, phase equilibria and environmental degradation of molybdenum (silicom,aluminum)(2) intermetallic compound

    NASA Astrophysics Data System (ADS)

    Eason, Paul Duane

    The Mo(Si,Al)2 C40 compound was chosen for investigation as a possible high temperature structural material. To produce the C40 phase, several processing routes were explored with emphasis on obtaining microstructure/property relationships (i.e. control of grain size and minimization of secondary phases). To facilitate processing of single phase material, the phase equilibria of the Mo-Si-Al ternary system were reevaluated with respect to the phases adjacent to the C40 compound. An anomalous environmental degradation appeared to be the primary obstacle to further study of the compound and was investigated accordingly. Several processing routes were assessed for the production of dense, nearly single-phase Mo(Si,Al)2. Hot powder compaction was chosen as the method of sample production as is the case with many refractory silicide based materials. Therefore, variations in the processing techniques came from the choice of precursor materials and methods of powder production. Mechanical alloying, arc-melting and comminution, and blending of both elemental and compound powders were all employed to produce charges for hot uniaxial pressing. The final compacts were compared on the basis of density, grain size and presence of secondary phases. Establishment of a Mo-Si-Al ternary isothermal phase diagram at 1400°C was performed. Multiphase alloy compositions were selected to identify the phase boundaries of the C40, C54, T1 and Mo3Al8 phase fields, as well as to verify the existence of the C54 phase at 1400°C. The alloys were equilibrated by heat treatment and analyzed for phase identification and quantitative compositional information. The environmental degradation phenomenon was approached as a classical "pest" with an emphasis of study on grain boundary chemistry and atmospheric dependence of attack. Both Auger spectroscopy and electron microscopy revealed carbon-impurity-induced grain boundary segregation responsible for the embrittlement and material loss. Means of

  3. Isotropic-nematic phase equilibria of hard-sphere chain fluids-Pure components and binary mixtures.

    PubMed

    Oyarzún, Bernardo; van Westen, Thijs; Vlugt, Thijs J H

    2015-02-14

    The isotropic-nematic phase equilibria of linear hard-sphere chains and binary mixtures of them are obtained from Monte Carlo simulations. In addition, the infinite dilution solubility of hard spheres in the coexisting isotropic and nematic phases is determined. Phase equilibria calculations are performed in an expanded formulation of the Gibbs ensemble. This method allows us to carry out an extensive simulation study on the phase equilibria of pure linear chains with a length of 7 to 20 beads (7-mer to 20-mer), and binary mixtures of an 8-mer with a 14-, a 16-, and a 19-mer. The effect of molecular flexibility on the isotropic-nematic phase equilibria is assessed on the 8-mer+19-mer mixture by allowing one and two fully flexible beads at the end of the longest molecule. Results for binary mixtures are compared with the theoretical predictions of van Westen et al. [J. Chem. Phys. 140, 034504 (2014)]. Excellent agreement between theory and simulations is observed. The infinite dilution solubility of hard spheres in the hard-sphere fluids is obtained by the Widom test-particle insertion method. As in our previous work, on pure linear hard-sphere chains [B. Oyarzún, T. van Westen, and T. J. H. Vlugt, J. Chem. Phys. 138, 204905 (2013)], a linear relationship between relative infinite dilution solubility (relative to that of hard spheres in a hard-sphere fluid) and packing fraction is found. It is observed that binary mixtures greatly increase the solubility difference between coexisting isotropic and nematic phases compared to pure components.

  4. Isotropic-nematic phase equilibria of hard-sphere chain fluids—Pure components and binary mixtures

    NASA Astrophysics Data System (ADS)

    Oyarzún, Bernardo; van Westen, Thijs; Vlugt, Thijs J. H.

    2015-02-01

    The isotropic-nematic phase equilibria of linear hard-sphere chains and binary mixtures of them are obtained from Monte Carlo simulations. In addition, the infinite dilution solubility of hard spheres in the coexisting isotropic and nematic phases is determined. Phase equilibria calculations are performed in an expanded formulation of the Gibbs ensemble. This method allows us to carry out an extensive simulation study on the phase equilibria of pure linear chains with a length of 7 to 20 beads (7-mer to 20-mer), and binary mixtures of an 8-mer with a 14-, a 16-, and a 19-mer. The effect of molecular flexibility on the isotropic-nematic phase equilibria is assessed on the 8-mer+19-mer mixture by allowing one and two fully flexible beads at the end of the longest molecule. Results for binary mixtures are compared with the theoretical predictions of van Westen et al. [J. Chem. Phys. 140, 034504 (2014)]. Excellent agreement between theory and simulations is observed. The infinite dilution solubility of hard spheres in the hard-sphere fluids is obtained by the Widom test-particle insertion method. As in our previous work, on pure linear hard-sphere chains [B. Oyarzún, T. van Westen, and T. J. H. Vlugt, J. Chem. Phys. 138, 204905 (2013)], a linear relationship between relative infinite dilution solubility (relative to that of hard spheres in a hard-sphere fluid) and packing fraction is found. It is observed that binary mixtures greatly increase the solubility difference between coexisting isotropic and nematic phases compared to pure components.

  5. Postperovskite phase equilibria in the MgSiO3-Al2O3 system.

    PubMed

    Tsuchiya, Jun; Tsuchiya, Taku

    2008-12-09

    We investigate high-P,T phase equilibria of the MgSiO(3)-Al(2)O(3) system by means of the density functional ab initio computation methods with multiconfiguration sampling. Being different from earlier studies based on the static substitution properties with no consideration of Rh(2)O(3)(II) phase, present calculations demonstrate that (i) dissolving Al(2)O(3) tends to decrease the postperovskite transition pressure of MgSiO(3) but the effect is not significant ( approximately -0.2 GPa/mol% Al(2)O(3)); (ii) Al(2)O(3) produces the narrow perovskite+postperovskite coexisting P,T area (approximately 1 GPa) for the pyrolitic concentration (x(Al2O3) approximately 6 mol%), which is sufficiently responsible to the deep-mantle D'' seismic discontinuity; (iii) the transition would be smeared (approximately 4 GPa) for the basaltic Al-rich composition (x(Al2O3) approximately 20 mol%), which is still seismically visible unless iron has significant effects; and last (iv) the perovskite structure spontaneously changes to the Rh(2)O(3)(II) with increasing the Al concentration involving small displacements of the Mg-site cations.

  6. New Computational Approach to Determine Liquid-Solid Phase Equilibria of Water Confined to Slit Nanopores.

    PubMed

    Kaneko, Toshihiro; Bai, Jaeil; Yasuoka, Kenji; Mitsutake, Ayori; Zeng, Xiao Cheng

    2013-08-13

    We devise a new computational approach to compute solid-liquid phase equilibria of confined fluids. Specifically, we extend the multibaric-multithermal ensemble method with an anisotropic pressure control to achieve the solid-liquid phase equilibrium for confined water inside slit nanopores (with slit width h ranging from 5.4 Å to 7.2 Å). A unique feature of this multibaric-multithermal ensemble is that the freezing points of confined water can be determined from the heat-capacity peaks. The new approach has been applied to compute the freezing point of two monolayer ices, namely, a high-density flat rhombic monolayer ice (HD-fRMI) and a high-density puckered rhombic monolayer ice (HD-pRMI) observed in our simulation. We find that the liquid-to-solid transition temperature (or the freezing point) of HD-pRMI is dependent on the slit width h, whereas that of HD-fRMI is nearly independent of the h.

  7. Phase equilibria and modeling of ammonium ionic liquid, C2NTf2, solutions.

    PubMed

    Domańska, Urszula; Marciniak, Andrzej; Królikowski, Marek

    2008-01-31

    Novel quaternary ammonium ionic liquid, ethyl(2-hydroxyethyl)dimethylammonium bis(trifluomethylsulfonyl)imide (C2NTf2), has been prepared from N,N-dimethylethanolamine as a substrate. The paper includes a specific basic characterization of the synthesized compound by NMR and the basic thermophysical properties: the melting point, enthalpy of fusion, enthalpy of solid-solid phase transition, glass transition determined by the differential scanning calorimetry (DSC), temperature of decomposition, and water content. The density of the new compound was measured. The solid-liquid or liquid-liquid phase equilibria of binary mixtures containing {C2NTf2+water or an alcohol (propan-1-ol, butan-1-ol, hexan-1-ol, octan-1-ol, decan-1-ol), aromatic hydrocarbons (benzene, toluene), aliphatic hydrocarbons (n-hexane, n-octane), dimethylsulfoxide (DMSO), or tetrahydrofuran (THF)} have been measured by a dynamic method in a wide range of temperatures from 230 to 430 K. These data were correlated by means of the nonrandom two-liquid (NRTL) equation utilizing temperature-dependent parameters derived from the solid-liquid or liquid-liquid equilibrium. From the solubility results, the negative value of the partition coefficient of ionic liquid in binary system octan-1-ol/water (log P) at 298.15 K has been calculated.

  8. Phase equilibria in fullerene-containing systems as a basis for development of manufacture and application processes for nanocarbon materials

    NASA Astrophysics Data System (ADS)

    Semenov, K. N.; Charykov, N. A.; Postnov, V. N.; Sharoyko, V. V.; Murin, I. V.

    2016-01-01

    This review is the first attempt to integrate the available data on all types of phase equilibria (solubility, extraction and sorption) in systems containing light fullerenes (C60 and C70). In the case of solubility diagrams, the following types of phase equilibria are considered: individual fullerene (C60 or C70)-solvent under polythermal and polybaric conditions; C60-C70-solvent, individual fullerene-solvent(1)-solvent(2), as well as multicomponent systems comprising a single fullerene or an industrial mixture of fullerenes and vegetable oils, animal fats or essential oils under polythermal conditions. All published experimental data on the extraction equilibria in C60-C70-liquid phase(1)-liquid phase(2) systems are described systematically and the sorption characteristics of various materials towards light fullerenes are estimated. The possibility of application of these experimental data for development of pre-chromatographic and chromatographic methods for separation of fullerene mixtures and application of fullerenes as nanomodifiers are described. The bibliography includes 87 references.

  9. Phase equilibria of molecular fluids via hybrid Monte Carlo Wang-Landau simulations: applications to benzene and n-alkanes.

    PubMed

    Desgranges, Caroline; Delhommelle, Jerome

    2009-06-28

    In recent years, powerful and accurate methods, based on a Wang-Landau sampling, have been developed to determine phase equilibria. However, while these methods have been extensively applied to study the phase behavior of model fluids, they have yet to be applied to molecular systems. In this work, we show how, by combining hybrid Monte Carlo simulations in the isothermal-isobaric ensemble with the Wang-Landau sampling method, we determine the vapor-liquid equilibria of various molecular fluids. More specifically, we present results obtained on rigid molecules, such as benzene, as well as on flexible chains of n-alkanes. The reliability of the method introduced in this work is assessed by demonstrating that our results are in excellent agreement with the results obtained in previous work on simple fluids, using either transition matrix or conventional Monte Carlo simulations with a Wang-Landau sampling, and on molecular fluids, using histogram reweighting or Gibbs ensemble Monte Carlo simulations.

  10. First-order mean-spherical approximation for interfacial phenomena: a unified method from bulk-phase equilibria study.

    PubMed

    Tang, Yiping

    2005-11-22

    The recently proposed first-order mean-spherical approximation (FMSA) [Y. Tang, J. Chem. Phys. 121, 10605 (2004)] for inhomogeneous fluids is extended to the study of interfacial phenomena. Computation is performed for the Lennard-Jones fluid, in which all phase equilibria properties and direct correlation function for density-functional theory are developed consistently and systematically from FMSA. Three functional methods, including fundamental measure theory for the repulsive force, local-density approximation, and square-gradient approximation, are applied in this interfacial investigation. Comparisons with the latest computer simulation data indicate that FMSA is satisfactory in predicting surface tension, density profile, as well as relevant phase equilibria. Furthermore, this work strongly suggests that FMSA is very capable of unifying homogeneous and inhomogeneous fluids, as well as those behaviors outside and inside the critical region within one framework.

  11. Proteolytic Equilibria of Vanillic Acid in the Ground and Excited States

    NASA Astrophysics Data System (ADS)

    Vusovich, O. V.; Tchaikovskaya, O. N.; Sokolova, I. V.; Vasil‧eva, N. Yu.

    2016-03-01

    Proteolytic equilibria of vanillic acid in aqueous solutions were studied using electronic spectroscopy. The pH ranges for anionic, dianionic, cationic, and neutral forms of vanillic acid in the ground and excited states were determined. The electron density distribution on atoms in the proteolytic forms was determined using quantum-chemistry methods. The anion formed as a result of dissociation of the carboxylic acid. The dianion formed in the presence of two and more equivalents of alkali as a result of proton loss from the phenol and carboxylic acid. The vanillic acid cation formed via protonation of the carbonyl oxygen. Differences in spectral features of the proteolytic forms in the ground and excited states were observed.

  12. Clathrate formation and phase equilibria in the thiourea-bromoform system

    NASA Astrophysics Data System (ADS)

    Chekhova, G. N.; Shubin, Yu. V.; Pinakov, D. V.; Alferova, N. I.

    2008-07-01

    Phase equilibria in the thiourea (host)-bromoform (guest) binary system were studied by physicochemical analysis methods over the temperature range 270 455 K. The stoichiometry and stability region were determined for the channel-type compound CHBr3 · 2.40(2)(NH2)2CS; the compound was observed for the first time. When heated, the clathrate incongruently decomposed at 424.0 ± 0.8 K to rhombic thiourea and the guest component. The solubility isotherm of the thiourea-bromoform-acetic acid system was studied to find that the compound was thermodynamically stable at 293 K over the range of guest component concentrations 100 35 wt %. A decrease in its content in an equilibrium mother liquor resulted in the appearance of X-ray diffraction reflections of the initial host α polymorph. Rhombohedral cell parameters were determined (space group R-3 c, a = 15.89(1) Å, c = 12.40(1) Å, V = 2711(6) Å3, d calcd = 2.000 g/cm3, and d expt = 1.98(2) g/cm3). The mode of packing of bromoform molecules was compared with the organization of the guest subsystem in inclusion compounds formed by the substances studied.

  13. Phase equilibria of haloalkanes dissolved in ethylsulfate- or ethylsulfonate-based ionic liquids.

    PubMed

    Deive, Francisco J; Rodríguez, Ana; Pereiro, Ana B; Shimizu, Karina; Forte, Paulo A S; Romão, Carlos C; Canongia Lopes, José N; Esperança, José M S S; Rebelo, Luís P N

    2010-06-03

    The temperature-composition phase diagrams of 40 binary mixtures composed of a haloalkane dissolved in either 1-ethyl-3-methylimidazolium ethylsulfate or 1-ethyl-3-methylimidazolium ethylsulfonate were measured from ambient temperature to the boiling point temperature of the solute. The coexistence curves corresponding to liquid-liquid equilibria (LLE) boundaries were visually determined and the experimental results have been correlated using either the nonrandom two-liquid (NRTL) model or a set of empirical equations capable of describing the corresponding upper critical solution temperatures (UCSTs) loci. The different types of LLE behavior were discussed in terms of the type of ionic liquid solvent, the alkyl-chain length of the solute, and the type and pattern of halogen substitution present in the haloalkane. Auxiliary simulation data (obtained by ab initio or by molecular dynamics methods) were used to corroborate some of the experimental findings. Also, they correlate in a semiquantitative way the observed LLE behavior with the dipole moments of the different solutes.

  14. An efficient and general approach for implementing thermodynamic phase equilibria information in geophysical and geodynamic studies

    NASA Astrophysics Data System (ADS)

    Afonso, Juan Carlos; Zlotnik, Sergio; Díez, Pedro

    2015-10-01

    We present a flexible, general, and efficient approach for implementing thermodynamic phase equilibria information (in the form of sets of physical parameters) into geophysical and geodynamic studies. The approach is based on Tensor Rank Decomposition methods, which transform the original multidimensional discrete information into a separated representation that contains significantly fewer terms, thus drastically reducing the amount of information to be stored in memory during a numerical simulation or geophysical inversion. Accordingly, the amount and resolution of the thermodynamic information that can be used in a simulation or inversion increases substantially. In addition, the method is independent of the actual software used to obtain the primary thermodynamic information, and therefore, it can be used in conjunction with any thermodynamic modeling program and/or database. Also, the errors associated with the decomposition procedure are readily controlled by the user, depending on her/his actual needs (e.g., preliminary runs versus full resolution runs). We illustrate the benefits, generality, and applicability of our approach with several examples of practical interest for both geodynamic modeling and geophysical inversion/modeling. Our results demonstrate that the proposed method is a competitive and attractive candidate for implementing thermodynamic constraints into a broad range of geophysical and geodynamic studies. MATLAB implementations of the method and examples are provided as supporting information and can be downloaded from the journal's website.

  15. Visual investigation of solid-liquid phase equilibria for nonflammable mixed refrigerant

    NASA Astrophysics Data System (ADS)

    Lee, C.; Yoo, J.; Park, I.; Park, J.; Cha, J.; Jeong, S.

    2015-12-01

    Non-flammable mixed refrigerant (NF-MR) Joule Thomson (J-T) refrigerators have desirable characteristics and wide cooling temperature range compared to those of pure J-T refrigerators. However, the operating challenge due to freezing is a critical issue to construct this refrigerator. In this paper, the solid-liquid phase equilibria (i.e. freezing point) of the NF-MR which is composed of Argon, R14 (CF4), and R218 (C3F8), has been experimentally investigated by a visualized apparatus. Argon, R14 and R218 mixtures are selected to be effectively capable of reaching 100 K in the MR J-T refrigerator system. Freezing points of the mixtures have been measured with the molar compositions from 0.1 to 0.8 for each component. Each test result is simultaneously acquired by a camcorder for visual inspection and temperature measurement during a warming process. Experimental results show that the certain mole fraction of Argon, R14, and R218 mixture can achieve remarkably low freezing temperature even below 77 K. This unusual freezing point depression characteristic of the MR can be a useful information for designing a cryogenic MR J-T refrigerator to reach further down to 77 K.

  16. The Gibbs free energy of nukundamite (Cu3.38Fe0.62S4): A correction and implications for phase equilibria

    USGS Publications Warehouse

    Seal, R.R.; Inan, E.E.; Hemingway, B.S.

    2001-01-01

    The Gibbs free energy of formation of nukundamite (Cu3.38Fe0.62S4) was calculated from published experimental studies of the reaction 3.25 Cu3.38Fe0.62S4 + S2 = 11 CuS + 2 FeS2 in order to correct an erroneous expression in the published record. The correct expression describing the Gibbs free energy of formation (kJ???mol-1) of nukundamite relative to the elements and ideal S2 gas is ??fG?? nukundamite T(K) = -549.75 + 0.23242 T + 3.1284 T0.5, with an uncertainty of 0.6%. An evaluation of the phase equilibria of nukundamite with associated phases in the system Cu-Fe-S as a function of temperature and sulfur fugacity indicates that nukundamite is stable from 224 to 501??C at high sulfidation states. At its greatest extent, at 434??C, the stability field of nukundamite is only 0.4 log f(S2) units wide, which explains its rarity. Equilibria between nukundamite and bornite, which limit the stability of both phases, involve bornite compositions that deviate significantly from stoichiometric Cu5FeS4. Under equilibrium conditions in the system Cu-Fe-S, nukundamite + chalcopyrite is not a stable assemblage at any temperature.

  17. Vapor-liquid phase equilibria of potassium chloride-water mixtures: Equation-of-state representation for KCl-H2O and NaCl-H2O

    USGS Publications Warehouse

    Hovey, J.K.; Pitzer, Kenneth S.; Tanger, J.C.; Bischoff, J.L.; Rosenbauer, R.J.

    1990-01-01

    Measurements of isothermal vapor-liquid compositions for KCl-H2O as a function of pressure are reported. An equation of state, which was originally proposed by Pitzer and was improved and used by Tanger and Pitzer to fit the vapor-liquid coexistence surface for NaCl-H2O, has been used for representation of the KCl-H2O system from 300 to 410??C. Improved parameters are also reported for NaCl-H2O from 300 to 500??C. ?? 1990 American Chemical Society.

  18. Local equilibria and state transfer of charged classical particles on a helix in an electric field

    NASA Astrophysics Data System (ADS)

    Plettenberg, J.; Stockhofe, J.; Zampetaki, A. V.; Schmelcher, P.

    2017-01-01

    We explore the effects of a homogeneous external electric field on the static properties and dynamical behavior of two charged particles confined to a helix. In contrast to the field-free setup which provides a separation of the center-of-mass and relative motion, the existence of an external force perpendicular to the helix axis couples the center-of-mass to the relative degree of freedom leading to equilibria with a localized center of mass. By tuning the external field various fixed points are created and/or annihilated through different bifurcation scenarios. We provide a detailed analysis of these bifurcations based on which we demonstrate a robust state transfer between essentially arbitrary equilibrium configurations of the two charges that can be induced by making the external force time dependent.

  19. Liquid-Liquid Phase Equilibria and Interactions between Droplets in Water-in-Oil Microemulsions.

    PubMed

    Yin, Tianxiang; Wang, Mingjie; Tao, Xiaoyi; Shen, Weiguo

    2016-12-20

    The liquid-liquid phase equilibria of [water/sodium bis(2-ethylhexyl)sulfosuccinate (AOT)/n-decane] with the molar ratio w0 of water to AOT being 37.9 and [water/AOT/ethoxylated-2,5,8,11-tetramethyl-6-dodecyne-5,8-diol(Dynol-604)/n-decane] with w0 = 37.9 and the mole fraction α of Dynol-604 in the total surfactants being 0.158 were measured in this study. From the data collected in the critical region, the critical exponent β corresponding to the width of the coexistence curve was determined, which showed good agreement with the 3D-Ising value. A thermodynamic approach based on the Carnahan-Starling-van der Waals type equation was proposed to describe the coexistence curves and to deduce the interaction properties between droplets in the microemulsions. The interaction enthalpies were found to be positive for the studied systems, which evidenced that the entropy effect dominated the phase separations as the temperature increased. The addition of Dynol-604 into the (water/AOT/n-decane) microemulsion resulted in the decrease in the critical temperature and the interaction enthalpy. Combining the liquid-liquid equilibrium data for (water/AOT/n-decane) microemulsions with various w0 values determined previously, it was shown that the interaction enthalpy decreased with w0 and tended to change its sign at low w0, which coincided with the results from the isothermal titration calorimetry investigation. All of these behaviors were interpreted by the effects of entropy and enthalpy and their competition, which resulted from the release of solvent molecules entrapped in the interface of microemulsion droplets and were dependent on the rigidity of the surfactant layers and the size of the droplet.

  20. Phase equilibria in the system CO 2-H 2O I: New equilibrium relations at low temperatures

    NASA Astrophysics Data System (ADS)

    Longhi, John

    2005-02-01

    Graphical analysis of free-energy relationships involving binary quadruple points and their associated univariant equilibria in the system CO 2-H 2O suggests the presence of at least 2 previously unrecognized quadruple points and a degenerate binary invariant point involving an azeotrope between CO 2-rich gas and liquid. Thermodynamic data extracted from the equilibrium involving clathrate (hydrate), gas, and ice (H = G+I) are employed along with published data to calculate the P-T range of the 3-ice equilibrium curve, S+I = H, where S is solid CO 2. This equilibrium curve intersects the H = G+I curve approximately where the latter curve intersects the S+H = G curve, thus confirming the existence of one of the inferred quadruple points involving the phases S, G, H, and I. Recognition of some binary equilibria probably have been hampered by extremely low mutual solubilities of CO 2 and H 2O in the fluids phases which, for example, render the S+H = G virtually indistinguishable from the CO 2-sublimation curve. To make the published portion of the L(liquid CO 2)-G-H equilibrium "connect" with the other new quadruple point involving S, L, G, and H, it is necessary to change the sense of the equilibrium from L = G+H at higher pressures to L+H = G at lower pressures by positing a L = G azeotrope at very low concentrations of H 2O. At the low-pressure origin of the azeotrope, which is only a few bars above the CO 2-triple point, the azeotrope curve intersects the 3-phase curve tangentially, creating a degenerate invariant point at which the 3-phase equilibrium changes from L+H = G at lower pressures to L = G+H at higher pressures. The azeotrope curve is offset at slightly lower temperature from the L = G+H curve until the 3-phase equilibrium terminates at the quadruple point involving G, L, H, and W (water). With further increase in pressure the azeotrope curve tracks the L = G+W equilibrium and apparently terminates at a critical end point in close proximity to critical

  1. CRYOCHEM, Thermodynamic Model for Cryogenic Chemical Systems: Solid-Vapor and Solid-Liquid-Vapor Phase Equilibria Toward Applications on Titan and Pluto

    NASA Astrophysics Data System (ADS)

    Tan, S. P.; Kargel, J. S.; Adidharma, H.; Marion, G. M.

    2014-12-01

    Until in-situ measurements can be made regularly on extraterrestrial bodies, thermodynamic models are the only tools to investigate the properties and behavior of chemical systems on those bodies. The resulting findings are often critical in describing physicochemical processes in the atmosphere, surface, and subsurface in planetary geochemistry and climate studies. The extremely cold conditions on Triton, Pluto and other Kuiper Belt Objects, and Titan introduce huge non-ideality that prevents conventional models from performing adequately. At such conditions, atmospheres as a whole—not components individually—are subject to phase equilibria with their equilibrium solid phases or liquid phases or both. A molecular-based thermodynamic model for cryogenic chemical systems, referred to as CRYOCHEM, the development of which is still in progress, was shown to reproduce the vertical composition profile of Titan's atmospheric methane measured by the Huygens probe (Tan et al., Icarus 2013, 222, 53). Recently, the model was also used to describe Titan's global circulation where the calculated composition of liquid in Ligeia Mare is consistent with the bathymetry and microwave absorption analysis of T91 Cassini fly-by data (Tan et al., 2014, submitted). Its capability to deal with equilibria involving solid phases has also been demonstrated (Tan et al., Fluid Phase Equilib. 2013, 360, 320). With all those previous works done, our attention is now shifting to the lower temperatures in Titan's tropopause and on Pluto's surface, where much technical development remains for CRYOCHEM to assure adequate performance at low temperatures. In these conditions, solid-vapor equilibrium (SVE) is the dominant phase behavior that determines the composition of the atmosphere and the existing ices. Another potential application is for the subsurface phase equilibrium, which also involves liquid, thus three-phase equilibrium: solid-liquid-vapor (SLV). This presentation will discuss the

  2. High temperature phase equilibria studies in the Bi-Sr-Ca-Cu-O-Ag system

    SciTech Connect

    Margulies, Lawrence

    1999-11-08

    A variety of experimental techniques were utilized to examine the high temperature phase equilibria in the Bi-Sr-Ca-Cu-O-Ag system. Quenching studies were used to determine the liquid solubility of Ag in the Bi2Sr2CaCu2O8 (Bi2212) melt and the details of the peritectic decomposition pathway of Bi2212 as a function on Ag content and oxygen partial pressure (PO2). A liquid immiscibility region between oxide and Ag liquids in the 8--98 at% range was found above 900 C. Two eutectics were found in the Bi2212-Ag pseudobinary. On the oxide rich side, a eutectic exists at approximately 4 at% Ag. On the Ag rich side, a eutectic exists at approximately 98 at% Ag at a temperature of 15 C below the melting point of pure Ag. Six distinct solid phases were found to be in equilibrium with the partial melt within the Ag content and PO2 range studied. The stability of these solid phases were found to be highly sensitive to PO2, and to a much lesser extent Ag content. High temperature x-ray diffraction (HTXRD) studies of this system are in conflict with these results. It is suggested that these discrepancies are due to experimental artifacts caused by the significant thermal gradients and lack of full bulk sampling which is inherent in conventional HTXRD designs. In part 2, a new furnace design compatible with synchrotron radiation sources is introduced to address these problems. This design allows for full bulk sampling in a low thermal gradient environment using Debye-Scherrer transmission geometry. Sample spinning is also introduced in the design to eliminate preferred orientation and incomplete powder averaging and allow for quantitative phase analysis and structural refinement. Studies on model systems are presented to demonstrate the capabilities for high resolution structural studies (Al2O3) and time resolved phase transformation studies (SrCO3). Finally, the Bi2212

  3. Thermodynamics and Phase Equilibria of Concurrent Assimilation and Fractional Crystallization (AFC) in Crustal Magma Bodies

    NASA Astrophysics Data System (ADS)

    Creamer, J. B.; Spera, F. J.; Bohrson, W. A.; Ghiorso, M. S.

    2009-12-01

    Mafic magmas generated by partial melting of mantle peridotites, eclogites or clinopyroxenites are hotter than, compositionally distinct from and have higher liquidus temperatures than the crustal rocks through which they ascend or are emplaced. The low thermal conductivity of crystalline and molten silicates implies that steep thermal gradients along the margins of propagating melt-filled fractures and stagnant magma bodies can develop and lead to crustal anatexis especially at depths >~10 km. Small differences in ambient deviatoric stresses within the crust can lead to the percolation of anatectic melts into adjacent magma. The magnitude of contamination is strongly dependant upon permeability which in turn depends upon the square of the volume fraction of anatectic melt, itself controlled by local phase equilibria. From the thermochemical vantage, AFC processes may be quantified using the Magma Chamber Simulator (MCS) by studying the variables that define the extent of AFC: thermal interaction mass ratio (ratio of pristine magma mass to mass of wallrock), bulk composition (including volatiles) of pristine magma and wallrock, the mean pressure and prevailing oxygen fugacity at which AFC occurs. Here we present MCS phase equilibria and major element solutions for a number of scenarios in which the sensible variables defining the extent of assimilation have been systematically varied. In particular, initial magma and wallrock temperatures, relative masses of wallrock and magma, oxygen fugacity and the mean pressure of AFC interaction are defined. The sub-systems are then allowed to proceed towards thermodynamic (thermal and chemical potential) equilibrium. Incremental enthalpy changes associated with magma cooling and crystallization are transferred to wallrock where heating and possible partial melting can occur. Fractional crystallization occurs in the magma and once the wallrock temperature exceeds its solidus, equilibrium melting in wallrock is enabled. When

  4. Re-investigation of phase equilibria in the system Al-Cu and structural analysis of the high-temperature phase η1-Al1-δCu.

    PubMed

    Ponweiser, Norbert; Lengauer, Christian L; Richter, Klaus W

    2011-11-01

    The phase equilibria and reaction temperatures in the system Al-Cu were re-investigated by a combination of optical microscopy, powder X-ray diffraction (XRD) at ambient and elevated temperature, differential thermal analysis (DTA) and scanning electron microscopy (SEM). A full description of the phase diagram is given. The phase equilibria and invariant reactions in the Cu-poor part of the phase diagram could be confirmed. The Cu-rich part shows some differences in phase equilibria and invariant reactions compared to the known phase diagram. A two phase field was found between the high temperature phase η1 and the low temperature phase η2 thus indicating a first order transition. In the ζ1/ζ2 region of the phase diagram recent findings on the thermal stability could be widely confirmed. Contrary to previous results, the two phase field between δ and γ1 is very narrow. The results of the current work indicate the absence of the high temperature β0 phase as well as the absence of a two phase field between γ1 and γ0 suggesting a higher order transition between γ1 and γ0. The structure of γ0 (I-43m, Cu5Zn8-type) was confirmed by means of high-temperature XRD. Powder XRD was also used to determine the structure of the high temperature phase η1-Al1-δCu. The phase is orthorhombic (space group Cmmm) and the lattice parameters are a = 4.1450(1) Å, b = 12.3004(4) Å and c = 8.720(1) Å; atomic coordinates are given.

  5. Thermodynamics and phase equilibria involving nano phases in the Cu-Ag system.

    PubMed

    Hajra, J P; Acharya, S

    2004-09-01

    The surface tensions of the Cu-Ag system have been evaluated using Butler's equations. Since the evaluation is dependent on the thermodynamic properties of the surface phases, they are calculated based on the first and second order differentials of the surface tension at infinite dilution. The present study establishes significant differences in the properties between the surface phase and bulk phases of the system. The study of the adsorption behaviour finds silver to be surface active relative to copper, which results in the preferential adsorption of silver in the alloys. Furthermore, in view of the differences in terms of fundamental thermodynamic properties between the two phases coupled with the volume-to-radius ratio as depicted by the Thomson-Freundlich concept, the nano phases of the system exhibit a pronounced increase in the adsorption behaviour relative to that of the planar interface of the system. As expected based on the above combined effect of the surface properties, present research shows a considerable decrease in the melting points of the metals, solid-solid, solid-liquid transition and eutectic temperature with a consequent increase in the solubilities of the terminal phases of the system.

  6. Leveraging Gibbs Ensemble Molecular Dynamics and Hybrid Monte Carlo/Molecular Dynamics for Efficient Study of Phase Equilibria.

    PubMed

    Gartner, Thomas E; Epps, Thomas H; Jayaraman, Arthi

    2016-11-08

    We describe an extension of the Gibbs ensemble molecular dynamics (GEMD) method for studying phase equilibria. Our modifications to GEMD allow for direct control over particle transfer between phases and improve the method's numerical stability. Additionally, we found that the modified GEMD approach had advantages in computational efficiency in comparison to a hybrid Monte Carlo (MC)/MD Gibbs ensemble scheme in the context of the single component Lennard-Jones fluid. We note that this increase in computational efficiency does not compromise the close agreement of phase equilibrium results between the two methods. However, numerical instabilities in the GEMD scheme hamper GEMD's use near the critical point. We propose that the computationally efficient GEMD simulations can be used to map out the majority of the phase window, with hybrid MC/MD used as a follow up for conditions under which GEMD may be unstable (e.g., near-critical behavior). In this manner, we can capitalize on the contrasting strengths of these two methods to enable the efficient study of phase equilibria for systems that present challenges for a purely stochastic GEMC method, such as dense or low temperature systems, and/or those with complex molecular topologies.

  7. Phase equilibria and salting-out effects in a cesium nitrate-triethylamine-water system at 5-25°C

    NASA Astrophysics Data System (ADS)

    Il'in, K. K.; Cherkasov, D. G.

    2013-04-01

    Phase equilibria and critical phenomena in a cesium nitrate-water-triethylamine system in which the constituent binary liquid system is stratified at the lower critical solution temperature (LCST) is studied in a range of 5-25°C by the visual polythermal method. It is found that introducing cesium nitrate into the water-triethylamine system leads to a slight reduction in the LCST (from 18.3 to 16.3°C) and to a decrease in the mutual solubility of the components. The distribution coefficients of triethylamine between aqueous and the organic phases of the monotectic state at different temperatures are calculated. It is found that the salting-out of triethylamine from aqueous solutions by cesium nitrate increases with rising temperature. The results of the salting-out effect of sodium, potassium, and cesium nitrates on a water-triethylamine binary system are compared.

  8. Selective adsorption and phase equilibria of confined fluids: Density-functional theory and Monte Carlo simulation

    NASA Astrophysics Data System (ADS)

    Sowers, Susanne Lynn

    1997-11-01

    Microporous sorbents such as carbons, silicas and aluminas are used commercially in a variety of separation, purification and selective reaction applications. A detailed study of the effects of the porous material characteristics on the adsorption equilibrium properties such as selectivity and phase equilibria of fluid mixtures can enhance our understanding of adsorption on a molecular level. Such knowledge will improve our utilization of such adsorbents and provide a tool for directing the future of tailoring sorbents for particular separation processes. The effect of pore size, shape and pressure on the selective adsorption of trace pollutants from an inert gas was studied using prototype mixtures of Lennard-Tones (LJ) N2/CCl4, CF4, and SO2. Both nonlocal density functional theory (DFT) and grand canonical Monte Carlo (GCMC) molecular simulations were used in order to investigate the validity of the theory, which is much quicker and easier to use. Our results indicate that there is an optimal pore size and shape for which the pollutant selectivity is greatly enhanced. In many industrial adsorption processes relative humidity can greatly affect the life of an adsorbent bed, as seen in breakthrough curves. Therefore, the influence of water vapor on the selective adsorption of CCl4 from a mixture of N2/CCl4/H20 in activated carbon was studied using GCMC simulations. The equilibrium adsorption properties are found to be dependent upon both the density of active sites on the pore walls and the relative humidity. Liquid-liquid transitions in porous materials are of interest in connection with oil recovery, lubrication, coating technology and pollution control. The results of a study on the effect of confinement on the liquid-liquid equilibrium of binary LJ mixtures using DFT are compared with those of molecular simulation and experiments. Our findings show that the phase coexistence for the confined mixture is in general decreased and shifted toward the component which

  9. Effect of Fluorine on Near-Liquidus Phase Equilibria of Basalts

    NASA Technical Reports Server (NTRS)

    Filiberto, Justin; Wood, Justin; Loan, Le; Dasgupta, Rajdeep; Shimizu, Nobumichi; Treiman, Allan H.

    2010-01-01

    Volatile species such as H2O, CO2, F, and Cl have significant impact in generation and differentiation of basaltic melts. Thus far experimental work has primarily focused on the effect of water and carbon dioxide on basalt crystallization, liquid-line of descent, and mantle melting [e.g., 1, 2] and the effects of halogens have received far less attention [3-4]. However, melts in the planetary interiors can have non-negligible chlorine and fluorine concentrations. Here, we explore the effects of fluorine on near-liquidus phase equilibria of basalt. We have conducted nominally anhydrous piston cylinder experiments using graphite capsules at 0.6 - 1.5 GPa on an Fe-rich model basalt composition. 1.75 wt% fluorine was added to the starting mix in the form of AgF2. Fluorine in the experimental glass was measured by SIMS and major elements of glass and minerals were analyzed by EPMA. Nominally volatile free experiments yield a liquidus temperature from 1330 C at 0.8GPa to 1400 at 1.6GPa and an olivine(Fo72)-pyroxene(En68)-liquid multiple saturation point at 1.25 GPa and 1375 C. The F-bearing experiments yield a liquiudus temperature from 1260 C at 0.6GPa to 1305 at 1.5GPa and an ol(Fo66)-pyx(En64)-MSP at 1 GPa and 1260 C. This shows that F depresses the basalt liquidus, extends the pyroxene stability field to lower pressure, and forces the liquidus phases to be more Fe-rich. KD(Fe-Mg/mineral-melt) calculated for both pyroxenes and olivines show an increase with increasing F content of the melt. Therefore, we infer that F complexes with Mg in the melt and thus increases the melt s silica activity, depressing the liquidus and changing the composition of the crystallizing minerals. Our study demonstrates that on a weight percent basis, the effect of fluorine is similar to the effect of H2O [1] and Cl [3] on freezing point depression of basalts. But on an atomic fraction basis, the effect of F on liquidus depression of basalts is xxxx compared to the effect of H. Future

  10. Heat capacity and phase equilibria of almandine, Fe3Al2Si3O12

    USGS Publications Warehouse

    Anovitz, Lawrence M.; Essene, E.J.; Metz, G.W.; Bohlen, S.R.; Westrum, E.F.; Hemingway, B.S.

    1993-01-01

    The heat capacity of a synthetic almandine, Fe3Al2Si3O12, was measured from 6 to 350 K using equilibrium, intermittent-heating quasi-adiabatic calorimetry and from 420 to 1000 K using differential scanning calorimetry. These measurements yield Cp298 = 342.80 ?? 1.4 J/mol ?? K and S298o = 342.60 J/mol ?? K. Mo??ssbauer characterizations show the almandine to contain less than 2 ?? 1% of the total iron as Fe3+. X-ray diffraction studies of this synthetic almandine yield a = 11.521 ?? 0.001 A?? and V298o = 115.11 +- 0.01 cm3/mol, somewhat smaller than previously reported. The low-temperature Cp data indicate a lambda transition at 8.7 K related to an antiferromagnetic-paramagnetic transition with TN = 7.5 K. Modeling of the lattice contribution to the total entropy suggests the presence of entropy in excess of that attributable to the effects of lattice vibrations and the magnetic transition. This probably arises from a low-temperature electronic transition (Schottky contribution). Combination of the Cp data with existing thermodynamic and phase equilibrium data on almandine yields ??Gf,298o = -4938.3 kJ/mol and ??Hf,298o= -5261.3 kJ/mol for almandine when calculated from the elements. The equilibrium almandine = hercynite + fayalite + quartz limits the upper T P for almandine and is metastably located at ca. 570??C at P = 1 bar, with a dP dT of +17 bars/??C. This agrees well with reversed experiments on almandine stability when they are corrected for magnetite and hercynite solid-solutions. In {norm of matrix}O2-T space, almandine oxidizes near QFM by the reactions almandine + O2 = magnetite + sillimanite + quartz and almandine + 02 = hercynite + magnetite + quartz. With suitable correction for reduced activities of solid phases, these equilibria provide useful oxygen barometers for medium- to high-grade metamorphic rocks. ?? 1993.

  11. Prediction of the phase equilibria of methane hydrates using the direct phase coexistence methodology

    NASA Astrophysics Data System (ADS)

    Michalis, Vasileios K.; Costandy, Joseph; Tsimpanogiannis, Ioannis N.; Stubos, Athanassios K.; Economou, Ioannis G.

    2015-01-01

    The direct phase coexistence method is used for the determination of the three-phase coexistence line of sI methane hydrates. Molecular dynamics (MD) simulations are carried out in the isothermal-isobaric ensemble in order to determine the coexistence temperature (T3) at four different pressures, namely, 40, 100, 400, and 600 bar. Methane bubble formation that results in supersaturation of water with methane is generally avoided. The observed stochasticity of the hydrate growth and dissociation processes, which can be misleading in the determination of T3, is treated with long simulations in the range of 1000-4000 ns and a relatively large number of independent runs. Statistical averaging of 25 runs per pressure results in T3 predictions that are found to deviate systematically by approximately 3.5 K from the experimental values. This is in good agreement with the deviation of 3.15 K between the prediction of TIP4P/Ice water force field used and the experimental melting temperature of ice Ih. The current results offer the most consistent and accurate predictions from MD simulation for the determination of T3 of methane hydrates. Methane solubility values are also calculated at the predicted equilibrium conditions and are found in good agreement with continuum-scale models.

  12. Prediction of the phase equilibria of methane hydrates using the direct phase coexistence methodology

    SciTech Connect

    Michalis, Vasileios K.; Costandy, Joseph; Economou, Ioannis G.; Tsimpanogiannis, Ioannis N.; Stubos, Athanassios K.

    2015-01-28

    The direct phase coexistence method is used for the determination of the three-phase coexistence line of sI methane hydrates. Molecular dynamics (MD) simulations are carried out in the isothermal–isobaric ensemble in order to determine the coexistence temperature (T{sub 3}) at four different pressures, namely, 40, 100, 400, and 600 bar. Methane bubble formation that results in supersaturation of water with methane is generally avoided. The observed stochasticity of the hydrate growth and dissociation processes, which can be misleading in the determination of T{sub 3}, is treated with long simulations in the range of 1000–4000 ns and a relatively large number of independent runs. Statistical averaging of 25 runs per pressure results in T{sub 3} predictions that are found to deviate systematically by approximately 3.5 K from the experimental values. This is in good agreement with the deviation of 3.15 K between the prediction of TIP4P/Ice water force field used and the experimental melting temperature of ice Ih. The current results offer the most consistent and accurate predictions from MD simulation for the determination of T{sub 3} of methane hydrates. Methane solubility values are also calculated at the predicted equilibrium conditions and are found in good agreement with continuum-scale models.

  13. Prediction of the phase equilibria of methane hydrates using the direct phase coexistence methodology.

    PubMed

    Michalis, Vasileios K; Costandy, Joseph; Tsimpanogiannis, Ioannis N; Stubos, Athanassios K; Economou, Ioannis G

    2015-01-28

    The direct phase coexistence method is used for the determination of the three-phase coexistence line of sI methane hydrates. Molecular dynamics (MD) simulations are carried out in the isothermal-isobaric ensemble in order to determine the coexistence temperature (T3) at four different pressures, namely, 40, 100, 400, and 600 bar. Methane bubble formation that results in supersaturation of water with methane is generally avoided. The observed stochasticity of the hydrate growth and dissociation processes, which can be misleading in the determination of T3, is treated with long simulations in the range of 1000-4000 ns and a relatively large number of independent runs. Statistical averaging of 25 runs per pressure results in T3 predictions that are found to deviate systematically by approximately 3.5 K from the experimental values. This is in good agreement with the deviation of 3.15 K between the prediction of TIP4P/Ice water force field used and the experimental melting temperature of ice Ih. The current results offer the most consistent and accurate predictions from MD simulation for the determination of T3 of methane hydrates. Methane solubility values are also calculated at the predicted equilibrium conditions and are found in good agreement with continuum-scale models.

  14. Phase equilibria, crystal structure and oxygen content of intermediate phases in the Y-Ba-Co-O system

    NASA Astrophysics Data System (ADS)

    Urusova, A. S.; Cherepanov, V. A.; Aksenova, T. V.; Gavrilova, L. Ya.; Kiselev, E. A.

    2013-06-01

    The phase equilibria in the Y-Ba-Co-O system were systematically studied at 1373 K in air. The intermediate phases formed in the Y-Ba-Co-O system at 1373 K in air were: YBaCo2O5+δ, YBaCo4O7 and BaCo1-yYyO3-δ (0.09≤y≤0.42). It was shown that YBaCo2O5+δ possesses tetragonal structure with the 3ap×3ap×2ap superstructure (sp. gr. P4/mmm). High-temperature X-ray diffraction analysis of the YBaCo2O5+δ in the temperature range from 298 K up to 1073 K under Po2=0.21 аtm has not shown any phase transformations. The value of oxygen content for the YBaCo2O5+δ at room temperature was estimated as 5.40 and at 1323 K it was equal to 5.04. Thermal expansion of sample shows a linear characteristics and the average thermal expansion coefficient (TEC) is about 13.8×10-6, K-1 in the temperature range 298-1273 K. The homogeneity range and crystal structure of the BaCo1-yYyO3-δ (0.09≤y≤0.42) solid solutions were determined by X-ray diffraction of quenched samples. All BaCo1-yYyO3-δ solid solutions were found to have cubic structure (sp. gr. Pm3m). The unit cell parameters were refined using Rietveld full-profile analysis. Oxygen nonstoichiometry of BaCo1-yYyO3-δ solid solutions with 0.1≤y≤0.4 was measured by means of thermogravimetric technique within the temperature range 298-1373 K in air. Thermal expansion of BaCo1-yYyO3-δ (у=0.0; 0.1; 0.2; 0.3) samples was studied within the temperature range 298-1200 K in air. The projection of isothermal-isobaric phase diagram for the Y-Ba-Co-O system to the compositional triangle of metallic components was presented.

  15. Vapor-liquid equilibria simulation and an equation of state contribution for dipole-quadrupole interactions.

    PubMed

    Vrabec, Jadran; Gross, Joachim

    2008-01-10

    A systematic investigation on vapor-liquid equilibria (VLEs) of dipolar and quadrupolar fluids is carried out by molecular simulation to develop a new Helmholtz energy contribution for equations of state (EOSs). Twelve two-center Lennard-Jones plus point dipole and point quadrupole model fluids (2CLJDQ) are studied for different reduced dipolar moments micro*2=6 or 12, reduced quadrupolar moments Q*2=2 or 4 and reduced elongations L*=0, 0.505, or 1. Temperatures cover a wide range from about 55% to 95% of the critical temperature of each fluid. The NpT+test particle method is used for the calculation of vapor pressure, saturated densities, and saturated enthalpies. Critical data and the acentric factor are obtained from fits to the simulation data. On the basis of this data, an EOS contribution for the dipole-quadrupole cross-interactions of nonspherical molecules is developed. The expression is based on a third-order perturbation theory, and the model constants are adjusted to the present 2CLJDQ simulation results. When applied to mixtures, the model is found to be in excellent agreement with results from simulation and experiment. The new EOS contribution is also compatible with segment-based EOS, such as the various forms of the statistical associating fluid theory EOS.

  16. DEVELOPMENT OF A HIGH-TEMPERATURE CERAMIC BRAZE: ANALYSIS OF PHASE EQUILIBRIA IN THE Pd-Ag-CuOx SYSTEM

    SciTech Connect

    Weil, K. Scott; Darsell, Jens T.

    2006-01-18

    This paper describes the effects of small palladium additions on the phase equilibria in the Ag-CuOx system. Below a concentration of 5 mol%, palladium was found to increase the temperature of the eutectic reaction present in the pseudobinary system, but have little effect on a higher temperature monotectic reaction. However once enough palladium was added to increase the pseudoternary solidus temperature to that of the lower boundary for this three-phase field (~970°C), the lower boundary begins to increase in temperature as well. The addition of palladium also causes the original eutectic point to move to lower silver concentrations, which also causes a convergence of the two new three-phase fields, CuOx + L1 + L2 and CuOx + α + L1. This suggests that with higher palladium concentrations, a peritectic reaction, α + L1 + L2 → CuOx, may eventually be observed in the system.

  17. Liquid/gas and liquid/liquid phase equilibria of the system water/bovine serum albumin.

    PubMed

    Antonov, Yurij; Eckelt, John; Sugaya, Rei; Wolf, Bernhard A

    2013-05-09

    The thermodynamic behavior of the system H2O/BSA was studied at 25 °C within the entire composition range: vapor pressure measurements via head space sampling gas chromatography demonstrate that the attainment of equilibria takes more than one week. A miscibility gap was detected via turbidity and the coexisting phases were analyzed. At 6 °C the two phase region extends from ca. 34 to 40 wt % BSA; it shrinks upon heating. The polymer rich phase is locally ordered, as can be seen under the optical microscope using crossed polarizers. The Flory-Huggins theory turns out to be inappropriate for the modeling of experimental results. A phenomenological expression is employed which uses three adjustable parameters and describes the vapor pressures quantitatively; it also forecasts the existence of a miscibility gap.

  18. Effect of three-body interactions on the vapor-liquid phase equilibria of binary fluid mixtures.

    PubMed

    Wang, Liping; Sadus, Richard J

    2006-08-21

    Gibbs-Duhem Monte Carlo simulations are reported for the vapor-liquid phase coexistence of binary argon+krypton mixtures at different temperatures. The calculations employ accurate two-body potentials in addition to contributions from three-body dispersion interactions resulting from third-order triple-dipole interactions. A comparison is made with experiment that illustrates the role of three-body interactions on the phase envelope. In all cases the simulations represent genuine predictions with input parameters obtained independently from sources other than phase equilibria data. Two-body interactions alone are insufficient to adequately describe vapor-liquid coexistence. In contrast, the addition of three-body interactions results in very good agreement with experiment. In addition to the exact calculation of three-body interactions, calculations are reported with an approximate formula for three-body interactions, which also yields good results.

  19. Breakup of a transient wetting layer in polymer blend thin films: unification with 1D phase equilibria.

    PubMed

    Coveney, Sam; Clarke, Nigel

    2013-09-20

    We show that lateral phase separation in polymer blend thin films can proceed via the formation of a transient wetting layer which breaks up to give a laterally segregated film. We show that the growth of lateral inhomogeneities at the walls in turn causes the distortion of the interface in the transient wetting layer. By addressing the 1D phase equilibria of a polymer blend thin film confined between selectively attracting walls, we show that the breakup of a transient wetting layer is due to wall-blend interactions; there are multiple values of the volume fraction at the walls which solve equilibrium boundary conditions. This mechanism of lateral phase separation should be general.

  20. Calculation of Phase Equilibria in the Y2O3-Yb2O3-ZrO2 System

    NASA Technical Reports Server (NTRS)

    Jacobson, Nathan S.; Liu, Zi-Kui; Kaufman, Larry; Zhang, Fan

    2001-01-01

    Rare earth oxide stabilized zirconias find a wide range of applications. An understanding of phase equilibria is essential to all applications. In this study, the available phase boundary data and thermodynamic data is collected and assessed. Calphad-type databases are developed to completely describe the Y2O3-ZrO2, Yb2O3-ZrO2, and Y2O3-Yb2O3 systems. The oxide units are treated as components and regular and subregular solution models are used. The resultant calculated phase diagrams show good agreement with the experimental data. Then the binaries are combined to form the database for the Y2O3-Yb2O3-ZrO2 psuedo-ternary.

  1. Effect of Fluorine on Near-Liquidus Phase Equilibria of Basalts

    NASA Astrophysics Data System (ADS)

    Filiberto, J.; Wood, J.; Le, L.; Dasgupta, R.; Shimizu, N.; Treiman, A. H.

    2010-12-01

    Volatile species, such as H2O, CO2, F, and Cl, are important in the generation and differentiation of basaltic melts. Thus far, experimental work has focused primarily on the effects of water and carbon dioxide on basalt crystallization, liquid-line of descent, and mantle melting [e.g., 1, 2]; the effects of halogens have received far less attention [3-4]. However, melts in the planetary interiors can have non-negligible chlorine and fluorine concentrations. Here, we explore the effects of fluorine on near-liquidus phase equilibria of a basalt. We have conducted nominally anhydrous piston cylinder experiments, in graphite capsules, at 0.6 - 1.5 GPa on an Fe-rich model basalt composition. 1.75 wt% fluorine was added to the starting mix as AgF2. Fluorine abundances in the experimental glass were measured by SIMS, and major element abundances in glass and minerals were analyzed by EPMA. Nominally volatile free experiments yield liquidus temperatures from 1330 °C at 0.8 GPa to 1400 °C at 1.6 GPa with an olivine (Fo72)-pyroxene (En68)-liquid multiple saturation at 1.25 GPa and 1375°C. The F-bearing experiments yield liquidus temperatures from 1260 °C at 0.6 GPa to 1305 °C at 1.5 GPa with an olivine (Fo66)-pyroxene (En64)-MSP at 1 GPa and 1260°C. This shows that F depresses the basalt liquidus, extends the pyroxene stability field to lower pressure, and forces the liquidus phases to be more Fe-rich. Mineral-melt Fe2+-Mg KD calculated for both pyroxenes and olivines increase with increasing F content of the melt. Therefore, we infer that F complexes with Mg in the melt and thus increases the melt’s silica activity, depresses the liquidus, and changes the composition of the crystallizing minerals. Our study demonstrates that on a weight percent basis, the effect of fluorine is similar to those of H2O [1] and Cl [3] on freezing point depression of basalts. But on an atomic percent basis, the effect of F on liquidus depression of basalts is 1.5-2 times greater than

  2. On the geometric phase in the spatial equilibria of nonlinear rods

    NASA Astrophysics Data System (ADS)

    Zhong, Peinan; Huang, Guojun; Yang, Guowei

    2017-01-01

    Geometric phases have natural manifestations in large deformations of geometrically exact rods. The primary concerns of this article are the physical implications and observable consequences of geometric phases arising from the deformed patterns exhibited by a rod subjected to end moments. This mechanical problem is classical and has a long tradition dating back to Kirchhoff. However, the perspective from geometric phases seems to go more deeply into relations between local strain states and global geometry of shapes, and infuses genuinely new insights and better understanding, which enable one to describe this kind of deformation in a neat and elegant way. On the other hand, visual representations of these deformations provide beautiful illustrations of geometric phases and render the meaning of the abstract concept of holonomy more direct and transparent.

  3. On the geometric phase in the spatial equilibria of nonlinear rods

    NASA Astrophysics Data System (ADS)

    Zhong, Peinan; Huang, Guojun; Yang, Guowei

    2017-04-01

    Geometric phases have natural manifestations in large deformations of geometrically exact rods. The primary concerns of this article are the physical implications and observable consequences of geometric phases arising from the deformed patterns exhibited by a rod subjected to end moments. This mechanical problem is classical and has a long tradition dating back to Kirchhoff. However, the perspective from geometric phases seems to go more deeply into relations between local strain states and global geometry of shapes, and infuses genuinely new insights and better understanding, which enable one to describe this kind of deformation in a neat and elegant way. On the other hand, visual representations of these deformations provide beautiful illustrations of geometric phases and render the meaning of the abstract concept of holonomy more direct and transparent.

  4. Sulfur in Hydrous, Oxidized Basaltic Magmas: Phase Equilibria and Melt Solubilities

    NASA Astrophysics Data System (ADS)

    Pichavant, M.; Scaillet, B.; di Carlo, I.; Rotolo, S.; Metrich, N.

    2006-05-01

    basalt, sulphides were found to coexist with anhydrite in a fO2 range as high as NNO+3.0. Melts at equilibrium with anhydrite have S concentrations, measured by electron microprobe, of 2070 ppm (basaltic andesite), 5600 ppm (K basalt) and 6500-6550 ppm (picritic basalt). These values reach concentrations similar to found previously for hydrous oxidized trachyandesite melts at 1000 ° C but are significantly less than recent determinations for dry basaltic melts saturated with sulfate at 1300 ° C. Two anhydrite-saturated glasses, investigated by XANES spectroscopy at the sulfur K-edge, show S to be present only as sulfate species. At lower fO2, between NNO and NNO+1, S concentrations in melts synthesized in AuPd capsules strongly decrease because most of the S present is sequestered in the Pd-rich phases. When Au capsules are used (basaltic andesite experiments), there is no marked effect of fO2 on S solubility in this fO2 range: 2250 ppm S (NNO+1.3, sulfide-saturated) vs. 2070 ppm S (NNO+4.1, anhydrite-saturated). This is consistent with the predominance of sulfate species at NNO+1.3 although sulfide species were also detected by XANES. Comparison between near-liquidus experiments with and without S shows no large influence of S on silicate phase equilibria. However, anhydrite crystallization removes a significant amount of Ca from the melt. This strongly affects melt chemistry, and induces major changes in the nature of liquidus silicate phases and in their composition.

  5. PHASE EQUILIBRIA INVESTIGATION OF BINARY, TERNARY, AND HIGHER ORDER SYSTEMS. PART IV. THE EFFECT OF MOLYBDENUM AND TUNGSTEN ON THE SUBCARBIDE SOLUTIONS IN THE VANADIUM-TANTALUM-CARBON AND NIOBIUM-TANTALUM-CARBON SYSTEMS.

    DTIC Science & Technology

    The phase equilibria investigations described in this report are in direct support of Air Force sponsored cutting tool research programs. The...the high temperature phase equilibria of possible alloy combinations is, therefore, a prerequisite for the fabrication of even test alloys. (Author)

  6. Calculations of phase equilibria for mixtures of triglycerides, fatty acids, and their esters in lower alcohols

    NASA Astrophysics Data System (ADS)

    Stepanov, D. A.; Ermakova, A.; Anikeev, V. I.

    2011-01-01

    The objects of study were mixtures containing triglycerides and lower alcohols and also the products of the transesterification of triglycerides, glycerol and fatty acid esters. The Redlich-Kwong-Soave equation of state was used as a thermodynamic model for the phase state of the selected mixtures over wide temperature, pressure, and composition ranges. Group methods were applied to determine the critical parameters of pure substances and their acentric factors. The parameters obtained were used to calculate the phase diagrams and critical parameters of mixtures containing triglycerides and lower alcohols and the products of the transesterification of triglycerides, glycerol and fatty acid esters, at various alcohol/oil ratios. The conditions of triglyceride transesterification in various lower alcohols providing the supercritical state of reaction mixtures were selected.

  7. Phase equilibria, crystal structure and oxygen content of intermediate phases in the Y–Ba–Co–O system

    SciTech Connect

    Urusova, A.S.; Cherepanov, V.A. Aksenova, T.V.; Gavrilova, L.Ya.; Kiselev, E.A.

    2013-06-01

    The phase equilibria in the Y–Ba–Co–O system were systematically studied at 1373 K in air. The intermediate phases formed in the Y–Ba–Co–O system at 1373 K in air were: YBaCo₂O5+δ, YBaCo₄O₇ and BaCo1–yYyO3–δ (0.09≤y≤0.42). It was shown that YBaCo₂O5+δ possesses tetragonal structure with the 3aₚ×3aₚ×2aₚ superstructure (sp. gr. P4/mmm). High-temperature X-ray diffraction analysis of the YBaCo₂O5+δ in the temperature range from 298 K up to 1073 K under Po₂=0.21 atm has not shown any phase transformations. The value of oxygen content for the YBaCo₂O5+δ at room temperature was estimated as 5.40 and at 1323 K it was equal to 5.04. Thermal expansion of sample shows a linear characteristics and the average thermal expansion coefficient (TEC) is about 13.8×10⁻⁶, K⁻¹ in the temperature range 298–1273 K. The homogeneity range and crystal structure of the BaCo1–yYyO3–δ (0.09≤y≤0.42) solid solutions were determined by X-ray diffraction of quenched samples. All BaCo1–yYyO3–δ solid solutions were found to have cubic structure (sp. gr. Pm3m). The unit cell parameters were refined using Rietveld full-profile analysis. Oxygen nonstoichiometry of BaCo1–yYyO3–δ solid solutions with 0.1≤y≤0.4 was measured by means of thermogravimetric technique within the temperature range 298–1373 K in air. Thermal expansion of BaCo1–yYyO3–δ (y=0.0; 0.1; 0.2; 0.3) samples was studied within the temperature range 298–1200 K in air. The projection of isothermal–isobaric phase diagram for the Y–Ba–Co–O system to the compositional triangle of metallic components was presented. - Graphical abstract: A projection of isobaric isothermal phase diagram of the Y–Ba–Co–O system to the metallic components

  8. Confinement-Induced Supercriticality and Phase Equilibria of Hydrocarbons in Nanopores.

    PubMed

    Luo, Sheng; Lutkenhaus, Jodie L; Nasrabadi, Hadi

    2016-11-08

    For over a century, the phase behavior of bulk fluids has been described as PVT (pressure-volume-temperature) three-dimensional properties, but it has become increasingly clear that the liquid-vapor phase behavior in confined geometries is significantly altered from the bulk. Efforts have been devoted to accessing confined phase transitions using sorption, molecular simulations, and theoretical methods. However, a comprehensive picture of PVT relationships for confined hydrocarbons remains uncertain. Herein, we introduce d (confining pore diameter) as a fourth dimension, and we present PVT-d behavior of confined fluids in nanopores. For the first time, a T-d phase diagram is presented for n-hexane, n-octane, and n-decane under multiple confinement scales (37.9, 14.8, 9.8, 6.0, 4.1, 3.3, and 2.2 nm cylindrical pore diameter) using experimental differential scanning calorimetry and PVT-d equation of state theory at atmospheric pressure. As pore diameter decreases from 37.9 to 4.1 nm, the bubble point increases by as much as 15 K above bulk, until we observe behavior consistent with a supercritical state, pointing to confinement-induced supercriticality. Remarkably, experimental and theoretical findings overlap very well, showing that this approach effectively captures the phase boundaries between the liquid, vapor, and supercritical fluid regions. The model and completed EOS are additionally extended to calculation of isothermal capillary adsorption, and its validity is discussed.

  9. A New Approach to Modeling Densities and Equilibria of Ice and Gas Hydrate Phases

    NASA Astrophysics Data System (ADS)

    Zyvoloski, G.; Lucia, A.; Lewis, K. C.

    2011-12-01

    The Gibbs-Helmholtz Constrained (GHC) equation is a new cubic equation of state that was recently derived by Lucia (2010) and Lucia et al. (2011) by constraining the energy parameter in the Soave form of the Redlich-Kwong equation to satisfy the Gibbs-Helmholtz equation. The key attributes of the GHC equation are: 1) It is a multi-scale equation because it uses the internal energy of departure, UD, as a natural bridge between the molecular and bulk phase length scales. 2) It does not require acentric factors, volume translation, regression of parameters to experimental data, binary (kij) interaction parameters, or other forms of empirical correlations. 3) It is a predictive equation of state because it uses a database of values of UD determined from NTP Monte Carlo simulations. 4) It can readily account for differences in molecular size and shape. 5) It has been successfully applied to non-electrolyte mixtures as well as weak and strong aqueous electrolyte mixtures over wide ranges of temperature, pressure and composition to predict liquid density and phase equilibrium with up to four phases. 6) It has been extensively validated with experimental data. 7) The AAD% error between predicted and experimental liquid density is 1% while the AAD% error in phase equilibrium predictions is 2.5%. 8) It has been used successfully within the subsurface flow simulation program FEHM. In this work we describe recent extensions of the multi-scale predictive GHC equation to modeling the phase densities and equilibrium behavior of hexagonal ice and gas hydrates. In particular, we show that radial distribution functions, which can be determined by NTP Monte Carlo simulations, can be used to establish correct standard state fugacities of 1h ice and gas hydrates. From this, it is straightforward to determine both the phase density of ice or gas hydrates as well as any equilibrium involving ice and/or hydrate phases. A number of numerical results for mixtures of N2, O2, CH4, CO2, water

  10. Transferable Potentials for Phase Equilibria. 4. United-Atom Description of Linear and Branched Alkenes and Alkylbenzenes

    SciTech Connect

    WICK,COLLIN D.; MARTIN,MARCUS G.; SIEPMANN,J. ILJA

    2000-07-12

    The Transferable Potentials for Phase Equilibria-United Atom (TraPPE-UA) force field for hydrocarbons is extended to alkenes and alkylbenzenes by introducing the following pseudo-atoms: CH{sub 2}(sp{sup 2}), CH(sp{sup 2}), CH(aro), R-C(aro) for the link to aliphatic side chains, and C(aro) for the link of two benzene rings. In this united-atom force field, the nonbonded interactions of the hydrocarbon pseudo-atoms are solely governed by Lennard-Jones 12-6 potentials, and the Lennard-Jones well depth and size parameters for the new pseudo-atoms were determined by fitting to the single-component vapor-liquid phase equilibria of a few selected model compounds. Configurational-bias Monte Carlo simulations in the NVT version of the Gibbs ensemble were carried out to calculate the single-component vapor-liquid coexistence curves for ethene, propene, 1-butene, trans- and cis-2-butene. 2-methylpropene, 1,5-hexadiene, 1-octene, benzene, toluene, ethylbenzene, propylbenzene, isopropylbenzene, o-, m-, and p-xylene, and naphthalene. The phase diagrams for the binary mixtures of (supercritical) ethene/n-heptane and benzene/n-pentane were determined from simulations in the NpT Gibbs ensemble. Although the TraPPE-UA force field is rather simple and makes use of relatively few different pseudo-atoms, its performance, as judged by comparisons to other popular force fields and available experimental data, is very satisfactory.

  11. Insight into the Am-O Phase Equilibria: A Thermodynamic Study Coupling High-Temperature XRD and CALPHAD Modeling.

    PubMed

    Epifano, Enrica; Guéneau, Christine; Belin, Renaud C; Vauchy, Romain; Lebreton, Florent; Richaud, Jean-Christophe; Joly, Alexis; Valot, Christophe; Martin, Philippe M

    2017-07-03

    In the frame of minor actinide transmutation, americium can be diluted in UO2 and (U, Pu)O2 fuels burned in fast neutron reactors. The first mandatory step to foresee the influence of Am on the in-reactor behavior of transmutation targets or fuel is to have fundamental knowledge of the Am-O binary system and, in particular, of the AmO2-x phase. In this study, we coupled HT-XRD (high-temperature X-ray diffraction) experiments with CALPHAD thermodynamic modeling to provide new insights into the structural properties and phase equilibria in the AmO2-x-AmO1.61+x-Am2O3 domain. Because of this approach, we were able for the first time to assess the relationships between temperature, lattice parameter, and hypostoichiometry for fcc AmO2-x. We showed the presence of a hyperstoichiometric existence domain for the bcc AmO1.61+x phase and the absence of a miscibility gap in the fcc AmO2-x phase, contrary to previous representations of the phase diagram. Finally, with the new experimental data, a new CALPHAD thermodynamic model of the Am-O system was developed, and an improved version of the phase diagram is presented.

  12. Phase Equilibria of the Carbon Dioxide + 1-Decanol System at High Pressures.

    PubMed

    Ioniţă, Simona; Feroiu, Viorel; Geană, Dan

    2013-11-14

    In this work experimental vapor-liquid equilibrium (VLE) data and three-phase vapor-liquid-liquid equilibrium (VLLE) data are presented for the carbon dioxide + 1-decanol system. The VLE data were measured at five temperatures, (303.2, 308.2, 323.2, 333.2, and 343.2) K, and pressures up to 16 MPa. The VLLE data cover pressure-temperature (P-T) values from 289 K and 5 MPa to the upper critical end point (UCEP). We have used two models to represent the complex fluid phase behavior (P-T critical curve, VLLE line, and VLE isotherms) of the carbon dioxide + 1-decanol system: the cubic general equation of state (GEOS) and Peng-Robinson (PR) equation in conjunction with van der Waals two parameters conventional mixing rules (2PCMR). A correlation method involving temperature-dependent interaction parameters and a semipredictive approach with independent temperature interaction parameters have been used. Comparisons with experimental data reported in this work and available in the literature indicate that the topology of fluid phase behavior is satisfactorily given by the semipredictive procedure both for the critical line and in subcritical region, considering the relative simple used cubic equations of state.

  13. Volumetric Properties and Fluid Phase Equilibria of CO2 + H2O

    SciTech Connect

    Capobianco, Ryan; Gruszkiewicz, Miroslaw {Mirek} S; Wesolowski, David J; Cole, David R; Bodnar, Robert

    2013-01-01

    The need for accurate modeling of fluid-mineral processes over wide ranges of temperature, pressure and composition highlighted considerable uncertainties of available property data and equations of state, even for the CO2 + H2O binary system. In particular, the solubility, activity, and ionic dissociation equilibrium data for the CO2-rich phase, which are essential for understanding dissolution/precipitation, fluid-matrix reactions, and solute transport, are uncertain or missing. In this paper we report the results of a new experimental study of volumetric and phase equilibrium properties of CO2 + H2O, to be followed by measurements for bulk and confined multicomponent fluid mixtures. Mixture densities were measured by vibrating tube densimetry (VTD) over the entire composition range at T = 200 and 250 C and P = 20, 40, 60, and 80 MPa. Initial analysis of the mutual solubilities, determined from volumetric data, shows good agreement with earlier results for the aqueous phase, but finds that the data of Takenouchi and Kennedy (1964) significantly overestimated the solubility of water in supercritical CO2 (by a factor of more than two at 200 C). Resolving this well-known discrepancy will have a direct impact on the accuracy of predictive modeling of CO2 injection in geothermal reservoirs and geological carbon sequestration through improved equations of state, needed for calibration of predictive molecular-scale models and large-scale reactive transport simulations.

  14. Three-phase equilibria in the binary system ethylene + eicosane and the ternary system propane + ethylene + eicosane

    SciTech Connect

    Gregorowicz, J.; Loos, T.W. de; Arons, J. . Lab. of Applied Thermodyanamics and Phase Equilibria)

    1993-07-01

    The solid eicosane-liquid-vapor (SLV) phase behavior in the binary system ethylene + eicosane was investigated. It was found that the SLV curve ends at a critical end point where liquid and vapor are critical in the presence of pure solid eicosane. In this binary system liquid-liquid-vapor (LLV) equilibria are metastable with respect to solid formation. Addition of propane to mixtures of ethylene and eicosane revealed stable LLV equlibria. P-T sections for seven ternary mixtures with different propane and eicosane concentrations were determined according to the synthetic method. On the basis of the results obtained, a rough estimate of the ternary tricritical point and the metastable binary LLV curve is performed.

  15. Simulation of phase equilibria and interfacial properties of binary mixtures on the liquid-vapour interface using lattice sums

    NASA Astrophysics Data System (ADS)

    López-Lemus, Jorge; Alejandre, José

    Molecular dynamics simulations of Lennard-Jones binary mixtures were performed to obtain phase equilibria and thermodynamic properties for the liquid-vapour interface. The dispersion interactions were handled using the lattice sum method where the full interaction is obtained and there is no requirement for any long range correction to the properties. The application of the method using the Lorentz-Berthelot combining rule for unlike interactions is discussed. The coexisting densities, adsorption of molecules at the interface and surface tension are the main results of this work. Coexisting properties were compared with Gibbs ensemble Monte Carlo results and with those of the grand canonical Monte Carlo method combined with the histogram reweighting technique, and good agreement was found. The lattice sum method results were compared with those of the spherically truncated and shifted potential to analyse the truncation effect. The adsorption of molecules at the interface and surface tension increase with interaction.

  16. Mie potentials for phase equilibria calculations: application to alkanes and perfluoroalkanes.

    PubMed

    Potoff, Jeffrey J; Bernard-Brunel, Damien A

    2009-11-05

    Transferable united-atom force fields, based on n - 6 Lennard-Jones potentials, are presented for normal alkanes and perfluorocarbons. It is shown that by varying the repulsive exponent the range of the potential can be altered, leading to improved predictions of vapor pressures while also reproducing saturated liquid densities to high accuracy. Histogram-reweighting Monte Carlo simulations in the grand canonical ensemble are used to determine the vapor liquid coexistence curves, vapor pressures, heats of vaporization, and critical points for normal alkanes methane through tetradecane, and perfluorocarbons perfluoromethane through perfluorooctane. For all molecules studied, saturated liquid densities are reproduced to within 1% of experiment. Vapor pressures for normal alkanes and perfluorocarbons were predicted to within 3% and 6% of experiment, respectively. Calculations performed for binary mixture vapor-liquid equilibria for propane + pentane show excellent agreement with experiment, while slight deviations are observed for the ethane + perfluoroethane mixture.

  17. Phase equilibria of the Sn-Ag-Cu-Ni quaternary system at the sn-rich corner

    NASA Astrophysics Data System (ADS)

    Chen, Sinn-Wen; Chang, Cheng-An

    2004-10-01

    Knowledge of phase equilibria of the Sn-Ag-Cu-Ni quaternary system at the Sn-rich corner is important for the understanding of the interfacial reactions at the Sn-Ag-Cu/Ni contacts, which are frequently encountered in recent microelectronic products. Various Sn-Ag-Cu-Ni alloys were prepared and equilibrated at 250°C. The alloys were then quenched and analyzed. The phases were determined by metallography, compositional analysis, and x-ray diffraction (XRD) analysis. No quaternary phases were found. The isoplethal sections at 60at.%Sn, 70at.%Sn, 80at.%Sn, and 90at.%Sn at 250°C are determined. The phase equilibrium relationship was proposed based on the quaternary experimental results and the 250°C isothermal sections of the four constituent ternary systems, Sn-Ag-Cu, Sn-Ag-Ni, Sn-Cu-Ni, and Cu-Ag-Ni. Because there are no ternary phases in all these three systems, all the compounds are in fact binary compounds with various solubilities of the other two elements.

  18. Theorization on ion-exchange equilibria: activity of species in 2-D phases.

    PubMed

    Tamura, Hiroki

    2004-11-01

    Ion-exchange reactions are naturally occurring at soil and sediment/water interphases, determining soil fertility and water quality. These ion-exchange reactions with inorganic and organic exchangers are applied to chemical analysis, recovery of useful ions from low-grade ores (potentially from sea water), water purification including the preparation of "ultrapure" water, production of foods and medicines, therapy, and other uses. It is important to theorize about or to model ion-exchange reactions for quantitative explanations of ion-exchange phenomena and for efficient operation of ion-exchange processes. This paper describes the modeling of ion-exchange equilibria for hydroxyl sites on metal oxides and carboxyl sites in resins with monovalent cations (alkali metal ions), a monovalent anion (nitrate ion), and divalent heavy metal ions. The procedure of modeling is as follows: the stoichiometry and material balance equations of the respective ion-exchange reactions were established based on findings here and by others. The equilibrium conditions were given by the Frumkin equation, where the mass-action relation is modified with lateral interactions between species at the interphase. The model equations were fitted to the measured data and model parameter values were determined by nonlinear regression analysis. The formation of bonds between ions and exchanger sites was evaluated by the equilibrium constant and the suppression of bond formation by electrostatic, geometric, and other lateral interactions was evaluated by the interaction constant. It was established that the properties of ions are determined by the valence, size, and hydration state of the ions. Monovalent ions (anions and cations) react with oxide surface hydroxyl and resin carboxyl sites as hydrated ions and form loose ion-site pairs by a weak electrostatic bond (nonspecific adsorption). However, the lateral interactions are large because of a large polarization of the ion-site pairs. When the

  19. Phase equilibria and structural investigations in the Ni-poor part of the system Al-Ge-Ni.

    PubMed

    Reichmann, Thomas L; Duarte, Liliana I; Effenberger, Herta S; Leinenbach, Christian; Richter, Klaus W

    2012-09-01

    The ternary phase diagram Al-Ge-Ni was investigated between 0 and 50 at.% Ni by a combination of differential thermal analysis (DTA), powder- and single-crystal X-ray diffraction (XRD), metallography and electron probe microanalysis (EPMA). Ternary phase equilibria and accurate phase compositions of the equilibrium phases were determined within two partial isothermal sections at 400 and 700 °C, respectively. The two binary intermediate phases AlNi and Al3Ni2 were found to form extended solid solutions with Ge in the ternary. Three new ternary phases were found to exist in the Ni-poor part of the phase diagram which were designated as τ1 (oC24, CoGe2-type), τ2 (at approximately Al67.5Ge18.0Ni14.5) and τ3 (cF12, CaF2-type). The ternary phases show only small homogeneity ranges. While τ1 was investigated by single crystal X-ray diffraction, τ2 and τ3 were identified from their powder diffraction pattern. Ternary phase reactions and melting behaviour were studied by means of DTA. A total number of eleven invariant reactions could be derived from these data, which are one ternary eutectic reaction, six transition reactions, three ternary peritectic reactions and one maximum. Based on the measured DTA values three vertical sections at 10, 20 and 35 at.% Ni were constructed. Additionally, all experimental results were combined to a ternary reaction scheme (Scheil diagram) and a liquidus surface projection.

  20. Phase equilibria and structural investigations in the Ni-poor part of the system Al–Ge–Ni

    PubMed Central

    Reichmann, Thomas L.; Duarte, Liliana I.; Effenberger, Herta S.; Leinenbach, Christian; Richter, Klaus W.

    2012-01-01

    The ternary phase diagram Al–Ge–Ni was investigated between 0 and 50 at.% Ni by a combination of differential thermal analysis (DTA), powder- and single-crystal X-ray diffraction (XRD), metallography and electron probe microanalysis (EPMA). Ternary phase equilibria and accurate phase compositions of the equilibrium phases were determined within two partial isothermal sections at 400 and 700 °C, respectively. The two binary intermediate phases AlNi and Al3Ni2 were found to form extended solid solutions with Ge in the ternary. Three new ternary phases were found to exist in the Ni-poor part of the phase diagram which were designated as τ1 (oC24, CoGe2-type), τ2 (at approximately Al67.5Ge18.0Ni14.5) and τ3 (cF12, CaF2-type). The ternary phases show only small homogeneity ranges. While τ1 was investigated by single crystal X-ray diffraction, τ2 and τ3 were identified from their powder diffraction pattern. Ternary phase reactions and melting behaviour were studied by means of DTA. A total number of eleven invariant reactions could be derived from these data, which are one ternary eutectic reaction, six transition reactions, three ternary peritectic reactions and one maximum. Based on the measured DTA values three vertical sections at 10, 20 and 35 at.% Ni were constructed. Additionally, all experimental results were combined to a ternary reaction scheme (Scheil diagram) and a liquidus surface projection. PMID:27087753

  1. Effect of Alloying Additions on Phase Equilibria and Creep Resistance of Alumina-Forming Austenitic Stainless Steels

    NASA Astrophysics Data System (ADS)

    Yamamoto, Y.; Santella, M. L.; Brady, M. P.; Bei, H.; Maziasz, P. J.

    2009-08-01

    The high-temperature creep properties of a series of alumina-forming austenitic (AFA) stainless steels based on Fe-20Ni-(12-14)Cr-(2.5-4)Al-(0.2-3.3)Nb-0.1C (weight percent) were studied. Computational thermodynamics were used to aid in the interpretation of data on microstructural stability, phase equilibria, and creep resistance. Phases of MC (M: mainly Nb), M23C6 (M: mainly Cr), B2 [ β-(Ni,Fe)Al], and Laves [Fe2(Mo,Nb)] were observed after creep-rupture testing at 750 °C and 170 MPa; this was generally consistent with the thermodynamic calculations. The creep resistance increased with increasing Nb additions up to 1 wt pct in the 2.5 and 3 Al wt pct alloy series, due to the stabilization of nanoscale MC particles relative to M23C6. Additions of Nb greater than 1 wt pct decreased creep resistance in the alloy series due to stabilization of the Laves phase and increased amounts of undissolved, coarse MC, which effectively reduced the precipitation of nanoscale MC particles. The additions of Al also increased the creep resistance moderately due to the increase in the volume fraction of B2 phase precipitates. Calculations suggested that optimum creep resistance would be achieved at approximately 1.5 wt pct Nb in the 4 wt pct Al alloy series.

  2. Effect of alloying additions on phase equilibria and creep resistance of alumina-forming austenitic stainless steels

    SciTech Connect

    Yamamoto, Yukinori; Santella, Michael L; Brady, Michael P; Bei, Hongbin; Maziasz, Philip J

    2009-01-01

    The high-temperature creep properties of a series of alumina-forming austenitic (AFA) stainless steels based on Fe-20Ni-(12-14)Cr-(2.5-4)Al-(0.2-3.3)Nb-0.1C (weight percent) were studied. Computational thermodynamics were used to aid in the interpretation of data on microstructural stability, phase equilibria, and creep resistance. Phases of MC (M: mainly Nb), M{sub 23}C{sub 6} (M: mainly Cr), B2 [{beta}-(Ni,Fe)Al], and Laves [Fe{sub 2}(Mo,Nb)] were observed after creep-rupture testing at 750 C and 170 MPa; this was generally consistent with the thermodynamic calculations. The creep resistance increased with increasing Nb additions up to 1 wt pct in the 2.5 and 3 Al wt pct alloy series, due to the stabilization of nanoscale MC particles relative to M{sub 23}C{sub 6}. Additions of Nb greater than 1 wt pct decreased creep resistance in the alloy series due to stabilization of the Laves phase and increased amounts of undissolved, coarse MC, which effectively reduced the precipitation of nanoscale MC particles. The additions of Al also increased the creep resistance moderately due to the increase in the volume fraction of B2 phase precipitates. Calculations suggested that optimum creep resistance would be achieved at approximately 1.5 wt pct Nb in the 4 wt pct Al alloy series.

  3. Chimera states in two populations with heterogeneous phase-lag

    NASA Astrophysics Data System (ADS)

    Martens, Erik A.; Bick, Christian; Panaggio, Mark J.

    2016-09-01

    The simplest network of coupled phase-oscillators exhibiting chimera states is given by two populations with disparate intra- and inter-population coupling strengths. We explore the effects of heterogeneous coupling phase-lags between the two populations. Such heterogeneity arises naturally in various settings, for example, as an approximation to transmission delays, excitatory-inhibitory interactions, or as amplitude and phase responses of oscillators with electrical or mechanical coupling. We find that breaking the phase-lag symmetry results in a variety of states with uniform and non-uniform synchronization, including in-phase and anti-phase synchrony, full incoherence (splay state), chimera states with phase separation of 0 or π between populations, and states where both populations remain desynchronized. These desynchronized states exhibit stable, oscillatory, and even chaotic dynamics. Moreover, we identify the bifurcations through which chimeras emerge. Stable chimera states and desynchronized solutions, which do not arise for homogeneous phase-lag parameters, emerge as a result of competition between synchronized in-phase, anti-phase equilibria, and fully incoherent states when the phase-lags are near ± /π 2 (cosine coupling). These findings elucidate previous experimental results involving a network of mechanical oscillators and provide further insight into the breakdown of synchrony in biological systems.

  4. Chimera states in two populations with heterogeneous phase-lag.

    PubMed

    Martens, Erik A; Bick, Christian; Panaggio, Mark J

    2016-09-01

    The simplest network of coupled phase-oscillators exhibiting chimera states is given by two populations with disparate intra- and inter-population coupling strengths. We explore the effects of heterogeneous coupling phase-lags between the two populations. Such heterogeneity arises naturally in various settings, for example, as an approximation to transmission delays, excitatory-inhibitory interactions, or as amplitude and phase responses of oscillators with electrical or mechanical coupling. We find that breaking the phase-lag symmetry results in a variety of states with uniform and non-uniform synchronization, including in-phase and anti-phase synchrony, full incoherence (splay state), chimera states with phase separation of 0 or π between populations, and states where both populations remain desynchronized. These desynchronized states exhibit stable, oscillatory, and even chaotic dynamics. Moreover, we identify the bifurcations through which chimeras emerge. Stable chimera states and desynchronized solutions, which do not arise for homogeneous phase-lag parameters, emerge as a result of competition between synchronized in-phase, anti-phase equilibria, and fully incoherent states when the phase-lags are near ±π2 (cosine coupling). These findings elucidate previous experimental results involving a network of mechanical oscillators and provide further insight into the breakdown of synchrony in biological systems.

  5. Direct calculation of liquid-vapor phase equilibria from transition matrix Monte Carlo simulation

    NASA Astrophysics Data System (ADS)

    Errington, Jeffrey R.

    2003-06-01

    An approach for directly determining the liquid-vapor phase equilibrium of a model system at any temperature along the coexistence line is described. The method relies on transition matrix Monte Carlo ideas developed by Fitzgerald, Picard, and Silver [Europhys. Lett. 46, 282 (1999)]. During a Monte Carlo simulation attempted transitions between states along the Markov chain are monitored as opposed to tracking the number of times the chain visits a given state as is done in conventional simulations. Data collection is highly efficient and very precise results are obtained. The method is implemented in both the grand canonical and isothermal-isobaric ensemble. The main result from a simulation conducted at a given temperature is a density probability distribution for a range of densities that includes both liquid and vapor states. Vapor pressures and coexisting densities are calculated in a straightforward manner from the probability distribution. The approach is demonstrated with the Lennard-Jones fluid. Coexistence properties are directly calculated at temperatures spanning from the triple point to the critical point.

  6. Characterization of phase equilibria and oxidation behavior of aluminum-lithium alloys by electron, ion, and neutron beams

    SciTech Connect

    Soni, K.K.

    1991-01-01

    Secondary ion mass spectrometry (SIMS) and neutron-depth profiling (NDP) were used, in a complementary way, for the characterization of the Li distribution in Al-Li alloys in order to study their phase equilibria and oxidation behavior. SIMS compositional imaging of alloys containing T{sub 1} (Al{sub 2}LiCu), T{sub 2} (Al{sub 6}Li{sub 3}Cu), and T{sub B} (Al{sub 7.5}Cu{sub 4}Li) showed a lack of equilibrium between these phases and a non-uniform Cu distribution. Observation regarding some trace-element distributions were also made. The second-phase particles were identified by electron diffraction and x-ray microanalysis as Al{sub 3}Fe and these particles contained no Li. Oxidation of binary Al-Li alloys at high temperature produced a characteristic nodular oxide morphology. Examination of the oxide/alloy interface indicated preferential nucleation of the oxide at the grain boundaries followed by initial lateral growth. The oxide layer also exhibited surface facets due to surface reconstruction during the reaction. Oxidation of Al-Li-Mg alloys led to depletion of both Li and Mg to nearly equal extent. From these depletion profiles, the interdiffusion coefficients for the Al-Li-Mg-(Cu) alloys were calculated.

  7. Vapor-liquid equilibria for solvent-polymer systems from a perturbed hard-sphere-chain equation of state

    SciTech Connect

    Gupta, R.B.; Prausnitz, J.M. |

    1996-04-01

    Vapor-liquid equilibria (VLE) for solvent-polymer mixtures at modest pressures are obtained from a perturbed hard-sphere-chain equation of state. This equation of state is the sum of a hard-sphere-chain term as the reference system and a van der Waals attractive term as the perturbation. The reference equation follows from the Percus-Yevick integral theory coupled with chain connectivity as described by Chiew. The effect of specific interactions, such as hydrogen bonding, is introduced through the proposal of Veytsman based on the statistical distribution of hydrogen bonds between donor and acceptor sites suggested by molecular structure. Calculated and observed vapor-liquid equilibria are presented for nonpolar, polar, and hydrogen-bonding solvent + homopolymer systems. Pure-component parameters (number of segments per molecule, segment-segment energy, and segment diameter) are obtained from pure-component properties: liquid density and vapor pressure data for normal fluids and pressure-volume-temperature data for polymers. A binary energy interaction parameter must be obtained from limited VLE data for each binary system; this parameter appears to be independent of temperature and composition over a useful range. Theoretical correlations and predictions are in good agreement with experiment.

  8. Phase equilibria of Fe-C binary alloys in a magnetic field

    NASA Astrophysics Data System (ADS)

    England, Roger Dale

    phase nucleation created by the addition of a high flux magnetic field. Additionally, a pure iron sample was analyzed and found to be unique, in that the transformation temperature decreased with the application of a static magnetic field, opposite to what occurs in the iron carbon alloys. While the presence of a two-phase field is a viable cause due to the chromium impurity content in the sample creating a dilute binary alloy versus a pure element, this effect could also be attributed to the high magnetic field increasing the number of state variables present.

  9. Direct phase coexistence molecular dynamics study of the phase equilibria of the ternary methane-carbon dioxide-water hydrate system.

    PubMed

    Michalis, Vasileios K; Tsimpanogiannis, Ioannis N; Stubos, Athanassios K; Economou, Ioannis G

    2016-09-14

    Molecular dynamics simulation is used to predict the phase equilibrium conditions of a ternary hydrate system. In particular, the direct phase coexistence methodology is implemented for the determination of the three-phase coexistence temperature of the methane-carbon dioxide-water hydrate system at elevated pressures. The TIP4P/ice, TraPPE-UA and OPLS-UA forcefields for water, carbon dioxide and methane respectively are used, in line with our previous studies of the phase equilibria of the corresponding binary hydrate systems. The solubility in the aqueous phase of the guest molecules of the respective binary and ternary systems is examined under hydrate-forming conditions, providing insight into the predictive capability of the methodology as well as the combination of these forcefields to accurately describe the phase behavior of the ternary system. The three-phase coexistence temperature is calculated at 400, 1000 and 2000 bar for two compositions of the methane-carbon dioxide mixture. The predicted values are compared with available calculations with satisfactory agreement. An estimation is also provided for the fraction of the guest molecules in the mixed hydrate phase under the conditions examined.

  10. Fractionation effects in phase equilibria of polydisperse hard-sphere colloids

    NASA Astrophysics Data System (ADS)

    Fasolo, Moreno; Sollich, Peter

    2004-10-01

    The equilibrium phase behavior of hard spheres with size polydispersity is studied theoretically. We solve numerically the exact phase equilibrium equations that result from accurate free energy expressions for the fluid and solid phases, while accounting fully for size fractionation between coexisting phases. Fluids up to the largest polydispersities that we can study (around 14%) can phase separate by splitting off a solid with a much narrower size distribution. This shows that experimentally observed terminal polydispersities above which phase separation no longer occurs must be due to nonequilibrium effects. We find no evidence of reentrant melting; instead, sufficiently compressed solids phase separate into two or more solid phases. Under appropriate conditions, coexistence of multiple solids with a fluid phase is also predicted. The solids have smaller polydispersities than the parent phase as expected, while the reverse is true for the fluid phase, which contains predominantly smaller particles but also residual amounts of the larger ones. The properties of the coexisting phases are studied in detail; mean diameter, polydispersity, and volume fraction of the phases all reveal marked fractionation. We also propose a method for constructing quantities that optimally distinguish between the coexisting phases, using principal component analysis in the space of density distributions. We conclude by comparing our predictions to Monte Carlo simulations at imposed chemical potential distribution, and find excellent agreement.

  11. Transferable potentials for phase equilibria-united atom description of five- and six-membered cyclic alkanes and ethers.

    PubMed

    Keasler, Samuel J; Charan, Sophia M; Wick, Collin D; Economou, Ioannis G; Siepmann, J Ilja

    2012-09-13

    While the transferable potentials for phase equilibria-united atom (TraPPE-UA) force field has generally been successful at providing parameters that are highly transferable between different molecules, the polarity and polarizability of a given functional group can be significantly perturbed in small cyclic structures, which limits the transferability of parameters obtained for linear molecules. This has motivated us to develop a version of the TraPPE-UA force field specifically for five- and six-membered cyclic alkanes and ethers. The Lennard-Jones parameters for the methylene group obtained from cyclic alkanes are transferred to the ethers for each ring size, and those for the oxygen atom are common to all compounds for a given ring size. However, the partial charges are molecule specific and parametrized using liquid-phase dielectric constants. This model yields accurate saturated liquid densities and vapor pressures, critical temperatures and densities, normal boiling points, heat capacities, and isothermal compressibilities for the following molecules: cyclopentane, tetrahydrofuran, 1,3-dioxolane, cyclohexane, oxane, 1,4-dioxane, 1,3-dioxane, and 1,3,5-trioxane. The azeotropic behavior and separation factor for the binary mixtures of 1,3-dioxolane/cyclohexane and ethanol/1,4-dioxane are qualitively reproduced.

  12. Postperovskite phase equilibria in the MgSiO3–Al2O3 system

    PubMed Central

    Tsuchiya, Jun; Tsuchiya, Taku

    2008-01-01

    We investigate high-P,T phase equilibria of the MgSiO3–Al2O3 system by means of the density functional ab initio computation methods with multiconfiguration sampling. Being different from earlier studies based on the static substitution properties with no consideration of Rh2O3(II) phase, present calculations demonstrate that (i) dissolving Al2O3 tends to decrease the postperovskite transition pressure of MgSiO3 but the effect is not significant (≈-0.2 GPa/mol% Al2O3); (ii) Al2O3 produces the narrow perovskite+postperovskite coexisting P,T area (≈1 GPa) for the pyrolitic concentration (xAl2O3 ≈6 mol%), which is sufficiently responsible to the deep-mantle D″ seismic discontinuity; (iii) the transition would be smeared (≈4 GPa) for the basaltic Al-rich composition (xAl2O3 ≈20 mol%), which is still seismically visible unless iron has significant effects; and last (iv) the perovskite structure spontaneously changes to the Rh2O3(II) with increasing the Al concentration involving small displacements of the Mg-site cations. PMID:19036928

  13. Phase equilibria constraints on pre-eruptive magma storage conditions for the 1956 eruption of Bezymianny Volcano, Kamchatka, Russia

    NASA Astrophysics Data System (ADS)

    Shcherbakov, Vasily D.; Neill, Owen K.; Izbekov, Pavel E.; Plechov, Pavel Yu.

    2013-08-01

    Phase equilibria experiments were performed on andesites from the catastrophic 1956 eruption of Bezymianny Volcano, Kamchatka, Russia, to determine pre-eruptive magma storage conditions. Fifteen experiments were conducted under water-saturated conditions, with oxygen fugacity equal to the Ni-NiO oxygen buffer, at temperatures between 775 and 1100 °C and pressures between 50 and 200 MPa. Simultaneous amphibole and plagioclase crystallization is reproduced at ≤ 850 °C and ≥ 200 MPa. The simultaneous crystallization temperature range of the plagioclase-clinopyroxene-orthopyroxene-Fe-Ti oxide assemblage increases with decreasing pressure, from 840 to 940 °C at 150 MPa to 940-1020 °C at 50 MPa. Melt inclusion compositions in plagioclase phenocrysts and matrix glass match experimental melt compositions reproduced at 50-100 MPa and ≤ 50 MPa, respectively. Presence of the silica phase in groundmass and mature amphibole breakdown rims suggests that magma has been stored at ca. 3 km depth prior to the final ascent for at least 40 days. Syn-eruptive ascent led to decompression-driven crystallization, which caused a temperature increase from 850-900 °C to 950-1000 °C.

  14. Experimental phase equilibria of a Mount St. Helens rhyodacite: a framework for interpreting crystallization paths in degassing silicic magmas

    NASA Astrophysics Data System (ADS)

    Riker, Jenny M.; Blundy, Jonathan D.; Rust, Alison C.; Botcharnikov, Roman E.; Humphreys, Madeleine C. S.

    2015-07-01

    We present isothermal (885 °C) phase equilibrium experiments for a rhyodacite from Mount St. Helens (USA) at variable total pressure (25-457 MPa) and fluid composition (XH2Ofl = 0.6-1.0) under relatively oxidizing conditions (NNO to NNO + 3). Run products were characterized by SEM, electron microprobe, and SIMS. Experimental phase assemblages and phase chemistry are consistent with those of natural samples from Mount St. Helens from the last 4000 years. Our results emphasize the importance of pressure and melt H2O content in controlling phase proportions and compositions, showing how significant textural and compositional variability may be generated in the absence of mixing, cooling, or even decompression. Rather, variations in the bulk volatile content of magmas, and the potential for fluid migration relative to surrounding melts, mean that magmas may take varied trajectories through pressure-fluid composition space during storage, transport, and eruption. We introduce a novel method for projecting isothermal phase equilibria into CO2-H2O space (as conventionally done for melt inclusions) and use this projection to interpret petrological data from Mount St. Helens dacites. By fitting the experimental data as empirical functions of melt water content, we show how different scenarios of isothermal magma degassing (e.g., water-saturated ascent, vapor-buffered ascent, and vapor fluxing) can have quite different textural and chemical consequences. We explore how petrological data might be used to infer degassing paths of natural magmas and conclude that melt CO2 content is a much more useful parameter in this regard than melt H2O.

  15. Polarization effects and phase equilibria in high-energy-density polyvinylidene-fluoride-based polymers.

    PubMed

    Ranjan, V; Yu, L; Nakhmanson, Serge; Bernholc, Jerry; Nardelli, M Buongiorno

    2010-09-01

    Using first-principles calculations, the phase diagrams of polyvinylidene fluoride (PVDF) and its copolymers under an applied electric field are studied and phase transitions between their nonpolar alpha and polar beta phases are discussed. The results show that the degree of copolymerization is a crucial parameter controlling the structural phase transition. In particular, for tetrafluoroethylene (TeFE) concentration above 12%, PVDF-TeFE is stabilized in the beta phase, whereas the alpha phase is stable for lower concentrations. As larger electric fields are applied, domains with smaller concentrations (< or = 12%) undergo a transition from the alpha to the beta phase until a breakdown field of approximately 600 MV m(-1) is reached. These structural phase transitions can be exploited for efficient storage of electrical energy.

  16. Phase equilibria study of the binary systems (1-butyl-3-methylimidazolium thiocyanate ionic liquid + organic solvent or water).

    PubMed

    Domańska, Urszula; Laskowska, M; Pobudkowska, Aneta

    2009-05-07

    (Solid + liquid) phase equilibria (SLE) for the binary systems, ionic liquid (IL) 1-butyl-3-methylimidazolium thiocyanate [BMIM][SCN] with an alcohol (1-octanol, 1-nonanol, 1-decanol, 1-undecanol, or 1-dodecanol) or water, and (liquid + liquid) phase equilibria (LLE) for the binary systems of [BMIM][SCN] with an alkane (n-hexane, n-heptane, n-octane, n-nonane, or n-decane), benzene, an alkylbenzenes (toluene or ethylbenzene), tetrahydrofuran (THF), cycloalkanes (cyclohexane or cycloheptane), or ethers (di-n-propyl ether, di-n-butyl ether, di-n-pentyl ether, n-butylmethyl ether, tert-butylmethyl ether (MTBE), or tert-butylethyl ether (ETBE)) have been determined at ambient pressure. A dynamic method was used over a broad range of mole fractions and temperatures from 250 to 430 K. In the case of systems IL + alkane, cycloalkane, or ether, the mutual immiscibility with an upper critical solution temperature (UCST) was detected, and in the systems of IL + benzene, alkylbenzene, or THF, the mutual immiscibility with a lower critical solution temperature (LCST) was observed. UV-vis spectroscopy was used to determine the very small compositions of the IL in the n-hexane (about 2 x 10(-5) IL mole fraction), benzene (about 2 x 10(-3) IL mole fraction), cyclohexane (about 2 x 10(-5) IL mole fraction), and THF (about 1.2 x 10(-2) IL mole fraction). For the binary systems containing alcohol, it was noticed that with increasing chain length of an alcohol, the solubility decreases. The basic thermal properties of the pure IL, that is, the glass-transition temperature as well as the heat capacity at the glass-transition temperature, have been measured using a differential scanning microcalorimetry technique (DSC). Decomposition of the IL was detected by the simultaneous TG/DTA experiments. Well-known UNIQUAC, Wilson, and NRTL equations have been used to correlate the experimental SLE data sets for alcohols and water. For the systems containing immiscibility gaps {IL + alkane

  17. Phase equilibria in the U-Si system from first-principles calculations

    NASA Astrophysics Data System (ADS)

    Noordhoek, Mark J.; Besmann, Theodore M.; Andersson, David; Middleburgh, Simon C.; Chernatynskiy, Aleksandr

    2016-10-01

    Density functional theory calculations have been used with spin-orbit coupling and on-site Coulomb correction (GGA + U) methods to investigate the U-Si system. Structural prediction methods were employed to identify alternate stable structures. Convex hulls of the U-Si system were constructed for each of the methods to highlight the competing energetics of various phases. For GGA calculations, new structures are predicted to be dynamically stable, but these have not been experimentally observed. When the GGA + U (Ueff > 1.3 eV) method is considered, the experimentally observed structures are predicted to be energetically preferred. Phonon calculations were used to investigate the energy predictions and showed that the use of the GGA + U method removes the significant imaginary frequencies observed for U3Si2 when the correction is not considered. Total and partial electron density of states calculations were also performed to understand the role of GGA + U methods and orbitals on the bonding and stability of U-Si compounds.

  18. Phase Equilibria of a S- and C-Poor Lunar Core

    NASA Technical Reports Server (NTRS)

    Righter, K.; Pando, K.; Go, B. M.; Danielson, L. R.; Habermann, M.

    2016-01-01

    The composition of the lunar core can have a large impact on its thermal evolution, possible early dynamo creation, and physical state. Geochemical measurements have placed better constraints on the S and C content of the lunar mantle. In this study we have carried out phase equilibrium studies of geochemically plausible S- and C-poor lunar core compositions in the Fe-Ni-S-C system, and apply them to the early history of the Moon. We chose two bulk core compositions, with differing S and C content based on geochemical analyses of S and C trapped melts in Apollo samples, and on the partitioning of S and C between metal and silicate. This approach allowed calculation of core S and C contents - 90% Fe, 9% Ni, 0.5% C, and 0.375% S by weight; a second composition contained 1% each of S and C. Experiments were carried out from 1473K to 1973K and 1 GPa to 5 GPa, in piston cylinder and multi- anvil apparatuses. Combination of the thermal model of with our results, shows that a solid inner core (and therefore initiation of a dynamo) may have been possible in the earliest history of the Moon (approximately 4.2 Ga ago), in agreement with. Thus a volatile poor lunar core may explain the thermal and magnetic history of the Moon.

  19. Phase equilibria, fluid structure, and diffusivity of a discotic liquid crystal.

    PubMed

    Cienega-Cacerez, Octavio; Moreno-Razo, José Antonio; Díaz-Herrera, Enrique; Sambriski, Edward John

    2014-05-14

    Molecular Dynamics simulations were performed for the Gay-Berne discotic fluid parameterized by GB(0.345, 0.2, 1.0, 2.0). The volumetric phase diagram exhibits isotropic (IL), nematic (ND), and two columnar phases characterized by radial distribution functions: the transversal fluid structure varies between a hexagonal columnar (CD) phase (at higher temperatures and pressures) and a rectangular columnar (CO) phase (at lower temperatures and pressures). The slab-wise analysis of fluid dynamics suggests the formation of grain-boundary defects in the CO phase. Longitudinal fluid structure is highly periodic with narrow peaks for the CO phase, suggestive of a near-crystalline (yet diffusive) system, but is only short-ranged for the CD phase. The IL phase does not exhibit anisotropic diffusion. Transversal diffusion is more favorable in the ND phase at all times, but only favorable at short times for the columnar phases. In the columnar phases, a crossover occurs where longitudinal diffusion is favored over transversal diffusion at intermediate-to-long timescales. The anomalous diffusivity is pronounced in both columnar phases, with three identifiable contributions: (a) the rattling of discogens within a transient "interdigitation" cage, (b) the hopping of discogens across columns, and (c) the drifting motion of discogens along the orientation of the director.

  20. Phase equilibria in DOPC/DPPC: Conversion from gel to subgel in two component mixtures.

    PubMed

    Schmidt, Miranda L; Ziani, Latifa; Boudreau, Michelle; Davis, James H

    2009-11-07

    Biological membranes contain a mixture of phospholipids with varying degrees of hydrocarbon chain unsaturation. Mixtures of long chain saturated and unsaturated lipids with cholesterol have attracted a lot of attention because of the formation of two coexisting fluid bilayer phases in such systems over a broad range of temperature and composition. Interpretation of the phase behavior of such ternary mixtures must be based on a thorough understanding of the phase behavior of the binary mixtures formed with the same components. This article describes the phase behavior of mixtures of 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) with 1,2-di-d(31)-palmitoyl-sn-glycero-3-phosphocholine (DPPC) between -20 and 50 degrees C. Particular attention has been paid to the phase coexistence below about 16 degrees C where the subgel phase appears. The changes in the shape of the spectrum (and its spectral moments) during the slow transformation process leads to the conclusion that below 16 degrees C the gel phase is metastable and the gel component of the two-phase mixture slowly transforms to the subgel phase with a slightly different composition. This results in a line of three-phase coexistence near 16 degrees C. Analysis of the transformation of the metastable gel domains into the subgel phase using the nucleation and growth model shows that the subgel domain growth is a two dimensional process.

  1. Phase equilibria in molecular hydrogen-helium mixtures at high pressures

    NASA Technical Reports Server (NTRS)

    Streett, W. B.

    1973-01-01

    Experiments on phase behavior in hydrogen-helium mixtures have been carried out at pressures up to 9.3 kilobars, at temperatures from 26 to 100 K. Two distinct fluid phases are shown to exist at supercritical temperatures and high pressures. Both the trend of the experimental results and an analysis based on the van der Waals theory of mixtures suggest that this fluid-fluid phase separation persists at temperatures and pressures beyond the range of these experiments, perhaps even to the limits of stability of the molecular phases. The results confirm earlier predictions concerning the form of the hydrogen-helium phase diagram in the region of pressure-induced solidification of the molecular phases at supercritical temperatures. The implications of this phase diagram for planetary interiors are discussed.

  2. Phase equilibria and trace element partitioning in a magma ocean to 260 kilobars

    NASA Technical Reports Server (NTRS)

    Herzberg, Claude

    1992-01-01

    A magma ocean can solidify in a way that is intermediate between perfect equilibrium and perfect fractional crystallization. In order to model quantitatively any fractional crystallization scenario, it is necessary to understand the geochemical characteristics of the phases that crystallize from a magma ocean, and how they vary with pressure. The crystallizing phase is called the liquidus phase, and their identities were determined by numerous experiments utilizing the multianvil apparatus. For chondritic compositions the liquidus phases are as follows: olivine at 1 atmosphere to 100 kilobars; garnet from 100 to about 260 kilobars; silicate perovskite from 260 kilobars to possibly the core-mantle boundary in the Earth.

  3. New insight into phase equilibria involving imidazolium bistriflamide ionic liquids and their mixtures with alcohols and water.

    PubMed

    Pereiro, Ana B; Deive, Francisco J; Rodríguez, Ana; Ruivo, Diana; Canongia Lopes, José N; Esperança, José M S S; Rebelo, Luís P N

    2010-07-15

    The fluid phase equilibria (liquid-liquid demixing behavior (LLE)) of mixtures of ionic liquids of the 1-alkyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide family, [C(n)mim][NTf(2)], with 2-methylpropanol or n-octanol were investigated. Binary mixtures of [C(4)mim][NTf(2)] + alcohol and [C(6)mim][NTf(2)] + alcohol were compared to pseudobinary mixtures of (0.5[C(2)mim] + 0.5[C(6)mim])[NTf(2)] + alcohol and (0.5[C(2)mim] + 0.5[C(10)mim])[NTf(2)] + alcohol, respectively. Additionally, the presence of water in the studied alcohols or as a third component in the system was analyzed in order to check any possible deviation from the LLE observed for the anhydrous systems. Systems containing small fractions of ionic liquid show similar LLE between the corresponding binary and pseudobinary systems; however, large differences are observed in the presence of water when the IL mass fraction is increased.

  4. Prediction of fluid phase equilibria and interfacial tension of triangle-well fluids using transition matrix Monte Carlo

    NASA Astrophysics Data System (ADS)

    Sengupta, Angan; Adhikari, Jhumpa

    2016-05-01

    The triangle-well (TW) potential is a simple model which is able to capture the essence of the intermolecular attraction in real molecules. Transition matrix Monte Carlo simulations in the grand canonical ensemble (GC-TMMC) are performed to investigate the role of the range of attraction on the features of fluid phase equilibria. As the TW potential range increases, the vapour-liquid coexistence curves shift towards a higher temperature range with the critical temperature and pressure increasing, and the critical density values decreasing. These GC-TMMC results are in excellent agreement with the predictions of Gibbs ensemble Monte Carlo and replica exchange Monte Carlo (REMC) simulations reported in literature. Using the GC-TMMC method, the vapour pressures are also computed directly from the particle number probability distributions (PNPDs). It has been noted in literature that the surface tension values are computationally more expensive and difficult to determine than other coexistence properties using molecular simulations. The PNPDs from GC-TMMC simulations along with Binder's formalism allow for the calculation of the interfacial tension with relative ease. Also, our simulation generated results for the interfacial tension are in good agreement with the literature data obtained using REMC (via the virial route) and the plots of our interfacial tension values as a function of temperature are smooth unlike the literature data.

  5. Multiple critical points and liquid liquid equilibria from the van der Waals like equations of state

    NASA Astrophysics Data System (ADS)

    Artemenko, Sergey; Lozovsky, Taras; Mazur, Victor

    2008-06-01

    The principal aim of this work is a comprehensive analysis of the phase diagram of water via the van der Waals like equations of state (EoSs) which are considered as superpositions of repulsive and attractive forces. We test more extensively the modified van der Waals EoS (MVDW) proposed by Skibinski et al (2004 Phys. Rev. E 69 061206) and refine this model by introducing instead of the classical van der Waals repulsive term a very accurate hard sphere EoS over the entire stable and metastable regions (Liu 2006 Preprint cond-mat/0605392). It was detected that the simplest form of MVDW EoS displays a complex phase behavior, including three critical points, and identifies four fluid phases (gas, low density liquid (LDL), high density liquid (HDL), and very high density liquid (VHDL)). Moreover the experimentally observed (Mallamace et al 2007 Proc. Natl Acad. Sci. USA 104 18387) anomalous behavior of the density of water in the deeply supercooled region (a density minimum) is reproduced by the MWDW EoS. An improvement of the repulsive part does not change the topological picture of the phase behavior of water in the wide range of thermodynamic variables. The new parameters set for second and third critical points are recognized by thorough analysis of experimental data for the loci of thermodynamic response function extrema.

  6. Structure and phase equilibria of the soybean lecithin/PEG 40 monostearate/water system.

    PubMed

    Montalvo, G; Pons, R; Zhang, G; Díaz, M; Valiente, M

    2013-11-26

    PEG stearates are extensively used as emulsifiers in many lipid-based formulations. However, the scheme of the principles of the lipid-surfactant polymer interactions are still poorly understood and need more studies. A new phase diagram of a lecithin/PEG 40 monostearate/water system at 30 °C is reported. First, we have characterized the binary PEG 40 monostearate/water system by the determination of the critical micelle concentration value and the viscous properties. Then, the ternary phase behavior and the influence of phase structure on their macroscopic properties are studied by a combination of different techniques, namely, optical microscopy, small-angle X-ray scattering, differential scanning calorimetry, and rheology. The phase behavior is complex, and some samples evolve even at long times. The single monophasic regions correspond to micellar, swollen lamellar, and lamellar gel phases. The existence of extended areas of phase coexistence (hexagonal, cubic, and lamellar liquid crystalline phases) may be a consequence of the low miscibility of S40P in the lecithin bilayer as well as of the segregation of the phospholipid polydisperse hydrophobic chains. The presence of the PEG 40 monostearate has less effect in the transformation to the cubic phase for lecithin than that found in other systems with simple glycerol-based lipids.

  7. Interpretation of open system petrogenetic processes: Phase equilibria constraints on magma evolution

    NASA Astrophysics Data System (ADS)

    Defant, Marc J.; Nielsen, Roger L.

    1990-01-01

    We have used a computer model (TRACES) to simulate low pressure differentiation of natural basaltic magmas in an attempt to investigate the chemical dynamics of open system magmatic processes. Our results, in the form of simulated liquid lines of descent and the calculated equilibrium mineralogy, were determined for perfect fractional crystallization; fractionation paired with recharge and eruption (PRF); fractionation paired with assimilation (AFC); and fractionation paired with recharge, eruption, and assimilation (FEAR). These simulations were calculated in an attempt to assess the effects of combinations of petrogenetic processes on major and trace element evolution of natural systems and to test techniques that have been used to decipher the relative roles of these processes. If the results of PRF calculations are interpreted in terms of a mass balance based fractionation model (e.g., Bryan et al., 1969), it is possible to generate low residuals even if one assumes that fractional crystallization was the only active process. In effect, the chemical consequences of recharge are invisible to mass balance models. Pearce element ratio analyses, however, can effectively discern the effects of PRF versus simple fractionation. The fractionating mineral proportions, and therefore, bulk distribution coefficients ( D¯) of a differentiating system are dependent on the recharge or assimilation rate. Comparison of the results of simulations assuming constant D¯ with the results calculated by TRACES show that the steady state liquid concentrations of some elements can differ by a factor of 2 to 5. If the PRF simulation is periodic, with episodes of mixing separated by intervals of fractionation, parallel liquidus mineral control lines are produced. Most of these control lines do not project back to the parental composition. This must be an important consideration when attempting to calculate a potential parental magma for any natural suite where magma chamber recharge has

  8. High-pressure Sapphire Cell for Phase Equilibria Measurements of CO2/Organic/Water Systems

    PubMed Central

    Pollet, Pamela; Ethier, Amy L.; Senter, James C.; Eckert, Charles A.; Liotta, Charles L.

    2014-01-01

    The high pressure sapphire cell apparatus was constructed to visually determine the composition of multiphase systems without physical sampling. Specifically, the sapphire cell enables visual data collection from multiple loadings to solve a set of material balances to precisely determine phase composition. Ternary phase diagrams can then be established to determine the proportion of each component in each phase at a given condition. In principle, any ternary system can be studied although ternary systems (gas-liquid-liquid) are the specific examples discussed herein. For instance, the ternary THF-Water-CO2 system was studied at 25 and 40 °C and is described herein. Of key importance, this technique does not require sampling. Circumventing the possible disturbance of the system equilibrium upon sampling, inherent measurement errors, and technical difficulties of physically sampling under pressure is a significant benefit of this technique. Perhaps as important, the sapphire cell also enables the direct visual observation of the phase behavior. In fact, as the CO2 pressure is increased, the homogeneous THF-Water solution phase splits at about 2 MPa. With this technique, it was possible to easily and clearly observe the cloud point and determine the composition of the newly formed phases as a function of pressure. The data acquired with the sapphire cell technique can be used for many applications. In our case, we measured swelling and composition for tunable solvents, like gas-expanded liquids, gas-expanded ionic liquids and Organic Aqueous Tunable Systems (OATS)1-4. For the latest system, OATS, the high-pressure sapphire cell enabled the study of (1) phase behavior as a function of pressure and temperature, (2) composition of each phase (gas-liquid-liquid) as a function of pressure and temperature and (3) catalyst partitioning in the two liquid phases as a function of pressure and composition. Finally, the sapphire cell is an especially effective tool to gather

  9. High-pressure sapphire cell for phase equilibria measurements of CO2/organic/water systems.

    PubMed

    Pollet, Pamela; Ethier, Amy L; Senter, James C; Eckert, Charles A; Liotta, Charles L

    2014-01-24

    The high pressure sapphire cell apparatus was constructed to visually determine the composition of multiphase systems without physical sampling. Specifically, the sapphire cell enables visual data collection from multiple loadings to solve a set of material balances to precisely determine phase composition. Ternary phase diagrams can then be established to determine the proportion of each component in each phase at a given condition. In principle, any ternary system can be studied although ternary systems (gas-liquid-liquid) are the specific examples discussed herein. For instance, the ternary THF-Water-CO2 system was studied at 25 and 40 °C and is described herein. Of key importance, this technique does not require sampling. Circumventing the possible disturbance of the system equilibrium upon sampling, inherent measurement errors, and technical difficulties of physically sampling under pressure is a significant benefit of this technique. Perhaps as important, the sapphire cell also enables the direct visual observation of the phase behavior. In fact, as the CO2 pressure is increased, the homogeneous THF-Water solution phase splits at about 2 MPa. With this technique, it was possible to easily and clearly observe the cloud point and determine the composition of the newly formed phases as a function of pressure. The data acquired with the sapphire cell technique can be used for many applications. In our case, we measured swelling and composition for tunable solvents, like gas-expanded liquids, gas-expanded ionic liquids and Organic Aqueous Tunable Systems (OATS)(1-4). For the latest system, OATS, the high-pressure sapphire cell enabled the study of (1) phase behavior as a function of pressure and temperature, (2) composition of each phase (gas-liquid-liquid) as a function of pressure and temperature and (3) catalyst partitioning in the two liquid phases as a function of pressure and composition. Finally, the sapphire cell is an especially effective tool to gather

  10. Direct molecular dynamics simulation of liquid-solid phase equilibria for two-component plasmas.

    PubMed

    Schneider, A S; Hughto, J; Horowitz, C J; Berry, D K

    2012-06-01

    We determine the liquid-solid phase diagram for carbon-oxygen and oxygen-selenium plasma mixtures using two-phase molecular dynamics simulations. We identify liquid, solid, and interface regions using a bond angle metric. To study finite-size effects, we perform 27,648- and 55,296-ion simulations. To help monitor nonequilibrium effects, we calculate diffusion constants D(i). For the carbon-oxygen system we find that D(O) for oxygen ions in the solid is much smaller than D(C) for carbon ions and that both diffusion constants are 80 or more times smaller than diffusion constants in the liquid phase. There is excellent agreement between our carbon-oxygen phase diagram and that predicted by Medin and Cumming. This suggests that errors from finite-size and nonequilibrium effects are small and that the carbon-oxygen phase diagram is now accurately known. The oxygen-selenium system is a simple two-component model for more complex rapid proton capture nucleosynthesis ash compositions for an accreting neutron star. Diffusion of oxygen, in a predominantly selenium crystal, is remarkably fast, comparable to diffusion in the liquid phase. We find a somewhat lower melting temperature for the oxygen-selenium system than that predicted by Medin and Cumming. This is probably because of electron screening effects.

  11. Phase equilibria and crystal chemistry of the R-Cu-Ti-O systems (R=lanthanides and Y)

    SciTech Connect

    Yang, Z.; Wong-Ng, W.; Kaduk, J.A.; Jang, M.; Liu, G.

    2009-05-15

    As part of the study of interaction of the Ba{sub 2}RCu{sub 3}O{sub 6+z} (R=lanthanides and Y) superconductor with SrTiO{sub 3} buffer, phase equilibria of the subsystem, R{sub 2}O{sub 3}-TiO{sub 2}-CuO (R=Nd, Y, and Yb), have been investigated in air at 960 deg. C. While the phase relationships of the two phase diagrams with smaller R (Y and Yb) are similar, substantial differences were found in the Nd{sub 2}O{sub 3}-TiO{sub 2}-CuO system, partly due to different phase formation in the binary R{sub 2}O{sub 3}-TiO{sub 2} and R{sub 2}O{sub 3}-CuO systems. R{sub 2}CuTiO{sub 6} and R{sub 2}Cu{sub 9}Ti{sub 12}O{sub 36} were the only ternary phases established in all the three diagrams. R{sub 2}Cu{sub 9}Ti{sub 12}O{sub 36} belongs to the perovskite-related [AC{sub 3}](B{sub 4})O{sub 12} family which is cubic Im3. Depending on the size of R{sup 3+}, R{sub 2}CuTiO{sub 6} crystallizes in two crystal systems: Pnma (R=La-Gd), and P6{sub 3}cm (R=Dy-Lu). The structure and crystal chemistry of the Pnma series of R{sub 2}CuTiO{sub 6} (R=La, Nd, Sm, Eu, and Gd) are discussed in detail in this paper. Patterns for selected members of R{sub 2}CuTiO{sub 6} have also been prepared and submitted for inclusion in the Powder Diffraction File (PDF). - Graphical abstract: Phase diagram of the Y{sub 2}O{sub 3}-CuO-TiO{sub 2} system prepared in air at 960 deg. C

  12. Phase equilibria study of the binary systems (N-hexylisoquinolinium thiocyanate ionic liquid + organic solvent or water).

    PubMed

    Królikowska, Marta; Karpińska, Monika; Zawadzki, Maciej

    2012-04-12

    Liquid-liquid phase equilibria (LLE) of binary mixtures containing a room-temperature ionic liquid N-hexylisoquinolinium thiocyanate, [HiQuin][SCN] with an aliphatic hydrocarbon (n-hexane, n-heptane), aromatic hydrocarbon (benzene, toluene, ethylbenzene, n-propylbenzene), cyclohexane, thiophene, water, and 1-alcohol (1-ethanol, 1-butanol, 1-hexanol, 1-octanol, 1-decanol) have been determined using a dynamic method from room temperature to the boiling-point of the solvent at ambient pressure. N-hexylisoquinolinium thiocyanate, [HiQuin][SCN] has been synthesized from N-hexyl-isoquinolinium bromide as a substrate. Specific basic characterization of the new compound including NMR spectra, elementary analysis, and water content have been done. The density and viscosity of pure ionic liquid were determined over a wide temperature range from 298.15 to 348.15 K. The mutual immiscibility with an upper critical solution temperature (UCST) for the binary systems {IL + aliphatic hydrocarbon, cyclohexane, or water} was detected. In the systems of {IL + aromatic hydrocarbon or thiophene} an immiscibility gap with a lower critical solution temperature (LCST) was observed. Complete miscibility in the liquid phase, over a whole range of ionic liquid mole fraction, was observed for the binary mixtures containing IL and an 1-alcohol. For the tested binary systems with immiscibility gap {IL + aliphatic hydrocarbon, aromatic hydrocarbon, cyclohexane, thiophene, or water}, the parameters of the LLE correlation have been derived using the NRTL equation. The basic thermal properties of the pure IL, that is, the glass-transition temperature as well as the heat capacity at the glass-transition temperature, have been measured using a differential scanning microcalorimetry technique (DSC). Decomposition of the IL was detected by simultaneous thermogravimetric/differential thermal analysis (TG/DTA) experiments.

  13. Transferable potentials for phase equilibria. 10. Explicit-hydrogen description of substituted benzenes and polycyclic aromatic compounds.

    PubMed

    Rai, Neeraj; Siepmann, J Ilja

    2013-01-10

    The explicit-hydrogen version of the transferable potentials for phase equilibria (TraPPE-EH) force field is extended to various substituted benzenes through the parametrization of the exocyclic groups -F, -Cl, -Br, -C≡N, and -OH and to polycyclic aromatic hydrocarbons through the parametrization of the aromatic linker carbon atom for multiple rings. The linker carbon together with the TraPPE-EH parameters for aromatic heterocycles constitutes a force field for fused-ring heterocycles. Configurational-bias Monte Carlo simulations in the Gibbs ensemble were carried out to compute vapor-liquid coexistence curves for fluorobenzene; chlorobenzene; bromobenzene; di-, tri-, and hexachlorobenzene isomers; 2-chlorofuran; 2-chlorothiophene; benzonitrile; phenol; dihydroxybenzene isomers; 1,4-benzoquinone; naphthalene; naphthalene-2-carbonitrile; naphthalen-2-ol; quinoline; benzo[b]thiophene; benzo[c]thiophene; benzoxazole; benzisoxazole; benzimidazole; benzothiazole; indole; isoindole; indazole; purine; anthracene; and phenanthrene. The agreement with the limited experimental data is very satisfactory, with saturated liquid densities and vapor pressures reproduced to within 1.5% and 15%, respectively. The mean unsigned percentage errors in the normal boiling points, critical temperatures, and critical densities are 0.9%, 1.2%, and 1.4%, respectively. Additional simulations were carried out for binary systems of benzene/benzonitrile, benzene/phenol, and naphthalene/methanol to illustrate the transferability of the developed potentials to binary systems containing compounds of different polarity and hydrogen-bonding ability. A detailed analysis of the liquid-phase structures is provided for selected neat systems and binary mixtures.

  14. Determination of thermodynamic parameters of tautomerization in gas phase by mass spectrometry and DFT calculations: Keto-enol versus nitrile-ketenimine equilibria.

    PubMed

    Giussi, Juan M; Gastaca, Belen; Albesa, Alberto; Cortizo, M Susana; Allegretti, Patricia E

    2011-02-01

    The study of tautomerics equilibria is really important because the reactivity of each compound with tautomeric capacity can be determined from the proportion of each tautomer. In the present work the tautomeric equilibria in some γ,δ-unsaturated β-hydroxynitriles and γ,δ-unsaturated β-ketonitriles were studied. The first family of compounds presents two possible theoretical tautomers, nitrile and ketenimine, while the second one presents four possible theoretical tautomers, keto-nitrile, enol (E and Z)-nitrile and keto-ketenimine. The equilibrium in gas phase was studied by gas chromatography-mass spectrometry (GC-MS). Tautomerization enthalpies were calculated by this methodology, and results were compared with those obtained by density functional theory (DFT) calculations, observing a good agreement between them. Nitrile tautomers were favored within the first family of compounds, while keto-nitrile tautomers were favored in the second family. Copyright © 2010 Elsevier B.V. All rights reserved.

  15. Influence of gas phase equilibria on the chemical vapor deposition of graphene.

    PubMed

    Lewis, Amanda M; Derby, Brian; Kinloch, Ian A

    2013-04-23

    We have investigated the influence of gas phase chemistry on the chemical vapor deposition of graphene in a hot wall reactor. A new extended parameter space for graphene growth was defined through literature review and experimentation at low pressures (≥0.001 mbar). The deposited films were characterized by scanning electron microscopy, Raman spectroscopy, and dark field optical microscopy, with the latter showing promise as a rapid and nondestructive characterization technique for graphene films. The equilibrium gas compositions have been calculated across this parameter space. Correlations between the graphene films grown and prevalent species in the equilibrium gas phase revealed that deposition conditions associated with a high acetylene equilibrium concentration lead to good quality graphene deposition, and conditions that stabilize large hydrocarbon molecules in the gas phase result in films with multiple defects. The transition between lobed and hexagonal graphene islands was found to be linked to the concentration of the monatomic hydrogen radical, with low concentrations associated with hexagonal islands.

  16. Isotropic-nematic phase equilibria in the Onsager theory of hard rods with length polydispersity.

    PubMed

    Speranza, Alessandro; Sollich, Peter

    2003-06-01

    We analyze the effect of a continuous spread of particle lengths on the phase behavior of rodlike particles, using the Onsager theory of hard rods. Our aim is to establish whether "unusual" effects such as isotropic-nematic-nematic (I-N-N) phase separation can occur even for length distributions with a single peak. We focus on the onset of I-N coexistence. For a log-normal distribution, we find that a finite upper cutoff on rod lengths is required to make this problem well posed. The cloud curve, which tracks the density at the onset of I-N coexistence as a function of the width of the length distribution, exhibits a kink; this demonstrates that the phase diagram must contain a three-phase I-N-N region. Theoretical analysis shows that in the limit of large cutoff, the cloud point density actually converges to zero, so that phase separation results at any nonzero density; this conclusion applies to all length distributions with fatter-than-exponentail tails. Finally, we consider the case of a Schulz distribution, with its exponential tail. Surprisingly, even here the long rods (and hence the cutoff) can dominate the phase behavior, and a kink in the cloud curve and I-N-N coexistence again result. Theory establishes that there is a nonzero threshold for the width of the length distribution above which these long-rod effects occur, and shows that the cloud and shadow curves approach nonzero limits for a large cutoff, both in good agreement with the numerical results.

  17. Phase Equilibria of Ternary and Quaternary Systems Containing Diethyl Carbonate with Water.

    PubMed

    Chen, Yao; Wen, Caiyu; Zhou, Xiaoming; Zeng, Jun

    2014-01-01

    In this study liquid phase equilibrium compositions were measured at 298.15 K under atmospheric pressure for (water + propan-1-ol + diethyl carbonate (DEC) + benzene or cyclohexane or heptane) quaternary systems and (water + DEC + propan-1-ol or benzene or cyclohexane) ternary systems. Good correlation of the experimental LLE data was seen for the measured systems by both modified and extended UNIQUAC models. The solubility of DEC in aqueous and organic phases is shown by equilibrium distribution coefficients calculated from the LLE data.

  18. Dual-wavelength Raman spectroscopy approach for studying fluid-phase equilibria using a single laser.

    PubMed

    Kiefer, Johannes

    2010-06-01

    A novel Raman spectroscopy setup for the investigation of multiphase fluid mixtures is proposed. The total output of a frequency-doubled Nd:YAG laser is separated into a strong 532 nm beam for generating Raman signals in the vapor phase and the weak residual of the fundamental 1064 nm radiation to be utilized as laser source for Raman scattering in the liquid phase. This approach will provide sufficient signal intensity from the gas (despite low density) for determination of mixture composition and at the same time it facilitates recording high-resolution spectra from the liquid in order to allow studying molecular physics phenomena together with concentration measurements.

  19. Molecular theory for the phase equilibria and cluster distribution of associating fluids with small bond angles.

    PubMed

    Marshall, Bennett D; Chapman, Walter G

    2013-08-07

    We develop a new theory for associating fluids with multiple association sites. The theory accounts for small bond angle effects such as steric hindrance, ring formation, and double bonding. The theory is validated against Monte Carlo simulations for the case of a fluid of patchy colloid particles with three patches and is found to be very accurate. Once validated, the theory is applied to study the phase diagram of a fluid composed of three patch colloids. It is found that bond angle has a significant effect on the phase diagram and the very existence of a liquid-vapor transition.

  20. A Classroom Experiment on Phase Equilibria Involving Orientational Disordering in Crystals.

    ERIC Educational Resources Information Center

    Mjojo, C. C.

    1985-01-01

    Background information, procedures used, and results obtained are provided for an experiment in which a phase diagram is determined using a differential scanning calorimeter. Commercial samples of D-camphoric anhydride (Eastman Kodak) and D,L-camphoric anhydride (Aldrich) were used in the experiment. (JN)

  1. Phase equilibria in ionic liquid-aromatic compound mixtures, including benzene fluorination effects.

    PubMed

    Blesic, Marijana; Lopes, José N Canongia; Pádua, Agílio A H; Shimizu, Karina; Gomes, Margarida F Costa; Rebelo, Luís Paulo N

    2009-05-28

    This work extends the scope of previous studies on the phase behavior of mixtures of ionic liquids with benzenes or its derivatives by determining the solid-liquid and liquid-liquid phase diagrams of mixtures containing an ionic liquid and a fluorinated benzene. The systems studied include 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide plus hexafluorobenzene or 1,3,5-trifluorobenzene and 1-ethyl-3-methylimidazolium triflate or N-ethyl-N-methylpyrrolidinium bis(trifluoromethanesulfonyl)imide plus benzene. The phase diagrams exhibit different kinds of solid-liquid behavior: the (usual) occurrence of eutectic points; the (not-so-usual) presence of congruent melting points and the corresponding formation of inclusion crystals; or the observation of different ionic liquid crystalline phases (polymorphism). These different types of behavior can be controlled by temperature annealing during crystallization or by the nature of the aromatic compound and can be interpreted, at a molecular level, taking into account the structure of the crystals or liquid mixtures, together with the unique characteristics of ionic liquids, namely the dual nature of their interactions with aromatic compounds.

  2. Transport and Phase Equilibria Properties for Steam Flooding of Heavy Oils

    SciTech Connect

    Gabitto, Jorge; Barrufet, Maria

    2002-11-20

    The objectives of this research included experimental determination and rigorous modeling and computation of phase equilibrium diagrams, volumetric, and transport properties of hydrocarbon/CO2/water mixtures at pressures and temperatures typical of steam injection processes for thermal recovery of heavy oils.

  3. The system Ta-V-Si: Crystal structure and phase equilibria

    SciTech Connect

    Khan, A.U.; Broz, P.; Bursik, J.; Grytsiv, A.; Chen, X.-Q.; Giester, G.; Rogl, P.

    2012-03-15

    Phase relations have been evaluated for the Ta-V-Si system at 1500 and 1200 Degree-Sign C. Three ternary phases were found: {tau}{sub 1}-(Ta,V){sub 5}Si{sub 3} (Mn{sub 5}Si{sub 3}-type), {tau}{sub 2}-Ta(Ta,V,Si){sub 2} (MgZn{sub 2}-type) and {tau}{sub 3}-Ta(Ta,V,Si){sub 2} (MgCu{sub 2}-type). The crystal structure of {tau}{sub 2}-Ta(Ta,V,Si){sub 2} was solved by X-ray single crystal diffraction (space group P6{sub 3}/mmc). Atom order in the crystal structures of {tau}{sub 1}-(Ta,V){sub 5}Si{sub 3} (Mn{sub 5}Si{sub 3} type) and {tau}{sub 3}-Ta(Ta,V,Si){sub 2} was derived from X-ray powder diffraction data. A large homogeneity range was found for {tau}{sub 1}-(Ta{sub x}V{sub 1-x}){sub 5}Si{sub 3} revealing random exchange of Ta and V at a constant Si content. At 1500 Degree-Sign C, the end points of the {tau}{sub 1}-phase solution (0.082{<=}x{<=}0.624) are in equilibrium with the solutions (Ta{sub 1-x}V{sub x}){sub 5}Si{sub 3} (Cr{sub 5}B{sub 3} type, 0{<=}x{<=}0.128) and (Ta{sub x}V{sub 1-x}){sub 5}Si{sub 3} (W{sub 5}Si{sub 3} type, 0{<=}x{<=}0.048). - Graphical abstract: Phase relations have been evaluated for the Ta-V-Si system at 1500 and 1200 Degree-Sign C. Highlights: Black-Right-Pointing-Pointer Phase relations have been evaluated for the Ta-V-Si system at 1500 and 1200 Degree-Sign C. Black-Right-Pointing-Pointer Three ternary phases were found at 1500 Degree-Sign C. Black-Right-Pointing-Pointer At 1500 Degree-Sign C, {tau}{sub 1}-phase has large homogeneity region (0.064{<=}x{<=}0.624).

  4. Monte Carlo simulations of high-pressure phase equilibria of CO2-H2O mixtures.

    PubMed

    Liu, Yang; Panagiotopoulos, Athanassios Z; Debenedetti, Pablo G

    2011-05-26

    Histogram-reweighting grand canonical Monte Carlo simulations were used to obtain the phase behavior of CO(2)-H(2)O mixtures over a broad temperature and pressure range (50 °C ≤ T ≤ 350 °C, 0 ≤ P ≤ 1000 bar). We performed a comprehensive test of several existing water (SPC, TIP4P, TIP4P2005, and exponential-6) and carbon dioxide (EPM2, TraPPE, and exponential-6) models using conventional Lorentz-Berthelot combining rules for the unlike-pair parameters. None of the models we studied reproduce adequately experimental data over the entire temperature and pressure range, but critical assessments were made on the range of T and P where particular model pairs perform better. Away from the critical region (T ≤ 250 °C), the exponential-6 model combination yields the best predictions for the CO(2)-rich phase, whereas the TraPPE/TIP4P2005 model combination provides the most accurate coexistence composition and pressure for the H(2)O-rich phase. Near the critical region (250 °C < T ≤ 350 °C), the critical points are not accurately estimated by any of the models studied, but the exponential-6 models are able to qualitatively capture the critical loci and the shape of the phase envelopes. Local improvements can be achieved at specific temperatures by introducing modification factors to the Lorentz-Berthelot combining rules, but the modified combining rule is still not able to achieve global improvements over the entire temperature and pressure range. Our work points to the challenge and importance of improving current atomistic models so as to accurately predict the phase behavior of this important binary mixture.

  5. Phase equilibria and structural investigations in the system Al-Fe-Si.

    PubMed

    Marker, Martin C J; Skolyszewska-Kühberger, Barbara; Effenberger, Herta S; Schmetterer, Clemens; Richter, Klaus W

    2011-12-01

    The Al-Fe-Si system was studied for an isothermal section at 800 °C in the Al-rich part and at 900 °C in the Fe-rich part, and for half a dozen vertical sections at 27, 35, 40, 50 and 60 at.% Fe and 5 at.% Al. Optical microscopy and powder X-ray diffraction (XRD) was used for initial sample characterization, and Electron Probe Microanalysis (EPMA) and Scanning Electron Microscopy (SEM) of the annealed samples was used to determine the exact phase compositions. Thermal reactions were studied by Differential Thermal Analysis (DTA). Our experimental results are generally in good agreement with the most recent phase diagram versions of the system Al-Fe-Si. A new ternary high-temperature phase τ12 (cF96, NiTi2-type) with the composition Al48Fe36Si16 was discovered and was structurally characterized by means of single-crystal and powder XRD. The variation of the lattice parameters of the triclinic phase τ1 with the composition Al2+x Fe3Si3-x (-0.3 < x < 1.3) was studied in detail. For the binary phase FeSi2 only small solubility of Al was found in the low-temperature modification LT-FeSi2 (ζβ ) but significant solubility in the high-temperature modification HT-FeSi2 (ζα ) (8.5 at.% Al). It was found that the high-temperature modification of FeSi2 is stabilized down to much lower temperature in the ternary, confirming earlier literature suggestions on this issue. DTA results in four selected vertical sections were compared with calculated sections based on a recent CALPHAD assessment. The deviations of liquidus values are significant suggesting the need for improvement of the thermodynamic models.

  6. Phase equilibria and structural investigations in the system Al–Fe–Si

    PubMed Central

    Marker, Martin C.J.; Skolyszewska-Kühberger, Barbara; Effenberger, Herta S.; Schmetterer, Clemens; Richter, Klaus W.

    2011-01-01

    The Al–Fe–Si system was studied for an isothermal section at 800 °C in the Al-rich part and at 900 °C in the Fe-rich part, and for half a dozen vertical sections at 27, 35, 40, 50 and 60 at.% Fe and 5 at.% Al. Optical microscopy and powder X-ray diffraction (XRD) was used for initial sample characterization, and Electron Probe Microanalysis (EPMA) and Scanning Electron Microscopy (SEM) of the annealed samples was used to determine the exact phase compositions. Thermal reactions were studied by Differential Thermal Analysis (DTA). Our experimental results are generally in good agreement with the most recent phase diagram versions of the system Al–Fe–Si. A new ternary high-temperature phase τ12 (cF96, NiTi2-type) with the composition Al48Fe36Si16 was discovered and was structurally characterized by means of single-crystal and powder XRD. The variation of the lattice parameters of the triclinic phase τ1 with the composition Al2+xFe3Si3−x (−0.3 < x < 1.3) was studied in detail. For the binary phase FeSi2 only small solubility of Al was found in the low-temperature modification LT-FeSi2 (ζβ) but significant solubility in the high-temperature modification HT-FeSi2 (ζα) (8.5 at.% Al). It was found that the high-temperature modification of FeSi2 is stabilized down to much lower temperature in the ternary, confirming earlier literature suggestions on this issue. DTA results in four selected vertical sections were compared with calculated sections based on a recent CALPHAD assessment. The deviations of liquidus values are significant suggesting the need for improvement of the thermodynamic models. PMID:27087751

  7. Phase equilibria of the oxide hydroxide halide systems of Sm, Eu, and Gd. The crystal structure of Gd 3O(OH) 5Br 2

    NASA Astrophysics Data System (ADS)

    Lance-Gomez, Edward Theodore; Haschke, John M.

    1980-12-01

    An investigation of hydrothermal phase equilibria in the halide-containing (Cl, Br, I) systems of Sm, Eu, and Gd has shown that diversities in behavior occur across the lanthanide ( Ln) series and within the halide group. In the chloride systems, the trihydroxide, two phases at a {Cl}/{Ln} ratio of 0.4, and Ln(OH) 2Cl phases are found. Equilibria in the bromide systems are more complex; Ln(OH) 3, Ln7(OH) 18Br 3, a high-temperature phase at {Br}/{Ln} = 0.45, Ln 3O(OH) 5Br 2, and Ln(OH) 2Br are observed. A single iodide-containing phase, Ln(OH) 2.67I 0.33, is found. X-Ray diffraction data are reported for all the previously unreported phases and the thermal decomposition behaviors of representative phases are described. The results of a single-crystal X-ray structure determination of orthorhombic ( Pmmn) Gd 2O(OH) 5Br 2 are reported and discussed.

  8. TRANSPORT AND PHASE EQUILIBRIA PROPERITIES FOR STEAM FLOODING OF HEAVY OILS

    SciTech Connect

    Jorge Gabitto; Maria Barrufet

    2002-09-01

    Hydrocarbon/water and CO{sub 2} systems are frequently found in petroleum recovery processes, petroleum refining, and gasification of coals, lignites and tar sands. Techniques to estimate the phase volume and phase composition are indispensable to design and improve oil recovery processes such as steam, hot water, or CO{sub 2}/steam combinations of flooding techniques typically used for heavy oils. An interdisciplinary research program to quantify transport, PVT, and equilibrium properties of selected oil/CO{sub 2}/water mixtures at pressures up to 10,000 psia and at temperatures up to 500 F has been put in place. The objectives of this research include experimental determination and rigorous modeling and computation of phase equilibrium diagrams, and volumetric properties of hydrocarbon/CO{sub 2}/water mixtures at pressures and temperatures typical of steam injection processes for thermal recovery of heavy oils. Highlighting the importance of phase behavior, researchers ([1], and [2]) insist on obtaining truly representative reservoir fluids samples for experimental analysis. The prevailing sampling techniques used for compositional analysis of the fluids have potential for a large source of error. These techniques bring the sample to atmospheric conditions and collect the liquid and vapor portion of the samples for further analysis. We developed a new experimental technique to determine phase volumes, compositions and equilibrium K-values at reservoir conditions. The new methodology is able to measure phase volume and composition at reservoir like temperatures and pressures. We use a mercury free PVT system in conjunction with a Hewlett Packard gas chromatograph capable of measuring compositions on line at high pressures and temperatures. This is made possible by an essentially negligible disturbance of the temperature and pressure equilibrium during phase volume and composition measurements. In addition, not many samples are withdrawn for compositional analysis

  9. Scale bridging description of coherent phase equilibria in the presence of surfaces and interfaces

    NASA Astrophysics Data System (ADS)

    Spatschek, R.; Gobbi, G.; Hüter, C.; Chakrabarty, A.; Aydin, U.; Brinckmann, S.; Neugebauer, J.

    2016-10-01

    We investigate phase separation including elastic coherency effects in the bulk and at surfaces and find a reduction of the solubility limit in the presence of free surfaces. This mechanism favors phase separation near free surfaces even in the absence of external stresses. We apply the theory to hydride formation in nickel, iron, and niobium and obtain a reduction of the solubility limit by up to two orders of magnitude at room temperature in the presence of free surfaces. We develop in particular a scale bridging description of the solubility limit in the low-temperature regime, where the long-ranged elastic effects are expressed through a geometrical solubility modification factor, which expresses the difference to bulk systems. This expression allows to include elastic coherency effects near surfaces, e.g., in ab initio simulations.

  10. The studies of phase equilibria and efficiency assessment for self-emulsifying lipid-based formulations.

    PubMed

    Shahba, Ahmad Abdul-Wahhab; Mohsin, Kazi; Alanazi, Fars Kaed

    2012-06-01

    The study was designed to build up a database for the evaluation of the self-emulsifying lipid formulations performance. A standard assessment method was constructed to evaluate the self-emulsifying efficiency of the formulations based on five parameters including excipients miscibility, spontaneity, dispersibility, homogeneity, and physical appearance. Equilibrium phase studies were conducted to investigate the phase changes of the anhydrous formulation in response to aqueous dilution. Droplet size studies were carried out to assess the influence of lipid and surfactant portions on the resulted droplet size upon aqueous dilution. Formulations containing mixed glycerides showed enhanced self-emulsification with both lipophilic and hydrophilic surfactants. Increasing the polarity of the lipid portion in the formulation leaded to progressive water solubilization capacity. In addition, formulations containing medium chain mixed glycerides and hydrophilic surfactants showed lower droplet size compared with their long chain and lipophilic counterparts. The inclusion of mixed glycerides in the lipid formulations enormously enhances the formulation efficiency.

  11. Sedimentation equilibria of ferrofluids: II. Experimental osmotic equations of state of magnetite colloids.

    PubMed

    Luigjes, Bob; Thies-Weesie, Dominique M E; Erné, Ben H; Philipse, Albert P

    2012-06-20

    The first experimental osmotic equation of state is reported for well-defined magnetic colloids that interact via a dipolar hard-sphere potential. The osmotic pressures are determined from the sedimentation equilibrium concentration profiles in ultrathin capillaries using a low-velocity analytical centrifuge, which is the subject of the accompanying paper I. The pressures of the magnetic colloids, measured accurately to values as low as a few pascals, obey Van 't Hoff's law at low concentrations, whereas at increasing colloid densities non-ideality appears in the form of a negative second virial coefficient. This virial coefficient corresponds to a dipolar coupling constant that agrees with the coupling constant obtained via independent magnetization measurements. The coupling constant manifests an attractive potential of mean force that is significant but yet not quite strong enough to induce dipolar chain formation. Our results disprove van der Waals-like phase behavior of dipolar particles for reasons that are explained.

  12. The role of intermolecular interactions in the prediction of the phase equilibria of carbon dioxide hydrates

    NASA Astrophysics Data System (ADS)

    Costandy, Joseph; Michalis, Vasileios K.; Tsimpanogiannis, Ioannis N.; Stubos, Athanassios K.; Economou, Ioannis G.

    2015-09-01

    The direct phase coexistence methodology was used to predict the three-phase equilibrium conditions of carbon dioxide hydrates. Molecular dynamics simulations were performed in the isobaric-isothermal ensemble for the determination of the three-phase coexistence temperature (T3) of the carbon dioxide-water system, at pressures in the range of 200-5000 bar. The relative importance of the water-water and water-guest interactions in the prediction of T3 is investigated. The water-water interactions were modeled through the use of TIP4P/Ice and TIP4P/2005 force fields. The TraPPE force field was used for carbon dioxide, and the water-guest interactions were probed through the modification of the cross-interaction Lennard-Jones energy parameter between the oxygens of the unlike molecules. It was found that when using the classic Lorentz-Berthelot combining rules, both models fail to predict T3 accurately. In order to rectify this problem, the water-guest interaction parameters were optimized, based on the solubility of carbon dioxide in water. In this case, it is shown that the prediction of T3 is limited only by the accuracy of the water model in predicting the melting temperature of ice.

  13. The role of intermolecular interactions in the prediction of the phase equilibria of carbon dioxide hydrates.

    PubMed

    Costandy, Joseph; Michalis, Vasileios K; Tsimpanogiannis, Ioannis N; Stubos, Athanassios K; Economou, Ioannis G

    2015-09-07

    The direct phase coexistence methodology was used to predict the three-phase equilibrium conditions of carbon dioxide hydrates. Molecular dynamics simulations were performed in the isobaric-isothermal ensemble for the determination of the three-phase coexistence temperature (T3) of the carbon dioxide-water system, at pressures in the range of 200-5000 bar. The relative importance of the water-water and water-guest interactions in the prediction of T3 is investigated. The water-water interactions were modeled through the use of TIP4P/Ice and TIP4P/2005 force fields. The TraPPE force field was used for carbon dioxide, and the water-guest interactions were probed through the modification of the cross-interaction Lennard-Jones energy parameter between the oxygens of the unlike molecules. It was found that when using the classic Lorentz-Berthelot combining rules, both models fail to predict T3 accurately. In order to rectify this problem, the water-guest interaction parameters were optimized, based on the solubility of carbon dioxide in water. In this case, it is shown that the prediction of T3 is limited only by the accuracy of the water model in predicting the melting temperature of ice.

  14. Phase equilibria of the Cu-Sn-Ti ternary system at 823K

    NASA Astrophysics Data System (ADS)

    Zhou, Guo-jun; Zhou, Yong; Luo, Yun

    2017-02-01

    The isothermal section in the Cu-Sn enrich part of the Cu-Sn-Ti ternary system at 823K was determined by using solid-solid-liquid diffusion triple approach. One ternary compound CuSnTi was found, and 12 three-phase fields were detected. The following 10 three-phase regions are well established: CuTi2+CuTi+Sn5Ti6, Sn5Ti6+Sn3Ti2+ CuSnTi, Liquid+Sn3Ti2+CuSnTi, Liquid+CuSnTi+Cu3Sn, CuTi+Cu4Ti3+Sn5Ti6, CuSnTi+Cu4Ti3+Sn5Ti6, CuSnTi+Cu3Sn+Cu41Sn11, CuSnTi+Cu41Sn11+Bcc_a2, CuSnTi+Cu4Ti+Cu, and CuSnTi+Bcc_a2+Cu. Phase relations in the Ti-enrich corner of this system require further investigation.

  15. Structure and phase equilibria of mixtures of the complex salt hexadecyltrimethylammonium polymethacrylate, water and different oils.

    PubMed

    Bernardes, Juliana Silva; Loh, Watson

    2008-02-15

    This work reports on phase diagrams for mixtures of a complex salt formed by a cationic surfactant and an oppositely charged polyelectrolyte, hexadecyltrimethylammonium polymethacrylate, in binary mixtures with water and in ternary mixtures containing water and organic solvents of different polarity ('oils'): decanol, octanol, p-xylene and cyclohexane. The liquid crystalline structures formed were identified by small angle X-ray scattering measurements, which also provided information about changes in the size of the aggregates as a function of the system composition. These results are analysed in comparison with others previously reported [Bernardes et al., J. Phys. Chem. B 110 (2006) 10332-10340] for the analog complex formed with polyacrylate and, in general, reveal that the presence of an extra methylene group in the polymer chain does not produce significant changes in the complex phase diagrams nor in the structure of the liquid crystalline phases formed. Additionally, the obtained results confirm once more the approach used to analyze these kinds of systems formed by polymer and oppositely charged surfactant.

  16. Development of Simulation Methods in the Gibbs Ensemble to Predict Polymer-Solvent Phase Equilibria

    NASA Astrophysics Data System (ADS)

    Gartner, Thomas; Epps, Thomas; Jayaraman, Arthi

    Solvent vapor annealing (SVA) of polymer thin films is a promising method for post-deposition polymer film morphology control. The large number of important parameters relevant to SVA (polymer, solvent, and substrate chemistries, incoming film condition, annealing and solvent evaporation conditions) makes systematic experimental study of SVA a time-consuming endeavor, motivating the application of simulation and theory to the SVA system to provide both mechanistic insight and scans of this wide parameter space. However, to rigorously treat the phase equilibrium between polymer film and solvent vapor while still probing the dynamics of SVA, new simulation methods must be developed. In this presentation, we compare two methods to study polymer-solvent phase equilibrium-Gibbs Ensemble Molecular Dynamics (GEMD) and Hybrid Monte Carlo/Molecular Dynamics (Hybrid MC/MD). Liquid-vapor equilibrium results are presented for the Lennard Jones fluid and for coarse-grained polymer-solvent systems relevant to SVA. We found that the Hybrid MC/MD method is more stable and consistent than GEMD, but GEMD has significant advantages in computational efficiency. We propose that Hybrid MC/MD simulations be used for unfamiliar systems in certain choice conditions, followed by much faster GEMD simulations to map out the remainder of the phase window.

  17. Phase equilibria controls on fluid chemistry at the Lucky Strike hydrothermal field, Mid- Atlantic Ridge

    NASA Astrophysics Data System (ADS)

    Pester, N. J.; Rough, M.; Ding, K.; Seyfried, W. E.

    2008-12-01

    Sampling efforts conducted at the Lucky Strike hydrothermal field (Mid-Atlantic Ridge, 37°N) in July 2008 add to time series data collected between 1993 and 1996. We report for the first time vent fluids enriched in dissolved chloride relative to seawater and CO2 concentrations as much as three times greater than previously recorded. Consistent with previous observations, fluids of higher chlorinity were venting near the margins of the lava lake located in the summit depression and vents with chloride depleted fluids were observed at shallower depths between the southern and eastern volcanic cones. The chloride variability is indicative of fluid phase separation occurring near the two-phase boundary in the NaCl-H2O system. Low Mg concentrations in the fluids indicate the low exit temperatures (T = 236-324°C) are primarily the result of conductive cooling. Of special interest is 2608 vent, which registered the highest temperature as well as the highest chloride and silica concentrations. All sampled vents, with exception of 2608, had CO2 concentrations in excess of 100 mmol/kg and uniform CH4 concentrations. The high CO2 values may indicate an increase in volcanic activity and an inverse relationship between chlorinity and CO2 suggest that fluid CO2 was acquired prior to or during phase separation. Conversely, 2608 had slightly higher CH4 than all other vents, suggesting an alternate, possibly sedimentary source. Recent seismic data from Lucky Strike suggest that large rift-bounding faults provide fluid pathways that penetrate down to a magma chamber located 3.25 km beneath the vent field (1700 m depth). This suggests a common heat source for the field and deviations in fluid chemistries (e.g. silica, 13.6-16.1 mmol/kg) likely reflect phase separation and/or differing upflow paths/residence times prior to exiting at the seafloor. All fluids have low H2 and H2S, indicating oxidizing reaction conditions. The presence of deeply penetrating faults support the previous

  18. Phase Equilibria of BaO-R2O3-CuO z Systems (R = Y and Lanthanides) under CO2-free Conditions

    NASA Astrophysics Data System (ADS)

    Wong-Ng, W.; Yang, Z.; Cook, L. P.; Frank, J.; Loung, M.; Huang, Q.

    2007-10-01

    For applications ranging from phase equilibria to the processing of second-generation high T c superconductor-coated-conductors, phase diagrams constructed under carbonate-free conditions are needed. Subsolidus phase equilibria of BaO-R2O3-CuO z (R = Ho) have been investigated at {p}_{{{{O}}_{{{2}}} }} = 100{Pa} (810°C), 21 kPa (875°C) and 0.1 MPa (850 and 930°C) by applying controlled atmosphere methods to minimize the presence of carbonate and CO2 and H2O contamination. Under carbonate-free conditions, most of these phase diagrams are different from those reported in the literature. In this paper, we also review and compare the phase diagrams of ten BaO-R2O3-CuO z systems (R = Nd, Sm, Eu, Gd, Dy, Y, Ho, Er, Tm and Yb) that were previously determined in this laboratory under {p}_{{{{O}}_{{{2}}} }} = 100{Pa}{.} Among these diagrams, a distinct trend of phase formation and tie-line relationships is observed.

  19. Phase equilibria along a basalt-rhyolite mixing line: implications for the origin of calc-alkaline intermediate magmas

    NASA Astrophysics Data System (ADS)

    Ussler, William; Glazner, Allen F.

    1989-02-01

    One-atmosphere, anhydrous phase equilibria determined for alkali basalt/high-silica rhyolite mixtures provide a model for crystallization of natural calc-alkaline mixed magmas. The compositional trend defined by these mixtures mimics the trends of many continental calc-alkaline volcanic suites. As with many naturally occurring suites, the mixtures studied straddle the low-pressure olivine-plagioclase-augite thermal divide. Magma mixing provides a convenient method for magmas to cross this thermal divide in the absence of magnetite crystallization. For the mixtures, Mg-rich olivine (Fo82 87) coexists alone with liquid over an exceptionally large range of temperature and silica content (up to 63 wt% SiO2). This indicates that the Mg-rich olivines found in many andesites and dacites are not necessarily out of equilibrium with the host magma, as is commonly assumed. Such crystals may be either primary phenocrysts, or inherited phenocrysts derived from a mafic magma that mixed with a silicic magma. For the bulk compositions studied, the distribution of Fe and Mg between olivine and liquid ( K D ) is equal to 0.3 and is independent of temperature and composition. This result extends to silicic andesites the applicability of K D arguments for tests of equilibrium between olivine and groundmass and for modeling of fractional crystallization. In contrast, the distribution of calcium and sodium between plagioclase and liquid varies significantly with temperature and composition. Therefore, plagioclase-liquid K D s cannot be used for fractional crystallization modeling or as a test of equilibrium. Calcic plagioclase from a basalt will be close to equilibrium with andesitic mixtures, but sodic plagioclase from a rhyolite will be greatly out of equilibrium. This explains the common observation that calcic plagioclase crystals in hybrid andesites are generally close to textural equilibrium with the surrounding groundmass, but sodic plagioclase crystals generally show remelting

  20. Acoustic determination of phase equilibria. Annual report, June 1991-May 1992

    SciTech Connect

    Colgate, S.O.

    1992-06-01

    Sonic speeds in gaseous n-butane and a simulated natural gas mixture were measured in a spherical acoustic resonator and reference state heat capacities and second virial coefficients inferred from the data. A high resolution cylindrical acoustic resonator was developed for study of the fast/slow sound phenomenon in gas mixtures, and experiments with it are underway.

  1. Phase Equilibria and Ionic Solvation in the Lithium Tetrafluoroborate-Dimethylsulfoxide System

    NASA Astrophysics Data System (ADS)

    Gafurov, M. M.; Kirillov, S. A.; Gorobets, M. I.; Rabadanov, K. Sh.; Ataev, M. B.; Tretyakov, D. O.; Aydemirov, K. M.

    2015-01-01

    The phase diagram and electrical conductivity isotherms for the lithium tetrafluoroborate (LiBF4)-dimethylsulfoxide (DMSO) system and Raman spectra of DMSO and the LiBF4-DMSO solution were studied. Spectroscopic signatures of a H-bond between DMSO and BF4 - ions were found. The bonds of Li+ ions to the solvent were stronger than the bonds in DMSO dimers because formation of the solvate destroyed dimeric DMSO molecules. The τω values for DMSO molecules in the Li+-ion solvate shell of the LiBF4-DMSO system were similar to those for associated solvent molecules.

  2. Solidification and phase equilibria in the Fe-C-Cr-NbC system

    NASA Astrophysics Data System (ADS)

    Gregolin, J. A. R.; Alcantara, N. G.

    1991-10-01

    A solidification model is developed and experimentally checked for Fe-C-Cr-Nb alloys in the white cast irons range. It is based on a partial quaternary Fe-C-Cr-NbC phase diagram and predicts the possible solidification paths for the alloys containing γ, with (Fe,Cr)7C3 and NbC as the microconstituents at room temperature. The dendritic γ to massive (Fe,Cr)7C3 transition in experimental alloy microstructures with NbC contents up to 22 pet is explained by this model. Thermal analysis is also used to compare the solidification paths and model approach.

  3. Liquidus temperatures and phase equilibria in the BaCl2-MCl-BaO systems

    NASA Astrophysics Data System (ADS)

    Nikolaeva, E. V.; Bovet, A. L.; Korzun, I. V.

    2017-02-01

    The liquidus temperatures of the BaO-BaCl2-MCl systems (with M = alkali metal) are determined by thermal analysis. The caloric effects observed during melting of the barium-containing chloride eutectic with barium oxide additions are studied. A chemical mechanism of barium oxide dissolution in the melts is confirmed. X-ray diffraction patterns taken for the melt solidified after experiment indicate the presence of barium oxychloride Ba4OCl6 in the solid phase. It is shown that the significant increase in the liquidus temperature in adding the barium oxide to barium-containing chloride molten mixtures is related to substantial changes in their composition and structure.

  4. The high-temperature phase equilibria of the Ni–Sn–Zn system: Isothermal sections

    PubMed Central

    Schmetterer, Clemens; Rajamohan, Divakar; Ipser, Herbert; Flandorfer, Hans

    2011-01-01

    In this work three complete isothermal sections of the Ni–Sn–Zn system at 700, 800 and 900 °C are presented. They were constructed based on experimental investigation of more than 60 alloy samples. Powder XRD, single crystal XRD, EPMA, and DTA measurements on selected samples were carried out. Two new ternary compounds, designated as τ2 (Ni5Sn4Zn) and τ3 (Ni7Sn9Zn5), were identified and their homogeneity ranges and crystal structures could be described. Whereas τ3 is only present at 700 °C, the τ2-phase was found at both 700 and 800 °C. No truly ternary compound could be found in the isothermal section at 900 °C. A seemingly ternary compound at 20 at% Sn in the Ni-rich part of Ni–Sn–Zn was found at 800 and 900 °C. Our XRD results, however, indicate that this phase is a ternary solid solution of Ni3Sn-HT from constituent binary Ni–Sn. It is stabilized to lower temperatures by additions of Zn. These new experimental results will provide valuable information to the thermodynamic description of alloy systems relevant for high-temperature lead-free soldering. PMID:27087750

  5. Influence of water solubility, phase equilibria, and capillary pressure on methane occurrence in sediments

    SciTech Connect

    Claypool, G.E.

    1996-12-31

    Microbial methane is generated in rapidly accumulating marine sediments (>40 m/my) where pore waters are deficient in dissolved oxygen and sulfate. Based on indirect geochemical evidence, microbial methane generation is largely confined to depths of between 10 and 1000 meters beneath the sea floor. Under shelf conditions (water depth <200 m), methane concentrations can exceed solubility in pore water and accumulate as free gas, or escape the sediment as bubbles, or be oxidized in surface sediments. Under some deeper-water conditions of continental slope and rise sediments, more of the methane can be retained and buried because of increased solubility, and because methane in excess of solubility can be stabilized as methane hydrate. Few direct measurements of methane concentration in subsurface pore waters have been made. However, methane-water phase transitions (gas-water contacts, base of gas hydrate reflector) on seismic records can be used with methane solubility relationships to estimate gas contents of sediments. Comparison of various environments shows a relatively narrow range of dissolved methane contents. In marine sediments, free gas (and methane hydrate) is stable only in contact with methane-saturated pore water. Finer-grained sediments can be supersaturated with respect to a gas (and gas hydrate?) phase because of capillary pressure inhibition of bubble (or hydrate?) formation. The amount of methane dissolved in marine sediment pore water is necessarily larger than that present as gas hydrate.

  6. Influence of water solubility, phase equilibria, and capillary pressure on methane occurrence in sediments

    SciTech Connect

    Claypool, G.E. )

    1996-01-01

    Microbial methane is generated in rapidly accumulating marine sediments (>40 m/my) where pore waters are deficient in dissolved oxygen and sulfate. Based on indirect geochemical evidence, microbial methane generation is largely confined to depths of between 10 and 1000 meters beneath the sea floor. Under shelf conditions (water depth <200 m), methane concentrations can exceed solubility in pore water and accumulate as free gas, or escape the sediment as bubbles, or be oxidized in surface sediments. Under some deeper-water conditions of continental slope and rise sediments, more of the methane can be retained and buried because of increased solubility, and because methane in excess of solubility can be stabilized as methane hydrate. Few direct measurements of methane concentration in subsurface pore waters have been made. However, methane-water phase transitions (gas-water contacts, base of gas hydrate reflector) on seismic records can be used with methane solubility relationships to estimate gas contents of sediments. Comparison of various environments shows a relatively narrow range of dissolved methane contents. In marine sediments, free gas (and methane hydrate) is stable only in contact with methane-saturated pore water. Finer-grained sediments can be supersaturated with respect to a gas (and gas hydrate ) phase because of capillary pressure inhibition of bubble (or hydrate ) formation. The amount of methane dissolved in marine sediment pore water is necessarily larger than that present as gas hydrate.

  7. Crystallization history of lunar picritic basalt sample 12002 - Phase-equilibria and cooling-rate studies

    NASA Technical Reports Server (NTRS)

    Walker, D.; Kirkpatrick, R. J.; Longhi, J.; Hays, J. F.

    1976-01-01

    Experimental crystallization of a lunar picrite composition (sample 12002) at controlled linear cooling rates produces systematic changes in the temperature at which crystalline phases appear, in the texture, and in crystal morphology as a function of cooling rate. Phases crystallize in the order olivine, chromium spinel, pyroxene, plagioclase, and ilmenite during equilibrium crystallization, but ilmenite and plagioclase reverse their order of appearance and silica crystallizes in the groundmass during controlled cooling experiments. The partition of iron and magnesium between olivine and liquid is independent of cooling rate, temperature, and pressure. Comparison of the olivine nucleation densities in the lunar sample and in the experiments indicates that the sample began cooling at about 1 deg C/hr. Pyroxene size, chemistry, and growth instability spacings, as well as groundmass coarseness, all suggest that the cooling rate subsequently decreased by as much as a factor of 10 or more. The porphyritic texture of this sample, then, is produced at a decreasing, rather than a discontinuously increasing, cooling rate.

  8. Phlogopite: high temperature solution calorimetry, thermodynamic properties, Al-Si and stacking disorder, and phase equilibria

    SciTech Connect

    Clemens, J.D.; Circone, S.; Navrotsky, A.; McMillan, P.F.; Smith, B.K.; Wall, V.J.

    1987-09-01

    Two structural features complicate the thermodynamics of synthetic and natural micas. The first is a varying degree of tetrahedral Al-Si disorder. Raman spectroscopic study of phlogopite synthesized above 600/sup 0/C suggests a disordered Al-Si distribution. Calculations of the P-T locus of the geologically important equilibrium: Phl + 3Qtz = 3En + Sa + H/sub 2/O, using the authors thermochemical data, agree within experimental error with the results of calculations based on the best available phase equilibrium data only if a tetrahedrally disordered phlogopite is assumed. Such calculations are very sensitive to uncertainties in ..delta..H/sup 0/ and ..delta..HG/sup 0/, and reversed phase equilibrium experiments remain essential to obtaining reliable estimates of thermodynamic properties. In contrast to these Al-Si disordered phlogopites, some biotites of low temperature parageneses (<600/sup 0/C) may have substantial Al-Si order. A variable Al-Si distribution has a substantial effect on the configurational entropy and therefore on the free energy of the mica in question. The second structural complication is stacking disorder, which is present in phlogopite synthesized at 650/sup 0/C but not in the 850/sup 0/C sample. The enthalpy difference between these two samples, determined by solution calorimetry, is smaller than the experimental uncertainty of +/- 1.0 kcal mol/sup -1/. Thus there appears to be little driving force for ordering, and micas with disordered stacking sequences may persist in many geologic environments.

  9. The high-temperature phase equilibria of the Ni-Sn-Zn system: Isothermal sections.

    PubMed

    Schmetterer, Clemens; Rajamohan, Divakar; Ipser, Herbert; Flandorfer, Hans

    2011-10-01

    In this work three complete isothermal sections of the Ni-Sn-Zn system at 700, 800 and 900 °C are presented. They were constructed based on experimental investigation of more than 60 alloy samples. Powder XRD, single crystal XRD, EPMA, and DTA measurements on selected samples were carried out. Two new ternary compounds, designated as τ2 (Ni5Sn4Zn) and τ3 (Ni7Sn9Zn5), were identified and their homogeneity ranges and crystal structures could be described. Whereas τ3 is only present at 700 °C, the τ2-phase was found at both 700 and 800 °C. No truly ternary compound could be found in the isothermal section at 900 °C. A seemingly ternary compound at 20 at% Sn in the Ni-rich part of Ni-Sn-Zn was found at 800 and 900 °C. Our XRD results, however, indicate that this phase is a ternary solid solution of Ni3Sn-HT from constituent binary Ni-Sn. It is stabilized to lower temperatures by additions of Zn. These new experimental results will provide valuable information to the thermodynamic description of alloy systems relevant for high-temperature lead-free soldering.

  10. Direct computation of two-phase icosahedral equilibria of lipid bilayer vesicles

    NASA Astrophysics Data System (ADS)

    Zhao, Siming; Healey, Timothy; Li, Qingdu

    2017-02-01

    Correctly formulated continuum models for lipid-bilayer membranes present a significant challenge to computational mechanics. In particular, the mid-surface behavior is that of a 2-dimensional fluid, while the membrane resists bending much like an elastic shell. Here we consider a well-known Helfrich-Cahn-Hilliard model for two-phase lipid-bilayer vesicles, incorporating mid-surface fluidity, curvature elasticity and a phase field. We present a systematic approach to the direct computation of vesical configurations possessing icosahedral symmetry, which have been observed in experiment and whose mathematical existence has recently been established. We first introduce a radial-graph formulation to overcome the difficulties associated with fluidity within a conventional Lagrangian description. We use the so-called subdivision surface finite element method combined with an icosahedral-symmetric mesh. The resulting discrete equations are well-conditioned and inherit equivariance properties under a representation of the icosahedral group. We use group-theoretic methods to obtain a reduced problem that captures all icosahedral-symmetric solutions of the full problem. Finally we explore the behavior of our reduced model, varying numerous physical parameters present in the mathematical model.

  11. Thermodynamic characteristics and phase equilibria in the alloys of the Ge-La system

    NASA Astrophysics Data System (ADS)

    Shevchenko, M. A.; Kudin, V. G.; Sudavtsova, V. S.; Ivanov, M. I.; Berezutskii, V. V.

    2017-08-01

    Mixing enthalpies of melts of the Ge-La system have been measured using isoperibolic calorimetry within two concentration ranges. For the first range (0 < x La < 0.16 at 1520 K and 0.16 < x La < 0.29 at 1570 K), agreement with the known literature data is observed within the experimental error. The second range (0.78 < x La < 1 at 1470 K and 0.7 < x La < 0.78 at 1580 K) has been studied for the first time. The melts are characterized by very strong exothermal effects of mixing, which have almost symmetrical concentration dependence: Δ H̅ La ∞ = Δ H̅ Ge ∞ = -245 kJ/mol at 1470 K. A thermodynamic optimization of the activities of the components and the phase diagram of the system have been conducted based on the obtained experimental data, using an ideal associated solution (IAS) model.

  12. Spin Equilibria in Monomeric Manganocenes: Solid State Magnetic and EXAFS Studies

    SciTech Connect

    Walter, M. D.; Sofield, C. D.; Booth, C. H.; Andersen, R. A.

    2009-02-09

    Magnetic susceptibility measurements and X-ray data confirm that tert-butyl-substituted manganocenes [(Me{sub 3}C){sub n}C{sub 5}H{sub 5?n}]{sub 2}Mn (n = 1, 2) follow the trend previously observed with the methylated manganocenes; that is, electron-donating groups attached to the Cp ring stabilize the low-spin (LS) electronic ground state relative to Cp{sub 2}Mn and exhibit higher spin-crossover (SCO) temperatures. However, introducing three CMe{sub 3} groups on each ring gives a temperature-invariant high-spin (HS) state manganocene. The origin of the high-spin state in [1,2,4-(Me{sub 3}C){sub 3}C{sub 5}H{sub 2}]{sub 2}Mn is due to the significant bulk of the [1,2,4-(Me{sub 3}C){sub 3}C{sub 5}H{sub 2}]{sup -} ligand, which is sufficient to generate severe inter-ring steric strain that prevents the realization of the low-spin state. Interestingly, the spin transition in [1,3-(Me{sub 3}C){sub 2}C{sub 5}H{sub 3}]{sub 2}Mn is accompanied by a phase transition resulting in a significant irreversible hysteresis ({Delta}T{sub c} = 16 K). This structural transition was also observed by extended X-ray absorption fine-structure (EXAFS) measurements. Magnetic susceptibility studies and X-ray diffraction data on SiMe{sub 3}-substituted manganocenes [(Me{sub 3}Si){sub n}C{sub 5}H{sub 5-n}]{sub 2}Mn (n = 1, 2, 3) show high-spin configurations in these cases. Although tetra- and hexasubstituted manganocenes are high-spin at all accessible temperatures, the disubstituted manganocenes exhibit a small low-spin admixture at low temperature. In this respect it behaves similarly to [(Me{sub 3}C)(Me{sub 3}Si)C{sub 5}H{sub 3}]{sub 2}Mn, which has a constant low-spin admixture up to 90 K and then gradually converts to high-spin. Thermal spin-trapping can be observed for [(Me{sub 3}C)(Me{sub 3}Si)C{sub 5}H{sub 3}]{sub 2}Mn on rapid cooling.

  13. Experimental Determinations of the Activity-Composition Relations and Phase Equilibria of H{sub 2}O-CO{sub 2}-NaCl Fluids

    SciTech Connect

    Anovitz, L.M.; Labotka, T.C.; Blencoe, J.G.; Singh, J.; Horita, J.

    1999-09-12

    An understanding of activity-composition (a/X) relations and phase equilibria for halite-bearing, mixed-species supercritical fluids is critically important in many geological and industrial applications. The authors have performed experiments on the a/X relations and phase equilibria of H{sub 2}O-CO{sub 2}-NaCl fluids at 5OO C, 500 bars, to obtain highly accurate and precise data for this ternary system. H{sub 2}O-CO{sub 2}-NaCl samples were reacted at a (H{sub 2}O) = 0.350, 0.425, 0.437, 0.448, 0.560, 0.606, 0.678, 0.798, and 0.841. Results indicate that fluids with these activities lie in the vapor-NaCl two-phase region, and that a fluid with the last value has a composition close to the three-phase (vapor + brine + halite) field. Data from these experiments and NaCl solubility runs also suggest that the vapor comer of the three-phase field lies near X(H{sub 2}O) = 0.760, X(NaCl) = 0.065, which is a significantly more water-rich composition than suggested by the model of [1].

  14. Phase Equilibria and Kinetic Crystallization Experiments on the Inyo Domes Rhyolite

    NASA Astrophysics Data System (ADS)

    Castro, J. M.; Gardner, J. E.

    2003-12-01

    Textural characterization of volcanic materials is a common approach used to decipher the conditions of magma ascent, prior to and during eruption. Such an approach is based on the well-established link between magma devolatilization and crystallization. Understanding of the functional relations between degassing and the kinetics of feldspar crystallization has advanced through experimental decompression of natural rhyolitic materials (e.g., Hammer and Rutherford, 2002), thus allowing comparisons between natural and synthetic textures to be used as a geospeedometer. Similar parameterizations of the growth of mafic silicates in silicic melts are sparse, and kinetic information (e.g., growth and nucleation rates) on the crystallization of pyroxene in rhyolitic melts are completely lacking. In light of the common presence of clinopyroxene in groundmass glasses of intermediate volcanic rocks and the abundance of this phase in microlite populations of many pyroclastic and effusive obsidians, we investigate the kinetics of clinopyroxene crystallization in response to isothermal decompression of the Inyo rhyolite. Isothermal decompression experiments are conducted on the low-Ba member of the Inyo rhyolite at H2O-saturation, 750° C, Pi=200 MPa, and NNO+1; initial conditions are guided both by previous studies and new constraints on the H2O-saturated stability regions of the natural mineral paragenesis determined by phase equilibrium experiments run over broad ranges in P (200 to 50 MPa) and T (700-900° C). Decompression paths involve an equilibration period (4-7 days) followed by multiple-step pressure drops of equal size (16 to 30 MPa) and duration, to varying final pressures (167 to 4.4 MPa). Integrated decompression rates vary from 0.045 MPa/min to 0.004 MPa/min, corresponding to total run durations ranging from 3 to 24 days. The observed crystallization sequence is: Fe-Ti oxide, cpx, biotite, plagioclase. In 3 and 6 day runs, clinopyroxene exhibits both low number

  15. Thermal analysis, phase equilibria, and superconducting properties in magnesium boride and carbon doped magnesium boride

    NASA Astrophysics Data System (ADS)

    Bohnenstiehl, Scot David

    In this work, the low temperature synthesis of MgB2 from Mg/B and MgH2/B powder mixtures was studied using Differential Scanning Calorimetry (DSC). For the Mg/B powder mixture, two exothermic reaction events were observed and the first reaction event was initiated by the decomposition of Mg(OH)2 on the surface of the magnesium powder. For the MgH 2/B powder mixture, there was an endothermic event at ˜375 °C (the decomposition of MgH2 into H2 and Mg) and an exothermic event ˜600 °C (the reaction of Mg and B). The Kissinger analysis method was used to estimate the apparent activation energy of the Mg and B reaction using DSC data with different furnace ramp rates. The limitations of MgB2 low temperature synthesis led to the development of a high pressure induction furnace that was constructed using a pressure vessel and an induction heating power supply. The purpose was to not only synthesize more homogeneous MgB2 samples, but also to determine whether MgB2 melts congruently or incongruently. A custom implementation of the Smith Thermal Analysis method was developed and tested on aluminum and AlB2, the closest analogue to MgB2. Measurements on MgB2 powder and a high purity Mg/B elemental mixture confirmed that MgB2 melts incongruently and decomposes into a liquid and MgB4 at ˜1445 °C at 10 MPa via peritectic decomposition. Another measurement using a Mg/B elemental mixture with impure boron suggested that ˜0.7 wt% carbon impurity in the boron raised the incongruent melting temperature to ˜1490-1500 °C. Lastly, the solubility limit for carbon in MgB2 was studied by making samples from B4C and Mg at 1530 °C, 1600 °C and 1700 °C in the high pressure furnace. All three samples had three phases: Mg, MgB2C2, and carbon doped MgB2. The MgB 2C2 and carbon doped MgB2 grain size increased with temperature and the 1700 °C sample had needle-like grains for both phases. The presence of the ternary phase, MgB2C2, suggested that the maximum doping limit for carbon in

  16. Experimental constraints on the Qitianling granite in south China: phase equilibria and petrogenetic implications

    NASA Astrophysics Data System (ADS)

    Huang, Fangfang; Scaillet, Bruno; Wang, Rucheng; Erdmann, Saskia; Chen, Yan; Faure, Michel; Liu, Hongsheng; Xie, Lei; Wang, Bo; Zhu, Jinchu

    2016-04-01

    In South China, the huge distribution of the Mesozoic metallogenic province reflects the abundant magmatism and associated mineralizations which occurred during that period. Building up the phase equilibrium diagrams of representative Mesozoic granites allows us to better understand Mesozoic magmatic events, an approach so far little applied to granites of South China. The Qitianling ganite is a representative Jurassic A-type metaluminous pluton which is associated with tin mineralization in South China. The dominant rock-types are hornblende-biotite monzonitic granites, biotite±hornblende bearing granites and fine-grained biotite-bearing granites. Three metaluminous granite samples (QTL38C, QTL14A and QTL13), of varying mafic character but all bearing hornblende, were chosen for constraining crystallization and magma generation conditions of the Qitianling composite batholith. Crystallization experiments were performed in the 100-700 MPa range, albeit mainly at 200 MPa, at an fO2 at NNO-1 or NNO +2.5, in a temperature range 700°C to 900°C. At 200 MPa, the water content in melt varies between 3 wt% and 6.5 wt% (water-saturated). Experimental results show that under H2O-saturated conditions and at NNO-1, ilmenite, magnetite and pyroxene are the liquidus phases, followed by hornblende, biotite and plagioclase. Hornblende is present only in the most mafic sample (QTL38C), below 900°C and above 5 wt% H2O. In contrast, for H2O-saturated conditions and at NNO+2.5, magnetite, pyroxene crystallize first, followed by biotite while ilmenite is rarely observed. Petrographic observations of natural samples show that magnetite and ilmenite coexist, whereas pyroxene is never observed. The Fe# value (Fe/Mg+Fe) of natural amphibole goes up to 0.69, being on average at 0.67. Experiments indicate that the crystallization of pyroxene occurs at early magmatic stages, but it breaks down to hornblende and biotite at low temperatures, explaining its absence in natural assemblages

  17. Phase equilibria of NdC1 3NaClKCl

    NASA Astrophysics Data System (ADS)

    Hosoya, Yuji; Terai, Takayuki; Tanaka, Satoru; Takahashi, Yoichi

    1997-08-01

    Molten chloride is considered to be applied to a fast-breeder-reactor fuel and a solvent in the pyrochemical reprocessing of spent nuclear fuel. In this work, phase diagrams for molten chloride systems were constructed, using NdCl 3 as an imitative substance in place of UCl 3 or PuCl 3. A compound of 3NdC1 3 · NaCl, which melts incongruently at 540°C to NdCl 3 and liquid and a eutectic at 437°C were found in the NdC1 3NaCl system. In the NdCl 3KCl system, many invariant reactions were observed: the decomposition of NdCl 3 · 2KCl and 2NdCl 3 · KCl at 444 and 474°C, respectively; a eutectic at 489°C; a peritectic at 506°C and a monotectic at 624°C. It is thought that there should be a peritectic compound of 6NdCl 3 · KCl above 474°C. A compound of 2NdC1 3 · NaCl · KCl was considered to exist in the ternary system of NdCl 3NaClKCl, to which attention should be paid in determining the composition of the fuel of the molten-salt fast breeder reactor.

  18. A transferable force field to predict phase equilibria and surface tension of ethers and glycol ethers.

    PubMed

    Ferrando, Nicolas; Lachet, Véronique; Pérez-Pellitero, Javier; Mackie, Allan D; Malfreyt, Patrice; Boutin, Anne

    2011-09-15

    We propose a new transferable force field to simulate phase equilibrium and interfacial properties of systems involving ethers and glycol ethers. On the basis of the anisotropic united-atom force field, only one new group is introduced: the ether oxygen atom. The optimized Lennard-Jones (LJ) parameters of this atom are identical whatever the molecule simulated (linear ether, branched ether, cyclic ether, aromatic ether, diether, or glycol ether). Accurate predictions are achieved for pure compound saturated properties, critical properties, and surface tensions of the liquid-vapor interface, as well as for pressure-composition binary mixture diagrams. Multifunctional molecules (1,2-dimethoxyethane, 2-methoxyethanol, diethylene glycol) have also been studied using a recently proposed methodology for the calculation of the intramolecular electrostatic energy avoiding the use of additional empirical parameters. This new force field appears transferable for a wide variety of molecules and properties. It is furthermore worth noticing that binary mixtures have been simulated without introducing empirical binary parameters, highlighting also the transferability to mixtures. Hence, this new force field gives future opportunities to simulate complex systems of industrial interest involving molecules with ether functions.

  19. Water-carbon dioxide solid phase equilibria at pressures above 4 GPa.

    PubMed

    Abramson, E H; Bollengier, O; Brown, J M

    2017-04-11

    A solid phase in the mixed water-carbon dioxide system, previously identified as carbonic acid, was observed in the high-pressure diamond-anvil cell. The pressure-temperature paths of both its melting and peritectic curves were measured, beginning at 4.4 GPa and 165 °C (where it exists in a quadruple equilibrium, together with an aqueous fluid and the ices H2O(VII) and CO2(I)) and proceeding to higher pressures and temperatures. Single-crystal X-ray diffraction revealed a triclinic crystal with unit cell parameters (at 6.5 GPa and 20 °C) of a = 5.88 Å, b = 6.59 Å, c = 6.99 Å, α = 88.7°, β = 79.7°, and γ = 67.7°. Raman spectra exhibit a major line at ~1080 cm(-1) and lattice modes below 300 cm(-1).

  20. Vapor-liquid phase equilibria of water modelled by a Kim-Gordon potential

    SciTech Connect

    Maerzke, K A; McGrath, M J; Kuo, I W; Tabacchi, G; Siepmann, J I; Mundy, C J

    2009-03-16

    Gibbs ensemble Monte Carlo simulations were carried out to investigate the properties of a frozen-electron-density (or Kim-Gordon, KG) model of water along the vapor-liquid coexistence curve. Because of its theoretical basis, such a KG model provides for seamless coupling to Kohn-Sham density functional theory for use in mixed quantum mechanics/molecular mechanics (QM/MM) implementations. The Gibbs ensemble simulations indicate rather limited transferability of such a simple KG model to other state points. Specifically, a KG model that was parameterized by Barker and Sprik to the properties of liquid water at 300 K, yields saturated vapor pressures and a critical temperature that are significantly under- and over-estimated, respectively.

  1. First-principles study of phase equilibria in Cu-Pt-Rh disordered alloys.

    PubMed

    Yuge, Koretaka

    2009-10-14

    Phase stability of Cu-Pt-Rh ternary disordered alloys is examined by a combination of cluster expansion techniques and Monte Carlo statistical simulation based on first-principles calculation. The sign of pseudo-binary ECIs indicates that neighboring Cu and Pt strongly prefer unlike-atom pairs, Pt and Rh weakly prefer unlike-atom pairs, and Cu and Rh atoms prefer like-atom pairs, indicating that the ternary alloy retains the ordering tendency of the constituent binary alloys. The formation energy of a random alloy at T = 1200 K exhibits a negative sign for a wide range of Pt-rich compositions, while at Pt-poor compositions of x≤0.25, the formation energy has a positive value. Calculated affinities for the random alloy show the variety of energetically favored bonds for the alloy: Cu-Pt bonds in both first-and second-nearest neighbor (1-NN and 2-NN) are energetically preferred for all the composition range, the Pt-Rh bond in 1-NN is preferred at Pt-rich compositions, the Pt-Rh in 2-NN and Rh-Cu in 1-NN bonds are unfavored for all compositions, and the Rh-Cu bond in 2-NN is unfavored for Pt-poor compositions. We elucidate that the ordering tendency of 1-NN and 2-NN Cu-Pt, 2-NN Pt-Rh and 1-NN Cu-Rh atoms in constituent binary alloys is retained for the whole composition range of Cu-Pt-Rh ternary alloys, while that of 1-NN Pt-Rh and 2-NN Cu-Rh atoms significantly depends on composition.

  2. Temperature and pressure based NMR studies of detergent micelle phase equilibria.

    PubMed

    Alvares, Rohan; Gupta, Shaan; Macdonald, Peter M; Prosser, R Scott

    2014-05-29

    Bulk thermodynamic and volumetric parameters (ΔGmic°, ΔHmic°, ΔSmic°, ΔCp,mic°, ΔVmic°, and Δκmic°) associated with the monomer–micelle equilibrium, were directly determined for a variety of common detergents [sodium n-dodecyl sulfate (SDS), n-dodecyl phosphocholine (DPC), n-dodecyl-β-d-maltoside (DDM), and 7-cyclohexyl-1-heptyl phosphocholine (CyF)] via 1H NMR spectroscopy. For each temperature and pressure point, the critical micelle concentration (cmc) was obtained from a single 1H NMR spectrum at a single intermediate concentration by referencing the observed chemical shift to those of pure monomer and pure micellar phases. This permitted rapid measurements of the cmc over a range of temperatures and pressures. In all cases, micelle formation was strongly entropically favored, while enthalpy changes were all positive, with the exception of SDS, which exhibited a modestly negative enthalpy of micellization. Heat capacity changes were also characteristically negative, while partial molar volume changes were uniformly positive, as expected for an aggregation process dictated by hydrophobic effects. Isothermal compressibility changes were found to be consistent with previous measurements using other techniques. Thermodynamic measurements were also related to spectroscopic studies of topology and micelle structure. For example, paramagnetic effects resulting from the addition of dioxygen provided microscopic topological details concerning the hydrophobicity gradient along the detergent chains within their respective micelles as detected by 1H NMR. In a second example, combined 13C and 1H NMR chemical shift changes arising from application of high pressure, or upon micellization, of CyF provided site-specific details regarding micelle topology. In this fashion, bulk thermodynamics could be related to microscopic topological details within the detergent micelle.

  3. Re-investigation of phase equilibria in the system Al–Cu and structural analysis of the high-temperature phase η1-Al1−δCu

    PubMed Central

    Ponweiser, Norbert; Lengauer, Christian L.; Richter, Klaus W.

    2011-01-01

    The phase equilibria and reaction temperatures in the system Al–Cu were re-investigated by a combination of optical microscopy, powder X-ray diffraction (XRD) at ambient and elevated temperature, differential thermal analysis (DTA) and scanning electron microscopy (SEM). A full description of the phase diagram is given. The phase equilibria and invariant reactions in the Cu-poor part of the phase diagram could be confirmed. The Cu-rich part shows some differences in phase equilibria and invariant reactions compared to the known phase diagram. A two phase field was found between the high temperature phase η1 and the low temperature phase η2 thus indicating a first order transition. In the ζ1/ζ2 region of the phase diagram recent findings on the thermal stability could be widely confirmed. Contrary to previous results, the two phase field between δ and γ1 is very narrow. The results of the current work indicate the absence of the high temperature β0 phase as well as the absence of a two phase field between γ1 and γ0 suggesting a higher order transition between γ1 and γ0. The structure of γ0 (I-43m, Cu5Zn8-type) was confirmed by means of high-temperature XRD. Powder XRD was also used to determine the structure of the high temperature phase η1-Al1−δCu. The phase is orthorhombic (space group Cmmm) and the lattice parameters are a = 4.1450(1) Å, b = 12.3004(4) Å and c = 8.720(1) Å; atomic coordinates are given. PMID:27103761

  4. Experiments on phase equilibria in hydrous tholeiitic systems: implications for the genesis of oceanic plagiogranites

    NASA Astrophysics Data System (ADS)

    Koepke, J.; Berndt, J.; Feig, S. T.

    2003-04-01

    For the genesis of oceanic plagiogranites at mid-ocean spreading systems, two models are under discussion: (1) Late-stage differentiation of a MORB-type melt and (2) partial melting of pre-existing gabbros within high-temperature shear zones. In this study, we have applied recent experimental data of the experimental lab in Hannover to the plagiogranite petrogenesis in order to test both models. The role of water during the genesis of these rocks (presence of amphibole as mafic phase in natural plagiogranites) was assessed by including water to the systems. Crystallization experiments were performed in a MORB system doped with different water contents at different redox conditions at 200 MPa (Berndt, 2002), and hydrous partial melting experiments were performed at 200 MPa on typical oceanic gabbros (Feig et al., this volume). For the experiments we have used an internally heated pressure vessel for high temperatures (up to 1250°C) equipped with a rapid-quench system and a hydrogen membrane for controlling the oxygen fugacity. Liquid lines of descent obtained via crystallization experiments are mainly controlled by oxygen fugacity and only to a little extent by water activity. SiO2-rich residual melts can be obtained under both oxidizing and reducing redox condition at low temperatures, but at least one fractionation step is required to reach high-silicic plagiogranites (SiO2 > 70 wt%). The partial melting of typical oceanic gabbro leads at low temperatures also to plagiogranitic melts. At 940°C, the normalized SiO2 contents of the experimental melts of the three investigated systems range between 60 and 61 wt%, and at 900°C from 63 and 68 wt%. These melts coexist with orthopyroxene, amphibole, plagioclase and in one sample also with olivine. The experimental melt compositions are compared with those of natural plagiogranites of different tectonic settings and show in general a broad compositional overlap with those. Our experiments imply, in concordance with the

  5. Phase equilibria at alkali-rich early proterozoic banded iron formation, Kursk magnetic anomaly, Russia

    NASA Astrophysics Data System (ADS)

    Sayko, K. A.; Gerasimov, V. Yu.; Poskryakova, M. V.

    2003-04-01

    Banded iron formation (BIF) rocks of Kursk Magnetic anomaly (KMA) are distinguished from well known Precambrian BIF by the alkali enrichment and aluminum depletion and as a total absence of the aluminum bearing minerals. From layered silicates the maximum saturated potassium phases seladonite and tetraferribiotite are of widespread occurrence instead stilpnomelane, minnesotaite and greenalite commonplace for low grade BIF. It has been widely distribution of the seladonite with the assemblage of tetraferribiotite, magnetite, hematite, and quartz distinguish ferruginous quartzites Mikhailovsk iron deposit (KMA) from well known Precambrian BIF of the ancient shields. From Fe-Mg silicates the aegirine, ribeckite and aluminum-less chlorite are present. The hematite and magnetite stability in the ferruginous quartzites assemblages suggest the high values of the oxygen fugacity near magnetite-hematite buffer. This is confirmed by somewhat increasing XMg values for seladonite, tetraferribiotite, chlorite, and ribeckite. The minerals producing with large amounts of ferric iron (seladonite, tetraferribiotite) in the ferruginous quartzites of Mikhailovsk iron deposit is caused by the oxygen fugacity high values. For example the ferrichamosite (Fe_5Fe3+(Fe3+Si_3)O10(OH)_8) is produced in place of the commonplace for the low-grade BIF greenalite (Fe_6Si_4O10(OH)_8). As a whole chlorites are a rarity in BIFs (Laird, 1989) through low rocks aluminum content and represent by chamosite (Gole, 1981), clinochlore and ripidolite (Miyano, Beukes, 1997). Chlorite in studied ferruginous quartzites has a uncommon aluminumless composition with high Fe3+ content and corresponds hypothetical end-member of chamosite - "ferrichamosite" and "ferriclinochlore" - "ferrichamosite" series (Burt, 1989). Uncommon aluminumless chlorite composition assumes that it appears during low-grade metamorphism and possible catagenesis: Mag + Hem + Qtz rightarrow H_2O rightarrow Fe-Chm + O_2 Sid + Qtz + Mag

  6. Liquid-liquid equilibria for soft-repulsive particles: improved equation of state and methodology for representing molecules of different sizes and chemistry in dissipative particle dynamics.

    PubMed

    Liyana-Arachchi, Thilanga P; Jamadagni, Sumanth N; Eike, David; Koenig, Peter H; Siepmann, J Ilja

    2015-01-28

    Three developments are presented that significantly expand the applicability of dissipative particle dynamics (DPD) simulations for symmetric and non-symmetric mixtures, where the former contain particles with equal repulsive parameter for self-interactions but a different repulsive parameter for cross-interactions, and the latter contain particles with different repulsive parameters also for the self-interactions. Monte Carlo and molecular dynamics simulations for unary phases covering a wide range of repulsive parameters and of densities for single-bead DPD particles point to deficiencies of the Groot and Warren equation of state (GW-EOS) [J. Chem. Phys. 107, 4423 (1997)]. A revised version, called rGW-EOS, is proposed here that is significantly more accurate over a wider range of parameters/densities. The second development is the generalization of the relationship between the Flory-Huggins χ parameter and the repulsive cross-interaction parameter when the two particles involved have different molecular volumes. The third aspect is an investigation of Gibbs ensemble Monte Carlo simulation protocols, which demonstrates the importance of volume fluctuations and excess volumes of mixing even for equimolar symmetric mixtures of DPD particles. As an illustrative example, the novel DPD methodology is applied to the prediction of the liquid-liquid equilibria for acetic anhydride/(n-hexane or n-octane) binary mixtures.

  7. Phase relations in the system NaCl-KCl-H2O: V. Thermodynamic-PTX analysis of solid-liquid equilibria at high temperatures and pressures

    USGS Publications Warehouse

    Sterner, S.M.; Chou, I.-Ming; Downs, R.T.; Pitzer, Kenneth S.

    1992-01-01

    The Gibbs energies of mixing for NaCl-KCl binary solids and liquids and solid-saturated NaCl-KCl-H2O ternary liquids were modeled using asymmetric Margules treatments. The coefficients of the expressions were calibrated using an extensive array of binary solvus and solidus data, and both binary and ternary liquidus data. Over the PTX range considered, the system exhibits complete liquid miscibility among all three components and extensive solid solution along the anhydrous binary. Solid-liquid and solid-solid phase equilibria were calculated by using the resulting equations and invoking the equality of chemical potentials of NaCl and KCl between appropriate phases at equilibrium. The equations reproduce the ternary liquidus and predict activity coefficients for NaCl and KCl components in the aqueous liquid under solid-saturation conditions between 673 and 1200 K from vapor saturation up to 5 kbar. In the NaCl-KCl anhydrous binary system, the equations describe phase equilibria and predict activity coefficients of the salt components for all stable compositions of solid and liquid phases between room temperature and 1200 K and from 1 bar to 5 kbar. ?? 1992.

  8. Experimental Phase Equilibria Studies of the Pb-Fe-O System in Air, in Equilibrium with Metallic Lead and at Intermediate Oxygen Potentials

    NASA Astrophysics Data System (ADS)

    Shevchenko, M.; Jak, E.

    2017-08-01

    The phase equilibria information on the Pb-Fe-O system is of practical importance for the improvement of the existing thermodynamic database of lead-containing slag systems (Pb-Zn-Fe-Cu-Si-Ca-Al-Mg-O). Phase equilibria of the Pb-Fe-O system have been investigated: (a) in air at temperatures between 1053 K and 1373 K (780 °C and 1100 °C); (b) in equilibrium with metallic lead at temperatures between 1053 K and 1373 K (780 °C and 1100 °C); and (c) at intermediate oxidation conditions for the liquid slag in equilibrium with two solids (spinel + magnetoplumbite), at temperatures between 1093 K and 1373 K (820 °C and 1100 °C). The high-temperature equilibration/quenching/electron probe X-ray microanalysis technique has been used to accurately determine the compositions of the phases in equilibrium in the system. The Pb and Fe concentrations in the phases were determined directly; preliminary thermodynamic modeling with FactSage was used to estimate the ferrous-to-ferric ratios and to present the results in the ternary diagram.

  9. A Distributed Computing Infrastructure for Computational Thermodynamic Calculations of Solid-Liquid Phase Equilibria

    NASA Astrophysics Data System (ADS)

    Ghiorso, M. S.; Kress, V. C.

    2004-12-01

    Software tools like MELTS (Ghiorso and Sack, 1995, CMP 119:197) and its derivatives (Ghiorso et al., 2002, G3 3:10.1029/2001GC000217) are sophisticated calculators used by geoscientists to quantify the chemistry of melt production, transport and storage. These tools utilize computational thermodynamics to evaluate the equilibrium state of the system under specified external conditions by minimizing a suitably constructed thermodynamic potential. Like any thermodynamically based tool, the principal advantage in employing these techniques to model igneous processes is the intrinsic ability to couple the chemistry and energetics of the evolution of the system in a self consistent and rigorous formalism. Access to MELTS is normally accomplished via a standalone X11-based executable or as a Java-based web applet. The latter is a dedicated client-server application rooted at the University of Chicago. Our on-going objective is the development of a distributed computing infrastructure to provide "MELTS-like" computations on demand to remote network users by utilizing a language independent client-server protocol based on CORBA. The advantages of this model are numerous. First, the burden of implementing and executing MELTS computations is centralized with a software implementation optimized to a compute cluster dedicated for that purpose. Improvements and updates to MELTS software are handled locally on the server side without intervention of the user and the server-model lessens the burden of supporting the computational code on a variety of hardware and OS platforms. Second, the client hardware platform does not incur the computational cost of performing a MELTS simulation and the remote user can focus on the task of incorporating results into their model. Third, the client user can write software in a computer language of their choosing and procedural calls to the MELTS library can be executed transparently over the network as if a local language-compatible library of

  10. Priming Silicic Giant Magma Bodies: Finding Evidence for Internal Forcing Versus External Triggering of Supereruptions by Phase Equilibria Modeling.

    NASA Astrophysics Data System (ADS)

    Tramontano, S.; Gualda, G. A. R.; Ghiorso, M. S.; Kennedy, B.

    2015-12-01

    It is important to understand what triggers silicic eruptions because of the implications for modern-day systems. The goal of this project is to use phase equilibria modeling (i.e. rhyolite-MELTS) to determine to what extent magmas within the crust are induced to erupt due to external triggers (e.g. earthquakes; new magma injection; neighboring eruptions) and to what extent they naturally evolve to a point where eruption is inevitable (e.g. by fluid exsolution and decrease in magma strength and density). Whole-rock compositions from four rhyolite tuffs across the globe associated with large or supereruptions (Mamaku Tuff, New Zealand; Peach Spring Tuff, SW USA; early and late-erupted Bishop Tuff, California; and Toba Tuff, Indonesia) are studied using rhyolite-MELTS modeling. Key physical properties of magma are strongly affected by the initial volatile content due to fluid exsolution. By running simulations with varying water contents, we can track the evolution of fluid exsolution during crystallization. Isobaric (constrained temperature change at constant pressure) and isochoric (constrained temperature change at constant volume) models were run for the four compositions. In constrained-pressure scenarios, fluid is free to exsolve as crystallization proceeds, and the total system volume can increase or decrease accordingly; this would require deformation of the surrounding crust to accommodate the magma volume change. In constrained-volume scenarios, bubble exsolution is limited to the volume change due to crystallization; in this case, pressure can decrease or increase (if bubbles are absent or present). For fixed-pressure scenarios, fluid exsolution is more extensive and leads to internal triggering, at least for fluid-saturated conditions; external triggering is more likely in fluid-undersaturated conditions. For fixed-volume scenarios, none of the systems cross a fragmentation threshold for the crystal contents typically observed in natural pumice. If

  11. Phase equilibria modelling and zircon dating for Precambrian metapelites from Xinghuadukou Group in Lvlin Forest of Erguna Massif, NE China

    NASA Astrophysics Data System (ADS)

    Xu, Jiulei; Zheng, Changqing; Tajcmanova, Lucie; Zhong, Xin; Xu, Xuechun; Han, Xiaomeng; Wang, Zhaoyuan

    2017-04-01

    Xinghuadukou Group, the basement metamorphic complex of Erguna Massif in NE China, is considered to be Mesoproterozoic with Sm-Nd age of 1157±32 Ma. However, the new zircon data from these metamorphic supracrustal rocks in Lvlin Forest show that they formed in Neoproterozoic with the age of 800 Ma. Old zircon age with 2.5 Ga, 2.0 Ga and 1.8 Ga, indicate that the Erguna Massif had an affinity to both Columbia and Rodinia continents. Furthermore, we also present 500 Ma metamorphic age in micashists and 500 Ma age of adjacent granitoids that might have thermally influenced its surrounding. No detailed studies have been undertaken on the metamorphic evolution of the Xinghuadukou Complex. The typical paragneissic mineral assemblage of garnet sillimanite mica schist is Grt+Sil+Bt+Mus+Qtz±Kfs. (Zhou et al., 2011) proposed that the Xinghuadukou Complex appears to have undergone similar granulite facies metamorphic conditions based on the similarity of mineral assemblages to the Mashan Complex in the Jiamusi Massif, NE China. However, the new phase equilibria modelling result shows that these rocks are high amphibolite facies product with 650℃. We can easily find K-feldspar formed by partial melting due to the consuming of muscovite. Also the remaining muscovite is directly connected with a fluid channel in thin sections which indicate that the remaining muscovite formed from retrograde with the existence of fluid. The zoned garnet has low MgO and high CaO content in rims and high MgO and low CaO content in core. It seems that this garnet has high pressure and low temperature (HP-LT) in rims and low pressure and high temperature (LP-HT) in core which would point to an anti-clockwise metamorphic evolution. Zhou, J.B., Wilde, S.A., Zhang, X.Z., Zhao, G.C., Liu, F.L., Qiao, D.W., Ren, S.M. and Liu, J.H., 2011b. A> 1300km late Pan-African metamorphic belt in NE China: new evidence from the Xing'an block and its tectonic implications. Tectonophysics, 509(3): 280-292.

  12. Monte Carlo simulations of 1,3,5-triamino-2,4,6-trinitrobenzene (TATB): Pressure and temperature effects for the solid phase and vapor-liquid phase equilibria.

    PubMed

    Rai, Neeraj; Bhatt, Divesh; Siepmann, J Ilja; Fried, Laurence E

    2008-11-21

    The transferable potentials for phase equilibria (TraPPE) force field was extended to nitro and amino substituents for aromatic rings via parametrization to the vapor-liquid coexistence curves of nitrobenzene and aniline, respectively. These groups were then transferred to model 1,3,5-triamino-2,4,6-trinitrobenzene (TATB). Without any further parametrization to solid state data, the TraPPE force field is able to predict TATB's unit cell lengths and angles at 295 K with mean unsigned percentage errors of 0.3% and 1.8% and the specific density within 0.5%. These predictions are comparable in accuracy to the GRBF model [Gee et al., J. Chem. Phys. 120, 7059 (2004)] that was parametrized directly to TATB's solid state properties. Both force fields are able to reproduce the pressure dependence of TATB's unit cell volume, but they underestimate its thermal expansion. Due to its energetic nature and unusually large cohesive energy, TATB is not chemically stable at temperature in its liquid range. Gibbs ensemble simulations allow one to determine TATB's vapor-liquid coexistence curve at elevated temperatures and the predicted critical temperature and density for the TraPPE and GRBF model are 937+/-8 and 1034+/-8 K, and 0.52+/-0.02 and 0.50+/-0.02 gcm(3), respectively.

  13. Prediction of the phase state of a natural condensed gas mixture

    SciTech Connect

    Kuranov, G.L.; Pukinskii, I.B.; Smirnova, N.A.; Avdeev, D.Yu.

    1995-07-20

    The authors have examined how the type of data on the fractional composition of debutanized gas condensate and the selection of a state equation can influence the prediction of the phase state of a natural condensed gas mixture. The authors have attempted to have the fractional composition of the mixture as found by single-pass evaporation approach that revealed by fractional distillation. The advantage of the vacancy quasichemical equation of states over the Redlich-Kwong-Soave equation in the calculation of phase equilibria has been shown.

  14. Phase Diagram Studies of ZnS Systems

    DTIC Science & Technology

    1988-09-01

    mechanical, processing of ZnS-base ’alloys’. Knowledge of the phase equilibria of various ZnS-rich systems is essential to achieve our objectives...initial studies of the solid-state phase equilibria in the ZnS-CdS and ZnS-Ga2s3 phase diagrams.

  15. Phase equilibria, crystal structure and properties of complex oxides in the Nd2O3-SrO-CoO system

    NASA Astrophysics Data System (ADS)

    Aksenova, T. V.; Efimova, T. G.; Lebedev, O. I.; Elkalashy, Sh. I.; Urusova, A. S.; Cherepanov, V. A.

    2017-04-01

    The phase equilibria in the ½Nd2O3-SrO-CoO system were systematically studied at 1373 K in air. The intermediate phases formed in the ½Nd2O3-SrO-CoO system at 1373 K in air are: Nd1-xSrxCoO3-δ (0.0≤x≤0.5 with orthorhombic structure, sp. gr. Pbnm and 0.6≤x≤0.95 whose structure was detected as cubic according to XRD sp. gr. Pm3m, but shown to be tetragonal by TEM due to the oxygen vacancy ordering), Nd2-ySryCoO4-δ (0.6≤y≤1.1 with tetragonal K2NiF4-type structure, sp. gr. I4/mmm) and Nd2-zSrzO3 (0.0≤z≤0.15 with hexagonal structure, sp. gr. P-3m1). The unit cell parameters for the single phase samples were refined by the Rietveld analysis. The changes of oxygen content in Nd1-xSrxCoO3-δ (0.6≤x≤0.95) and Ruddlesden-Popper oxide Nd2-ySryCoO4-δ were examined by TGA. All were found to be oxygen deficient phases. High-temperature dilatometry allows calculating the thermal expansion coefficient and evaluating the chemical expansion coefficient at high temperature. The projection of isothermal-isobaric phase diagram for the Nd-Sr-Co-O system at 1373 K in air to the compositional triangle of metallic components has been constructed. The phase equilibria in the studied Nd-Sr-Co-O system were compared to La-Sr-Co-O and Nd-M-Co-O (M=Ca and Ba).

  16. Subseafloor phase equilibria in high-temperature hydrothermal fluids of the Lucky Strike Seamount (Mid-Atlantic Ridge, 37°17‧N)

    NASA Astrophysics Data System (ADS)

    Pester, Nicholas J.; Reeves, Eoghan P.; Rough, Mikaella E.; Ding, Kang; Seewald, Jeffrey S.; Seyfried, William E.

    2012-08-01

    As part of an integrated study conducted at the Lucky Strike Seamount (Mid-Atlantic Ridge, 37°17'N) in 2008, gas-tight sampling devices were used to collect high-temperature (˜300 °C) hydrothermal fluids issuing from sulfide structures distributed throughout the vent field located in the summit depression. Compared with previous observations from 1993 to 1997, the most substantial changes in vent fluid compositions are dramatically increased CO2 concentrations (˜5×, up to 133 mmol/L) and the observation of vent fluids enriched in dissolved chloride relative to seawater. Combined with an increase in δ13C values by ˜4‰ in 2008, the elevated CO2 indicates replenishment of the magmatic heat source and may be indicative of a recent magmatic event. The additional supporting fluid chemistry is, however, similar to that of the previous sampling intervals, necessitating a reassessment of the subseafloor controls on vent fluid chemistry at Lucky Strike in the context of recently obtained geophysical data that provides the depth/extent of a steady-state magma chamber. Two-phase behavior is indicated by the chloride variability in the vent fluids; and comparison with experimental data for the associated chloride-dependent partitioning of minor/trace elements suggests the possibility of a similar source fluid for all the vent structures, while limiting the likelihood of shallow phase separation and subseafloor mixing for the hydrothermal end-members. A recently calibrated Fe/Mn geothermometer indicates minimum subseafloor equilibration temperatures of 350-385 °C. However, constraints imposed by dissolved Si/Cl in conjunction with geophysical observations are consistent with peak reaction conditions at temperatures of 430-475 °C and pressures near the top of the axial magma chamber (˜410-480 bars), where magmatic CO2 becomes entrained in the circulating fluids. The distance between the magma chamber and the seafloor at Lucky Strike is substantially greater than at

  17. Effects of volatiles on phase equilibria of a basalt from Piton de la Fournaise (Réunion island): experimental results and comparison with natural products.

    NASA Astrophysics Data System (ADS)

    Brugier, Yann-Aurélien; Pichavant, Michel; di Muro, Andréa; Bourdier, Jean-Louis

    2015-04-01

    The eruptive activity of the Piton de la Fournaise (PdF) hotspot volcano is monitored by geophysical, geochemical and petrological approaches. Nevertheless, the structure of the feeding system and magma reservoirs is still debated. 4 different lava groups occur at PdF: (1) Steady State Basalts (SSB), the dominant group in the recent activity, (2) the Differentiated Lavas group, typical of the early activity, (3) the Picrites group with olivine-rich lavas (oceanites) characteristic of La Réunion volcanism and (4) the Abnormal Group (AbG) that contains lavas with mixed geochemical characteristics. To understand the petrogenetic relations between the 4 groups of lavas, constrain the structure of the feeding system and the magma storage conditions, experimental phase equilibria have been determined under fluid-present conditions, with either H2O or H2O+CO2 added, for a SSB lava from the 2009 eruption. Experiments have been performed both at high pressures (HP) and 1atm. The HP experiments were carried out in an IHPV, pressurized with Ar-H2 mixtures, at 50MPa and 400MPa. The 1atm experiments used a vertical CO-CO2 gas mixing furnace. Experimental products were analyzed by SEM, EMPA and µ-FTIR Spectroscopy. Results at 50 MPa lead to a crystallization sequence in the order olivine (ol, + spinel), clinopyroxene (cpx), plagioclase (plag). Volatile concentrations in experimental glasses range from 0.5 to 1 wt% for H2O and 30 to 180 ppm for CO2, within the range of glass inclusions in olivine phenocrysts. Fo contents in ol, Mg# in cpx and An contents in plag are in agreement with compositions of natural phenocrysts, suggesting that our experiments closely approach the shallow magmatic evolution at PdF. Preliminary experiments at 400 MPa indicate a change in the crystallization sequence, olivine being replaced by cpx as the liquidus phase. Our data are in marked contrast with previous experimental results under volatile-free conditions. Experiments at 1 atm are in progress

  18. Ligation-state hydrogen exchange: coupled binding and folding equilibria in ribonuclease P protein.

    PubMed

    Henkels, Christopher H; Oas, Terrence G

    2006-06-21

    Bacillus subtilis ribonuclease P protein (P protein) is predominantly unfolded (D) at physiological pH and low ionic strength; however, small molecule anionic ligands (e.g., sulfate) directly bind to and stabilize the folded state (NL2). Because the D + 2L <--> NL2 transition is experimentally two-state, high-energy states such as the singly bound, folded species (NL) and the unliganded folded species (N) are generally difficult to detect at equilibrium. To study the conformational properties of these ensembles, NMR-detected amide hydrogen exchange (HX) rates of P protein were measured at four sulfate (i.e., ligand) concentrations, a method we denote "ligation-state hydrogen exchange". The ligand concentration dependence of the HX rate of 47 residues was fit to a model with four possible HX pathways, corresponding to the local and/or global opening reactions from NL2 and NL, the local opening of N, and the global opening of N to D. Data analysis permits the calculation of the residue-specific free energy of opening from each ensemble as well as the fractional amide HX flux through each pathway. Results indicate that the predominant route of HX is through the NL and N states, which represent only 0.45% and 0.0005% of the total protein population in 20 mM sodium sulfate, respectively. Despite the low population of N, a region of protected amides was identified. Therefore, exchange through unliganded forms must be accounted for prior to the interpretation of HX-based protein-interaction studies. We offer a simple test to determine if HX occurs through the liganded or unliganded form.

  19. Experimental determination and prediction of (solid+liquid) phase equilibria for binary mixtures of heavy alkanes and fatty acids

    NASA Astrophysics Data System (ADS)

    Benziane, Mokhtar; Khimeche, Kamel; Dahmani, Abdellah; Nezar, Sawsen; Trache, Djalal

    2012-06-01

    Solid-liquid equilibria for three binary mixtures, n-Eicosane (1) + Lauric acid (2), n-Tetracosane (1) + Stearic acid (2), and n-Octacosane (1) + Palmitic acid (2), were measured using a differential scanning calorimeter. Simple eutectic behaviour was observed for these systems. The experimental results were correlated by means of the modified UNIFAC (Larsen and Gmehling versions), UNIQUAC and ideal models. The root-mean-square deviations of the solubility temperatures for all measured data vary from 0.26 to 3.15 K and depend on the particular model used. The best solubility correlation was obtained with the UNIQUAC model.

  20. Phase equilibria study in binary systems (tetra-n-butylphosphonium tosylate ionic liquid + 1-alcohol, or benzene, or n-alkylbenzene).

    PubMed

    Domańska, Urszula; Paduszyński, Kamil

    2008-09-04

    Ambient pressure (solid + liquid) equilibria (SLE) and (liquid + liquid) equilibria (LLE) of binary systems--ionic liquid (IL) tetra- n-butylphosphonium p-toluenesulfonate + 1-alcohol (1-butanol, 1-hexanol, 1-octanol, 1-decanol, or 1-dodecanol), benzene, or n-alkylbenzene (toluene, ethylbenzene, n-propylbenzene)-have been determined by using dynamic method in a broad range of mole fractions and temperatures from 250 to 335 K. For binaries containing alcohol, simple eutectic diagrams were observed with complete miscibility in the liquid phase. Only in the case of system [IL + n-propylbenzene] was mutual immiscibility with an upper critical solution temperature (UCST) with low solubility of the IL in the alcohol and high solubility of the alcohol in the IL detected. The basic thermal properties of pure IL, i.e., melting and glass-transition temperatures as well as enthalpy of melting, have been measured with differential scanning microcalorimetry technique (DSC). Well-known UNIQUAC, Wilson, NRTL, NRTL1, and NRTL2 equations have been fitted to obtain experimental data sets. For the system containing immiscibility gap [IL + n-propylbenzene], parameters of the equations have been derived only from SLE data. As a measure of goodness of correlations, root-mean square deviations of temperature have been used. These experimental results were compared to the previously measured binary systems with tetra- n-butylphosphonium methanesulfonate. Changing anion from methanesulfonate to p-toluenesulfonate decreases solubilities in systems with alcohols and increases the solubilities in binary systems with benzene and alkylbenzenes.

  1. Transferable potentials for phase equilibria. 9. Explicit hydrogen description of benzene and five-membered and six-membered heterocyclic aromatic compounds.

    PubMed

    Rai, Neeraj; Siepmann, J Ilja

    2007-09-13

    The explicit hydrogen version of the transferable potentials for phase equilibria (TraPPE-EH) force field is extended to benzene, pyridine, pyrimidine, pyrazine, pyridazine, thiophene, furan, pyrrole, thiazole, oxazole, isoxazole, imidazole, and pyrazole. While the Lennard-Jones parameters for carbon, hydrogen (two types), nitrogen (two types), oxygen, and sulfur are transferable for all 13 compounds, the partial charges are specific for each compound. The benzene dimer energies for sandwich, T-shape, and parallel-displaced configurations obtained for the TraPPE-EH force field compare favorably with high-level electronic structure calculations. Gibbs ensemble Monte Carlo simulations were carried out to compute the single-component vapor-liquid equilibria for benzene, pyridine, three diazenes, and eight five-membered heterocycles. The agreement with experimental data is excellent with the liquid densities and vapor pressures reproduced within 1 and 5%, respectively. The critical temperatures and normal boiling points are predicted with mean deviations of 0.8 and 1.6%, respectively.

  2. Chemical potentials and phase equilibria of Lennard-Jones mixtures: a self-consistent integral equation approach.

    PubMed

    Wilson, D Scott; Lee, Lloyd L

    2005-07-22

    We explore the vapor-liquid phase behavior of binary mixtures of Lennard-Jones-type molecules where one component is supercritical, given the system temperature. We apply the self-consistency approach to the Ornstein-Zernike integral equations to obtain the correlation functions. The consistency checks include not only thermodynamic consistencies (pressure consistency and Gibbs-Duhem consistency), but also pointwise consistencies, such as the zero-separation theorems on the cavity functions. The consistencies are enforced via the bridge functions in the closure which contain adjustable parameters. The full solution requires the values of not only the monomer chemical potentials, but also the dimer chemical potentials present in the zero-separation theorems. These are evaluated by the direct chemical-potential formula [L. L. Lee, J. Chem. Phys. 97, 8606 (1992)] that does not require temperature nor density integration. In order to assess the integral equation accuracy, molecular-dynamics simulations are carried out alongside the states studied. The integral equation results compare well with simulation data. In phase calculations, it is important to have pressure consistency and valid chemical potentials, since the matching of phase boundaries requires the equality of the pressures and chemical potentials of both the liquid and vapor phases. The mixtures studied are methane-type and pentane-type molecules, both characterized by effective Lennard-Jones potentials. Calculations on one isotherm show that the integral equation approach yields valid answers as compared with the experimental data of Sage and Lacey. To study vapor-liquid phase behavior, it is necessary to use consistent theories; any inconsistencies, especially in pressure, will vitiate the phase boundary calculations.

  3. Optimized Mie potentials for phase equilibria: Application to noble gases and their mixtures with n-alkanes

    NASA Astrophysics Data System (ADS)

    Mick, Jason R.; Soroush Barhaghi, Mohammad; Jackman, Brock; Rushaidat, Kamel; Schwiebert, Loren; Potoff, Jeffrey J.

    2015-09-01

    Transferrable force fields, based on n-6 Mie potentials, are presented for noble gases. By tuning the repulsive exponent, ni, it is possible to simultaneously reproduce experimental saturated liquid densities and vapor pressures with high accuracy, from the normal boiling point to the critical point. Vapor-liquid coexistence curves for pure fluids are calculated using histogram reweighting Monte Carlo simulations in the grand canonical ensemble. For all noble gases, saturated liquid densities and vapor pressures are reproduced to within 1% and 4% of experiment, respectively. Radial distribution functions, extracted from NVT and NPT Monte Carlo simulations, are in similarly excellent agreement with experimental data. The transferability of the optimized force fields is assessed through calculations of binary mixture vapor-liquid equilibria. These mixtures include argon + krypton, krypton + xenon, methane + krypton, methane + xenon, krypton + ethane, and xenon + ethane. For all mixtures, excellent agreement with experiment is achieved without the introduction of any binary interaction parameters or multi-body interactions.

  4. Optimized Mie potentials for phase equilibria: Application to noble gases and their mixtures with n-alkanes.

    PubMed

    Mick, Jason R; Soroush Barhaghi, Mohammad; Jackman, Brock; Rushaidat, Kamel; Schwiebert, Loren; Potoff, Jeffrey J

    2015-09-21

    Transferrable force fields, based on n-6 Mie potentials, are presented for noble gases. By tuning the repulsive exponent, ni, it is possible to simultaneously reproduce experimental saturated liquid densities and vapor pressures with high accuracy, from the normal boiling point to the critical point. Vapor-liquid coexistence curves for pure fluids are calculated using histogram reweighting Monte Carlo simulations in the grand canonical ensemble. For all noble gases, saturated liquid densities and vapor pressures are reproduced to within 1% and 4% of experiment, respectively. Radial distribution functions, extracted from NVT and NPT Monte Carlo simulations, are in similarly excellent agreement with experimental data. The transferability of the optimized force fields is assessed through calculations of binary mixture vapor-liquid equilibria. These mixtures include argon + krypton, krypton + xenon, methane + krypton, methane + xenon, krypton + ethane, and xenon + ethane. For all mixtures, excellent agreement with experiment is achieved without the introduction of any binary interaction parameters or multi-body interactions.

  5. Tales from supereruptions: Combining pumice and mineral textures with phase equilibria to constrain the evolution of giant silicic magma bodies in the crust

    NASA Astrophysics Data System (ADS)

    Gualda, G. A. R.; Pamukcu, A. S.; Wright, K. A.; Ghiorso, M. S.; Miller, C. F.

    2014-12-01

    Supereruption deposits demonstrate that giant magma bodies sporadically exist within the Earth's crust. We rely on study of such deposits to better understand the underlying magma bodies and their eruptions. We are studying several deposits: Bishop Tuff (BT, CA USA), Peach Spring Tuff (PST, SW USA), and Oruanui Tuff (OT, NZ). We combine quantitative textural characterization in 3D via x-ray tomography (XRT), focusing particularly on CSDs of major and accessory minerals; characterization of mineral zoning, particularly of Ti and CL in quartz, including inferences from diffusion chronometry; documentation of glass inclusion textures in 3D via XRT, with implications to crystallization timescales; and phase equilibria modeling (rhyolite-MELTS), including glass (inclusion and matrix) composition geobarometry, to constrain crystallization conditions. CSDs ubiquitously record a growth-dominated regime, characterized by limited nucleation, consistent with pre-eruptive crystallization under low supersaturation. Phenocryst interiors are largely unzoned, consistent with phase equilibria predictions of nearly invariant, effectively isothermal crystallization. Glass compositions record storage over a large spread of depths (~125-250 MPa) for early and late-erupted BT, while the OT represents multiple magma batches evacuated from different depths. Diffusion chronometry and melt inclusion faceting suggest pre-eruptive crystallization over centennial timescales. CSDs and mineral textures also record syn-eruptive crystallization, which results in huge numbers of small crystals, revealing extensive nucleation prior to eruption. Crystal rims develop on pre-existing phenocrysts, and they can be obvious if compositionally distinct from interiors (BT and PST). In PST, evidence for rim crystallization from hotter magma is very strong. BT contrasts with PST in many ways; evidence for heating is ambiguous, and pumice properties are difficult to reconcile with magma mixing, while the

  6. On the topological stability of magnetostatic equilibria

    NASA Technical Reports Server (NTRS)

    Tsinganos, K. C.; Rosner, R.; Distler, J.

    1984-01-01

    The topological stability of MHD equilibria is investigated by exploring the formal analogy, in the ideal MHD limit, between the topology of magnetic lines of force in coordinate space and the topology of integral surfaces of one- and two-dimensional Hamiltonian systems in phase space. It is demonstrated that in an astrophysical setting, symmetric magnetostatic equilibria satisfying the ideal MHD equations are exceptional. The principal result of the study is that previous infinitesimal perturbation theory calculations can be generalized to include finite-amplitude and symmetry-breaking effects. The effect of the ergodicity of perturbed symmetric equilibria on heat dispersal in magnetically dominated plasmas is discussed.

  7. Elucidation of the chemistry of enzyme-bound thiamin diphosphate prior to substrate binding: defining internal equilibria among tautomeric and ionization states.

    PubMed

    Nemeria, Natalia; Korotchkina, Lioubov; McLeish, Michael J; Kenyon, George L; Patel, Mulchand S; Jordan, Frank

    2007-09-18

    Both solution and crystallographic studies suggest that the 4'-aminopyrimidine ring of the thiamin diphosphate coenzyme participates in catalysis, likely as an intramolecular general acid-base catalyst via the unusual 1',4'-iminopyrimidine tautomer. It is indeed uncommon for a coenzyme to be identified in its rare tautomeric form on its reaction pathways, yet this has been possible with thiamin diphosphate, in some cases even in the absence of substrate [Nemeria, N., Chakraborty, S., Baykal, A., Korotchkina, L., Patel, M. S., and Jordan, F. (2007) Proc. Natl. Acad. Sci. U.S.A. 104, 78-82.]. The ability to detect both the aminopyrimidine and iminopyrimidine tautomeric forms of thiamin diphosphate on enzymes has enabled us to assign the predominant tautomeric form present in individual intermediates on the pathway. Herein, we report the pH dependence of these tautomeric forms providing the first data for the internal thermodynamic equilibria on thiamin diphosphate enzymes for the various ionization and tautomeric forms of this coenzyme on four enzymes: benzaldehyde lyase, benzoylformate decarboxylase, pyruvate oxidase, and the E1 component of the human pyruvate dehydrogenase multienzyme complex. Evidence is provided for an important function of the enzyme environment in altering both the ionization and tautomeric equilibria on the coenzyme even prior to addition of substrate. The pKa for the 4'-aminopyrimidinium moiety coincides with the pH for optimum activity thereby ensuring that all ionization states and tautomeric states are accessible during the catalytic cycle. The dramatic influence of the protein on the internal equilibria also points to conditions under which the long-elusive ylide intermediate could be stabilized.

  8. Phase equilibria in the nominally Al65Cu23Fe12 system at 3, 5 and 21 GPa: Implications for the quasicrystal-bearing Khatyrka meteorite

    NASA Astrophysics Data System (ADS)

    Stagno, Vincenzo; Bindi, Luca; Steinhardt, Paul J.; Fei, Yingwei

    2017-10-01

    Two of the three natural quasiperiodic crystals found in the Khatyrka meteorite show a composition within the Al-Cu-Fe system. Icosahedrite, with formula Al63Cu24Fe13, coexists with the new Al62Cu31Fe7 quasicrystal plus additional Al-metallic minerals such as stolperite (AlCu), kryachkoite [(Al,Cu)6(Fe,Cu)], hollisterite (AlFe3), khatyrkite (Al2Cu) and cupalite (AlCu), associated to high-pressure phases like ringwoodite/ahrensite, coesite, and stishovite. These high-pressure minerals represent the evidence that most of the Khatyrka meteoritic fragments formed at least at 5 GPa and 1200 °C, if not at more extreme conditions. On the other hand, experimental studies on phase equilibria within the representative Al-Cu-Fe system appear mostly limited to ambient pressure conditions, yet. This makes the interpretation of the coexisting mineral phases in the meteoritic sample quite difficult. We performed experiments at 3, 5 and 21 GPa and temperatures of 800-1500 °C using the multi-anvil apparatus to investigate the phase equilibria in the Al65Cu23Fe12 system representative of the first natural quasicrystal, icosahedrite. Our results, supported by single-crystal X-ray diffraction and analyses by scanning electron microscopy, confirm the stability of icosahedrite at high pressure and temperature along with additional coexisting Al-bearing phases representative of khatyrkite and stolperite as those found in the natural meteorite. One reversal experiment performed at 5 GPa and 1200 °C shows the formation of the icosahedral quasicrystal from a pure Al, Cu and Fe mixture, a first experimental synthesis of icosahedrite under those conditions. Pressure appears to not play a major role in the distribution of Al, Cu and Fe between the coexisting phases, icosahedrite in particular. Results from this study extend our knowledge on the stability of icosahedral AlCuFe at higher temperature and pressure than previously examined, and provide a new constraint on the stability of

  9. Pressure effects on phase equilibria and solid solubility in MgO-Y2O3 nanocomposites

    NASA Astrophysics Data System (ADS)

    Akdoǧan, E. K.; Şavklιyιldιz, I.; Berke, B.; Zhong, Z.; Wang, L.; Weidner, D.; Croft, M. C.; Tsakalakos, T.

    2012-03-01

    We study the temperature and pressure dependence of phase evolution in the 0.5MgO-0.5Y2O3 nanocomposite system using a diamond anvil apparatus in conjunction with in situ synchrotron energy dispersive x-ray diffraction at 7 GPa hydrostatic pressure. At (298 K, 7.0 GPa), structural transformations in the Y2O3 phase are observed, giving rise to the co-existence of its cubic, hexagonal, and monoclinic polymorphs together with cubic MgO. An increase in temperature to 1273 K causes the crystallinity of the Y2O3 hexagonal and monoclinic phases to increase. Isothermal and isobaric hold at (1273 K, 7.0 GPa) for 60 min results in yttrium dissolution in cubic MgO, causing ˜1.0% expansive volumetric lattice strain despite the large differences in the ionic radii of the cations. Cooling the nanocomposite to (298 K, 0 GPa) after a 60 min soak yields four phase co-existence among cubic MgO and cubic, hexagonal, and monoclinic Y2O3. The residual MgO unit cell volume expansion is 0.69% at 298 K, indicating solid solution formation at room temperature despite large differences in the ionic radii of Mg2+ and Y3+. The macroscopic shrinkage due to densification is 3% by volume. Thermodynamic considerations suggest that the relative molar partial volume of Y3+ in MgO is a negative quantity, indicating that the partial molar volume of Y3+ in the solid solution is smaller than its molar volume in the pure state. Aging of the nanocomposites for 240 h does not change the observed 4 phase co-existence. We propose a crystallographic model in which the observed volumetric expansion of the MgO unit cell is primarily attributed to two hydrostatic expansive strain components accompanying solid solution formation: (i) Coulomb repulsion among O2- ions in the immediate vicinity of Mg2+ vacancies, and (ii) misfit strain due to differences in ionic radii upon Y3+ substitution on Mg2+ sites.

  10. The heat capacity of a natural monticellite and phase equilibria in the system CaO-MgO-SiO2-CO2

    USGS Publications Warehouse

    Sharp, Z.D.; Essene, E.J.; Anovitz, Lawrence M.; Metz, G.W.; Westrum, E.F.; Hemingway, B.S.; Valley, J.W.

    1986-01-01

    The heat capacity of a natural monticellite (Ca1.00Mg.09Fe.91Mn.01Si0.99O3.99) measured between 9.6 and 343 K using intermittent-heating, adiabatic calorimetry yields Cp0(298) and S2980 of 123.64 ?? 0.18 and 109.44 ?? 0.16 J ?? mol-1 K-1 respectively. Extrapolation of this entropy value to end-member monticellite results in an S0298 = 108.1 ?? 0.2 J ?? mol-1 K-1. High-temperature heat-capacity data were measured between 340-1000 K with a differential scanning calorimeter. The high-temperature data were combined with the 290-350 K adiabatic values, extrapolated to 1700 K, and integrated to yield the following entropy equation for end-member monticellite (298-1700 K): ST0(J ?? mol-1 K-1) = S2980 + 164.79 In T + 15.337 ?? 10-3 T + 22.791 ?? 105 T-2 - 968.94. Phase equilibria in the CaO-MgO-SiO2 system were calculated from 973 to 1673 K and 0 to 12 kbar with these new data combined with existing data for akermanite (Ak), diopside (Di), forsterite (Fo), merwinite (Me) and wollastonite (Wo). The location of the calculated reactions involving the phases Mo and Fo is affected by their mutual solid solution. A best fit of the thermodynamically generated curves to all experiments is made when the S0298 of Me is 250.2 J ?? mol-1 K-1 less than the measured value of 253.2 J ?? mol-1 K-1. A best fit to the reversals for the solid-solid and decarbonation reactions in the CaO-MgO-SiO2-CO2 system was obtained with the ??G0298 (kJ ?? mole-1) for the phases Ak(-3667), Di(-3025), Fo(-2051), Me(-4317) and Mo(-2133). The two invariant points - Wo and -Fo for the solid-solid reactions are located at 1008 ?? 5 K and 6.3 ?? 0.1 kbar, and 1361 ?? 10 K and 10.2 ?? 0.2 kbar respectively. The location of the thermodynamically generated curves is in excellent agreement with most experimental data on decarbonation equilibria involving these phases. ?? 1986.

  11. 3-Hydroxy-4-methyl-4-pentenonitrile and 4-methyl-3-oxo-4-pentenonitrile: Study of the tautomerics equilibria in gas phase and in solution.

    PubMed

    Giussi, Juan M; Ponzinibbio, Agustín; Cortizo, M Susana; Allegretti, Patricia E

    2010-10-01

    In the present work the tautomerics equilibria in 3-hydroxy-4-methyl-4-pentenonitrile and 4-methyl-3-oxo-4-pentenonitrile have been studied. The first compound presents two possible theoretical tautomers, nitrile and ketenimine. The second compound presents four possible theoretical tautomers ketonitrile, nitrile-enol (E and Z) and keto-ketenimine. The study of the equilibrium in gas phase was performed by gas chromatography-mass spectrometry (GC-MS), and in solution by proton nuclear magnetic resonance spectrometry ((1)H NMR). In gas phase, the ketonitrile tautomer was favoured, a result which was supported by theoretical calculations by the use of AM1 semi-empiric calculation. The experimental tautomerization heat values were in good agreement with the theoretical ones. The (1)H NMR spectra gave the additional evidence for the coexistence of the tautomers ketonitrile and enolnitrile for 4-methyl-3-oxo-4-pentenonitrile. The nitrile-ketenimine equilibrium for both compounds could not be observed by (1)H NMR spectra because of the low sensibility of this method. The ketonitrile-enolnitrile tautomerization heat of 4-methyl-3-oxo-4-pentenonitrile has been calculated and compared with the corresponding one in gas phase to evaluate the solvent effect. Copyright 2010 Elsevier B.V. All rights reserved.

  12. Extension of Toth function from gas-solid to liquid-solid equilibria and application to reversed-phase liquid chromatography systems

    SciTech Connect

    Gritti, Fabrice; Guiochon, Georges A

    2006-03-01

    The extension of the {Psi} function developed by Toth from equilibria taking place at gas-solid interfaces to those taking place at liquid-solid interfaces was investigated. The results were applied to conventional liquid-solid systems used in reversed-phase liquid chromatography (RPLC). The adsorbents in these systems are made of porous silica having a hydrophobic solid surface obtained by chemically bonding C{sub 18} alkyl chains to a porous silica gel then endcapping the surface with trimethylsilyl groups. The liquid is an aqueous solution of an organic solvent, most often methanol or acetonitrile. The probe compound used here is phenol. Adsorption data of phenol were measured using the dynamic frontal analysis (FA) method. The excess adsorption of the organic solvent was measured using the minor disturbance (MD) method. Activity coefficients in the bulk were estimated through the UNIFAC group contributions. The results show that the {Psi} function predicts 90% of the total free energy of immersion, {Delta}F, of the solid when the concentration of phenol is moderate (typically less than 10 g/L). At higher concentrations, the nonideal behavior of the bulk liquid phase becomes significant and it may contribute up to about 30% of {Delta}F. The high concentration of adsorbed molecules of phenol at the interface decreases the interfacial tension, {sigma}, by about 18 mN/m, independently of the structure of the adsorbed phase and of the nature of the organic solvent.

  13. Riemannian geometry study of vapor-liquid phase equilibria and supercritical behavior of the Lennard-Jones fluid.

    PubMed

    May, Helge-Otmar; Mausbach, Peter

    2012-03-01

    The behavior of thermodynamic response functions and the thermodynamic scalar curvature in the supercritical region have been studied for a Lennard-Jones fluid based on a revised modified Benedict-Webb-Rubin equation of state. Response function extrema are sometimes used to estimate the Widom line, which is characterized by the maxima of the correlation lengths. We calculated the Widom line for the Lennard-Jones fluid without using any response function extrema. Since the volume of the correlation length is proportional to the Riemannian thermodynamic scalar curvature, the locus of the Widom line follows the slope of maximum curvature. We show that the slope of the Widom line follows the slope of the isobaric heat capacity maximum only in the close vicinity of the critical point and that, therefore, the use of response function extrema in this context is problematic. Furthermore, we constructed the vapor-liquid coexistence line for the Lennard-Jones fluid using the fact that the correlation length, and therefore the thermodynamic scalar curvature, must be equal in the two coexisting phases. We compared the resulting phase envelope with those from simulation data where multiple histogram reweighting was used and found striking agreement between the two methods.

  14. Petrology, phase equilibria and monazite geochronology of granulite-facies metapelites from deep drill cores in the Ordos Block of the North China Craton

    NASA Astrophysics Data System (ADS)

    He, Xiao-Fang; Santosh, M.; Bockmann, Kiara; Kelsey, David E.; Hand, Martin; Hu, Jianmin; Wan, Yusheng

    2016-10-01

    Among the various Precambrian crustal blocks in the North China Craton (NCC), the geology and evolution of the Ordos Block remain largely enigmatic due to paucity of outcrop. Here we investigate granulite-facies metapelites obtained from deep-penetrating drill holes in the Ordos Block and report petrology, calculated phase equilibria and in-situ monazite LA-ICP-MS geochronology. The rocks we studied are two samples of cordierite-bearing garnet-sillimanite-biotite metapelitic gneisses and one graphite-bearing, two-mica granitic gneiss. The peak metamorphic age from LA-ICP-MS dating of monazite in all three samples is in the range of 1930-1940 Ma. The (U + Pb)-Th chemical ages through EPMA dating reveals that monazite occurring as inclusions in garnet are older than those in the matrix. Calculated metamorphic phase diagrams for the cordierite-bearing metapelite suggest peak P-T conditions ca. 7-9 kbar and 775-825 °C, followed by decompression and evolution along a clockwise P-T path. Our petrologic and age data are consistent with those reported from the Khondalite Belt in the Inner Mongolia Suture Zone in the northern part of the Ordos Block, suggesting that these granulite-facies metasediments represent the largest Paleoproterozoic accretionary belt in the NCC.

  15. Determining age of Pan African metamorphism using Sm-Nd garnet-whole rock geochronology and phase equilibria modeling in the Tasriwine ophiolite, Sirwa, Anti-Atlas Morocco

    NASA Astrophysics Data System (ADS)

    Inglis, Jeremy D.; Hefferan, Kevin; Samson, Scott D.; Admou, Hassan; Saquaque, Ali

    2017-03-01

    Sm-Nd garnet-whole rock geochronology and phase equilibria modeling have been used to determine the age and conditions of regional metamorphism within the Tasriwine ophiolite complex, Sirwa, Morocco. Pressure and temperature estimates obtained using a NaCaKFMASHT phase diagram (pseudosection) and garnet core and rim compositions predict that garnet growth began at ∼0.72 GPa and ∼615 °C and ended at ∼0.8 GPa and ∼640 °C. A bulk garnet Sm-Nd age of 647.2 ± 1.7 Ma, calculated from a four point isochron that combines whole rock, garnet full dissolution and two successively more aggressive partial dissolutions, provides a precise date for garnet formation and regional metamorphism. The age is over 15 million years younger than a previous age estimate of regional metamorphism of 663 ± 13 Ma based upon a SHRIMP U-Pb date from rims on zircon from the Iriri migmatite. The new data provide further constraints on the age and nature of regional metamorphism in the Anti-Atlas mountains and emphasizes that garnet growth during regional metamorphism may not necessarily coincide with magmatism/anatexis which predominate the signature witnessed by previous U-Pb studies. The ability to couple PT estimates for garnet formation with high precision Sm-Nd geochronology highlights the utility of garnet studies for uncovering the detailed metamorphic history of the Anti-Atlas mountain belt.

  16. Computational Thermodynamic Study to Predict Complex Phase Equilibria in the Nickel-Base Superalloy Rene N6

    NASA Technical Reports Server (NTRS)

    Copland, Evan H.; Jacobson, Nathan S.; Ritzert, Frank J.

    2001-01-01

    A previous study by Ritzert et al. on the formation and prediction of topologically closed packed (TCP) phases in the nickel-base superalloy Rene' N6 is re-examined with computational thermodynamics. The experimental data on phase distribution in forty-four alloys with a composition within the patent limits of the nickel-base superalloy Rene' N6 provide a good basis for comparison to and validation of a commercial nickel superalloy database used with ThermoCalc. Volume fraction of the phases and partitioning of the elements are determined for the forty-four alloys in this dataset. The baseline heat treatment of 400 h at 1366 K was used. This composition set is particularly interesting since small composition differences lead to dramatic changes in phase composition. In general the calculated values follow the experimental trends. However, the calculations indicated no TCP phase formation when the experimental measurements gave a volume percent of TCP phase less than 2 percent. When TCP phases were predicted, the calculations under-predict the volume percent of TCP phases by a factor of 2 to 8. The calculated compositions of the gamma and gamma' phases show fair agreement with the measurements. However, the calculated compositions of the P Phase do not agree with those measured. This may be due to inaccuracies in the model parameters for P phase and/or issues with the microprobe analyses of these phases. In addition, phase fraction diagrams and sigma and P phase solvus temperatures are calculated for each of the alloys. These calculations indicate that P phase is the primary TCP phase formed for the alloys considered here at 1366 K. Finally, a series of isopleths are calculated for each of the seven alloying elements. These show the effect of each alloying element on creating TCP phases.

  17. Using nanogranitoids and phase equilibria modeling to unravel anatexis in the crustal footwall of the Ronda peridotites (Betic Cordillera, S Spain)

    NASA Astrophysics Data System (ADS)

    Bartoli, Omar; Acosta-Vigil, Antonio; Tajčmanová, Lucie; Cesare, Bernardo; Bodnar, Robert J.

    2016-07-01

    Anatexis in the crustal footwall of Ronda peridotites (Betic Cordillera, S Spain) is apparently related to the hot emplacement of this mantle slab over metasedimentary rocks. In this study, we combine the analysis of melt inclusions (MI) and phase equilibria calculations on quartzo-feldspathic mylonites (former migmatites) occurring at the contact with the mantle rocks, in the region of Sierra Alpujata (Ojén unit). The goal is to better characterize anatexis in these rocks and to provide new constraints on the geodynamic evolution of the crustal footwall. Such data are important for understanding the mechanisms of crustal emplacement of the mantle slice. The quartzo-feldspathic mylonites are characterized by the mineral assemblage Qtz + Pl + Kfs + Sil + Grt + Ilm + Bt ± Ap ± Gr. Clusters of MI are observed both at the core and toward the rim of peritectic garnet. In each cluster, MI range from totally glassy to nanogranitoids, consisting of Qtz + Kfs + Bt + Ms + Pl aggregates. The trapped melt is leucogranitic and peraluminous with variable Na2O/K2O values and low H2O contents (≈ 2-4 wt%). Phase equilibria modeling in the MnO-Na2O-CaO-K2O-FeO-MgO-Al2O3-SiO2-H2-TiO2-O2-C (MnNCaKFMASHTOC) system with graphite-saturated fluid constrains the P-T conditions of melting at ≈ 6 kbar, ≈ 820 °C. MI data support the fluid-absent character of melting. The investigated MI represent the primary anatectic melts produced during prograde anatexis of the host rocks via biotite dehydration melting. Field, compositional, and textural observations indicate that mylonitic migmatites represent strongly deformed former diatexites. The comparison between the new data and some recently published information on migmatites located further from the contact with the peridotites and toward the bottom of the crustal footwall, raises some important issues which question the previously proposed geodynamic models for this region. Among them, (i) the crustal footwall at Sierra Alpujata

  18. High-pressure anatectic paragneisses from the Namche Barwa, Eastern Himalayan Syntaxis: Textural evidence for partial melting, phase equilibria modeling and tectonic implications

    NASA Astrophysics Data System (ADS)

    Guilmette, C.; Indares, A.; Hébert, R.

    2011-05-01

    Rare kyanite-bearing anatectic paragneisses are found as boudins within sillimanite-bearing paragneisses of the core of the Namche Barwa Antiform, Tibet. In the present study, we document an occurrence from the NW side of the Yarlung Zangbo River. These rocks mainly consist of the assemblage garnet + K-feldspar + kyanite ± biotite + quartz + rutile ± plagioclase with kyanite locally pseudomorphed by sillimanite. The documented textures are consistent with the rocks having undergone biotite-dehydration melting in the kyanite stability field, under high-P granulite facies conditions, and having experienced melt extraction. However textures related to melt crystallization are ubiquitous both in polymineralic inclusions in garnet and in the matrix, suggesting that a melt fraction had remained in these rocks. Phase equilibria modelling was undertaken in the NCKFMASTHO system with THERMOCALC. P-T pseudosections built with the bulk compositions of one aluminous and one sub-aluminous paragneiss samples predict a biotite-kyanite-garnet-quartz-plagioclase-K-feldspar-liquid-rutile ± ilmenite field, in which biotite-dehydration melting occurs, located in the P-T range of ~ 800-875 °C and ~ 10-17 kbar. In addition, the topologies of these pseudosections are consistent with substantial melt loss during prograde metamorphism. A second set of P-T pseudosections with melt-reintegrated model bulk compositions were thus constructed to evaluate the effect of melt loss. The integration of textural information, precise mineral modes, mineral chemistry, and phase equilibria modelling allowed to constrain a P-T path where the rocks are buried to lower crustal depths at peak P-T conditions higher than 14 kbar and 825 °C, possibly in the order of 15-16 kbar and 850 °C, followed by decompression and cooling to P-T conditions of around 9 kbar and 810 °C, under which the remaining melt was solidified. The implications for granite production at the NBA and for Himalayan tectonic models

  19. Braided magnetic fields: equilibria, relaxation and heating

    NASA Astrophysics Data System (ADS)

    Pontin, D. I.; Candelaresi, S.; Russell, A. J. B.; Hornig, G.

    2016-05-01

    We examine the dynamics of magnetic flux tubes containing non-trivial field line braiding (or linkage), using mathematical and computational modelling, in the context of testable predictions for the laboratory and their significance for solar coronal heating. We investigate the existence of braided force-free equilibria, and demonstrate that for a field anchored at perfectly-conducting plates, these equilibria exist and contain current sheets whose thickness scales inversely with the braid complexity—as measured for example by the topological entropy. By contrast, for a periodic domain braided exact equilibria typically do not exist, while approximate equilibria contain thin current sheets. In the presence of resistivity, reconnection is triggered at the current sheets and a turbulent relaxation ensues. We finish by discussing the properties of the turbulent relaxation and the existence of constraints that may mean that the final state is not the linear force-free field predicted by Taylor’s hypothesis.

  20. Study of phase equilibria in the CO(NH2)2-KH2PO4-K2HPO4-H2O system at 25°C using an optimized method of cross sections

    NASA Astrophysics Data System (ADS)

    Noskov, M. N.; Mazunin, S. A.

    2015-06-01

    Phase equilibria are studied in ternary contouring systems and in the CO(NH2)2-KH2PO4-K2HPO4-H2O quaternary system at 25°C using an optimized method of cross sections. It is found that an incongruent chemical compound forms between the components of a system with the composition 2KH2PO4 · K2HPO4. The compositions of eutonic and peritonic solutions and the solid phases saturating them are determined. The lines of monovariant equilibria and the crystallization surface of potassium dihydrogen phosphate are studied. The location of the eutonic and peritonic solutions and monovariant equilibrium lines near the plane are shown.

  1. Computation of liquid-liquid equilibria and phase stabilities: implications for RH-dependent gas/particle partitioning of organic-inorganic aerosols

    NASA Astrophysics Data System (ADS)

    Zuend, A.; Marcolli, C.; Peter, T.; Seinfeld, J. H.

    2010-05-01

    Semivolatile organic and inorganic aerosol species partition between the gas and aerosol particle phases to maintain thermodynamic equilibrium. Liquid-liquid phase separation into an organic-rich and an aqueous electrolyte phase can occur in the aerosol as a result of the salting-out effect. Such liquid-liquid equilibria (LLE) affect the gas/particle partitioning of the different semivolatile compounds and might significantly alter both particle mass and composition as compared to a one-phase particle. We present a new liquid-liquid equilibrium and gas/particle partitioning model, using as a basis the group-contribution model AIOMFAC (Zuend et al., 2008). This model allows the reliable computation of the liquid-liquid coexistence curve (binodal), corresponding tie-lines, the limit of stability/metastability (spinodal), and further thermodynamic properties of the phase diagram. Calculations for ternary and multicomponent alcohol/polyol-water-salt mixtures suggest that LLE are a prevalent feature of organic-inorganic aerosol systems. A six-component polyol-water-ammonium sulphate system is used to simulate effects of relative humidity (RH) and the presence of liquid-liquid phase separation on the gas/particle partitioning. RH, salt concentration, and hydrophilicity (water-solubility) are identified as key features in defining the region of a miscibility gap and govern the extent to which compound partitioning is affected by changes in RH. The model predicts that liquid-liquid phase separation can lead to either an increase or decrease in total particulate mass, depending on the overall composition of a system and the particle water content, which is related to the hydrophilicity of the different organic and inorganic compounds. Neglecting non-ideality and liquid-liquid phase separations by assuming an ideal mixture leads to an overestimation of the total particulate mass by up to 30% for the composition and RH range considered in the six-component system simulation

  2. Computation of liquid-liquid equilibria and phase stabilities: implications for RH-dependent gas/particle partitioning of organic-inorganic aerosols

    NASA Astrophysics Data System (ADS)

    Zuend, A.; Marcolli, C.; Peter, T.; Seinfeld, J. H.

    2010-08-01

    Semivolatile organic and inorganic aerosol species partition between the gas and aerosol particle phases to maintain thermodynamic equilibrium. Liquid-liquid phase separation into an organic-rich and an aqueous electrolyte phase can occur in the aerosol as a result of the salting-out effect. Such liquid-liquid equilibria (LLE) affect the gas/particle partitioning of the different semivolatile compounds and might significantly alter both particle mass and composition as compared to a one-phase particle. We present a new liquid-liquid equilibrium and gas/particle partitioning model, using as a basis the group-contribution model AIOMFAC (Zuend et al., 2008). This model allows the reliable computation of the liquid-liquid coexistence curve (binodal), corresponding tie-lines, the limit of stability/metastability (spinodal), and further thermodynamic properties of multicomponent systems. Calculations for ternary and multicomponent alcohol/polyol-water-salt mixtures suggest that LLE are a prevalent feature of organic-inorganic aerosol systems. A six-component polyol-water-ammonium sulphate system is used to simulate effects of relative humidity (RH) and the presence of liquid-liquid phase separation on the gas/particle partitioning. RH, salt concentration, and hydrophilicity (water-solubility) are identified as key features in defining the region of a miscibility gap and govern the extent to which compound partitioning is affected by changes in RH. The model predicts that liquid-liquid phase separation can lead to either an increase or decrease in total particulate mass, depending on the overall composition of a system and the particle water content, which is related to the hydrophilicity of the different organic and inorganic compounds. Neglecting non-ideality and liquid-liquid phase separations by assuming an ideal mixture leads to an overestimation of the total particulate mass by up to 30% for the composition and RH range considered in the six-component system

  3. A contribution to the understanding of phase equilibria (structure of Sr[sub 7]ZrSi[sub 6]O[sub 21])

    SciTech Connect

    Plaisier, J.R.; Graaff, R.A.G. de; Ijdo, D.J.W. . Inst. of Chemistry); Huntelaar, M.E. )

    1994-07-01

    The crystal structure of Sr[sub 7]ZrSi[sub 6]O[sub 21] is described. Sr[sub 7]ZrSi[sub 6]O[sub 21], M[sub r] = 1,209.10, triclinic, P[bar 1], a = 8.398(3)[angstrom], b = 8.435(2)[angstrom], c = 8.445(3)[angstrom], [alpha] = 106.13(3)[degree], [beta] = 106.49(3)[degree], [gamma] = 105.90(3)[degree], V = 509.0(3)[angstrom][sup 3], Z = 1, D[sub x] = 3.944(3) Mgr/m[sup 3]. [gamma](MoK[alpha]) = 0.71069[angstrom], F(000) = 558, room temperature, final R = 0.073 for 1,145 observed reflections. The structure is pseudo rhombohedral, R[bar 3], a[sub hex] = 13.474[angstrom], c[sub hex] = 9.714[angstrom], Z = 3. The crystal structure determination establishes the formula for the compound earlier described in phase equilibria studies as Sr[sub 6]ZrSi[sub 5]O[sub 18].

  4. Sapphirine-bearing granulites from the Tongbai orogen, China: Petrology, phase equilibria, zircon U-Pb geochronology and implications for Paleozoic ultrahigh temperature metamorphism

    NASA Astrophysics Data System (ADS)

    Xiang, Hua; Zhong, Zeng-Qiu; Li, Ye; Qi, Min; Zhou, Han-Wen; Zhang, Li; Zhang, Ze-Ming; Santosh, M.

    2014-11-01

    We report here for the first time the occurrence of sapphirine-bearing granulites within the Qinling Group of the Qinling-Tongbai orogen and provide robust evidence for extreme crustal metamorphism at ultrahigh-temperature (UHT) conditions. We document the UHT indicator of sapphirine and spinel in a mafic granulite consisting of orthopyroxene, biotite, plagioclase, amphibole and rutile/ilmenite. The ferromagnesian minerals in the sapphirine-bearing granulite have high XMg [Mg/(Mg + Fe)] (orthopyroxene XMg = 0.84-0.95; biotite XMg = 0.81; amphibole XMg = 0.87-0.96). The phase equilibria modeling demonstrates that the early spinel-bearing assemblage is stable at 923-950 °C and 6.7-8.9 kbar, and the peak assemblage of Opx + Pl + Spr/Spl + Amp + Bt + Ilm (+ melt) defines a field at 922-947 °C and 8.4-10.2 kbar. Rutiles have variable Zr concentrations but mostly cluster at ca. 1,500 and 3400 ppm. Zr-in-rutile geothermometry yielded high temperatures of up to 890-940 °C. Zircon U-Pb dating of the granulite constrains the timing of the immediate post-peak and retrograde metamorphic stages as 429 ± 7 Ma and 412 ± 4 Ma, respectively. The UHT metamorphism, together with extensive occurrence of coeval magmatic suites suggests that the Tongbai orogen experienced a Paleozoic Andean-type orogeny probably derived from mid-oceanic ridge subduction of the Qinling Ocean.

  5. Phase equilibria, formation, crystal and electronic structure of ternary compounds in Ti-Ni-Sn and Ti-Ni-Sb ternary systems

    NASA Astrophysics Data System (ADS)

    Romaka, V. V.; Rogl, P.; Romaka, L.; Stadnyk, Yu.; Melnychenko, N.; Grytsiv, A.; Falmbigl, M.; Skryabina, N.

    2013-01-01

    The phase equilibria of the Ti-Ni-Sn and Ti-Ni-Sb ternary systems have been studied in the whole concentration range by means of X-ray and EPM analyses at 1073 K and 873 K, respectively. Four ternary intermetallic compounds TiNiSn (MgAgAs-type), TiNi2-xSn (MnCu2Al-type), Ti2Ni2Sn (U2Pt2Sn-type), and Ti5NiSn3 (Hf5CuSn3-type) are formed in Ti-Ni-Sn system at 1073 K. The TiNi2Sn stannide is characterized by homogeneity in the range of 50-47 at% of Ni. The Ti-Ni-Sb ternary system at 873 K is characterized by formation of three ternary intermetallic compounds, Ti0.8NiSb (MgAgAs-type), Ti5Ni0.45Sb2.55 (W5Si3-type), and Ti5NiSb3 (Hf5CuSn3-type). The solubility of Ni in Ti0.8NiSb decreases number of vacancies in Ti site up to Ti0.91Ni1.1Sb composition.

  6. Phase equilibria in the system H{sub 2}O-NaCl-KCl-MgCl{sub 2} relevant to salt cake processing

    SciTech Connect

    Bodnar, R.J.; Vityk, M.O.; Hryn, J.N.; Mavrogenes, J.

    1997-02-01

    One waste product in recycling of Al is salt cake, a mixture of Al, salts, and residue oxides. Several methods have been proposed to recycle salt cake, one involving high-temperature leaching of salts from the salt cake. The salt composition can be approximated as a mixture predominantly of NaCl and KCl salts, with lesser amounts of Mg chloride. In order to better assess the feasibility of recycling salt cake, an experimental study was conducted of phase equilibria in the system H{sub 2}O-NaCl-KCl-MgCl{sub 2} at pressure (P), temperature (T), and composition conditions appropriate for high- temperature salt cake recycling. These experiments were designed to evaluate the effect of small amounts (2-10 wt%) of MgCl{sub 2} on solubilities of halite (NaCl) and sylvite (KCl) in saturated solutions (30-50 wt% NaCl+KCl; NaCl:KCl = 1:1 and 3:1) at elevated P and T.

  7. High-temperature phase equilibria in the Al-rich corner of the Al-Ti-C system

    SciTech Connect

    Frage, N.; Frumin, N.; Levin, L.; Polak, M.; Dariel, M.P.

    1998-04-01

    A thermodynamic analysis of the Al-rich corner in the ternary Al-Ti-C diagram, providing phase relations and regions of phase stability, is presented. An invariant four-phase equilibrium between Al, Al{sub 4}C{sub 3}, Al{sub 3}Ti, and TiC{sub x} takes place at 0.53 at. pct Ti, 7.10{sup {minus}6} at. pct C, and TiC{sub 0.883} at 966 K. The carbon content of the TiC{sub x} phase, which extends from x = 0.48 to 0.98, exerts a significant effect on phase relationships in this ternary system. In particular, it is shown that stoichiometric TiC is not stable in the presence of liquid Al. For example, at 1,300 K, a two-phase equilibrium between Al{sub L} and TiC{sub x} exists only in the 0.91 < x < 0.82 range. Thus, the interaction of Al{sub L} with stoichiometric TiC leads to the formation of the Al{sub 4}C{sub 3} aluminum carbide phase, whereas for x < 0.82, only the intermetallic compound Al{sub 3}Ti can form at this temperature. The results of this analysis were confirmed by X-ray diffraction (XRD) measurements of relevant composites.

  8. Hydrothermal phase equilibria in Ln 2O 3-H 2O-CO 2 systems . I. The lighter lanthanides

    NASA Astrophysics Data System (ADS)

    Tareen, J. A. K.; Kutty, T. R. N.

    1980-10-01

    Phase diagrams for Nd 2O 3-H 2O-CO 2 and Gd 2O 3-H 2O-CO 2 systems at 1500 atm are given along with the results of selected runs in La, Sm and Eu systems. The stable phases in systems of La and Nd, are Ln(OH)CO 3-B, Ln 2O 2CO 3-II and LnOOH, in addition to the Ln(OH) 3 phase at extremely low partial pressures of CO 2 in the system. The systems become more and more complex with decreasing ionic radi and the number of stable carbonate phases increases. Ln 2(CO 3) 3 · 3H 2O orthorhombic (tengerate-like phase) is stable from Sm to Gd in addition to the other phases. The Gd(OH)CO 3-A (ancylite-like phase) is hydrothermally stable at XCO 2 ⩾ 0.5 while its hexagonal polymorph, Gd(OH)CO 3-B is stable at low partial pressures of CO 2 in the system.

  9. Phase Equilibria and Crystal Chemistry in Portions of the System SrO-CaO-Bi2O3-CuO, Part IV— The System CaO-Bi2O3-CuO

    PubMed Central

    Burton, B. P.; Rawn, C. J.; Roth, R. S.; Hwang, N. M.

    1993-01-01

    New data are presented on the phase equilibria and crystal chemistry of the binary systems CaO-Bi2O3 and CaO-CuO and the ternary CaO-Bi2O3-CuO. Symmetry data and unit cell dimensions based on single crystal and powder x-ray diffraction measurements are reported for several of the binary CaO-Bi2O3 phases, including corrected compositions for Ca4Bi6O13 and Ca2Bi2O5. The ternary system contains no new ternary phases which can be formed in air at ~700–900 °C. PMID:28053484

  10. Phase equilibria in four-component system consisting of water, a nonionic surfactant mixture, and oleic acid

    SciTech Connect

    Matveenko, V.N.; Drovetskii, B.Yu.; Kirasanov, E.A.

    1994-05-01

    The phase diagram of the system consisting of water, Tween 20, Span 80, and oleic acid has been obtained; the coexisting phases have been identified; and the character of the equilibrium of microemulsion, liquid crystal, and molecular solution has been described. In the water-Tween 20-oleic acid system, the ratio of the water volume to the surfactant volume is identical in all of the coexisting phases; this proves the existence of a corresponding field variable in a system with a nonionic surfactant.

  11. Phase and Extractive Equilibria in the Water-Inorganic Salting-out Agent-Polyethyleneglycol Alkyl Ether Systems

    NASA Astrophysics Data System (ADS)

    Kudryashova, O. S.; Denisova, S. A.; Lesnov, A. E.; Popova, M. A.

    2008-04-01

    The solubility isotherms were constructed for the ternary systems H2O-DS-10 synthanol-(NH4)2SO4 and H2O—ALM-10 synthanol-KSCN at 298 K. The regions of two-phase liquid equilibrium were revealed. The interphase distribution of some metal ions was examined. It was established that cobalt(II) and zinc ions were quantitatively extracted into the phase of the surface-active substance in the system with potassium thiocyanate.

  12. A class of phase-like states

    NASA Astrophysics Data System (ADS)

    Wünsche, Alfred

    2001-08-01

    We investigate a class of phase-like states |ν;ɛ> with an integer parameter ν = 0,1,... which contains the coherent phase states |ɛ> as the special case ν = 0. Many characteristics, such as the number statistics and the Susskind-Glogower phase distribution, can be calculated in a closed way and are discussed. The parameter ν can be continuously interpolated and extended to a real parameter up to arbitrary ν>-1. Problems of the definition of phase variances are discussed. The class of states is compared with the so-called `phase-optimized' states and it is found that the case ν = 2 of them is near to these states. The properties of the considered class of states |ν;ɛ> provide additional arguments to consider the coherent phase states corresponding to ν = 0 as the genuine phase-optimized states. Since the Lommel polynomials play a role in the Fock-state representation of `phase-optimized' states as is shown and to prevent misinterpretation, it is proposed to rename these states `Lommel states'. In the limiting case of high mean number, they make the transition to Chebyshev states of second kind and are near to the case ν = 1 of the class of phase-like states |ν;ɛ>. The mathematical tools connected with a generalization of the geometric series are given in an appendix.

  13. Nonadditive Mixed State Phases in Neutron Optics

    SciTech Connect

    Klepp, J.; Sponar, S.; Filipp, S.; Lettner, M.; Badurek, G.; Hasegawa, Y.

    2009-03-10

    In a neutron polarimetry experiment mixed neutron spin phases are determined. We consider evolutions leading to purely geometric, purely dynamical and combined phases. It is experimentally demonstrated that the sum of the geometric and dynamical phases--both obtained in separate measurements--is not equal to the associated total phase as obtained from a third measurement, unless the system is in a pure state. In this sense, mixed state phases are not additive.

  14. Phase equilibria in electrochemically oxidized La 2CuO 4δ. Transport measurements versus chemical analysis

    NASA Astrophysics Data System (ADS)

    Ondoño-Castillo, S.; Michel, C. R.; Seffar, A.; Fontcuberta, J.; Casañ-Pastor, N.

    1994-12-01

    A comparative study of physical and chemical methods for the analysis of the number and identity of holes in electrochemically oxidized La 2CuO 4+δ is reported. A combination of TGA and iodometric chemical analyses shows the existence of two species with different oxidation potentials. Susceptibility and resistivity measurements show the existence of at least two segregated superconducting phases, while Seebeck measurements shows a large change in the number of carriers for a constant value of δ; this atypical behavior is consistent though with the chemical data and implies the existence of a phase equilibrium within the oxide.

  15. Computational Aspects of Equilibria

    NASA Astrophysics Data System (ADS)

    Yannakakis, Mihalis

    Equilibria play a central role in game theory and economics. They characterize the possible outcomes in the interaction of rational, optimizing agents: In a game between rational players that want to optimize their payoffs, the only solutions in which no player has any incentive to switch his strategy are the Nash equilibria. Price equilibria in markets give the prices that allow the market to clear (demand matches supply) while the traders optimize their preferences (utilities). Fundamental theorems of Nash [34] and Arrow-Debreu [2] established the existence of the respective equilibria (under suitable conditions in the market case). The proofs in both cases use a fixed point theorem (relying ultimately on a compactness argument), and are non-constructive, i.e., do not yield an algorithm for constructing an equilibrium. We would clearly like to compute these predicted outcomes. This has led to extensive research since the 60’s in the game theory and mathematical economics literature, with the development of several methods for computation of equilibria, and more generally fixed points. More recently, equilibria problems have been studied intensively in the computer science community, from the point of view of modern computation theory. While we still do not know definitely whether equilibria can be computed in general efficiently or not, these investigations have led to a better understanding of the computational complexity of equilibria, the various issues involved, and the relationship with other open problems in computation. In this talk we will discuss some of these aspects and our current understanding of the relevant problems. We outline below the main points and explain some of the related issues.

  16. Phase equilibria study of {N-hexylisoquinolinium bis{(trifluoromethyl)sulfonyl}imide + aromatic hydrocarbons or an alcohol} binary systems.

    PubMed

    Domańska, Urszula; Zawadzki, Maciej; Tshibangu, M Marc; Ramjugernath, Deresh; Letcher, Trevor M

    2011-04-14

    Isoquinolinium ionic liquid (IL) has been synthesized from N-hexylisoquinolinium bromide as a substrate. Specific basic characterization of the synthesized compound is included, which includes NMR spectra, elementary analysis, and water content. The basic thermal properties of the pure IL, that is, melting and solid-solid transition temperatures, as well as the enthalpy of fusion, or solid-solid transition have been measured using a differential scanning microcalorimetry technique. The density and viscosity as a function of temperature have been measured for the pure IL at temperatures higher than the melting temperature and were extrapolated to T = 298.15 K. The temperature-composition phase diagrams of 8 binary mixtures composed of the IL N-hexylisoquinolinium bis{(trifluoromethyl)sulfonyl}imide, ([HiQuin][NTf(2)]) and an aromatic hydrocarbon (benzene, or toluene, or ethylbenzene, n-propylbenzene) or an alcohol (1-butanol, or 1-hexanol, or 1-octanol, or 1-decanol) have been determined from ambient temperature to the boiling-point temperature of the solvent at ambient pressure. A dynamic method was used over a broad range of mole fractions and temperatures from 270 to 330 K. For the binary systems, the eutectic diagrams were observed with immiscibility in the liquid phase with an upper critical solution temperature (UCST). In the case of the mixture {IL + benzene, or alkylbenzene} the eutectic systems with mutual immiscibility in the liquid phase with very high UCSTs were observed. These points were not detectable with our method and were observed at low IL mole fraction. For mixtures with alcohols, it was observed that with an increasing chain length of an alcohol, the solubility decreases and the UCST increases. The coexistence curves corresponding to liquid-liquid phase equilibrium boundaries and the solid-liquid phase equilibrium has been correlated using the well-known nonrandom two-liquid (NRTL) model.

  17. Calculation of CO2 activities using scapolite equilibria: constraints on the presence and composition of a fluid phase during high grade metamorphism

    NASA Astrophysics Data System (ADS)

    Moecher, David P.; Essene, Eric J.

    1991-07-01

    Thermodynamic and phase equilibrium data for scapolite have been used to calculate CO2 activities ( aCO2) and to evaluate the presence or absence of a fluid phase in high-grade scapolite bearing meta-anorthosite, granulites, calc-silicates, and mafix xenoliths. The assemblage scapolite-plagioclase-garnet±quartz may be used to calculate or limit aCO2 by the reaction Meionite+Quartz = Grossular+Anorthite+CO2. Granulites from four high-grade terranes (Grenville Province, Canada; Sargut Belt, India; Furua Complex, Tanzania; Bergen Arcs, Norway) yield aCO2=0.4-1, with most >0.7. For scapolite-bearing granulites from the Furua Complex, in which aCO2≥0.9, calculated H2O activities ( aH2O) based on phlogopite dehydration equilibria are uniformly low (0.1 0.2). The aCO2 calculated for meta-anorthosite from the Grenville Province, Ontario, ranges from 0.2 to 0.8. For Grenville meta-anorthosite also containing epidote, the aH2O calculated from clinozoisite dehydration ranges from 0.2 to 0.6. Calc-silicates from the Grenville, Sargur, and Furua terranes mostly yield aCO2< 0.5. The presence of calcite and/or wollastonite provides additional evidence for the low aCO2 in calc-silicates. Samples from six xenolith localities (Lashaine, Tanzania; Eifel, W. Germany; Lesotho; Delegate, Gloucester, and Hill 32, Australia) yield a wide range of aCO2 (0.1 to >1). The calculated fluid activities are consistent with metamorphism (1) in the presence of a mixed CO2-H2O fluid phase in which CO2 is the dominant fluid species but other C-O-H-S species are minor, (2) in the absence of a bulk fluid phase (“fluid-absent metamorphism”), or (3) in the presence of a fluid-bearing melt phase. The results for many granulites and Grenville meta-anorthosite are consistent with the presence of a CO2-rich, mixed CO2-H2O fluid phase. In contrast the relatively restricted and low values of aCO2 for calc-silicates require an H2O-rich fluid or absence of a fluid phase during metamorphism. The range of

  18. Phase equilibria and distribution constants of metal ions in diantipyryl alkane-organic acid-hydrochloric acid-water systems

    NASA Astrophysics Data System (ADS)

    Degtev, M. I.; Popova, O. N.; Yuminova, A. A.

    2014-08-01

    The ability of antipyrine and its derivatives (diantipyryl alkanes) to form separating systems in the presence of salicylic (sulfosalicylic) acid and hydrochloric acid and water is studied. The optimum volume of the organic phase, the composition of complexes, and the mechanism for the distribution of metal ions are determined, depending on the concentrations of the main components and the salting-out agent. The complex distribution and extraction constants are calculated.

  19. Solid-Phase Equilibria for Metal-Silicon-Oxygen Ternary Systems I: Mg, Ca, Sr and Ba

    DTIC Science & Technology

    1990-07-01

    both Sr and Ba to their respective disilicides . An intermediate situation exists for the Ca oxides and silicates, in which excess Si can react with CaO...Si depends on their structural and electrical properties , and significant amounts of research would be required to grow such films and evaluate their... properties . The phase diagrams in Figs. 2-4 can also be used to estimate whether or not various forms of the new oxide superconductors are compatible

  20. Central State University: Phase III Report

    ERIC Educational Resources Information Center

    Ohio Board of Regents, 2013

    2013-01-01

    This document is the final report on Central State University's implementation of Section 371 of Ohio Amended Substitute House Bill 153. Implementation of Phase I action items required that deliverables and timelines be shifted to give Central State the best opportunity for early success. In Phase II, Central State responded aggressively to a…

  1. Phase equilibria in the P(2)O(5)-CaO-CaF(2)-NaF-H(2)O quinary system and the formation of apatite

    NASA Astrophysics Data System (ADS)

    Martin, Roger Isaac

    Phase equilibria among calcium phosphates in the Hsb3POsb4-Ca(OH)sb2-Hsb2O ternary system were determined as a basis for research in the formation of hydroxyapatite, a biomaterial. The acidic portion of the ternary diagram was established. Ca(Hsb2POsb4)sb2 was not stable for temperatures below 100sp°C. The experimental and theoretical dissolution paths of Ca(Hsb2POsb4)sb2{*}Hsb2O were compared. It is possible for the initial dissolution of Ca(Hsb2POsb4)sb2{*}Hsb2O to supersaturate the system with respect to hydroxyapatite because Ca(Hsb2POsb4)sb2{*}Hsb2O is "twice" incongruently soluble. Hydroxyapatite composition is variable with a Ca/P ratio ranging from 1.5 to 1.67. Hydroxyapatite formation from acid-base reactions of CaHPOsb4 and Casb4(POsb4)sb2O was investigated for composition at the terminal limits. The total heats-of-reaction (Delta Hsb{r}) were determined to be 261.3 and 320 kJ/mol for the formation of calcium deficient and stoichiometric hydroxyapatite, respectively. Activation energies of 84.7 and 87.4 kJ/mol were calculated for the formation of calcium deficient and stoichiometric hydroxyapatite, respectively. Heats-of-formation (Delta Hsb{f}) for Casb4(POsb4)sb2O and Casb9HPOsb4(POsb4)sb5OH were calculated to be -4764.1 and -1207.7 kJ/mol, respectively. The effects of magnesium on hydroxyapatite formation in vitro from CaHPOsb4 and Casb4(POsb4)sb2O at 37.4sp°C were investigated. Magnesium is a biological agent with 0.78 mM concentrations in blood. Magnesium inhibited nucleation for 1 mM concentrations and above for a 5 liquid-to-solids ratio. However, a 5 mM concentration of MgClsb2 slightly accelerated the growth rate. The activity of magnesium is approximately 6% of its concentration. Therefore the inorganic chemical activity of magnesium may not significantly inhibit the formation of bioapatites. Phase equilibria in the Psb2Osb5-CaO-CaFsb2-Hsb2O system at 37.4sp°C was determined and dental fluorosis explained. Fluoroapatite dissolves

  2. Results From in Situ High P-T Melting and Phase Equilibria Experiments on the Allende Meteorite

    NASA Astrophysics Data System (ADS)

    Danielson, L.; Righter, K.; Leinenweber, K.; Wang, Y.

    2007-12-01

    Because chondritic materials are thought to be the building blocks of terrestrial planets and planetesimals, crystallization of chondritic and peridotitic material can be used to simulate accretion and differentiation of a bulk planet. The objective of this study is to measure the liquidus phases and temperatures for a number of planetary mantle analog materials at P>20 GPa. Experiments were conducted in the Large Volume Press at the Advanced Photon Source, Argonne National Laboratory. Phases were identified using energy-dispersive X-ray diffraction (EDXRD) with a fixed diffraction angle (2θ) of ~6° and data collection times of 60 sec. Heating runs up to 2200°C were performed at 400, 600, and 700 tons, sampling a pressure range from 18-32 GPa. A 3mm TEL beamline modified Fei-type assembly was used in experiments: a Re furnace with lanthanum chromite insulating sleeve, alumina or MgO end caps, graphite capsule packed with powdered starting materials, and X-ray windows of a slit in the Re furnace and alumina or graphite plugs in the lanthanum chromite. A pressed pellet of MgO powder doped with diamond powder was used as a pressure standard and packed between the capsule and thermocouple. The majorite liquidus temperature occurs near 2050°C, comparable to previous results (Agee et al. 1995; Asahara et al., 2004). The majorite-Mg-perovskite cotectic occurs at 22 GPa, as opposed to around 25 GPa. However, given the limited number of experiments and uncertainties introduced from previously not applying (1) a P-T relationship from relaxation of the assembly during heating, and (2) a thermal gradient from temperatures measured at the thermocouple across the capsule, significant differences in P and T are not surprising. It is possible to apply a P-T correction based on (1) and (2) above, and identify a majorite-ferropericlase cotectic for previous studies at around 22 GPa. This is particularly true for Agee et al. (1995), where calibrations were performed at 1200

  3. Density functional models of the interfacial tensions near the critical endpoints and tricritical point of three-phase equilibria.

    PubMed

    Koga, K; Widom, B

    2016-06-22

    We treat two different density-functional models of the structures and tensions of the interfaces between phases on approach to the tricritical point of three-phase equilibrium. The major objective is to account for some of the results of earlier experimental measurements of these tensions. The thermodynamic background is first reviewed, including representations of the properties near the critical endpoints and tricritical point and of the wetting transitions that may occur on approach to those critical points. The first of the models treated is analytically soluble. Its properties are illuminating but at the price of some artificiality paid for its analytical solubility. The second model, called model T, is in a class of those treated in the past and analyzed numerically. Some of its properties are obtained with sufficient precision to allow one to conclude with near certainty what the analytically exact results would be. This model, too, illuminates the experimental measurements. It is noted where its properties are in accord with those of the analytically soluble model and where the two differ.

  4. Phase equilibria, crystal structure, oxygen nonstoichiometry and thermal expansion of complex oxides in the Nd2O3 - SrO - Fe2O3 system

    NASA Astrophysics Data System (ADS)

    Aksenova, T. V.; Vakhromeeva, A. E.; Elkalashy, Sh. I.; Urusova, A. S.; Cherepanov, V. A.

    2017-07-01

    The phase equilibria in the ½ Nd2O3 - SrO - ½ Fe2O3 system were systematically studied at 1373 K in air. The homogeneity ranges and crystal structure of the solid solutions Nd1-xSrxFeO3-δ with 0.0≤x≤0.6 (sp. gr. Pbnm) and with 0.7≤x≤0.9 (sp. gr. Pm3m), Sr2-yNdyFeO4-δ with 0.7≤y≤0.9 (sp. gr. I4/mmm), Sr3-zNdzFe2O7-δ with 0.0≤z≤0.4 and 1.8≤z≤1.9 (sp. gr. I4/mmm) and Sr4-uNduFe3O10-δ with 0.7≤u≤0.9 (sp. gr. I4/mmm) were determined by X-ray diffraction analysis of quenched samples. The structural parameters of single-phase oxides were refined by the Rietveld profile method. The changes of oxygen content in the solid solutions Nd1-xSrxFeO3-δ (0.2≤x≤0.9), Sr3-zNdzFe2O7-δ (0.0≤z≤0.4 and z=1.9) and Sr4-uNduFe3O10-δ (0.7≤u≤0.9) versus temperature in air were determined by thermogravimetric analysis. Gradual substitution of neodymium by strontium leads to the decrease of the oxygen content. The average thermal expansion coefficients for the Nd1-xSrxFeO3-δ (0.6≤x≤0.8) samples were calculated within the temperature range 298-1373 K in air. The project of isothermal-isobaric phase diagram for the Nd-Sr-Fe-O system to the compositional triangle of metallic components was presented.

  5. Phase equilibria, formation, crystal and electronic structure of ternary compounds in Ti-Ni-Sn and Ti-Ni-Sb ternary systems

    SciTech Connect

    Romaka, V.V.; Rogl, P.; Romaka, L.; Stadnyk, Yu.; Melnychenko, N.; Grytsiv, A.; Falmbigl, M.; Skryabina, N.

    2013-01-15

    The phase equilibria of the Ti-Ni-Sn and Ti-Ni-Sb ternary systems have been studied in the whole concentration range by means of X-ray and EPM analyses at 1073 K and 873 K, respectively. Four ternary intermetallic compounds TiNiSn (MgAgAs-type), TiNi{sub 2-x}Sn (MnCu{sub 2}Al-type), Ti{sub 2}Ni{sub 2}Sn (U{sub 2}Pt{sub 2}Sn-type), and Ti{sub 5}NiSn{sub 3} (Hf{sub 5}CuSn{sub 3}-type) are formed in Ti-Ni-Sn system at 1073 K. The TiNi{sub 2}Sn stannide is characterized by homogeneity in the range of 50-47 at% of Ni. The Ti-Ni-Sb ternary system at 873 K is characterized by formation of three ternary intermetallic compounds, Ti{sub 0.8}NiSb (MgAgAs-type), Ti{sub 5}Ni{sub 0.45}Sb{sub 2.55} (W{sub 5}Si{sub 3}-type), and Ti{sub 5}NiSb{sub 3} (Hf{sub 5}CuSn{sub 3}-type). The solubility of Ni in Ti{sub 0.8}NiSb decreases number of vacancies in Ti site up to Ti{sub 0.91}Ni{sub 1.1}Sb composition. - Graphical abstract: Isothermal section of the Ti-Ni-Sn phase diagram and DOS distribution in hypothetical TiNi{sub 1+x}Sn solid solution. Highlights: Black-Right-Pointing-Pointer Ti-Ni-Sn phase diagram was constructed at 1073 K. Black-Right-Pointing-Pointer Four ternary compounds are formed: TiNiSn, TiNi{sub 2-x}Sn, Ti{sub 2}Ni{sub 2}Sn, and Ti{sub 5}NiSn{sub 3}. Black-Right-Pointing-Pointer Three ternary compounds exist in Ti-Ni-Sb system at 873 K. Black-Right-Pointing-Pointer The TiNi{sub 2}Sb compound is absent.

  6. Phase equilibria in system LiCl-NaCl-H2O at 308 and 348 K

    NASA Astrophysics Data System (ADS)

    Wang, Shi-qiang; Guo, Ya-fei; Liu, Dong-fang; Deng, Tian-long

    2016-12-01

    The solubilities and densities of the solutions in the ternary system LiCl-NaCl-H2O at 308 and 348 K were determined by the method of isothermal dissolution equilibrium. There are one invariant point, two univariant isotherm dissolution curves, and two crystallization regions corresponding to monohydrate (LiCl · H2O) and NaCl, respectively. This system at both temperatures belongs to hydrate type I, and neither double salt nor solid solution was found. A comparison of the phase diagram for the ternary system at 273-348 K shows that the area of crystallization region of LiCl · H2O is decreased with the increasing of temperature, while that of NaCl is increased obviously. The solution density of the ternary system at two temperatures changes regularly with the increasing of LiCl concentration.

  7. Phase-equilibria for design of coal-gasification processes: dew points of hot gases containing condensible tars. Final report

    SciTech Connect

    Prausnitz, J.M.

    1980-05-01

    This research is concerned with the fundamental physical chemistry and thermodynamics of condensation of tars (dew points) from the vapor phase at advanced temperatures and pressures. Fundamental quantitative understanding of dew points is important for rational design of heat exchangers to recover sensible heat from hot, tar-containing gases that are produced in coal gasification. This report includes essentially six contributions toward establishing the desired understanding: (1) Characterization of Coal Tars for Dew-Point Calculations; (2) Fugacity Coefficients for Dew-Point Calculations in Coal-Gasification Process Design; (3) Vapor Pressures of High-Molecular-Weight Hydrocarbons; (4) Estimation of Vapor Pressures of High-Boiling Fractions in Liquefied Fossil Fuels Containing Heteroatoms Nitrogen or Sulfur; and (5) Vapor Pressures of Heavy Liquid Hydrocarbons by a Group-Contribution Method.

  8. Phase equilibria diagrams, crystal growth peculiarities and Raman investigations of lead and sodium-bismuth tungstate-molybdate solid solutions

    NASA Astrophysics Data System (ADS)

    Lebedev, Andrei V.; Avanesov, Samvel A.; Yunalan, Tyliay M.; Klimenko, Valeriy A.; Ignatyev, Boris V.; Isaev, Vladislav A.

    2016-02-01

    In this paper a comprehensive study of lead and sodium-bismuth tungstate-molybdate solid solutions was carried out, including the clarification of their structural peculiarities and phase diagrams of PbMoO4-PbWO4 and NaBi(MoO4)2-NaBi(WO4)2 systems, the study of spontaneous Raman spectra of these compounds, as well as preliminary experiments on single crystals growth of lead tungstate-molybdate. The linewidths, peak and integral intensities of the totally symmetric Raman vibrations of solid solutions were estimated in comparison with known SRS-active crystals. The conditions of the Czochralski growth of optically transparent lead tungstate-molybdate mixed crystals were found and SRS effect was observed in these crystals when pumping by 12 ns 1064 nm laser pulses.

  9. Sorption equilibria of vapor-phase organic pollutants on unsaturated soils and soil minerals. Final report, Mar 85-Mar 89

    SciTech Connect

    Lion, L.W.; Ong, S.K.; Linder, S.R.; Swager, J.L.; Schwager, S.J.

    1990-04-01

    Most groundwater pollutants are volatile organic compounds; however, there is relatively little understanding of the sorption reactions that control the transport and fate of organic vapors in the vadose zone. This investigation identified the physical/chemical properties of the soil matrix and organic vapors which control vapor-solid phase distribution. The dominant property which regulates vapor sorption in the unsaturated zone is the moisture content of the soil. Under very dry conditions, soil mineral/vapor interactions are regulated by specific surface area, indicating the dominance of a relatively non-specific physical adsorption process. However, at moisture contents exceeding an average surface coverage of four to eight layers of water, vapor uptake is controlled by partitioning reactions into soil moisture and soil organic matter.

  10. Phase Equilibria, Crystal Structure and Hydriding/Dehydriding Mechanism of Nd4Mg80Ni8 Compound

    PubMed Central

    Luo, Qun; Gu, Qin-Fen; Zhang, Jie-Yu; Chen, Shuang-Lin; Chou, Kuo-Chih; Li, Qian

    2015-01-01

    In order to find out the optimal composition of novel Nd-Mg-Ni alloys for hydrogen storage, the isothermal section of Nd-Mg-Ni system at 400 °C is established by examining the equilibrated alloys. A new ternary compound Nd4Mg80Ni8 is discovered in the Mg-rich corner. It has the crystal structure of space group I41/amd with lattice parameters of a = b = 11.2743(1) Å and c = 15.9170(2) Å, characterized by the synchrotron powder X-ray diffraction (SR-PXRD). High-resolution transmission electron microscopy (HR-TEM) is used to investigate the microstructure of Nd4Mg80Ni8 and its hydrogen-induced microstructure evolution. The hydrogenation leads to Nd4Mg80Ni8 decomposing into NdH2.61-MgH2-Mg2NiH0.3 nanocomposites, where the high density phase boundaries provide a great deal of hydrogen atoms diffusion channels and nucleation sites of hydrides, which greatly enhances the hydriding/dehydriding (H/D) properties. The Nd4Mg80Ni8 exhibits a good cycle ability. The kinetic mechanisms of H/D reactions are studied by Real Physical Picture (RPP) model. The rate controlling steps are diffusion for hydriding reaction in the temperature range of 100 ~ 350 °C and surface penetration for dehydriding reaction at 291 ~ 347 °C. In-situ SR-PXRD results reveal the phase transformations of Mg to MgH2 and Mg2Ni to Mg2NiH4 as functions of hydrogen pressure and hydriding time. PMID:26471964

  11. Phase Equilibria, Crystal Structure and Hydriding/Dehydriding Mechanism of Nd4Mg80Ni8 Compound

    NASA Astrophysics Data System (ADS)

    Luo, Qun; Gu, Qin-Fen; Zhang, Jie-Yu; Chen, Shuang-Lin; Chou, Kuo-Chih; Li, Qian

    2015-10-01

    In order to find out the optimal composition of novel Nd-Mg-Ni alloys for hydrogen storage, the isothermal section of Nd-Mg-Ni system at 400 °C is established by examining the equilibrated alloys. A new ternary compound Nd4Mg80Ni8 is discovered in the Mg-rich corner. It has the crystal structure of space group I41/amd with lattice parameters of a = b = 11.2743(1) Å and c = 15.9170(2) Å, characterized by the synchrotron powder X-ray diffraction (SR-PXRD). High-resolution transmission electron microscopy (HR-TEM) is used to investigate the microstructure of Nd4Mg80Ni8 and its hydrogen-induced microstructure evolution. The hydrogenation leads to Nd4Mg80Ni8 decomposing into NdH2.61-MgH2-Mg2NiH0.3 nanocomposites, where the high density phase boundaries provide a great deal of hydrogen atoms diffusion channels and nucleation sites of hydrides, which greatly enhances the hydriding/dehydriding (H/D) properties. The Nd4Mg80Ni8 exhibits a good cycle ability. The kinetic mechanisms of H/D reactions are studied by Real Physical Picture (RPP) model. The rate controlling steps are diffusion for hydriding reaction in the temperature range of 100 ~ 350 °C and surface penetration for dehydriding reaction at 291 ~ 347 °C. In-situ SR-PXRD results reveal the phase transformations of Mg to MgH2 and Mg2Ni to Mg2NiH4 as functions of hydrogen pressure and hydriding time.

  12. Simulation of chemical potentials and phase equilibria in two- and three-dimensional square-well fluids: finite size effects.

    PubMed

    Vörtler, Horst L; Schäfer, Katja; Smith, William R

    2008-04-17

    We study the simulation cell size dependence of chemical potential isotherms in subcritical square-well fluids by means of series of canonical ensemble Monte Carlo simulations with increasing numbers of particles, for both three-dimensional bulk systems and two-dimensional planar layers, using Widom-like particle insertion methods. By estimating the corresponding vapor/liquid coexistence densities using a Maxwell-like equal area rule for the subcritical chemical potential isotherms, we are able to study the influence of system size not only on chemical potentials but also on the coexistence properties. The chemical potential versus density isotherms show van der Waals-like loops in the subcritical vapor/liquid coexistence range that exhibit distinct finite size effects for both two- and three-dimensional fluids. Generally, in agreement with recent findings for related studies of Lennard-Jones fluids, the loops shrink with increasing number of particles. In contrast to the subcritical isotherms themselves, the equilibrium vapor/liquid densities show only a weak system size dependence and agree quantitatively with the best-known literature values for three-dimensional fluids. This allows our approach to be used to accurately predict the phase coexistence properties. Our resulting phase equilibrium results for two-dimensional square-well fluids are new. Knowledge concerning finite size effects of square-well systems is important not only for the simulation of thermodynamic properties of simple fluids, but also for the simulation of models of more complex fluids (such as aqueous or polymer fluids) involving square-well interactions.

  13. Phase Equilibria, Crystal Structure and Hydriding/Dehydriding Mechanism of Nd4Mg80Ni8 Compound.

    PubMed

    Luo, Qun; Gu, Qin-Fen; Zhang, Jie-Yu; Chen, Shuang-Lin; Chou, Kuo-Chih; Li, Qian

    2015-10-16

    In order to find out the optimal composition of novel Nd-Mg-Ni alloys for hydrogen storage, the isothermal section of Nd-Mg-Ni system at 400 °C is established by examining the equilibrated alloys. A new ternary compound Nd4Mg80Ni8 is discovered in the Mg-rich corner. It has the crystal structure of space group I41/amd with lattice parameters of a = b = 11.2743(1) Å and c = 15.9170(2) Å, characterized by the synchrotron powder X-ray diffraction (SR-PXRD). High-resolution transmission electron microscopy (HR-TEM) is used to investigate the microstructure of Nd4Mg80Ni8 and its hydrogen-induced microstructure evolution. The hydrogenation leads to Nd4Mg80Ni8 decomposing into NdH2.61-MgH2-Mg2NiH0.3 nanocomposites, where the high density phase boundaries provide a great deal of hydrogen atoms diffusion channels and nucleation sites of hydrides, which greatly enhances the hydriding/dehydriding (H/D) properties. The Nd4Mg80Ni8 exhibits a good cycle ability. The kinetic mechanisms of H/D reactions are studied by Real Physical Picture (RPP) model. The rate controlling steps are diffusion for hydriding reaction in the temperature range of 100 ~ 350 °C and surface penetration for dehydriding reaction at 291 ~ 347 °C. In-situ SR-PXRD results reveal the phase transformations of Mg to MgH2 and Mg2Ni to Mg2NiH4 as functions of hydrogen pressure and hydriding time.

  14. Gibbs Energy Modeling of Digenite and Adjacent Solid-State Phases

    NASA Astrophysics Data System (ADS)

    Waldner, Peter

    2017-08-01

    All sulfur potential and phase diagram data available in the literature for solid-state equilibria related to digenite have been assessed. Thorough thermodynamic analysis at 1 bar total pressure has been performed. A three-sublattice approach has been developed to model the Gibbs energy of digenite as a function of composition and temperature using the compound energy formalism. The Gibbs energies of the adjacent solid-state phases covelitte and high-temperature chalcocite are also modeled treating both sulfides as stoichiometric compounds. The novel model for digenite offers new interpretation of experimental data, may contribute from a thermodynamic point of view to the elucidation of the role of copper species within the crystal structure and allows extrapolation to composition regimes richer in copper than stoichiometric digenite Cu2S. Preliminary predictions into the ternary Cu-Fe-S system at 1273 K (1000 °C) using the Gibbs energy model of digenite for calculating its iron solubility are promising.

  15. Effect of chlorine on near-liquidus phase equilibria of an Fe-Mg-rich tholeiitic basalt

    NASA Astrophysics Data System (ADS)

    Filiberto, Justin; Dasgupta, Rajdeep; Gross, Juliane; Treiman, Allan H.

    2014-07-01

    The importance of Cl in basalt petrogenesis has been recognized, yet constraints on its effect on liquidus crystallization of basalts are scarce. In order to quantify the role of Cl in basaltic systems, we have experimentally determined near-liquidus phase relations of a synthetic Fe-Mg-rich basalt, doped with 0.0-2.5 wt% dissolved Cl, at 0.7, 1.1, and 1.5 GPa. Results have been parameterized and compared with previous data from literature. The effect of Cl on mineral chemistry and liquidus depression is dependent on the starting basaltic composition. The liquidus depression measured for a SiO2-rich, Al2O3-poor basalt is smaller than that observed for a basaltic melt depleted in silica and enriched in FeOT and Al2O3. The effect of Cl on depression of the olivine-orthopyroxene-liquid multiple saturation pressure does not seem to vary with the starting composition of the basaltic liquid. This suggests that Cl may significantly promote the generation of silica-poor, Fe-Al-rich magmas in the Earth, Mars, and the Moon.

  16. Phase equilibria in the palladium-rich part of the Pd-Au-Cu-Sn quaternary system

    NASA Astrophysics Data System (ADS)

    Kareva, M. A.; Kabanova, E. G.; Zhmurko, G. P.; Kuznetsov, V. N.

    2017-02-01

    The solubility of tin in the phases of Pd-Au-Sn and Pd-Cu-Sn ternary systems and a Pd-Au-Cu-Sn quaternary system with a fixed Pd: Au: Cu ratio of 11.1: 1: 4.6 is studied via microstructural, X-ray diffraction, and energy dispersive analysis. It is found that a quaternary alloy in equilibrium with a solid solution based on Pd, Au, and Sn contains a τ1 compound with structure which is derivative of the In type. It contains 15 at % Sn and is a solid solution of the same compounds identified earlier in Pd-Au-Sn and Pd-Cu-Sn ternary systems. In addition, a quaternary alloy with a content of 20 at % Sn also contains a τ2 compound with the Pd2CuSn own type and can barely dissolve gold. The obtained data are used to construct a three-dimensional model of the Pd-rich part of the isothermal tetrahedron of the Pd-Au-Cu-Sn system and diagrams of the tin solubility isolines in palladium-rich alloys of the quaternary system at 500°C.

  17. Vapor Pressure Plus: An Experiment for Studying Phase Equilibria in Water, with Observation of Supercooling, Spontaneous Freezing, and the Triple Point

    ERIC Educational Resources Information Center

    Tellinghuisen, Joel

    2010-01-01

    Liquid-vapor, solid-vapor, and solid-liquid-vapor equilibria are studied for the pure substance water, using modern equipment that includes specially fabricated glass cells. Samples are evaporatively frozen initially, during which they typically supercool to -5 to -10 [degrees]C before spontaneously freezing. Vacuum pumping lowers the temperature…

  18. Vapor Pressure Plus: An Experiment for Studying Phase Equilibria in Water, with Observation of Supercooling, Spontaneous Freezing, and the Triple Point

    ERIC Educational Resources Information Center

    Tellinghuisen, Joel

    2010-01-01

    Liquid-vapor, solid-vapor, and solid-liquid-vapor equilibria are studied for the pure substance water, using modern equipment that includes specially fabricated glass cells. Samples are evaporatively frozen initially, during which they typically supercool to -5 to -10 [degrees]C before spontaneously freezing. Vacuum pumping lowers the temperature…

  19. Constraining magma storage conditions at a restless volcano in the Main Ethiopian Rift using phase equilibria models

    NASA Astrophysics Data System (ADS)

    Gleeson, Matthew L. M.; Stock, Michael J.; Pyle, David M.; Mather, Tamsin A.; Hutchison, William; Yirgu, Gezahegn; Wade, Jon

    2017-05-01

    The Main Ethiopian Rift hosts a number of peralkaline volcanic centres, several of which show signs of recent unrest. Due to the low number of historical eruptions recorded in the region and lack of volcanic monitoring, conditions of magma storage in the Main Ethiopian Rift remain poorly constrained. Aluto is one of these restless volcanic centres and identifying magma storage conditions is vital for evaluating the significance of recent periods of unrest. Using Aluto as a case study, we explore magma storage conditions using Rhyolite-MELTS thermodynamic modelling software. We performed 150 fractional crystallisation models using a primitive basalt as the starting composition, and for a range of pressures (50-300 MPa), initial H2O contents (0.5-3 wt%) and oxygen fugacities (QFM - 2-QFM + 1). Predicted liquid lines of descent from these models are compared with published whole-rock data and, together with new observations of natural phase assemblages and erupted mineral compositions, provide constraints on magma storage conditions. Using a statistical approach to compare empirical data and thermodynamic model outputs, we find that compositions of evolved peralkaline rhyolites from Aluto are best reproduced by protracted (90%) isobaric fractional crystallisation from a rift-related basaltic composition, without the need for significant crustal assimilation. The required extent of fractional crystallisation suggests that much of the magmatic system may exist as a highly crystalline mush with only a small lens of rhyolitic melt. The best agreement between models and natural samples is at low pressures (150 MPa), low initial H2O concentrations (0.5 wt%) and an oxygen fugacity near the QFM buffer. The depth of magma storage derived from these results ( 5.6 ± 1 km) is consistent with the source depths modelled from measured ground deformation. Data from other peralkaline volcanic centres in the Main Ethiopian Rift (Boset and Gedemsa), and other locations globally (e

  20. Phase equilibria in the Tb-Mg-Co system at 500 °C, crystal structure and hydrogenation properties of selected compounds

    SciTech Connect

    Shtender, V.V.; Denys, R.V.; Zavaliy, I.Yu.; Zelinska, O.Ya.; Paul-Boncour, V.; Pavlyuk, V.V.

    2015-12-15

    The isothermal section of the Tb–Mg–Co phase diagram at 500 °C has been built on the basis of XRD analysis of forty samples prepared by powder metallurgy. The existence of two ternary compounds Tb{sub 4}Mg{sub 3}Co{sub 2} and Tb{sub 4}MgCo was confirmed. The formation of two solid solutions, Tb{sub 1−x}Mg{sub x}Co{sub 3} (0≤x≤0.4) and Tb{sub 1-−x}Mg{sub x}Co{sub 2} (0≤x≤0.6), was found for the first time. It is shown that Tb{sub 5}Mg{sub 24} also dissolves a small amount of Co. Other binary compounds do not dissolve the third component. The Tb{sub 4}MgCo and TbMgCo{sub 4} compounds form hydrides (12.7 and 5.3 at.H/f.u. capacity, respectively) that retain the original structure of metallic matrices. Upon thermal desorption the Tb{sub 4}MgCoH{sub 12.7} hydride was stable up to 300 °C and disproportionated at higher temperature. Two other hydrides, Tb{sub 4}Mg{sub 3}Co{sub 2}H{sub ∼4} and Tb{sub 2}MgCo{sub 9}H{sub 12}, are unstable in air and decompose into the initial compounds. - Highlights: • The phase equilibria at 500 °°C in the Tb–Mg–Co system has been studied. • The existence of two ternary compounds, Tb{sub 4}Mg{sub 3}Co{sub 2} and Tb{sub 4}MgCo, was confirmed. • The formation of two solid solutions, Tb{sub 1−x}Mg{sub x}Co{sub 3} and Tb{sub 1−x}Mg{sub x}Co{sub 2}, was found. • Hydrogen sorption–desorption properties have been studied for the selected alloys.

  1. Molecular dynamics study on evaporation and condensation of n-dodecane at liquid-vapor phase equilibria.

    PubMed

    Cao, Bing-Yang; Xie, Jian-Fei; Sazhin, Sergei S

    2011-04-28

    Molecular dynamics simulations are performed to study the evaporation and condensation of n-dodecane (C(12)H(26)) at temperatures in the range 400-600 K. A modified optimized potential for liquid simulation model is applied to take into account the Lennard-Jones, bond bending and torsion potentials with the bond length constrained. The equilibrium liquid-vapor n-dodecane interface thickness is predicted to be ~1.2-2.0 nm. It is shown that the molecular chains lie preferentially parallel to the interface in the liquid-vapor transition region. The predicted evaporation/condensation coefficient decreased from 0.9 to 0.3 when temperature increased from 400 to 600 K. These values can be used for the formulation of boundary conditions in the kinetic modeling of droplet heating and evaporation processes; they are noticeably different from those predicted by the transition state theory. We also present the typical molecular behaviors in the evaporation and condensation processes. The molecular exchange in condensation, typical for simple molecules, has never been observed for n-dodecane molecular chains.

  2. Phase Equilibria Study in the TeO2-Na2O-SiO2 System in Air Between 723 K (500 °C) and 1473 K (1200 °C)

    NASA Astrophysics Data System (ADS)

    Santoso, Imam; Taskinen, Pekka

    2016-08-01

    Knowledge of phase equilibria in the TeO2-Na2O-SiO2 system at elevated temperatures is important for ceramic and glass industries and for improving the operation of the smelting process of tellurium-containing materials. A review of previous investigations has indicated, however, that there are omissions in the available datasets on the liquidus temperatures of the molten TeO2-Na2O-SiO2 mixtures. The employed experimental method included equilibration of mixtures made from high purity oxides, rapid quenching of the equilibrated samples in water and followed by compositional analysis of the phases using an electron probe X-ray microanalyzer. The liquidus and phase equilibria in the TeO2-SiO2, TeO2-Na2O, and SiO2-TeO2-Na2O systems have been studied for a wide range of compositions between 723 K (500 °C) and 1473 K (1200 °C) at TeO2, SiO2, and Na2SiO3 saturations. New data have been generated in the SiO2-TeO2-Na2O system at SiO2 saturation. The liquidus compositions in the TeO2-Na2O system at TeO2 saturation have been compared with the previous data and an assessed phase diagram.

  3. Approximate equilibria for Bayesian games

    NASA Astrophysics Data System (ADS)

    Mallozzi, Lina; Pusillo, Lucia; Tijs, Stef

    2008-07-01

    In this paper the problem of the existence of approximate equilibria in mixed strategies is central. Sufficient conditions are given under which approximate equilibria exist for non-finite Bayesian games. Further one possible approach is suggested to the problem of the existence of approximate equilibria for the class of multicriteria Bayesian games.

  4. Determination of Epsomite-Hexahydrite Equilibria by the Humidity-Buffer Technique at 0.1 MPa with Implications for Phase Equilibria in the System MgSO4-H2O

    NASA Astrophysics Data System (ADS)

    Chou, I.-Ming; Seal, Robert R.

    2003-11-01

    Epsomite (MgSO4.7H2O) and hexahydrite (MgSO4.6H2O) are common minerals found in marine evaporite deposits, in saline lakes as precipitates, in weathering zones of coal and metallic deposits, in some soils and their efflorescences, and possibly on the surface of Europa as evaporite deposits. Thermodynamic properties of these two minerals reported in the literature are in poor agreement. In this study, epsomite-hexahydrite equilibria were determined along four humidity-buffer curves at 0.1 MPa and between 25 and 45°C. Results obtained for the reaction epsomite = hexahydrite + H2O, as demonstrated by very tight reversals along each humidity buffer, can be represented by ln K(+/- 0.012) = 20.001 - 7182.07/T, where K is the equilibrium constant, and T is temperature in Kelvin. The derived standard Gibbs free energy of reaction is 10.13 +/- 0.07 kJ/mol, which is essentially the same value as that calculated from vapor pressure measurements reported in the literature. However, this value is at least 0.8 kJ/mol lower than those calculated from the data derived mostly from calorimetric measurements.

  5. Determination of epsomite-hexahydrite equilibria by the humidity-buffer technique at 0.1 MPa with implications for phase equilibria in the system MgSO4-H2O.

    USGS Publications Warehouse

    Chou, I.-Ming; Seal, R.R.

    2003-01-01

    Epsomite (MgSO(4).7H(2)O) and hexahydrite (MgSO(4).6H(2)O) are common minerals found in marine evaporite deposits, in saline lakes as precipitates, in weathering zones of coal and metallic deposits, in some soils and their efflorescences, and possibly on the surface of Europa as evaporite deposits. Thermodynamic properties of these two minerals reported in the literature are in poor agreement. In this study, epsomite-hexahydrite equilibria were determined along four humidity-buffer curves at 0.1 MPa and between 25 and 45 degrees C. Results obtained for the reaction epsomite = hexahydrite + H(2)O, as demonstrated by very tight reversals along each humidity buffer, can be represented by ln K(+/- 0.012) = 20.001 - 7182.07/T, where K is the equilibrium constant, and T is temperature in Kelvin. The derived standard Gibbs free energy of reaction is 10.13 +/- 0.07 kJ/mol, which is essentially the same value as that calculated from vapor pressure measurements reported in the literature. However, this value is at least 0.8 kJ/mol lower than those calculated from the data derived mostly from calorimetric measurements.

  6. Determination of epsomite-hexahydrite equilibria by the humidity-buffer technique at 0.1 MPa with implications for phase equilibria in the system MgSO4-H2O.

    PubMed

    Chou, I-Ming; Seal, Robert R

    2003-01-01

    Epsomite (MgSO(4).7H(2)O) and hexahydrite (MgSO(4).6H(2)O) are common minerals found in marine evaporite deposits, in saline lakes as precipitates, in weathering zones of coal and metallic deposits, in some soils and their efflorescences, and possibly on the surface of Europa as evaporite deposits. Thermodynamic properties of these two minerals reported in the literature are in poor agreement. In this study, epsomite-hexahydrite equilibria were determined along four humidity-buffer curves at 0.1 MPa and between 25 and 45 degrees C. Results obtained for the reaction epsomite = hexahydrite + H(2)O, as demonstrated by very tight reversals along each humidity buffer, can be represented by ln K(+/- 0.012) = 20.001 - 7182.07/T, where K is the equilibrium constant, and T is temperature in Kelvin. The derived standard Gibbs free energy of reaction is 10.13 +/- 0.07 kJ/mol, which is essentially the same value as that calculated from vapor pressure measurements reported in the literature. However, this value is at least 0.8 kJ/mol lower than those calculated from the data derived mostly from calorimetric measurements.

  7. Phase-imprinted multiphoton subradiant states

    NASA Astrophysics Data System (ADS)

    Jen, H. H.

    2017-08-01

    We propose to generate the multiphoton subradiant states and investigate their fluorescences in an array of two-level atoms. These multiphoton states are created initially from the timed Dicke states. Then we can use either a Zeeman or Stark field gradient pulse to imprint linearly increasing phases on the atoms, and this phase-imprinting process unitarily evolves the system to the multiphoton subradiant states. The fluorescence engages a long-range dipole-dipole interaction which originates from a system-reservoir coupling in the dissipation. We locate some of the subradiant multiphoton states from the eigenmodes and show that an optically thick atomic array is best for the preparation of the state with the most reduced decay rate. This phase-imprinting process enables quantum-state engineering of the multiphoton subradiant states and realizes a potential quantum storage of the photonic qubits in the two-level atoms.

  8. Stochastic Kuramoto oscillators with discrete phase states

    NASA Astrophysics Data System (ADS)

    Jörg, David J.

    2017-09-01

    We present a generalization of the Kuramoto phase oscillator model in which phases advance in discrete phase increments through Poisson processes, rendering both intrinsic oscillations and coupling inherently stochastic. We study the effects of phase discretization on the synchronization and precision properties of the coupled system both analytically and numerically. Remarkably, many key observables such as the steady-state synchrony and the quality of oscillations show distinct extrema while converging to the classical Kuramoto model in the limit of a continuous phase. The phase-discretized model provides a general framework for coupled oscillations in a Markov chain setting.

  9. Phase equilibria in subseafloor hydrothermal systems: A review of the role of redox, temperature, pH and dissolved Cl on the chemistry of hot spring fluids at mid-ocean ridges

    NASA Astrophysics Data System (ADS)

    Seyfried, W. E., Jr.; Ding, Kang

    Time series measurements of the chemistry of hot spring fluids at mid-ocean ridges (MOR) have revealed steady state concentrations of dissolved species that indicate solubility control by mineral phases in subseafloor reaction zones [Campbell et al., 1988a; Bowers et al., 1988; Butterfield et al. 1994]. That MOR hot spring fluids have relatively low measured pH values (3.1 to 3.9), and are variably depleted in Mg and SO4, while enriched in Ca, K, and Si [Von Damm, 1990] relative to seawater, is entirely consistent with heterogeneous equilibria involving feldspar, chlorite, epidote ± quartz and NaCl fluids at temperatures in the vicinity of 375-400°C [Seyfried et al., 1991]. The high concentrations of so-called "soluble" elements, such as Li, Rb, Cs, and B [Von Damm et al., 1985; Spivack and Edmond, 1987], however, require an abundance of fresh rock (basalt/diabase) relative to the mass of seawater (i.e., low fluid/rock ratio). That these elements also fall to reveal significant compositional changes in fluids from specific hot springs sampled several times over a six year period [Campbell et al., 1985a; Butterfield et al. 1994; Butterfield and Massoth 1994] indicates a non-static and expanding reaction zone caused by penetration of seawater into previously unaltered portions of a solidified magma chamber. Although most vent fluids reveal short term stability [Campbell et al. 1988a; Butterfield and Massoth 1994], this is not always the case, as evidenced by the temporal evolution of the composition of vent fluids at the North Cleft segment of the Juan de Fuca Ridge [Butterfield et al. 1991; Butterfield and Massoth, 1994], and at 9-10degN EPR [Von Damm et al. 1991].

  10. Effect of trans-cis photoisomerization on phase equilibria and phase transition of liquid-crystalline azobenzene chromophore and its blends with reactive mesogenic diacrylate.

    PubMed

    Kim, Namil; Li, Quan; Kyu, Thein

    2011-03-01

    Photoisomerization-induced phase transition of neat liquid-crystalline azobenzene chromophore (LCAC) and its effect on phase diagrams of its mixtures with reactive mesogenic diacrylate monomer (RM257) have been investigated experimentally and theoretically. Upon irradiation with ultraviolet light, the nematic phase of LCAC transformed to isotropic, while the crystal phase showed corrugated textures on the surface (i.e., ripples). The phase-transition temperatures and corresponding morphologies of the blends have been investigated by means of differential scanning calorimetry and optical microscopy. A theoretical phase diagram of a binary nematic and crystalline system was constructed by self-consistently solving the combined free energies of Flory-Huggins, Maier-Saupe, and phase-field theory. The calculation revealed various coexistence regions such as nematic + liquid (N₁ + L₂), crystal + liquid (Cr₁ + L₂), crystal + nematic (Cr₁ + N₂), and crystal + crystal (Cr₁ + Cr₂) over a broad range of compositions including the single-phase nematic (N₁, N₂) of the corresponding constituents. The calculated liquidus lines were in good accord with the depressed mesophase-isotropic transition points. The present paper demonstrates the effect of trans-cis photoisomerization on the mesophase transitions of neat LCAC and the phase diagram of LCAC-RM257 as well as on the ripple formation (i.e., periodic undulation) on the azobenzene crystals.

  11. Effect of trans-cis photoisomerization on phase equilibria and phase transition of liquid-crystalline azobenzene chromophore and its blends with reactive mesogenic diacrylate

    NASA Astrophysics Data System (ADS)

    Kim, Namil; Li, Quan; Kyu, Thein

    2011-03-01

    Photoisomerization-induced phase transition of neat liquid-crystalline azobenzene chromophore (LCAC) and its effect on phase diagrams of its mixtures with reactive mesogenic diacrylate monomer (RM257) have been investigated experimentally and theoretically. Upon irradiation with ultraviolet light, the nematic phase of LCAC transformed to isotropic, while the crystal phase showed corrugated textures on the surface (i.e., ripples). The phase-transition temperatures and corresponding morphologies of the blends have been investigated by means of differential scanning calorimetry and optical microscopy. A theoretical phase diagram of a binary nematic and crystalline system was constructed by self-consistently solving the combined free energies of Flory-Huggins, Maier-Saupe, and phase-field theory. The calculation revealed various coexistence regions such as nematic + liquid (N1 + L2), crystal + liquid (Cr1 + L2), crystal + nematic (Cr1 + N2), and crystal + crystal (Cr1 + Cr2) over a broad range of compositions including the single-phase nematic (N1, N2) of the corresponding constituents. The calculated liquidus lines were in good accord with the depressed mesophase-isotropic transition points. The present paper demonstrates the effect of trans-cis photoisomerization on the mesophase transitions of neat LCAC and the phase diagram of LCAC-RM257 as well as on the ripple formation (i.e., periodic undulation) on the azobenzene crystals.

  12. High-grade metamorphism during Archean-Paleoproterozoic transition associated with microblock amalgamation in the North China Craton: Mineral phase equilibria and zircon geochronology

    NASA Astrophysics Data System (ADS)

    Yang, Qiong-Yan; Santosh, M.; Tsunogae, Toshiaki

    2016-10-01

    Metamorphic regimes in Archean terranes provide important keys to the plate tectonic processes in early Earth. The North China Craton (NCC) is one of the ancient continental nuclei in Asia and recent models propose that the cratonic architecture was built through the assembly of several Archean microcontinental blocks into larger crustal blocks. Here we investigate garnet- and pyroxene-bearing granulite facies rocks along the periphery of the Jiaoliao microcontinental block in the NCC. The garnet-bearing granulites contain peak mineral assemblage of garnet + clinopyroxene + orthopyroxene + magnetite + plagioclase + quartz ± biotite ± ilmenite. Mineral phase equilibria computations using pseudosection and geothermobarometry suggest peak P-T condition of 800-830 °C and 7-8 kbar for metamorphism. Isopleths using XMg of orthopyroxene and XCa of garnet in another sample containing the peak mineral assemblage of garnet + orthopyroxene + quartz + magnetite ± fluid yield peak P-T conditions of 860-920 °C and 11-14 kbar. Geochemical data show tonalitic to granodioritic composition and arc-related tectonic setting for the magmatic protoliths of these rocks. Zircon LA-ICP-MS analyses yield well-defined discordia with upper intercept ages of 2562 ± 20 Ma (MSWD = 0.94) and 2539 ± 21 Ma (MSWD = 0.59) which is correlated with the timing of emplacement of the magmatic protolith. A younger group of zircons with upper intercept ages of 2449 ± 41 Ma (MSWD = 0.83); N = 6 as 2449 ± 41 Ma (MSWD = 0.83; N = 6) and 2480 ± 44 Ma (MSWD = 1.2; N = 9) constrains the timing of metamorphism. Zircon Lu-Hf data show dominantly positive εHf(t) values (up to 8.5), and yield crustal residence ages (TDMC) in the range of 2529 to 2884 Ma, suggesting magma sources from Meso-Neoarchean juvenile components. The high temperature and medium to high pressure metamorphism is considered to have resulted from the subduction-collision tectonics associated with microblock amalgamation in the NCC at

  13. Phase Equilibria of the Cu-Ti-Er System at 773 K (500 °C) and Stability of the CuTi3 Phase

    NASA Astrophysics Data System (ADS)

    Zhan, Yongzhong; Peng, Dan; She, Jia

    2012-11-01

    The phase relationships of the Cu-Ti-Er ternary phase diagram at 773 K (500 °C) were investigated mainly by means of X-ray powder diffraction (XRD), scanning electron microscopy (SEM) with energy dispersive spectroscopy (EDS), and differential thermal analysis (DTA). It is confirmed in this work that the binary compounds Cu9Er2 and Cu7Er2 exist in the Cu-Er binary system at 773 K (500 °C). The stability of the CuTi3 phase is confirmed in the Cu-Ti system. After heat treatment at 1023 K (750 °C) for 90 hours, the phase CuTi3 is observed in the microstructure of the alloy 25Cu75Ti. The temperature of the eutectoid transformation, namely, β-Ti ↔ α-Ti + CuTi3, is determined to be 1078 K (805 °C) in this work. The 773 K (500 °C) isothermal section consists of 14 single-phase regions, 25 two-phase regions, and 12 three-phase regions. None of the phases in this system reveals a remarkable homogeneity range at 773 K (500 °C).

  14. Structural Characterization of Thermochromic and Spin Equilibria in Solid-State Ni(detu)4Cl2 (detu = N,N'-Diethylthiourea).

    PubMed

    Alfurayj, Ibrahim A; Young, Victor G; Jensen, Michael P

    2016-02-15

    Consecutive thermochromic lattice distortional and spin crossover equilibria in solid-state Ni(detu)4Cl2 (detu = N,N'-diethylthiourea) are investigated by variable-temperature X-ray crystallography (173-333 K), DFT calculations, and differential scanning calorimetry. Thermochromism and anomalous magnetism were reported previously (S. L. Holt, Jr., et al. J. Am. Chem. Soc. 1964, 86, 519-520); the latter was attributed to equilibration of a singlet ground state and a thermally accessible triplet state, but structural data were not obtained. A crystal structure at 173(2) K revealed [Ni(detu)4](2+) centers with distorted planar ligation of nickel(II) to the four sulfur atoms, with an average Ni-S bond length of 2.226(3) Å. The nickel ion was displaced out-of-plane by 0.334 Å toward a proximal apical chloride at a nonbonding distance of 3.134(1) Å. Asymmetry in the trans S-Ni-S angles was coupled to a monoclinic ↔ tetragonal lattice distortion (T(1/2) = 254 ± 11 K), resulting in thermochromism. Spin crossover occurs by tetragonal modulation of nickel(II) with approach of the proximal chloride at higher temperatures (T(1/2) = 383 ± 18 K), which is consistent with a contraction of -0.096(4) Å in the Ni···Cl separation observed at 293 K. A high-spin (S = 1) square-pyramidal [Ni(dmtu)4Cl](+) model (dmtu = N,N'-dimethylthiourea) was optimized by DFT calculations, which estimated limiting equatorial Ni-S bond lengths of 2.45 Å and an apical Ni-Cl bond of 2.43 Å. Electronic spectra of the spin isomers were calculated by TD-DFT methods. Assignment of the FTIR spectrum was assisted by frequency calculations and isotope substitution.

  15. Phase equilibria modeling applied to fluid inclusions: Liquid-vapor equilibria and calculation of the molar volume in the CO[sub 2]-CH[sub 4]-N[sub 2] system

    SciTech Connect

    Thiery, R.; Dubessy, J. ); Vidal, J. )

    1994-02-01

    Quantitative use of fluid inclusions requires the determination of composition and molar volume. The molar volume can be calculated in the CO[sub 2]-CH[sub 4]N[sub 2] system from both the determination of the temperature of a L + V [yields] L (or V) equilibrium if the composition is known independently, provided an equation of state (EOS) reproduces the P-V-T-X properties of each phase at equilibrium. This study is applicable to fluids for which the sequence of phase transition is S[sub CO2] + L + V [yields] L + V [yields] L (or V) at increasing temperature. The molar volume is determined by following a two-step algorithm: (1) the pressure is calculated from a two-parameter cubic EOS with interaction parameters optimized along experimental L-V isotherms (2) the molar volume is then calculated by the correlation of LEE and KESLER (1975) with the pressure calculated in the first step. Projections of polybaric L-V isotherms in [upsilon]-X diagrams of the CO[sub 2]-CH[sub 4], CO[sub 2]-N[sub 2], and CH[sub 4]-N[sub 2] systems can be directly applied to fluid inclusion studies. In addition, it is shown that the molar volume of CO[sub 2]-rich fluids (X[sub CO2] > 0.6) in the ternary system can be estimated with sufficient accuracy using empirical formulae relating to the [upsilon]-X diagrams of the CO[sub 2]-CH[sub 4] and CO[sub 2]-N[sub 2] binary systems.

  16. Investigation of the Phase Equilibria and Phase Transformations Associated with the BISMUTH(2) STRONTIUM(2) Calcium COPPER(2) Oxygen(y) Superconductor

    NASA Astrophysics Data System (ADS)

    Holesinger, Terry George

    Compositional measurements of the Bi_2Sr_2CaCu_2O_{y} (2212) solid solution region were performed in the TEM in order to separate intergrowth and solid solubility effects. Most of the solid solubility is accounted for by changes in the Sr and Ca concentrations. Changes in the Bi concentration account for the rest. Based on these results, two substitution schemes were determined to occur. The first is just the interchange between Sr and Ca. The second involves the substitution of Bi for Sr or Ca. It appears to be unfavorable for Sr or Ca to substitute for Bi. The Cu content of the 2212 phase was found to be nearly constant. The 2212 phase was found with 12 other phases in this work, most of which were also solid solutions. Hence variations in the overall cation stoichiometry and oxygen partial pressure are accommodated by changes in (1) the amount, types, and composition of the secondary phases, (2) the number of intergrowths within the 2212 phase (apparent composition), and/or (3) the solid solution composition of the 2212 phase (actual composition). Crystallization of nominal 2212 glasses was found to proceed in two steps with the formation of Bi_2Sr_{2-x}Ca_ {x}CuO_{y} (2201) and Cu_2O followed by Bi_2Sr_{3-x}Ca_{x}O _{y}, CaO, and SrO. The 2212 phase converts from the 2201 phase with increasing temperatures and was kinetically limited by diffusion below 800 ^circC. At 800^circ C and above, a nearly full conversion to the 2212 phase was achieved after only one minute although considerably longer anneal times were necessary for the system to reach equilibrium. From the results of the solidification study, an eutectic was determined to separate the 2212/2201 phases that are stable at high oxygen partial pressures from the Bi_2Sr_{3-x}Ca _{x}O_{y} (23x) and rm Bi_2Sr_{2-x}Ca _{x}O_{y} (22x) phases present at low oxygen partial pressures. At high oxygen partial pressures, it was found that the separation of CaO in the melt and the initial crystallization of alkaline

  17. Phase-covariant cloning of coherent states

    NASA Astrophysics Data System (ADS)

    Sacchi, Massimiliano F.

    2007-04-01

    We consider the problem of phase-covariant cloning for coherent states. We show that an experimental scheme based on ideal phase measurement and feedforward outperforms the semiclassical procedure of ideal phase measurement and preparation in terms of fidelity. A realistic scheme where the ideal phase measurement is replaced with double-homodyne detection is shown to be unable to overcome the semiclassical cloning strategy. On the other hand, such a realistic scheme is better than semiclassical cloning based on double-homodyne phase measurement and preparation.

  18. Study on vapor-liquid equilibria and surface tensions for nonpolar fluids by renormalization group theory and density gradient theory.

    PubMed

    Fu, Dong

    2006-10-05

    An equation of state (EOS) applicable for both the uniform and nonuniform fluids is established by using the density-gradient theory (DGT). In the bulk phases, the EOS reduces to statistical associating fluid theory (SAFT). By combining the EOS with the renormalization group theory (RGT), the vapor-liquid-phase equilibria and surface tensions for 10 nonpolar chainlike fluids are investigated from low temperature up to the critical point. The obtained results agree well with the experimental data.

  19. Quantum Communication Using Macroscopic Phase Entangled States

    DTIC Science & Technology

    2015-12-10

    goals of our program was to investigate several different ways in which to implement the Kerr medium that allows a single photon to change the phase ...E7(/(3+21(180%(5 ,QFOXGHDUHDFRGH 1 i. Quantum Communication Using Macroscopic Phase Entangled States Final Report Reporting...media that can produce a shift in the phase of a laser pulse provided that a single photon from another source and at a different frequency is also

  20. Oxidation State of Nakhlites as inferred from Fe-Ti oxide Equilibria and Augite/Melt Europium Partitioning

    NASA Technical Reports Server (NTRS)

    Makishima, J.; McKay, G.; Le, L.; Miyamoto, M.; Mikouchi, T.

    2007-01-01

    Recent studies have shown that Martian magmas had wide range of oxygen fugacities (fO2) and that this variation is correlated with the variation of La/Yb ratio and isotopic characteristics of the Martian basalts, shergottite meteorites. The origin of this correlation must have important information about mantle sources and Martian evolution. In order to understand this correlation, it is necessary to know accurate value of oxidation state of other Martian meteorite groups. Nakhlites, cumulate clinopyroxenites, are another major group of Martian meteorites and have distinctly different trace element and isotopic characteristics from shergottites. Thus, estimates of oxidation state of nakhlites will give us important insight into the mantle source in general. Several workers have estimated oxidation state of nakhlites by using Fe-Ti oxide equilibrium. However, Fe-Ti oxides may not record the oxidation state of the parent melt of the nakhlite because it is a late-stage mineral. Furthermore, there is no comprehensive study which analyzed all nakhlite samples at the same time. Therefore, in this study (1) we reduced the uncertainty of the estimate using the same electron microprobe and the same standards under the same condition for Fe-Ti oxide in 6 nakhlites and (2) we also performed crystallization experiments to measure partition coefficients of Eu into pyroxene in the nakhlite system in order to estimate fO2 when the pyroxene core formed (i.e. Eu oxybarometer [e.g. 2,6]).

  1. Phase equilibria and molecular packing in the N,N-dimethyldodecylamine oxide/gramicidin D/water system studied by 2H nuclear magnetic resonance spectroscopy.

    PubMed Central

    Orädd, G; Lindblom, G; Arvidson, G; Gunnarsson, K

    1995-01-01

    A partial phase diagram of the system N,N-dimethyldodecylamine oxide (DDAO)/water/gramicidin D was determined by 2H-NMR. Both 2H2O and perdeuterated DDAO (DDAO-d31) were studied by solid state NMR techniques. Addition of gramicidin D to the micellar (L1), normal hexagonal (HI) and cubic (I) phases of DDAO induces phase separations, giving two-phase regions, which all contain a lamellar (L alpha) phase. The L alpha phase containing gramicidin is characterized by larger order parameters for DDAO-d31 compared with the corresponding order parameters in the L alpha and HI phases of DDAO-d31/H2O. The L alpha phase may stay in equilibrium with any other phase in the phase diagram. The DDAO exchange between the coexisting phases is slow on the NMR timescale, which is why the recorded NMR spectrum consists of superimposed spectra from the different phases occurring in the sample. Gramicidin D can be solubilized in appreciable quantities only in the lamellar phase of DDAO-d31. Increasing amounts of gramicidin in the liquid crystalline phases result in a continuous increase in the molecular ordering up to about 5 mol% gramicidin, where a plateau is reached. This is consistent with a recent theoretical model describing the influence on the ordering of lipids by a membrane protein with larger hydrophobic thickness than the lipid bilayer. The solvent used for dissolving gramicidin at the incorporation of the peptide in the lipid aggregates has no effect on the 2H-NMR lineshapes of DDAO-d31. It is concluded that gramicidin is solubilized in the L alpha phase and that it always adopts the channel conformation independent of a particular solvent. The channel conformation is also supported by CD studies. In some of the samples, macroscopic orientation of the lipid aggregates is observed. It is concluded that DDAO-d31 in the binary system favors an orientation with the long axis of the hydrocarbon chain perpendicular to the magnetic field, whereas when gramicidin D is present the

  2. Propagating confined states in phase dynamics

    NASA Technical Reports Server (NTRS)

    Brand, Helmut R.; Deissler, Robert J.

    1992-01-01

    Theoretical treatment is given to the possibility of the existence of propagating confined states in the nonlinear phase equation by generalizing stationary confined states. The nonlinear phase equation is set forth for the case of propagating patterns with long wavelengths and low-frequency modulation. A large range of parameter values is shown to exist for propagating confined states which have spatially localized regions which travel on a background with unique wavelengths. The theoretical phenomena are shown to correspond to such physical systems as spirals in Taylor instabilities, traveling waves in convective systems, and slot-convection phenomena for binary fluid mixtures.

  3. Propagating confined states in phase dynamics

    NASA Technical Reports Server (NTRS)

    Brand, Helmut R.; Deissler, Robert J.

    1992-01-01

    Theoretical treatment is given to the possibility of the existence of propagating confined states in the nonlinear phase equation by generalizing stationary confined states. The nonlinear phase equation is set forth for the case of propagating patterns with long wavelengths and low-frequency modulation. A large range of parameter values is shown to exist for propagating confined states which have spatially localized regions which travel on a background with unique wavelengths. The theoretical phenomena are shown to correspond to such physical systems as spirals in Taylor instabilities, traveling waves in convective systems, and slot-convection phenomena for binary fluid mixtures.

  4. Instability of magnetic equilibria in barotropic stars

    NASA Astrophysics Data System (ADS)

    Mitchell, J. P.; Braithwaite, J.; Reisenegger, A.; Spruit, H.; Valdivia, J. A.; Langer, N.

    2015-02-01

    In stably stratified stars, numerical magnetohydrodynamics simulations have shown that arbitrary initial magnetic fields evolve into stable equilibrium configurations, usually containing nearly axisymmetric, linked poloidal and toroidal fields that stabilize each other. In this work, we test the hypothesis that stable stratification is a requirement for the existence of such stable equilibria. For this purpose, we follow numerically the evolution of magnetic fields in barotropic (and thus neutrally stable) stars, starting from two different types of initial conditions, namely random disordered magnetic fields, as well as linked poloidal-toroidal configurations resembling the previously found equilibria. With many trials, we always find a decay of the magnetic field over a few Alfvén times, never a stable equilibrium. This strongly suggests that there are no stable equilibria in barotropic stars, thus clearly invalidating the assumption of barotropic equations of state often imposed on the search of magnetic equilibria. It also supports the hypothesis that, as dissipative processes erode the stable stratification, they might destabilize previously stable magnetic field configurations, leading to their decay.

  5. Determination of the tautomeric equilibria of pyridoyl benzoyl β-diketones in the liquid and solid state through the use of deuterium isotope effects on (1)H and (13)C NMR chemical shifts and spin coupling constants.

    PubMed

    Hansen, Poul Erik; Borisov, Eugeny V; Lindon, John C

    2015-02-05

    The tautomeric equilibria for 2-pyridoyl-, 3-pyridoyl-, and 4-pyridoyl-benzoyl methane have been investigated using deuterium isotope effects on (1)H and (13)C chemical shifts both in the liquid and the solid state. Equilibria are established both in the liquid and the solid state. In addition, in the solution state the 2-bond and 3-bond J((1)H-(13)C) coupling constants have been used to confirm the equilibrium positions. The isotope effects due to deuteriation at the OH position are shown to be superior to chemical shift in determination of equilibrium positions of these almost symmetrical -pyridoyl-benzoyl methanes. The assignments of the NMR spectra are supported by calculations of the chemical shifts at the DFT level. The equilibrium positions are shown to be different in the liquid and the solid state. In the liquid state the 4-pyridoyl derivative is at the B-form (C-1 is OH), whereas the 2-and 3-pyridoyl derivatives are in the A-form. In the solid state all three compounds are on the B-form. The 4-pyridoyl derivative shows unusual deuterium isotope effects in the solid, which are ascribed to a change of the crystal structure of the deuteriated compound. Copyright © 2013 Elsevier B.V. All rights reserved.

  6. Phase Equilibria and Crystal Chemistry in Portions of the System SrO-CaO-Bi2O3-CuO, Part II—The System SrO-Bi2O3-CuO

    PubMed Central

    Roth, R. S.; Rawn, C. J.; Burton, B. P.; Beech, F.

    1990-01-01

    New data are presented on the phase equilibria and crystal chemistry of the binary systems Sr0-Bi203 and SrO-CuO and the ternary system SrO-Bi2O3-CuO. Symmetry data and unit cell dimensions based on single crystal and powder x-ray diffraction measurements are reported for all the binary SrO-Bi2O3 phases, including a new phase identified as Sr6Bi2O9. The ternary system contains at least four ternary phases which can be formed in air at ~900 °C. These are identified as Sr2Bi2CuO6, Sr8Bi4Cu5O19+x, Sr3Bi2Cu2O8 and a solid solution (the Raveau phase) which, for equilibrium conditions at ~900 °C, corresponds approximately to the formula Sr1.8−xBi2.2+xCu1±x/2Oz.(0.0⩽x⩽~0.15). Superconductivity in this phase apparently occurs only in compositions that correspond to negative values of x. Compositions that lie outside the equilibrium Raveau-phase field often form nearly homogeneous Raveau-phase products. Typically this occurs after relatively brief heat treatments, or in crystallization of a quenched melt. PMID:28179779

  7. Phase equilibria and crystal chemistry in portions of the system SrO-CaO-Bi2O3-CuO, part 2 - the system SrO-Bi2O3-CuO

    SciTech Connect

    Roth, R.S.; Rawn, C.J.; Burton, B.P.; Beech, F.

    1990-01-01

    New data are presented on the phase equilibria and crystal chemistry of the binary systems SrO-Bi2O3 and SrO-CuO and the ternary system SrO-Bi2O3-CuO. Symmetry data and unit cell dimensions based on single crystal and powder x-ray diffraction measurement are reported for all the binary SrO-Bi2O3 phases, including a new phase identified as Sr6Bi2O9. The ternary system contains at least four ternary phases which can be formed in air at about 900 C. These are identified as Sr2Bi2CuO6, Sr8Bi4Cu5O(19 + x) Sr3Bi2Cu2O8 and a solid solution (the Raveau phase) which, For equilibrium conditions at about 900 C, corresponds approximately to the formula Sr(1.8-x)Bi(22+x)Cu(1 + or - x/2)Oz(0.0 = or < about 0.15). Superconductivity in the phase apparently occurs only in compositions that correspond to negative values of x. Compositions that lie outside the equilibrium Raveau-phase field often form nearly homogenous Raveau-phase products. Typically this occurs after relatively brief heat treatments, or in crystallization of a quenched melt.

  8. Liquid-vapor equilibria of ionic liquids from a SAFT equation of state with explicit electrostatic free energy contributions.

    PubMed

    Guzmán, Orlando; Ramos Lara, J Eloy; Del Río, Fernando

    2015-05-07

    Statistically associating fluid theory (SAFT) provides closed-form free energies by perturbation methods. We propose here a SAFT equation of state for ionic liquids that models the contribution from Coulomb forces after that of the Restricted Primitive Model (RPM) in the Mean Spherical Approximation (MSA). The resulting SAFT-MSA equation, fitted to simulated orthobaric curves of imidazolium based ionic liquids, predicts experimental density data with errors ≈1% and the characteristic decrease of all critical coordinates with increasing cation size. The SAFT-MSA equation can be applied to calculate thermodynamic coefficients, the speed of sound and surface tension (among other properties) of pure ionic liquids and can be generalized straightforwardly to mixtures.

  9. Vapor-liquid equilibria for an R134a/lubricant mixture: Measurements and equation-of-state modeling

    SciTech Connect

    Huber, M.L.; Holcomb, C.D.; Outcalt, S.L.; Elliott, J.R.

    2000-07-01

    The authors measured bubble point pressures and coexisting liquid densities for two mixtures of R-134a and a polyolester (POE) lubricant. The mass fraction of the lubricant was approximately 9% and 12%, and the temperature ranged from 280 K to 355 K. The authors used the Elliott, Suresh, and Donohue (ESD) equation of state to model the bubble point pressure data. The bubble point pressures were represented with an average absolute deviation of 2.5%. A binary interaction parameter reduced the deviation to 1.4%. The authors also applied the ESD model to other R-134a/POE lubricant data in the literature. As the concentration of the lubricant increased, the performance of the model deteriorated markedly. However, the use of a single binary interaction parameter reduced the deviations significantly.

  10. Vent fluid chemistry of the Rainbow hydrothermal system (36°N, MAR): Phase equilibria and in situ pH controls on subseafloor alteration processes

    NASA Astrophysics Data System (ADS)

    Seyfried, W. E., Jr.; Pester, Nicholas J.; Ding, Kang; Rough, Mikaella

    2011-03-01

    The Rainbow hydrothermal field is located at 36°13.8'N-33°54.15'W at 2300 m depth on the western flank of a non-volcanic ridge between the South AMAR and AMAR segments of the Mid-Atlantic Ridge. The hydrothermal field consists of 10-15 active chimneys that emit high-temperature (˜365 °C) fluid. In July 2008, vent fluids were sampled during cruise KNOX18RR, providing a rich dataset that extends in time information on subseafloor chemical and physical processes controlling vent fluid chemistry at Rainbow. Data suggest that the Mg concentration of the hydrothermal end-member is not zero, but rather 1.5-2 mmol/kg. This surprising result may be caused by a combination of factors including moderately low dissolved silica, low pH, and elevated chloride of the hydrothermal fluid. Combining end-member Mg data with analogous data for dissolved Fe, Si, Al, Ca, and H 2, permits calculation of mineral saturation states for minerals thought appropriate for ultramafic-hosted hydrothermal systems at temperatures and pressures in keeping with constraints imposed by field observations. These data indicate that chlorite solid solution, talc, and magnetite achieve saturation in Rainbow vent fluid at a similar pH (T,P) (400 °C, 500 bar) of approximately 4.95, while higher pH values are indicated for serpentine, suggesting that serpentine may not coexist with the former assemblage at depth at Rainbow. The high Fe/Mg ratio of the Rainbow vent fluid notwithstanding, the mole fraction of clinochlore and chamosite components of chlorite solid solution at depth are predicted to be 0.78 and 0.22, respectively. In situ pH measurements made at Rainbow vents are in good agreement with pH (T,P) values estimated from mineral solubility calculations, when the in situ pH data are adjusted for temperature and pressure. Calculations further indicate that pH (T,P) and dissolved H 2 are extremely sensitive to changes in dissolved silica owing to constraints imposed by chlorite solid solution

  11. Nitroxyl and its anion in aqueous solutions: Spin states, protic equilibria, and reactivities toward oxygen and nitric oxide

    PubMed Central

    Shafirovich, Vladimir; Lymar, Sergei V.

    2002-01-01

    The thermodynamic properties of aqueous nitroxyl (HNO) and its anion (NO−) have been revised to show that the ground state of NO− is triplet and that HNO in its singlet ground state has much lower acidity, pKa(1HNO/3NO−) ≈ 11.4, than previously believed. These conclusions are in accord with the observed large differences between 1HNO and 3NO− in their reactivities toward O2 and NO. Laser flash photolysis was used to generate 1HNO and 3NO− by photochemical cleavage of trioxodinitrate (Angeli's anion). The spin-allowed addition of 3O2 to 3NO− produced peroxynitrite with nearly diffusion-controlled rate (k = 2.7 × 109 M−1⋅s−1). In contrast, the spin-forbidden addition of 3O2 to 1HNO was not detected (k ≪ 3 × 105 M−1⋅s−1). Both 1HNO and 3NO− reacted sequentially with two NO to generate N3O\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\setlength{\\oddsidemargin}{-69pt} \\begin{document} \\begin{equation*}{\\mathrm{_{3}^{-}}}\\end{equation*}\\end{document} as a long-lived intermediate; the rate laws of N3O\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\setlength{\\oddsidemargin}{-69pt} \\begin{document} \\begin{equation*}{\\mathrm{_{3}^{-}}}\\end{equation*}\\end{document} formation were linear in concentrations of NO and 1HNO (k = 5.8 × 106 M−1⋅s−1) or NO and 3NO− (k = 2.3 × 109 M−1⋅s−1). Catalysis by the hydroxide ion was observed for the reactions of 1HNO with both O2 and NO. This effect is explicable by a spin-forbidden deprotonation by OH− (k = 4.9 × 104 M−1⋅s−1) of the relatively unreactive 1HNO into the extremely reactive 3NO−. Dimerization of 1HNO to produce N2O occurred much more slowly (k = 8 × 106 M−1⋅s−1) than previously suggested. The implications of these

  12. Hydration states of AFm cement phases

    SciTech Connect

    Baquerizo, Luis G.; Matschei, Thomas; Scrivener, Karen L.; Saeidpour, Mahsa; Wadsö, Lars

    2015-07-15

    The AFm phase, one of the main products formed during the hydration of Portland and calcium aluminate cement based systems, belongs to the layered double hydrate (LDH) family having positively charged layers and water plus charge-balancing anions in the interlayer. It is known that these phases present different hydration states (i.e. varying water content) depending on the relative humidity (RH), temperature and anion type, which might be linked to volume changes (swelling and shrinkage). Unfortunately the stability conditions of these phases are insufficiently reported. This paper presents novel experimental results on the different hydration states of the most important AFm phases: monocarboaluminate, hemicarboaluminate, strätlingite, hydroxy-AFm and monosulfoaluminate, and the thermodynamic properties associated with changes in their water content during absorption/desorption. This data opens the possibility to model the response of cementitious systems during drying and wetting and to engineer systems more resistant to harsh external conditions.

  13. Phase Space Transition States for Deterministic Thermostats

    NASA Astrophysics Data System (ADS)

    Ezra, Gregory; Wiggins, Stephen

    2009-03-01

    We describe the relation between the phase space structure of Hamiltonian and non-Hamiltonian deterministic thermostats. We show that phase space structures governing reaction dynamics in Hamiltonian systems, such as the transition state, map to the same type of phase space structures for the non-Hamiltonian isokinetic equations of motion for the thermostatted Hamiltonian. Our results establish a general theoretical framework for analyzing thermostat dynamics using concepts and methods developed in reaction rate theory. Numerical results are presented for the isokinetic thermostat.

  14. Thermodynamic assessment of hydrothermal alkali feldspar-mica-aluminosilicate equilibria

    NASA Astrophysics Data System (ADS)

    Sverjensky, Dimitri A.; Hemley, J. J.; D'angelo, W. M.

    1991-04-01

    The thermodynamic properties of minerals retrieved from consideration of solid-solid and dehydration equilibria with calorimetric reference values, and those of aqueous species derived from studies of electrolytes, are not consistent with experimentally measured high-temperature solubilities in the systems K 2O- and Na 2O-Al 2O 3-SiO 2-H 2O-HCl (e.g., K-fs - Ms - Qtz - K + - H +). This introduces major inaccuracies into the computation of ionic activity ratios and the acidities of diagenetic, metamorphic, and magmatic hydrothermal fluids buffered by alkali silicate-bearing assemblages. We report a thermodynamic analysis of revised solubility equilibria in these systems that integrates the thermodynamic properties of minerals obtained from phase equilibria studies ( BERMAN, 1988) with the properties of aqueous species calculated from a calibrated equation of state ( SHOCK and HELGESON, 1988). This was achieved in two separate steps. First, new values of the free energies and enthalpies of formation at 25°C and 1 bar for the alkali silicates muscovite and albite were retrieved from the experimental solubility equilibria at 300°C and P sat. Because the latter have stoichiometric reaction coefficients different from those for solid-solid and dehydration equilibria, our procedure preserves exactly the relative thermodynamic properties of the alkali-bearing silicates ( BERMAN, 1988). Only simple arithmetic adjustments of -1,600 and -1,626 ( ±500) cal/mol to all the K- and Na-bearing silicates, respectively, in BERMAN (1988) are required. In all cases, the revised values are within ±0.2% of calorimetric values. Similar adjustments were derived for the properties of minerals from HELGESON et al. (1978). Second, new values of the dissociation constant of HCl were retrieved from the solubility equilibria at temperatures and pressures from 300-600°C and 0.5-2.0 kbars using a simple model for aqueous speciation. The results agree well with the conductance

  15. Thermodynamic assessment of hydrothermal alkali feldspar-mica-aluminosilicate equilibria

    USGS Publications Warehouse

    Sverjensky, D.A.; Hemley, J.J.; d'Angelo, W. M.

    1991-01-01

    The thermodynamic properties of minerals retrieved from consideration of solid-solid and dehydration equilibria with calorimetric reference values, and those of aqueous species derived from studies of electrolytes, are not consistent with experimentally measured high-temperature solubilities in the systems K2O- and Na2O-Al2O3-SiO2-H2O-HCl (e.g., K-fs - Ms - Qtz - K+ - H+). This introduces major inaccuracies into the computation of ionic activity ratios and the acidities of diagenetic, metamorphic, and magmatic hydrothermal fluids buffered by alkali silicate-bearing assemblages. We report a thermodynamic analysis of revised solubility equilibria in these systems that integrates the thermodynamic properties of minerals obtained from phase equilibria studies (Berman, 1988) with the properties of aqueous species calculated from a calibrated equation of state (Shock and Helgeson, 1988). This was achieved in two separate steps. First, new values of the free energies and enthalpies of formation at 25??C and 1 bar for the alkali silicates muscovite and albite were retrieved from the experimental solubility equilibria at 300??C and Psat. Because the latter have stoichiometric reaction coefficients different from those for solid-solid and dehydration equilibria, our procedure preserves exactly the relative thermodynamic properties of the alkali-bearing silicates (Berman, 1988). Only simple arithmetic adjustments of -1,600 and -1,626 (??500) cal/mol to all the K- and Na-bearing silicates, respectively, in Berman (1988) are required. In all cases, the revised values are within ??0.2% of calorimetric values. Similar adjustments were derived for the properties of minerals from Helgeson et al. (1978). Second, new values of the dissociation constant of HCl were retrieved from the solubility equilibria at temperatures and pressures from 300-600??C and 0.5-2.0 kbars using a simple model for aqueous speciation. The results agree well with the conductance-derived dissociation

  16. Protected boundary states in gapless topological phases

    NASA Astrophysics Data System (ADS)

    Matsuura, Shunji; Chang, Po-Yao; Schnyder, Andreas P.; Ryu, Shinsei

    2013-06-01

    We systematically study gapless topological phases of (semi-)metals and nodal superconductors described by Bloch and Bogoliubov-de Gennes Hamiltonians. Using K-theory, a classification of topologically stable Fermi surfaces in (semi-)metals and nodal lines in superconductors is derived. We discuss a generalized bulk-boundary correspondence that relates the topological features of the Fermi surfaces and superconducting nodal lines to the presence of protected zero-energy states at the boundary of the system. Depending on the case, the boundary states are either linearly dispersing (i.e. Dirac or Majorana states) or dispersionless, forming two-dimensional surface flat bands or one-dimensional arc surface states. We study examples of gapless topological phases in symmetry classes AIII and DIII, focusing in particular on nodal superconductors, such as nodal noncentrosymmetric superconductors. For some cases we explicitly compute the surface spectrum and examine the signatures of the topological boundary states in the surface density of states. We also discuss the robustness of the surface states against disorder.

  17. Entangled states and superradiant phase transitions

    SciTech Connect

    Aparicio Alcalde, M.; Cardenas, A. H.; Svaiter, N. F.; Bezerra, V. B.

    2010-03-15

    The full Dicke model is composed of a single bosonic mode and an ensemble of N identical two-level atoms. In the model, the coupling between the bosonic mode and the atoms generates resonant and nonresonant processes. We also consider a dipole-dipole interaction between the atoms, which is able to generate entangled states in the atomic system. By assuming thermal equilibrium with a reservoir at temperature {beta}{sup -1}, the transition from fluorescent to superradiant phase and the quantum phase transition are investigated. It is shown that the critical behavior of the full Dicke model is not modified by the introduction of the dipole-dipole interaction.

  18. Sedimentation and multiphase equilibria in suspensions of colloidal hard rods.

    PubMed

    Savenko, S V; Dijkstra, Marjolein

    2004-11-01

    Sedimentation and multiphase equilibria in a suspension of hard colloidal rods are explored by analyzing the (macroscopic) osmotic equilibrium conditions. We observe that gravity enables the system to explore a whole range of phases varying from the most dilute phase to the densest phase, i.e., from the isotropic (I), to the nematic (N), to the smectic (Sm), to the crystal (K) phase. We determine the phase diagrams for hard spherocylinders with a length-to-diameter ratio of 5 for a semi-infinite system and a system with fixed container height using a bulk equation of state obtained from simulations. Our results show that gravity leads to multiphase coexistence for the semi-infinite system, as we observe I, I+N, I+N+Sm , or I+N+Sm+K coexistence, while the finite system shows I, N, Sm, K, I+N, N+Sm, Sm+K, I+N+Sm, N+Sm+K , and I+N+Sm+K phase coexistence. In addition, we compare our theoretical predictions for the phase behavior and the density profiles with Monte Carlo simulations for the semi-infinite system and we find good agreement with our theoretical predictions.

  19. Phase Equilibria in the Fe-Mo-Ti Ternary System at 1173 K (900 °C) and 1023 K (750 °C)

    NASA Astrophysics Data System (ADS)

    Knowles, A. J.; Jones, N. G.; Jones, C. N.; Stone, H. J.

    2017-09-01

    Alloys with fine-scale eutectic microstructures comprising Ti-based A2 and TiFe B2 phases have been shown to have excellent mechanical properties. In this study, the potential of alloys with further refined A2-B2 microstructures formed through solid-state precipitation has been explored by analyzing a series of six alloys within the Fe-Mo-Ti ternary system. Partial isothermal sections of this system at 1173 K (900 °C) and 1023 K (750 °C) were constructed, from which the ternary solubility limits of the A2 (Ti, Mo), B2 TiFe, D85 Fe7Mo6, and C14 Fe2Ti phases were determined. With these data, the change in solubility of Fe in the A2 phase with temperature, which provides the driving force for precipitation of B2 TiFe, was determined and used to predict the maximum potential volume fraction of B2 TiFe precipitates that may be formed in an A2 (Ti, Mo) matrix.

  20. Phase Equilibria in the Fe-Mo-Ti Ternary System at 1173 K (900 °C) and 1023 K (750 °C)

    NASA Astrophysics Data System (ADS)

    Knowles, A. J.; Jones, N. G.; Jones, C. N.; Stone, H. J.

    2017-07-01

    Alloys with fine-scale eutectic microstructures comprising Ti-based A2 and TiFe B2 phases have been shown to have excellent mechanical properties. In this study, the potential of alloys with further refined A2-B2 microstructures formed through solid-state precipitation has been explored by analyzing a series of six alloys within the Fe-Mo-Ti ternary system. Partial isothermal sections of this system at 1173 K (900 °C) and 1023 K (750 °C) were constructed, from which the ternary solubility limits of the A2 (Ti, Mo), B2 TiFe, D85 Fe7Mo6, and C14 Fe2Ti phases were determined. With these data, the change in solubility of Fe in the A2 phase with temperature, which provides the driving force for precipitation of B2 TiFe, was determined and used to predict the maximum potential volume fraction of B2 TiFe precipitates that may be formed in an A2 (Ti, Mo) matrix.

  1. Self-organized criticality and punctuated equilibria

    NASA Astrophysics Data System (ADS)

    Bak, Per; Boettcher, Stefan

    1997-02-01

    Many natural phenomena evolve intermittently, with periods of tranquillity interrupted by bursts of activity, rather than following a smooth gradual path. Examples include earthquakes, volcanic eruptions, solar flares, gamma-ray bursts, and biological evolution. Stephen Jay Gould and Niles Eldredge have coined the term “punctuated equilibria” for this behavior. We argue that punctuated equilibria reflects the tendency of dynamical systems to evolve towards a critical state, and review recent work on simple models. A good metaphoric picture is one where the systems are temporarily trapped in valleys of deformable, interacting landscapes. Similarities with spin glasses are pointed out. Punctuated equilibria are essential for the emergence of complex phenomena. The periods of stasis allow the system to remember its past history; yet the intermittent events permit further change.

  2. Reversed-phase ion-pair liquid chromatographic method for determination of reaction equilibria involving ionic species: exemplification of the method using ligand substitution reactions of ethylenediaminetetraacetatochromium(III) ion with acetate and phosphate ions.

    PubMed

    Sato, Emiko; Miya, Seiko; Saitoh, Kazunori; Saito, Shingo; Shibukawa, Masami

    2011-02-18

    A reversed-phase ion-pair liquid chromatographic method is presented for the determination of reaction equilibria involving ionic species of the same charge sign as reactant and product compounds. It has been demonstrated that ion-exchange chromatography or reversed-phase ion-pair chromatography is a useful tool for the determination of equilibrium constants of chemical reactions involving ionic species such as metal complexation reactions. Previous work with these methods has been based on the assumption that the limiting retention factors of the reactant and product species are constant independent of concentration of the chemical species (X) in the mobile phase, which reacts with the analyte compound. However, when all the reactant and product species are ions of the same charge sign as that of the species X, it is virtually impossible to apply these methods to the equilibrium constant determination because the retention factors of both the reactant and product species may depend on the concentration of X. In this study, an alternative approach was developed that estimates the limiting retention factors of ionic species from the dependence of the retention factor on the ionic strength of the mobile phase. Ligand substitution reactions of ethylenediaminetetraacetatochromium(III) ion with acetate and phosphate ions were used as model reactions to test this method. The equilibrium constants determined by this method are in good agreement with those obtained by a UV-visible spectrophotometric method.

  3. Phase Equilibria Studies in the System ZnO-``FeO''-Al2O3-CaO-SiO2 Relevant to Imperial Smelting Furnace Slags: Part I

    NASA Astrophysics Data System (ADS)

    Zhao, Baojun; Hayes, Peter C.; Jak, Evgueni

    2010-04-01

    The phase equilibria and liquidus temperatures in the system ZnO-“FeO”-Al2O3-CaO-SiO2 in equilibrium with metallic iron have been determined experimentally in the temperature range of 1423 K to 1553 K. The experimental conditions were focused on the composition range relevant to Imperial Smelting Furnace slags. The results are presented in the form of a pseudo-ternary section ZnO-“FeO”-(CaO + SiO2 + Al2O3) in which CaO/SiO2 = 0.93 and (CaO + SiO2)/Al2O3 = 7.0. It was found that wustite and spinel are the major primary phases and that zincite and melilite are also present in the composition range investigated. Wustite (Fe2+,Zn)O and spinel (Fe2+,Zn)O (A1,Fe3+)2O3 solid solutions are formed in this system, and the ZnO concentration in the spinel phase is found to be much greater than in the liquid phase.

  4. Phase Equilibria Studies in the System ZnO-``FeO''-Al2O3-CaO-SiO2 Relevant to Imperial Smelting Furnace Slags: Part II

    NASA Astrophysics Data System (ADS)

    Zhao, Baojun; Hayes, Peter C.; Jak, Evgueni

    2010-04-01

    The phase equilibria and the liquidus temperatures in the system ZnO-“FeO”-Al2O3-CaO-SiO2 have been determined experimentally in equilibrium with metallic iron. Specifically, the effects of Al2O3 concentrations in Imperial Smelting Furnace slags are identified, and the results are presented in the form of pseudo-ternary sections ZnO-“FeO”-(Al2O3 + CaO + SiO2) in which CaO/SiO2 = 0.93 and (CaO + SiO2)/Al2O3 = 5.0 and 3.5, respectively. It was found that, in the presence of Al2O3, the spinel phase is formed, the spinel primary phase field expands, and the wustite and melilite primary phase fields are reduced in size with an increasing Al2O3 concentration. The implications of the findings to industrial practice are discussed.

  5. Inverse plasma equilibria

    SciTech Connect

    Hicks, H.R.; Dory, R.A.; Holmes, J.A.

    1983-01-01

    We illustrate in some detail a 2D inverse-equilibrium solver that was constructed to analyze tokamak configurations and stellarators (the latter in the context of the average method). To ensure that the method is suitable not only to determine equilibria, but also to provide appropriately represented data for existing stability codes, it is important to be able to control the Jacobian, tilde J is identical to delta(R,Z)/delta(rho, theta). The form chosen is tilde J = J/sub 0/(rho)R/sup l/rho where rho is a flux surface label, and l is an integer. The initial implementation is for a fixed conducting-wall boundary, but the technique can be extended to a free-boundary model.

  6. Phase Equilibria in the System "FeO"-CaO-SiO2-Al2O3-MgO at Different CaO/SiO2 Ratios

    NASA Astrophysics Data System (ADS)

    Jang, Kyoung-oh; Ma, Xiaodong; Zhu, Jinming; Xu, Haifa; Wang, Geoff; Zhao, Baojun

    2017-06-01

    The "FeO"-containing slags play an important role in the operation of an ironmaking blast furnace (BF), in particular the primary slags such as the system "FeO"-CaO-SiO2-Al2O3-2 mass pct MgO with CaO/SiO2 weight ratios of 1.3, 1.5, and 1.8 saturated with metallic iron. To investigate the characteristics of such a slag system and its behavior in BF, the phase equilibria and liquidus temperatures in the slag system have been experimentally determined using the high-temperature equilibration and quenching technique followed by an electron probe X-ray microanalysis (EPMA). Isotherms between 1553 K and 1603 K (1280 °C and 1330 °C) were determined in the primary phase fields of dicalcium silicate, melilite, spinel, and monoxide [(Mg,Fe2+)O]. Pseudo-ternary phase diagrams of (CaO + SiO2)-Al2O3-"FeO" with a fixed MgO concentration at 2 mass pct and at CaO/SiO2 ratios of 1.3, 1.5, and 1.8 have been discussed, respectively, simplifying the complexity of the slag system for easy understanding and applying in BF operation. It was found that the liquidus temperatures increase in melilite and spinel primary phase fields, but decrease in dicalcium silicate and monoxide primary phase fields with increasing Al2O3/(CaO + SiO2) ratio. In addition, the liquidus temperatures decrease with increasing "FeO" concentration in dicalcium silicate and melilite primary phase fields, while showing an increasing trend in the spinel and monoxide primary phase fields. The data resulted from this study can be used to improve and optimize currently available database of thermodynamic models used in FactSage.

  7. Phase Equilibria in the System "FeO"-CaO-SiO2-Al2O3-MgO at Different CaO/SiO2 Ratios

    NASA Astrophysics Data System (ADS)

    Jang, Kyoung-oh; Ma, Xiaodong; Zhu, Jinming; Xu, Haifa; Wang, Geoff; Zhao, Baojun

    2017-03-01

    The "FeO"-containing slags play an important role in the operation of an ironmaking blast furnace (BF), in particular the primary slags such as the system "FeO"-CaO-SiO2-Al2O3-2 mass pct MgO with CaO/SiO2 weight ratios of 1.3, 1.5, and 1.8 saturated with metallic iron. To investigate the characteristics of such a slag system and its behavior in BF, the phase equilibria and liquidus temperatures in the slag system have been experimentally determined using the high-temperature equilibration and quenching technique followed by an electron probe X-ray microanalysis (EPMA). Isotherms between 1553 K and 1603 K (1280 °C and 1330 °C) were determined in the primary phase fields of dicalcium silicate, melilite, spinel, and monoxide [(Mg,Fe2+)O]. Pseudo-ternary phase diagrams of (CaO + SiO2)-Al2O3-"FeO" with a fixed MgO concentration at 2 mass pct and at CaO/SiO2 ratios of 1.3, 1.5, and 1.8 have been discussed, respectively, simplifying the complexity of the slag system for easy understanding and applying in BF operation. It was found that the liquidus temperatures increase in melilite and spinel primary phase fields, but decrease in dicalcium silicate and monoxide primary phase fields with increasing Al2O3/(CaO + SiO2) ratio. In addition, the liquidus temperatures decrease with increasing "FeO" concentration in dicalcium silicate and melilite primary phase fields, while showing an increasing trend in the spinel and monoxide primary phase fields. The data resulted from this study can be used to improve and optimize currently available database of thermodynamic models used in FactSage.

  8. Experimental determination of phase equilibria of a basalt from Piton de la Fournaise (La Réunion island): 1 atm data and high pressure results in presence of volatiles.

    NASA Astrophysics Data System (ADS)

    Brugier, Yann-Aurélien; Pichavant, Michel; di Muro, Andréa

    2015-04-01

    To understand the petrogenetic relations between the 4 groups of lavas erupted at Piton de la Fournaise (PdF), constrain the structure of the feeding system and the magma storage conditions, experimental phase equilibria have been determined, both at 1 atm and high pressures (HP), on a lava representative of Steady State Basalts (SSB). The lava (SiO2=49.2 wt%, MgO=7.8 wt%, CaO/Al2O3= 0.81) was fused at 1400°C, 1 atm in air. The resulting glass was crushed and the powder directly used as starting material. The 1atm experiments were performed with the wire-loop method in a vertical CO-CO2 gas mixing furnace. To minimize Fe-loss from the charge, experiments were repeated under constant T-fO2 conditions to progressively saturate the suspension wire with Fe. Intermediate charges were dissolved in HF and the charge from the last cycle retained for detailed study. Analyses of experimental products are in progress. The HP experiments were carried out in an internally heated pressure vessel, at 50MPa and 400MPa, between 1100-1200°C and under fluid-present conditions. Glass (30-50 mg) plus 10% in mass of volatiles (H2O or H2O+CO2) were loaded in Au80Pd20 capsules. Distilled water and Ag2C2O4 (CO2 source) were weighted to give charges with xH2O initial (molar H2O / (H2O+CO2)) ranging from 1 to 0. Run durations lasted for 2-14h. Redox conditions were controlled by loading a given proportion of H2 gas in the vessel (3 bar H2 for 50MPa, 5 bar H2 for 400MPa). Experimental fH2 were determined by solid Pd-Co sensors, leading to fO2 conditions approaching NNO-1. All experiments were rapidly drop quenched and products analyzed by SEM, EMPA and µ-FTIR Spectroscopy. To overcome Fe-loss, both capsule Fe pre-saturation and charge Fe pre-enrichment were tested. The first method was shown to be time-consuming and fraught with difficulties while the second is still being developed. Consequently, the experimental data presented here were obtained with no attempt to circumvent Fe loss

  9. Transferable SAFT-VR models for the calculation of the fluid phase equilibria in reactive mixtures of carbon dioxide, water, and n-alkylamines in the context of carbon capture.

    PubMed

    Mac Dowell, N; Pereira, F E; Llovell, F; Blas, F J; Adjiman, C S; Jackson, G; Galindo, A

    2011-06-30

    The amine functional groups are fundamental building blocks of many molecules that are central to life, such as the amino acids, and to industrial processes, such as the alkanolamines, which are used extensively for gas absorption. The modeling of amines and of mixtures of amines with water (H(2)O) and carbon dioxide (CO(2)) is thus relevant to a number of applications. In this contribution, we use the statistical associating fluid theory for potentials of variable range (SAFT-VR) to describe the fluid phase behavior of ammonia + H(2)O + CO(2) and n-alkyl-1-amine + H(2)O + CO(2) mixtures. Models are developed for ammonia (NH(3)) and n-alkyl-1-amines up to n-hexyl-1-amine (CH(3)NH(2) to C(6)H(13)NH(2)). The amines are modeled as homonuclear chain molecules formed from spherical segments with additional association sites incorporated to mediate the effect of hydrogen-bonding interactions. The SAFT-VR approach provides a representation of the pure component fluid phase equilibria, on average, to within 1.48% of the experimental data in relative terms for the saturated liquid densities and vapor pressures. A simple empirical correlation is derived for the SAFT-VR parameters of the n -alkylamine series as a function of molecular weight. Aqueous mixtures of the amines are modeled using a model of water taken from previous work. The models developed for the mixtures are of high fidelity and can be used to calculate the binary fluid phase equilibrium of these systems to within 2.28% in relative terms for the temperature or pressure and 0.027 in absolute terms for the mole fraction. Regions of both vapor-liquid and liquid-liquid equilibria are considered. We also consider the reactive mixtures of amines and CO(2) in aqueous solution. To model the reaction of CO(2) with the amine, an additional site is included on the otherwise nonassociating CO(2) model. The unlike interaction parameters for the NH(3) + H(2)O + CO(2) ternary mixture are obtained by comparison to the

  10. Four motional invariants in axisymmetric tori equilibria

    SciTech Connect

    A ring gren, O.; Moiseenko, V.E.

    2006-05-15

    In addition to the standard set ({epsilon},{mu},p{sub {phi}}) of three invariants in axisymmetric tori, there exists a fourth independent radial drift invariant I{sub r}. For confined particles, the net radial drift has to be zero, whereby the drift orbit average I{sub r}= of the gyro center radial Clebsch coordinate is constant. To lowest order in the banana width, the radial invariant is the gyro center radial coordinate r{sub 0}(x,v), and to this order the gyro center moves on a magnetic flux surface. The gyro center orbit projected on the (r,z) plane determines the radial invariant and first order banana width corrections to I{sub r} are calculated. The radial drift invariant exists for trapped as well as passing particles. The new invariant is applied to construct Vlasov equilibria, where the magnetic field satisfies a generalized Grad-Shafranov equation with a poloidal plasma current and a bridge to ideal magnetohydrodynamic equilibria is found. For equilibria with sufficiently small banana widths and radial drift excursions, the approximation I{sub r}{approx_equal}r{sub 0}(x,v) can be used for the equilibrium state.

  11. Phase diagram of two interacting helical states

    NASA Astrophysics Data System (ADS)

    Santos, Raul A.; Gutman, D. B.; Carr, Sam T.

    2016-06-01

    We consider two coupled time-reversal-invariant helical edge modes of the same helicity, such as would occur on two stacked quantum spin Hall insulators. In the presence of interaction, the low-energy physics is described by two collective modes, one corresponding to the total current flowing around the edge and the other one describing relative fluctuations between the two edges. We find that quite generically, the relative mode becomes gapped at low temperatures, but only when tunneling between the two helical modes is nonzero. There are two distinct possibilities for the gapped state depending on the relative size of different interactions. If the intraedge interaction is stronger than the interedge interaction, the state is characterized as a spin-nematic phase. However, in the opposite limit, when the interaction between the helical edge modes is strong compared to the interaction within each mode, a spin-density wave forms, with emergent topological properties. First, the gap protects the conducting phase against localization by weak nonmagnetic impurities; second, the protected phase hosts localized zero modes on the ends of the edge that may be created by sufficiently strong nonmagnetic impurities.

  12. Code System to Model Aqueous Geochemical Equilibria.

    SciTech Connect

    PETERSON, S. R.

    2001-08-23

    Version: 00 MINTEQ is a geochemical program to model aqueous solutions and the interactions of aqueous solutions with hypothesized assemblages of solid phases. It was developed for the Environmental Protection Agency to perform the calculations necessary to simulate the contact of waste solutions with heterogeneous sediments or the interaction of ground water with solidified wastes. MINTEQ can calculate ion speciation/solubility, adsorption, oxidation-reduction, gas phase equilibria, and precipitation/dissolution ofsolid phases. MINTEQ can accept a finite mass for any solid considered for dissolution and will dissolve the specified solid phase only until its initial mass is exhausted. This ability enables MINTEQ to model flow-through systems. In these systems the masses of solid phases that precipitate at earlier pore volumes can be dissolved at later pore volumes according to thermodynamic constraints imposed by the solution composition and solid phases present. The ability to model these systems permits evaluation of the geochemistry of dissolved traced metals, such as low-level waste in shallow land burial sites. MINTEQ was designed to solve geochemical equilibria for systems composed of one kilogram of water, various amounts of material dissolved in solution, and any solid materials that are present. Systems modeled using MINTEQ can exchange energy and material (open systems) or just energy (closed systems) with the surrounding environment. Each system is composed of a number of phases. Every phase is a region with distinct composition and physically definable boundaries. All of the material in the aqueous solution forms one phase. The gas phase is composed of any gaseous material present, and each compositionally and structurally distinct solid forms a separate phase.

  13. A Locust Phase Change Model with Multiple Switching States and Random Perturbation

    NASA Astrophysics Data System (ADS)

    Xiang, Changcheng; Tang, Sanyi; Cheke, Robert A.; Qin, Wenjie

    2016-12-01

    Insects such as locusts and some moths can transform from a solitarious phase when they remain in loose populations and a gregarious phase, when they may swarm. Therefore, the key to effective management of outbreaks of species such as the desert locust Schistocercagregaria is early detection of when they are in the threshold state between the two phases, followed by timely control of their hopper stages before they fledge because the control of flying adult swarms is costly and often ineffective. Definitions of gregarization thresholds should assist preventive control measures and avoid treatment of areas that might not lead to gregarization. In order to better understand the effects of the threshold density which represents the gregarization threshold on the outbreak of a locust population, we developed a model of a discrete switching system. The proposed model allows us to address: (1) How frequently switching occurs from solitarious to gregarious phases and vice versa; (2) When do stable switching transients occur, the existence of which indicate that solutions with larger amplitudes can switch to a stable attractor with a value less than the switching threshold density?; and (3) How does random perturbation influence the switching pattern? Our results show that both subsystems have refuge equilibrium points, outbreak equilibrium points and bistable equilibria. Further, the outbreak equilibrium points and bistable equilibria can coexist for a wide range of parameters and can switch from one to another. This type of switching is sensitive to the intrinsic growth rate and the initial values of the locust population, and may result in locust population outbreaks and phase switching once a small perturbation occurs. Moreover, the simulation results indicate that the switching transient patterns become identical after some generations, suggesting that the evolving process of the perturbation system is not related to the initial value after some fixed number of

  14. Solid-state phase diagram of the zinc sulfide-cadmium sulfide system

    SciTech Connect

    Fedorov, V.A.; Ganshin, V.A.; Korkishko, Y.N. )

    1993-01-01

    The II-VI wide-band compounds zinc sulfide, cadmium sulfide and Cd[sub x]ZN[sub 1[minus]x]S ternary alloys has been of considerable technological interest due to their semiconducting, optical and mechanical properties and are of considerable importance as photoconductors, phosphors, infrared and solar-cell window materials and materials for short-wavelength optoelectronic applications. Structures and phase relation in the ZnS-CdS system were investigated in the temperature range 150-700 C and the boundaries describing the equilibria between the zinc-blend and wurtzite Cd[sub x]An[sub 1[minus]x]S solid solutions were determined by examining the ion exchange processes Cd[sup 2+] [r arrow] Zn[sup 2+] in the ZnS powder. The complete thermodynamical description of the ZnS-CdS system is proposed. It was found, that Cd[sub x]Z[sub n[minus]1]S solid solutions of both modifications obey a regular solution model. Enthalpies of the zinc-blend-to-wurtzite structural phase transition in CdS (550[plus minus]50 J/mol) and in ZnS (1700[plus minus]100 J/mol) were defined. The solid state phase diagram calculated from defined thermodynamical parameters agrees well with the experimental data.

  15. Equilibria bearing on the behavior of titanate phases during crystallization of iron silicate melts under strongly reducing conditions. [in lunar rocks

    NASA Technical Reports Server (NTRS)

    Lipin, B. R.; Muan, A.

    1974-01-01

    Titanate phase relations at liquidus temperatures are determined for the CaAl2Si2O8-Fe2TiO4-FeTi2O5 system in contact with metallic iron by reflected- and transmitted-light microscopy, electron microprobe, and X-ray diffraction analyses. Results of critical equilibration runs are presented, various primary phase areas and liquidus isotherms are illustrated, and the geometry of the system is described. Three piercing points are determined, and it is noted that the compositional interrelations among coexisting crystalline and liquid phases as well as the sequence of the various titanate phases are indicative of the significant effects of the various cations on the relative stability of these phases. It is found that Al2O3 exerts a strong stabilizing effect on the phase assemblage of ulvospinel plus ferropseudobrookite relative to ilemite.

  16. Phase Equilibria of ``Cu2O''-``FeO''-CaO-MgO-Al2O3 Slags at PO2 of 10-8.5 atm in Equilibrium with Metallic Copper for a Copper Slag Cleaning Production

    NASA Astrophysics Data System (ADS)

    Henao, Hector M.; Pizarro, Claudio; Font, Jonkion; Moyano, Alex; Hayes, Peter C.; Jak, Evgueni

    2010-12-01

    Limited data are available on phase equilibria of the multicomponent slag system at the oxygen partial pressures used in the copper smelting, converting, and slag-cleaning processes. Recently, experimental procedures have been developed and have been applied successfully to characterize several complex industrial slags. The experimental procedures involve high-temperature equilibration on a substrate and quenching followed by electron probe X-ray microanalysis. This technique has been used to construct the liquidus for the “Cu2O”-“FeO”-SiO2-based slags with 2 wt pct of CaO, 0.5 wt pct of MgO, and 4.0 wt pct of Al2O3 at controlled oxygen partial pressures in equilibrium with metallic copper. The selected ranges of compositions and temperatures are directly relevant to the copper slag-cleaning processes. The new experimental equilibrium results are presented in the form of ternary sections and as a liquidus temperature vs Fe/SiO2 weight ratio diagram. The experimental results are compared with the FactSage thermodynamic model calculations.

  17. Stabilizer codes and equientangled bases from phase states

    NASA Astrophysics Data System (ADS)

    Mansour, Mostafa; Daoud, Mohammed

    2017-08-01

    We develop a comprehensive approach of stabilizer codes and provide a scheme generating equientangled basis interpolating between the product basis and maximally entangled basis. The key ingredient is the theory of phase states for finite-dimensional systems (qudits). In this respect, we derive entangled phase states for a multiqudit system whose dynamics is governed by a two-qudit interaction Hamiltonian. We construct the stabilizer codes for this family of entangled phase states. The stabilizer phase states are defined as the common eigenvectors of the stabilizer group generators which are explicitly specified. Furthermore, we construct equally entangled bases from bipartite as well as multipartite entangled qudit phase states.

  18. Two- and three-phase equilibria of polydisperse Yukawa hard-sphere fluids confined in random porous media: high temperature approximation and scaled particle theory.

    PubMed

    Hvozd, Taras V; Kalyuzhnyi, Yurij V

    2017-02-15

    We have studied the phase behavior of polydisperse Yukawa hard-sphere fluid confined in random porous media using extension and combination of high temperature approximation and scaled particle theory. The porous media are represented by the matrix of randomly placed hard-sphere obstacles. Due to the confinement, polydispersity effects are substantially enhanced. At an intermediate degree of fluid polydispersity and low density of the matrix, we observe two-phase coexistence with two critical points, and cloud and shadow curves forming closed loops of ellipsoidal shape. With the increase of the matrix density and the constant degree of polydispersity, these two critical points merge and disappear, and at lower temperatures the system fractionates into three coexisting phases. A similar phase behavior was observed in the absence of the porous media caused, however, by the increase of the polydispersity.

  19. Sulfate Mineral Phase Equilibria as a Function of Relative Humidity. Intermediate Compositions in the (Mg,Fe,Cu)SO4-H2O System at 1 atm

    NASA Astrophysics Data System (ADS)

    Anderson, J. L.; Peterson, R. C.

    2007-07-01

    Careful characterization of minerals present at the martian surface requires a detailed understanding of hydrous sulfate phase relationships. This study explores the effect of metal substitution on the hydration behaviour of hydrous metal sulfates.

  20. In situ high temperature X-Ray diffraction study of the phase equilibria in the UO2-PuO2-Pu2O3 system

    NASA Astrophysics Data System (ADS)

    Belin, Renaud C.; Strach, Michal; Truphémus, Thibaut; Guéneau, Christine; Richaud, Jean-Christophe; Rogez, Jacques

    2015-10-01

    The region of the U-Pu-O phase diagram delimited by the compounds UO2-PuO2-Pu2O3 is known to exhibit a miscibility gap at low temperature. Consequently, MOX fuels with a composition entering this region could decompose into two fluorite phases and thus exhibit chemical heterogeneities. The experimental data on this domain found in the literature are scarce and usually provided using DTA that is not suitable for the investigation of such decomposition phenomena. In the present work, new experimental data, i.e. crystallographic phases, lattice parameters, phase fractions and temperature of phase separation, were measured in the composition range 0.14 < Pu/(U + Pu) < 0.62 and 1.85 < O/(U + Pu) < 2 from 298 to 1750 K using a novel in situ high temperature X-ray diffraction apparatus. A very good agreement is found between the temperature of phase separation determined from our results and using the thermodynamic model of the U-Pu-O system based on the CALPHAD method. Also, the combined use of thermodynamic calculations and XRD results refinement proved helpful in the determination of the O/M ratio of the samples during cooling. The methodology used in the current work might be useful to investigate other oxides systems exhibiting a miscibility gap.

  1. Berry's phase for coherent states of Landau levels

    SciTech Connect

    Yang, Wen-Long; Chen, Jing-Ling

    2007-02-15

    The Berry phases for coherent states and squeezed coherent states of Landau levels are calculated. Coherent states of Landau levels are interpreted as a result of a magnetic flux moved adiabatically from infinity to a finite place on the plane. The Abelian Berry phase for coherent states of Landau levels is an analog of the Aharonov-Bohm effect. Moreover, the non-Abelian Berry phase is calculated for the adiabatic evolution of the magnetic field B.

  2. Study of improved methods for predicting chemical equilibria. Final technical report, April 1, 1993--August 31, 1997

    SciTech Connect

    Lenz, T.G.; Vaughan, J.D.

    1997-10-01

    A long-standing goal of chemical engineers and chemists has been the development of techniques for accurate prediction of the thermodynamic properties of isolated molecules. The thermochemical functions for an ideal gas then provide a means of computing chemical equilibria, and such computations can be extended to condensed phase chemical equilibria with appropriate physical property data. Such capability for predicting diverse chemical equilibria is important in today`s competitive international economic environment, where bringing new products to market rapidly and efficiently is crucial. The purpose of this project has been to develop such computational methods for predicting chemical equilibria.

  3. Experimental Investigation and Thermodynamic Assessment of Phase Equilibria in the PLLA/Dioxane/Water Ternary System for Applications in the Biomedical Field.

    PubMed

    Ruggiero, Flavia; Netti, Paolo Antonio; Torino, Enza

    2015-12-01

    Fundamental understanding of thermodynamic of phase separation plays a key role in tuning the desired features of biomedical devices. In particular, phase separation of ternary solution is of remarkable interest in processes to obtain biodegradable and biocompatible architectures applied as artificial devices to repair, replace, or support damaged tissues or organs. In these perspectives, thermally induced phase separation (TIPS) is the most widely used technique to obtained porous morphologies and, in addition, among different ternary systems, polylactic acid (PLLA)/dioxane/water has given promising results and has been largely studied. However, to increase the control of TIPS-based processes and architectures, an investigation of the basic energetic phenomena occurring during phase separation is still required. Here we propose an experimental investigation of the selected ternary system by using isothermal titration calorimetric approach at different solvent/antisolvent ratio and a thermodynamic explanation related to the polymer-solvents interactions in terms of energetic contribution to the phase separation process. Furthermore, relevant information about the phase diagrams and interaction parameters of the studied systems are furnished in terms of liquid-liquid miscibility gap. Indeed, polymer-solvents interactions are responsible for the mechanism of the phase separation process and, therefore, of the final features of the morphologies; the knowledge of such data is fundamental to control processes for the production of membranes, scaffolds and several nanostructures. The behavior of the polymer at different solvent/nonsolvent ratios is discussed in terms of solvation mechanism and a preliminary contribution to the understanding of the role of the hydrogen bonding in the interface phenomena is also reported. It is the first time that thermodynamic data of a ternary system are collected by mean of nano-isothermal titration calorimetry (nano-ITC). Supporting

  4. Three-phase solid-liquid-vapor equilibria in the binary hydrocarbon systems methane-n-hexane and methane-benzene

    SciTech Connect

    Luks, K.; Hottovy, J.D.; Kohn, J.P.

    1981-10-01

    Pressure, temperature, liquid-phase compositions, and liquid-phase molar volumes are presented along the solid-liquid-vapor (SLV) loci of the binary systems methane-n-hexane and methane-benzene. The data were taken by using cryoscopic techniques and are compared to the solid-liquid (SL) data at elevated pressures of Kuebler and McKinley. The standard deviations of the smoothed SLV data for liquid-phase solute composition presented herein from the raw SLV data are 3.7% for the methane-n-hexane system and 8.6% for the low-temperature branch of the methane-benzene system. The corresponding standard deviation for the high-temperature (high solute composition) branch for the system methane-benzene is less than 0.7%. 8 refs.

  5. Correct Representation of Conformational Equilibria.

    ERIC Educational Resources Information Center

    Fulop, F.; And Others

    1983-01-01

    In representing conformational equilibria of compounds having only one chiral center, erroneous formulas showing different antipodes on the two sides of the equilibrium are rare. In contrast, with compounds having two or more chiral centers especially with saturated heterocycles, this erroneous representation occurs frequently in the chemical…

  6. Equations of State and Phase Diagrams of Ammonia

    ERIC Educational Resources Information Center

    Glasser, Leslie

    2009-01-01

    We present equations of state relating the phases and a three-dimensional phase diagram for ammonia with its solid, liquid, and vapor phases, based on fitted authentic experimental data and including recent information on the high-pressure solid phases. This presentation follows similar articles on carbon dioxide and water published in this…

  7. Equations of State and Phase Diagrams of Ammonia

    ERIC Educational Resources Information Center

    Glasser, Leslie

    2009-01-01

    We present equations of state relating the phases and a three-dimensional phase diagram for ammonia with its solid, liquid, and vapor phases, based on fitted authentic experimental data and including recent information on the high-pressure solid phases. This presentation follows similar articles on carbon dioxide and water published in this…

  8. Symmetric Topological Phases and Tensor Network States

    NASA Astrophysics Data System (ADS)

    Jiang, Shenghan

    Classification and simulation of quantum phases are one of main themes in condensed matter physics. Quantum phases can be distinguished by their symmetrical and topological properties. The interplay between symmetry and topology in condensed matter physics often leads to exotic quantum phases and rich phase diagrams. Famous examples include quantum Hall phases, spin liquids and topological insulators. In this thesis, I present our works toward a more systematically understanding of symmetric topological quantum phases in bosonic systems. In the absence of global symmetries, gapped quantum phases are characterized by topological orders. Topological orders in 2+1D are well studied, while a systematically understanding of topological orders in 3+1D is still lacking. By studying a family of exact solvable models, we find at least some topological orders in 3+1D can be distinguished by braiding phases of loop excitations. In the presence of both global symmetries and topological orders, the interplay between them leads to new phases termed as symmetry enriched topological (SET) phases. We develop a framework to classify a large class of SET phases using tensor networks. For each tensor class, we can write down generic variational wavefunctions. We apply our method to study gapped spin liquids on the kagome lattice, which can be viewed as SET phases of on-site symmetries as well as lattice symmetries. In the absence of topological order, symmetry could protect different topological phases, which are often referred to as symmetry protected topological (SPT) phases. We present systematic constructions of tensor network wavefunctions for bosonic symmetry protected topological (SPT) phases respecting both onsite and spatial symmetries.

  9. Silicate and Carbonatite Melts in the Mantle: Adding CO2 to the pMELTS Thermodynamic Model of Silicate Phase Equilibria

    NASA Astrophysics Data System (ADS)

    Antoshechkina, P. M.; Shorttle, O.

    2016-12-01

    The current rhyolite-MELTS algorithm includes a mixed H2O-CO2 vapor phase, and a self-consistent speciation model for CO2 and CaCO3 in the silicate liquid (Ghiorso & Gualda 2012; 2015). Although intended primarily to model crustal differentiation and degassing, GG15 captures much of the experimentally-observed melting behavior of CO2-rich mafic lithologies, including generation of small-degree carbonatite melts, a miscibility gap between carbonatite and silicate liquids at low P and a smooth transition to a single carbonated-silicate melt at high P (e.g. Dasgupta et al. 2007). However, solid and liquid carbonate phases were not used in calibration of GG15, and it is suitable only for P < 3 GPa. We present a preliminary model, based on pMELTS (Ghiorso et al. 2002), for melting of nominally-anhydrous carbonated peridotite and pyroxenite. In Antoshechkina et al. (2015; and references therein) we developed a scheme for calibration of molar volumes that directly interfaces with a MySQL database, adapted from LEPR (Hirschmann et al. 2008). Here, we further extend our database, e.g. to include multiple carbonate phases, and combine the calibration scheme with the libalphaMELTS interface to the rhyolite-MELTS, pMELTS, and H2O-CO2 fluid thermodynamic models (see magmasource.caltech.edu/alphamelts). We use a Monte-Carlo type calibration approach to fit the observed phases and compositions, though stop short of a fully Bayesian formulation. The CO2-fluid experimental database has been updated to include more recent and higher P studies, adding approximately 40 pure fluid plus liquid constraints that conform to the selection criteria used in GG15. To further expand the database, we plan to use some or all of: solid carbonate-bearing experiments; coexisting silicate and carbonatite liquids; phase-present, and phase-absent constraints. As a first approximation, we include four carbonate phases: pure calcite and aragonite, and binary solutions for dolomite-ankerite and magnesite

  10. Thermodynamic studies of pyrrhotite pyrite equilibria in the Ag Fe S system by solid-state galvanic cell technique at 518 723 K and total pressure of 1 atm

    NASA Astrophysics Data System (ADS)

    Osadchii, Evgeniy G.; Chareev, Dmitriy A.

    2006-11-01

    The reaction FeS 2(cr) + 2Ag(cr) = 'FeS'(cr) + Ag 2S(cr) was studied by measuring the temperature dependence of the electromotive force (EMF) of the all-solid-state galvanic cell with common gas space: (-)Pt|Ag|AgI|AgS,'FeS',FeS|Pt(+) The measurements were carried out in the flow of argon at atmospheric pressure to prevent oxidation. AgI was used as a solid electrolyte. From the measurements of EMF as a function of temperature, two linear (Δ rCp = 0) trends were obtained, which characterize the equilibrium hexagonal pyrrhotite + pyrite (po + py) and the β-γ first-order phase transition in hexagonal pyrrhotite (Δ trsHm(γ-β) = (4020 ± 200) J mol -1) at (601 ± 2) K. The latter is presumably related to the γ-paramagnetic-β-antiferromagnetic Neel's transition. For these measurements, the lower temperature limit (518 K) corresponds to the equilibrium sulfides + metallic silver ( E = 0); and the upper temperature limit (723 K) is determined by the upper temperature at which the contribution of electron conductivity to AgI ion conductive properties may be significant. From experimental results of this study and literature data for Ag 2S, the temperature dependence of the gaseous sulfur activity was determined in the following equilibria: pyrite + high-temperature hexagonal pyrrhotite (γ + py), pyrite + low-temperature pyrrhotite (β + py): logaS(γ+py)=(15.64±0.035)-(15455±23)·T-1,(601

  11. Spontaneous decay of periodic magnetostatic equilibria

    DOE PAGES

    East, William E.; Zrake, Jonathan; Yuan, Yajie; ...

    2015-08-28

    In order to understand the conditions which lead a highly magnetized, relativistic plasma to become unstable, and in such cases how the plasma evolves, we study a prototypical class of magnetostatic equilibria where the magnetic field satisfies ∇ x B = αB , where \\alpha is spatially uniform, on a periodic domain. Using numerical solutions we show that generic examples of such equilibria are unstable to ideal modes (including incompressible ones) which are marked by exponential growth in the linear phase. We characterize the unstable mode, showing how it can be understood in terms of merging magnetic and current structures,more » and explicitly demonstrate its instability using the energy principle. Following the nonlinear evolution of these solutions, we find that they rapidly develop regions with relativistic velocities and electric fields of comparable magnitude to the magnetic field, liberating magnetic energy on dynamical timescales and eventually settling into a configuration with the largest allowable wavelength. Furthermore, these properties make such solutions a promising setting for exploring the mechanisms behind extreme cosmic sources of gamma rays.« less

  12. Spontaneous decay of periodic magnetostatic equilibria

    SciTech Connect

    East, William E.; Zrake, Jonathan; Yuan, Yajie; Blandford, Roger D.

    2015-08-28

    In order to understand the conditions which lead a highly magnetized, relativistic plasma to become unstable, and in such cases how the plasma evolves, we study a prototypical class of magnetostatic equilibria where the magnetic field satisfies ∇ x B = αB , where \\alpha is spatially uniform, on a periodic domain. Using numerical solutions we show that generic examples of such equilibria are unstable to ideal modes (including incompressible ones) which are marked by exponential growth in the linear phase. We characterize the unstable mode, showing how it can be understood in terms of merging magnetic and current structures, and explicitly demonstrate its instability using the energy principle. Following the nonlinear evolution of these solutions, we find that they rapidly develop regions with relativistic velocities and electric fields of comparable magnitude to the magnetic field, liberating magnetic energy on dynamical timescales and eventually settling into a configuration with the largest allowable wavelength. Furthermore, these properties make such solutions a promising setting for exploring the mechanisms behind extreme cosmic sources of gamma rays.

  13. Investigation of the phase equilibria and phase transformations associated with the Bi2Sr2CaCu2Oy superconductor

    SciTech Connect

    Holesinger, Terry

    1993-12-09

    The solid solution region and reaction kinetics of the Bi2Sr2CaCu2Oy (2212) superconductor were examined as a function of temperature and oxygen partial pressure. Crystallization studies from the glassy and molten states were undertaken to determine the phase transformation and kinetics associated with the formation of 2212 and other competing phases. Crystallization of nominal 2212 glasses was found to proceed in two steps with the formation of Bi2Sr2-xCaxCuOy (2201) and Cu2O followed by Bi2Sr3-xCaxOy, CaO, and SrO. The 2212 phase converts from the 2201 phase with increasing temperatures. However, its formation below 800 C was kinetically limited. At 800 C and above, a nearly full conversion to the 2212 phase was achieved after only one minute although considerably longer anneal times were necessary for the system to reach equilibrium. In low oxygen partial pressures, the solidus is reduced to approximately 750 C. Solidification studies revealed an eutectic structure separating the incongruently melting 2212/2201 phases at high oxygen partial pressures from the congruently melting Bi2Sr3-xCaxOy (23x) and Bi2Sr2-xCaxOy (22x) phases present at low oxygen partial pressures. During solidification in various oxygen partial pressures, the separation of CaO in the melt and the initial crystallization of alkaline-earth cuprates leaves behind a Bi-rich liquid from which it is impossible to form single-phase 2212. Hence, significant amounts of 2201 were also present in these samples. These problems could be reduced by melt processing in inert atmospheres. Bulk 2212 material produced in this manner was found to possess high transition temperatures, high intergranular critical current densities below 20K, and modest critical current densities at 77K.

  14. Thermodynamic modeling of the phase behavior of binary systems of ionic liquids and carbon dioxide with the group contribution equation of state.

    PubMed

    Breure, Bianca; Bottini, Susana B; Witkamp, Geert-Jan; Peters, Cor J

    2007-12-27

    The group contribution equation of state (GC-EOS) was applied to predict the phase behavior of binary systems of ionic liquids of the homologous families 1-alkyl-3-methylimidazolium hexafluorophosphate and tetrafluoroborate with CO2. Pure group parameters for the new ionic liquid functional groups [-mim][PF6] and [-mim][BF4] and interaction parameters between these groups and the paraffin (CH3, CH2) and CO2 groups were estimated. The GC-EOS extended with the new parameters was applied to predict high-pressure phase equilibria in binary mixtures of the ionic liquids [emim][PF6], [bmim][PF6], [hmim][PF6], [bmim][BF4], [hmim][BF4], and [omim][BF4] with CO2. The agreement between experimental and predicted bubble point data for the ionic liquids was excellent for pressures up to 20 MPa, and even for pressures up to about 100 MPa, the agreement was good. The results show the capability of the GC-EOS to describe phase equilibria of systems consisting of ionic liquids.

  15. Review of the phase equilibria and thermodynamics of binary and ternary systems composed of IFR fuel component metals (U, Pu, and Zr) and nitrogen

    SciTech Connect

    Leibowitz, L.; Veleckis, E.; Blomquist, R. A.

    1987-09-01

    Studies of the interactions of IFR fuel alloys with stainless steel cladding materials have shown evidence for segregation of metallic alloy components at the fuel-cladding interface. The phenomenon seems to be related to the availability of nitrogen and other reactive elements. For the interpretation of surface segregation results it will be necessary to establish (1) the composition of the phases formed in the ternary alloys under the action of nitrogen, (2) diffusion characteristics of various components in these phases and those of nitrogen itself, and (3) activity gradients established in the component metals providing driving forces for material migration. In this technical memorandum we present a literature survey and evaluation of the binary and ternary systems formed among uranium, plutonium, zirconium, and nitrogen. Both the phase diagram data and available thermodynamics are included. The following systems were surveyed: U-N, Pu-N, Zr-N, U-Pu, U-Zr, Pu-Zr, U-Pu-Zr, U-Pu-N, U-Zr-N, and Pu-Zr-N.

  16. Beltrami–Bernoulli equilibria in plasmas with degenerate electrons

    SciTech Connect

    Berezhiani, V. I.; Shatashvili, N. L.; Mahajan, S. M.

    2015-02-15

    A new class of Double Beltrami–Bernoulli equilibria, sustained by electron degeneracy pressure, is investigated. It is shown that due to electron degeneracy, a nontrivial Beltrami–Bernoulli equilibrium state is possible even for a zero temperature plasma. These states are, conceptually, studied to show the existence of new energy transformation pathways converting, for instance, the degeneracy energy into fluid kinetic energy. Such states may be of relevance to compact astrophysical objects like white dwarfs, neutron stars, etc.

  17. A Multistep Equilibria-Redox-Complexation Demonstration to Illustrate Le Chatelier's Principle.

    ERIC Educational Resources Information Center

    Berger, Tomas G.; Mellon, Edward K.

    1996-01-01

    Describes a process that can be used to illustrate a number of chemical principles including Le Chatelier's principle, redox chemistry, equilibria versus steady state situations, and solubility of species. (JRH)

  18. EQUILGAS: Program to estimate temperatures and in situ two-phase conditions in geothermal reservoirs using three combined FT-HSH gas equilibria models

    NASA Astrophysics Data System (ADS)

    Barragán, Rosa María; Núñez, José; Arellano, Víctor Manuel; Nieva, David

    2016-03-01

    Exploration and exploitation of geothermal resources require the estimation of important physical characteristics of reservoirs including temperatures, pressures and in situ two-phase conditions, in order to evaluate possible uses and/or investigate changes due to exploitation. As at relatively high temperatures (>150 °C) reservoir fluids usually attain chemical equilibrium in contact with hot rocks, different models based on the chemistry of fluids have been developed that allow deep conditions to be estimated. Currently either in water-dominated or steam-dominated reservoirs the chemistry of steam has been useful for working out reservoir conditions. In this context, three methods based on the Fischer-Tropsch (FT) and combined H2S-H2 (HSH) mineral-gas reactions have been developed for estimating temperatures and the quality of the in situ two-phase mixture prevailing in the reservoir. For these methods the mineral buffers considered to be controlling H2S-H2 composition of fluids are as follows. The pyrite-magnetite buffer (FT-HSH1); the pyrite-hematite buffer (FT-HSH2) and the pyrite-pyrrhotite buffer (FT-HSH3). Currently from such models the estimations of both, temperature and steam fraction in the two-phase fluid are obtained graphically by using a blank diagram with a background theoretical solution as reference. Thus large errors are involved since the isotherms are highly nonlinear functions while reservoir steam fractions are taken from a logarithmic scale. In order to facilitate the use of the three FT-HSH methods and minimize visual interpolation errors, the EQUILGAS program that numerically solves the equations of the FT-HSH methods was developed. In this work the FT-HSH methods and the EQUILGAS program are described. Illustrative examples for Mexican fields are also given in order to help the users in deciding which method could be more suitable for every specific data set.

  19. Pyrochlore-rich titanate ceramics for the immobilization of plutonium: redox effects on phase equilibria in cerium- and thorium- substituted analogs

    SciTech Connect

    Ryerson, F J; Ebbinghaus, B

    2000-05-25

    Three compositions representing plutonium-free analogs of a proposed Ca-Ti-Gd-Hf-U-PU oxide ceramic for the immobilization of plutonium were equilibrated at 1 atm, 1350 C over a range of oxygen fugacities between air and that equivalent to the iron-wuestite buffer. The cerium analog replaces Pu on a mole-per-mole basic with Ce; the thorium analog replaces Pu with Th. A third material has 10 wt% Al{sub 2}O{sub 3} added to the cerium analog to encourage the formation of a Hf-analog of, CaHfTi{sub 2}O{sub 7}, zirconolite, which is referred to as hafnolite. The predominant phase produced in each formulation under all conditions is pyrochlore, A{sub 2}T{sub 2}O{sub 7}, where the T site is filled by Ti, and Ca, the lanthanides, Hf, U and Pu are accommodated on the A-site. Other lanthanide and uranium-bearing phases encountered include brannerite (UTi{sub 2}O{sub 6}), hafnolite (CaHfTi{sub 2}O{sub 7}), perovskite (CaTiO{sub 3}) and a calcium-lanthanide aluminotitanate with nominal stoichiometry (Ca,Ln)Ti{sub 2}Al{sub 9}O{sub 19}, where Ln is a lanthanide. The phase compositions show progressive shifts with decreasing oxygen fugacity. All of the phases observed have previously been identified in titanate-based high-level radioactive waste ceramics and demonstrate the flexibility of these ceramics to variations in processing parameters. The main variation is an increase in the uranium concentrations of pyrochlore and brannerite which must be accommodated by variations in modal abundance. Pyrochlore compositions are consistent with existing spectroscopic data suggesting that uranium is predominantly pentavalent in samples synthesized in air. A simple model based on ideal stoichiometry suggests the U{sup +4}/{Sigma}U varies linearly with log fO{sub 2} and that all of the uranium is quadravalent at the iron-wuestite buffer.

  20. Fluorite solubility equilibria in selected geothermal waters

    USGS Publications Warehouse

    Nordstrom, D.K.; Jenne, E.A.

    1977-01-01

    Calculation of chemical equilibria in 351 hot springs and surface waters from selected geothermal areas in the western United States indicate that the solubility of the mineral fluorite, CaF2, provides an equilibrium control on dissolved fluoride activity. Waters that are undersaturated have undergone dilution by non-thermal waters as shown by decreased conductivity and temperature values, and only 2% of the samples are supersaturated by more than the expected error. Calculations also demonstrate that simultaneous chemical equilibria between the thermal waters and calcite as well as fluorite minerals exist under a variety of conditions. Testing for fluorite solubility required a critical review of the thermodynamic data for fluorite. By applying multiple regression of a mathematical model to selected published data we have obtained revised estimates of the pK (10,96), ??Gof (-280.08 kcal/mole), ??Hof (-292.59 kcal/mole), S?? (16.39 cal/deg/mole) and CoP (16.16 cal/deg/mole) for CaF2 at 25??C and 1 atm. Association constants and reaction enthalpies for fluoride complexes with boron, calcium and iron are included in this review. The excellent agreement between the computer-based activity products and the revised pK suggests that the chemistry of geothermal waters may also be a guide to evaluating mineral solubility data where major discrepancies are evident. ?? 1977.

  1. The clathrate Ba{sub 8}Cu{sub x}Ge{sub 46-x-y}square{sub y}: Phase equilibria and crystal structure

    SciTech Connect

    Melnychenko-Koblyuk, Nataliya; Grytsiv, Andriy; Rogl, Peter; Schmid, Harald; Giester, Gerald

    2009-07-15

    Phase relations at 700 deg. C, 800 deg. C and solidus temperatures have been derived for the clathrate system Ba{sub 8}Cu{sub x}Ge{sub 46-x-y}square{sub y} via X-ray single crystal and powder diffractometry combined with electron probe micro analysis and differential thermal analysis. The ternary clathrate phase derives from binary Ba{sub 8}Ge{sub 43}square{sub 3} and extends up to x=6. Structure investigations define cubic primitive symmetry with the space group type Pm3-barn consistent with a clathrate type I structure throughout the entire homogeneity region 0=5.5. - Graphical Abstract: Cages and atom thermal displacement parameters in clathrate Ba{sub 8}Cu{sub x}Ge{sub 46-x-y}square{sub y} for Ba{sub 8}Cu{sub 2}Ge{sub 42}square{sub 2} and Ba{sub 8}Cu{sub 6}Ge{sub 40}.

  2. Recent Hydrothermal Fluid Chemistry from EPR 13°N: Phase Equilibria Constraints with Applicability to the Integrated Study of Basalt-Hosted Hydrothermal Systems

    NASA Astrophysics Data System (ADS)

    Pester, N. J.; Ding, K.; Seyfried, W. E.

    2009-12-01

    Fluid sampling and in-situ chemical sensor deployments were conducted at 13°N hydrothermal field (depth = 2600 m) on the East Pacific Rise (EPR) in January, 2008. Maximum recorded vent exit temperatures were 350°C. End-member dissolved Cl concentrations range from 339 to 646 mmol/kg. Data collected by other investigators in 1982 and 1984 suggest a single Cl enriched (740-900 mmol/kg) fluid source. This differs greatly from the current data, where both Cl depleted and enriched fluids are simultaneously venting no more than 370 meters apart. Such (inferred) phase separation processes suggest an active magmatic heat source is influencing recent hydrothermal activity at 13°N. This is in good agreement with combined tomographic imaging and multichannel seismic data that show an axial magma chamber ~1.5 km below the vent field. The two highest temperature vents (both ~350°C), Grand Bonum (Cl = 646 mmol/kg) and Dorian (Cl = 462 mmol/kg) yielded low-Mg (2.2 mmol/kg) samples and are of particular importance for interpreting subseafloor reaction processes. Dissolved CH4, H2 and H2S concentrations from Dorian are slightly elevated relative to Grand Bonum, which is consistent with inherent vapor-liquid partitioning associated with phase separation. However, CO2 concentrations from Grand Bonum are 3 times higher, which suggests these two fluids are not primary conjugates and the Grand Bonum fluids are more deeply sourced, tapping a higher proportion of magmatic gas. A recently calibrated Fe/Mn geothermometer, based on experimental basalt alteration data between 300-450°C, suggests the high and low salinity fluids last equilibrated at approximately 430 and 398°C, respectively. Although appreciably higher than the exit temperatures, in both cases, higher temperatures are possible given the temperature sensitivity and rapid re-equilibration of these two species, especially above 300°C. The relatively minor Cl deviations suggest phase separation at/near the two-phase

  3. Phase equilibria in the system Nd2O3- P2O5- H2O and growth of NdP5O14 single crystals under hydrothermal conditions

    NASA Astrophysics Data System (ADS)

    Yoshimura, Masahiro; Fujii, Kazutaka; Sōmiya, Shigeyuki

    1985-04-01

    Phase equilibria in the system Nd2O3- P2O5- H2O were determined under hydrothermal conditions at 500 and 350°C under 100 MPa by quenching techniques. There exist three types of neodymium phosphates: NdPO 4, NdP 3O 9 and NdP 5O 14, and a liquid phase of highly condensed phosphoric acid at both temperatures. The composition of the liquid phase with which NdP 5O 14 and NdP 3O 9 or NdP 3O 9 and NdPO 4 could coexist at 500°C was 3% Nd2O3-80% P2O5-17% H2O or 4% Nd2O3-74% P2O5 -22% H2O respectively, while that at 350°C changed to 2% Nd2O3-78% P2O5-20% H2O or 2% Nd2O3-75% P2O5-23% H2O respectively. These results indicate that the solubility curve of NdP 5O 14 had a positive slope against temperature, which allowed us to apply a temperature gradient method for the crystal growth of NdP 5O 14. Polyhedral crystals of 0.5 mm in maximum size were grown at the upper part of a gold capsule ( T⋍400°C) through the transportation due to Δ T=100°C after 10 days. These crystals had flat and smooth surfaces and contained less bubble-shaped inclusions than crystals synthesized under isothermal conditions. Crystals obtained at the lower part of the gold capsule ( T=500°C) were polyhedral 1 mm in maximum size. Growth experiments with Δ T=50°C yielded no crystals at the upper part in the capsule ( T⋍450°C), probably due to an insufficient transportation.

  4. The hydrous phase equilibria (to 3 kbar) of an andesite and basaltic andesite from western Mexico: constraints on water content and conditions of phenocryst growth

    NASA Astrophysics Data System (ADS)

    Moore, Gordon; Carmichael, I. S. E.

    We have conducted high pressure (to 3 kbar), water saturated melting experiments on an andesite (62 wt% SiO2) and a basaltic andesite (55 wt% SiO2) from western Mexico. A close comparison between the experimental phase assemblages and their compositions, and the phenocryst assemblages of the lavas, is found in water saturated liquids, suggesting that the CO2 content was minimal in the fluid phase. Thus the historic lavas from Volcan Colima (with phenocrysts of orthopyroxene, augite, plagioclase, and hornblende) were stored at a temperature between 950-975°C, at a pressure between 700-1500 bars, and with a water content of 3.0-5.0 wt%. A hornblende andesite (spessartite) from Mascota, of nearly identical composition but with only amphibole phenocrysts, had a similar temperature but equilibrated at a minimum of 2000 bars pressure with a dissolved water content of at least 5.5 wt% in the liquid. Experiments on the basaltic andesite show that the most common natural phenocryst assemblages (olivine, +/-augite, +/-plagioclase) could have precipitated at temperatures from 1000-1150°C, in liquids with a wide range of dissolved water content ( 2.0-6.0 wt%) and a corresponding pressure range. A lava of the same bulk composition with phenocrysts of hornblende, olivine, plagioclase, and augite is restricted to temperatures below 1000°C and pressures below 2500bars, corresponding to <5.5 wt% water in the residual liquid. Although there is some evidence for mixing in the andesites (sporadic olivine phenocrysts), the broad theme of the history of both lava types is that the phenocryst assemblages for both the andesitic magmas and basaltic andesitic magmas are generated from degassing and reequilibration on ascent of initially hydrous parents containing greater than 6 wt% water. Indeed andesitic magmas could be related to a basaltic andesite parent by hornblende-plagioclase fractionation under the same hydrous conditions.

  5. Phase equilibria and crystal chemistry of the CaO-½Sm2O3-CoOz system at 885 °C in air

    NASA Astrophysics Data System (ADS)

    Wong-Ng, W.; Laws, W.; Lapidus, S. H.; Kaduk, J. A.

    2015-10-01

    The CaO-½Sm2O3-CoOz system prepared at 885 °C in air consists of two calcium cobaltate compounds, namely, the 2D thermoelectric oxide solid solution, (Ca3-xSmx)Co4O9-z (0 ≤ x ≤ 0.5) which has a misfit layered structure, and the 1D Ca3Co2O6 which consists of chains of alternating CoO6 trigonal prisms and CoO6 octahedra. Ca3Co2O6 was found to be a point compound without the substitution of Sm on the Ca site. A solid solution region of distorted perovskite, (Sm1-xCax)CoO3-z (0 ≤ x ≤ 0.22, space group Pnma) was established. The reported Sm2CoO4 phase was not observed at 885 °C, but a ternary Ca-doped oxide, (Sm1+xCa1-x)CoO4-z (Bmab) where 0 < x ≤ 0.15 was found to be stable at this temperature. In the peripheral binary systems, Sm was not present in the Ca site of CaO, while a small solid solution region was identified for (Sm1-xCax)O(3-z)/2 (0 ≤ x ≤ 0.075). Ten solid solution tie-line regions and six three-phase regions were determined in the CaO-½Sm2O3-CoOz system in air.

  6. Phase equilibria and crystal chemistry of the CaO-½Gd2O3-CoOz system at 885 °C in air

    NASA Astrophysics Data System (ADS)

    Wong-Ng, W.; Laws, W.; Lapidus, S. H.; Ribaud, L.; Kaduk, J. A.

    2017-10-01

    The CaO-½Gd2O3-CoOz system prepared at 885 °C in air consists of two thermoelectric calcium cobaltate compounds, namely, the 2D thermoelectric oxide solid solution, (Ca3-xGdx)Co4O9-z (0 ≤ x ≤ 0.42) which has a misfit layered structure, and the 1D Ca3Co2O6 compound which consists of chains of alternating CoO6 trigonal prisms and CoO6 octahedra. Ca3Co2O6 was found to be a point compound. In the peripheral binary systems, Gd was not present in the Ca site of CaO, while a small solid solution region was identified for (Gd1-xCax)O(3-z)/2 (0 ≤ x ≤ 0.075). A solid solution region of distorted perovskite, (Gd1-xCax)CoO3-z (0 ≤ x ≤ 0.24, space group Pnma) was established. The structure of a member of the solid solution, (Gd0.92Ca0.08)CoO3-z, was determined using high resolution synchrotron radiation. A ternary oxide compound CaGdCoO4-z which has an orthorhombic structure (Bmab) was found to be stable at this temperature. Five solid solution tie-line regions and six three-phase regions were determined in the CaO-½Gd2O3-CoOz system. A comparison of the phase diagrams of the CaO-½R2O3-CoOz (R = La, Sm and Gd) systems is provided.

  7. Crystal chemistry and phase equilibria of the CaO-½Eu2O3-CoOz system at 885 °C

    NASA Astrophysics Data System (ADS)

    Wong-Ng, W.; Laws, W.; Kaduk, J. A.

    2016-08-01

    The CaO-½Eu2O3-CoOz system prepared at 885 °C in air consists of two calcium cobaltate compounds, namely, the 2D thermoelectric oxide solid solution, (Ca3-xEux)Co4O9-z (0 ≤ x ≤ 0.5) which has a misfit layered structure, and the 1D Ca3Co2O6 compound which consists of chains of alternating CoO6 trigonal prisms and CoO6 octahedra. Ca3Co2O6 was found to be a point compound without the substitution of Eu on the Ca site when prepared at 885 °C. A solid solution region of distorted perovskite, (Eu1-xCax)CoO3-z (0 ≤ x ≤ 0.22, space group Pnma) was established. The (Eu0.91(1)Ca0.09(1))CoO3-z perovskite member has a distorted structure with tilt angles θ (17.37°), ϕ (8.20°), and ω (19.16°) which represent rotations of an octahedron about the pseudo-cubic perovskite [110]p, [001]p and [111]p axes. The reported Eu2CoO4 phase was not observed at 885 °C, but a ternary Ca-doped oxide, (Eu1+xCa1-x)CoO4-z (Bmab) where 0 ≤ x ≤ 0.10 was found to be stable at this temperature. In the peripheral binary systems, Eu was not present in the Ca site of CaO, while a small solid solution region was identified for (Eu1-xCax)O(3-z)/2 (0 ≤ x ≤ 0.05). Seven solid solution tie-line regions and six three-phase regions were determined in the CaO-½Eu2O3-CoOz system in air.

  8. Phase equilibria and crystal chemistry of the CaO–½Sm2O3–CoOz system at 885 °C in air

    DOE PAGES

    Wong-Ng, W.; Laws, W.; Lapidus, S. H.; ...

    2015-06-27

    The CaO–½Sm2O3–CoOz system prepared at 885 °C in air consists of two calcium cobaltate compounds, namely, the 2D thermoelectric oxide solid solution, (Ca3$-$xSmx)Co4O9$-$z (0 ≤ x ≤ 0.5) which has a misfit layered structure, and the 1D Ca3Co2O6 which consists of chains of alternating CoO6 trigonal prisms and CoO6 octahedra. Ca3Co2O6 was found to be a point compound without the substitution of Sm on the Ca site. A solid solution region of distorted perovskite, (Sm1$-$xCax)CoO3$-$z (0 ≤ x ≤ 0.22, space group Pnma) was established. The reported Sm2CoO4 phase was not observed at 885 °C, but a ternary Ca-doped oxide,more » (Sm1+xCa1$-$x)CoO4$-$z (Bmab) where 0 < x ≤ 0.15 was found to be stable at this temperature. In the peripheral binary systems, Sm was not present in the Ca site of CaO, while a small solid solution region was identified for (Sm1$-$xCax)O(3$-$z)/2 (0 ≤ x ≤ 0.075). Lastly, ten solid solution tie-line regions and six three-phase regions were determined in the CaO–½Sm2O3–CoOz system in air.« less

  9. Central State University: Phase II Report

    ERIC Educational Resources Information Center

    Ohio Board of Regents, 2012

    2012-01-01

    In accordance with Ohio Amended Substitute House Bill 153, the Chancellor submitted to the state Legislature and the Governor a plan, developed in consultation with Central State University, that assures the Central State Supplement will be used to promote the goals of increasing enrollment, improving course completion, and increasing the number…

  10. Subsolidus phase equilibria and properties in the system Bi 2O 3:Mn 2O 3±x:Nb 2O 5

    NASA Astrophysics Data System (ADS)

    Vanderah, T. A.; Lufaso, M. W.; Adler, A. U.; Levin, I.; Nino, J. C.; Provenzano, V.; Schenck, P. K.

    2006-11-01

    Subsolidus phase relations have been determined for the Bi-Mn-Nb-O system in air (750-900 °C). Phases containing Mn 2+, Mn 3+, and Mn 4+ were all observed. Ternary compound formation was limited to pyrochlore (A 2B 2O 6O'), which formed a substantial solid solution region at Bi-deficient stoichiometries (relative to Bi 2(Mn,Nb) 2O 7) suggesting that ≈14-30% of the A-sites are occupied by Mn (likely Mn 2+). X-ray powder diffraction data confirmed that all Bi-Mn-Nb-O pyrochlores form with structural displacements, as found for the analogous pyrochlores with Mn replaced by Zn, Fe, or Co. A structural refinement of the pyrochlore 0.4000:0.3000:0.3000 Bi 2O 3:Mn 2O 3±x:Nb 2O 5 using neutron powder diffraction data is reported with the A and O' atoms displaced (0.36 and 0.33 Å, respectively) from ideal positions to 96g sites, and with Mn 2+ on A-sites and Mn 3+ on B-sites (Bi 1.6Mn 2+0.4(Mn 3+0.8Nb 1.2)O 7, Fd3¯m (♯227), a=10.478(1) Å); evidence of A or O' vacancies was not found. The displacive disorder is crystallographically analogous to that reported for Bi 1.5Zn 0.92Nb 1.5O 6.92, which has a similar concentration of small B-type ions on the A-sites. EELS spectra for this pyrochlore were consistent with an Mn oxidation between 2+ and 3+. Bi-Mn-Nb-O pyrochlores exhibited overall paramagnetic behavior with negative Curie-Weiss temperature intercepts, slight superparamagnetic effects, and depressed observed moments compared to high-spin, spin-only values. At 300 K and 1 MHz the relative dielectric permittivity of Bi 1.600Mn 1.200Nb 1.200O 7 was ≈128 with tan δ=0.05; however, at lower frequencies the sample was conductive which is consistent with the presence of mixed-valent Mn. Low-temperature dielectric relaxation such as that observed for Bi 1.5Zn 0.92Nb 1.5O 6.92 and other bismuth-based pyrochlores was not observed. Bi-Mn-Nb-O pyrochlores were readily obtained as single crystals and also as textured thin films using pulsed laser deposition.

  11. Scapolite phase equilibria and carbon isotope variations in high grade rocks: Tests of the CO sub 2 -flooding hypothesis of granulite gneiss

    SciTech Connect

    Moecher, D.P.

    1988-01-01

    Scapolite decarbonation reactions and carbon isotope analysis of CO{sub 2} extracted from scapolite are used to determine the presence, composition, and source of fluid components in high grade rocks. Scapolite-plagioclase-garnet-quartz assemblages, common to many lithologies in high grade terranes, monitors CO{sub 2} activity (aCO{sub 2}) by the reaction 2 Meionite + Quarts = 5 Anorthite + Grossular + 2 CO{sub 2}. The P-T-X location of this reaction was calculated using an internally consistent thermodynamic data set for meionite and phases in the CASCH system. Activity-composition relations for meionite in scapolite were calculated from the thermodynamic data set and compositional data on natural scapolite-plagioclase-calcite assemblages. Equilibration pressures of scapolite assemblages were calculated from clinopyroxene-garnet-plagioclass-quartz barometers calibrated for this study. The aCO{sub 2} was calculated for a variety of high grade gneisses from the southwestern Grenville Province and other terranes. Granulites typically yield low to moderate values of aCO{sub 2} (less than 0.5). Calc-silicates and meta-anorthosite yield moderate aCO{sub 2}. Deep crustal xenoliths yield a range of aCO{sub 2}.

  12. Phase equilibria in the Tb-Mg-Co system at 500 °C, crystal structure and hydrogenation properties of selected compounds

    NASA Astrophysics Data System (ADS)

    Shtender, V. V.; Denys, R. V.; Zavaliy, I. Yu.; Zelinska, O. Ya.; Paul-Boncour, V.; Pavlyuk, V. V.

    2015-12-01

    The isothermal section of the Tb-Mg-Co phase diagram at 500 °C has been built on the basis of XRD analysis of forty samples prepared by powder metallurgy. The existence of two ternary compounds Tb4Mg3Co2 and Tb4MgCo was confirmed. The formation of two solid solutions, Tb1-xMgxCo3 (0≤x≤0.4) and Tb1--xMgxCo2 (0≤x≤0.6), was found for the first time. It is shown that Tb5Mg24 also dissolves a small amount of Co. Other binary compounds do not dissolve the third component. The Tb4MgCo and TbMgCo4 compounds form hydrides (12.7 and 5.3 at.H/f.u. capacity, respectively) that retain the original structure of metallic matrices. Upon thermal desorption the Tb4MgCoH12.7 hydride was stable up to 300 °C and disproportionated at higher temperature. Two other hydrides, Tb4Mg3Co2H∼4 and Tb2MgCo9H12, are unstable in air and decompose into the initial compounds.

  13. Recent developments in Bayesian inference of tokamak plasma equilibria and high-dimensional stochastic quadratures

    NASA Astrophysics Data System (ADS)

    von Nessi, G. T.; Hole, M. J.; The MAST Team

    2014-11-01

    We present recent results and technical breakthroughs for the Bayesian inference of tokamak equilibria using force-balance as a prior constraint. Issues surrounding model parameter representation and posterior analysis are discussed and addressed. These points motivate the recent advancements embodied in the Bayesian Equilibrium Analysis and Simulation Tool (BEAST) software being presently utilized to study equilibria on the Mega-Ampere Spherical Tokamak (MAST) experiment in the UK (von Nessi et al 2012 J. Phys. A 46 185501). State-of-the-art results of using BEAST to study MAST equilibria are reviewed, with recent code advancements being systematically presented though out the manuscript.

  14. Outlook on the phase equilibria of the innovative system of "protected glycerol": 1,4-dioxaspiro[4.5]decane-2-methanol and alternative solvents.

    PubMed

    Melo, Catarina I; Rodrigues, Ana I; Bogel-Łukasik, Rafał; Bogel-Łukasik, Ewa

    2012-02-23

    Fundamental data on 1,4-dioxaspiro[4.5]decane-2-methanol are scarce. This work presents the foremost systematic data on the solubility of 1,4-dioxaspiro[4.5]decane-2-methanol in sustainable solvents such as water and ionic liquids accompanied by the interpretation of interactions occurring in such binary systems. 1,4-Dioxaspiro[4.5]decane-2-methanol, here called protected glycerol, has been synthesized in order to protect the two hydroxyl groups of glycerol, thus avoiding the formation of side products in a specific process. A series of imidazolium salts accompanied by pyridinium, phosphonium, and ammonium ones with various types of counterions were used in this study. The liquid-liquid and solid-liquid equilibrium measurements in binary systems were carried out by using a dynamic method at atmospheric pressure over the temperature range from 273.00 to 378.30 K or below the boiling point of the solvent. Among all tested sustainable solvents, protected glycerol exhibited limited solubility, with only a few of them in the temperature range studied. The majority of the examined ionic liquids, either hydrophilic or hydrophobic, showed complete miscibility with this monohydroxyol. The Fourier-transform infrared (FTIR) spectroscopy studies of solute and solvents showing a miscibility gap and of their mixtures were performed to obtain insight into major inter- and intramolecular interactions in the investigated systems. Furthermore, the differential scanning calorimetry was used for the first time to determine the melting point, the enthalpy of melting, and the temperature and enthalpy of the solid-solid phase transition of 1-allyl-3-methylimidazolium chloride [Amim][Cl]. The results for the solubility of protected glycerol in sustainable solvents can be used to design future alternative reactions, such as telomerization with protected glycerol in ionic liquids for more specific building blocks and extraction/or separation that involves these mixtures.

  15. Geometric Phase for Adiabatic Evolutions of General Quantum States

    SciTech Connect

    Wu, Biao; Liu, Jie; Niu, Qian; Singh, David J

    2005-01-01

    The concept of a geometric phase (Berry's phase) is generalized to the case of noneigenstates, which is applicable to both linear and nonlinear quantum systems. This is particularly important to nonlinear quantum systems, where, due to the lack of the superposition principle, the adiabatic evolution of a general state cannot be described in terms of eigenstates. For linear quantum systems, our new geometric phase reduces to a statistical average of Berry's phases. Our results are demonstrated with a nonlinear two-level model.

  16. On steady electromagnetic equilibria

    NASA Astrophysics Data System (ADS)

    Lehnert, B.

    1986-12-01

    The existence of steady electromagnetic equilibrium states predicted by an extended Lorentz invariant formulation of Maxwell's equations is analyzed. General equilibrium solutions are outlined which lead to integrated field quantities of the system, such as total charge qo, magnetic moment Mo, mass mo and angular momentum so. The quantization of moMo/qo in terms of Bohr magnetons is shown to be equivalent to the proposed resonance condition of circulating self-confined radiation. Exact equilibrium solutions were deduced in two simple cases, thereby leading to a so of the same order as that of the electron, and to a qo one order of magnitude larger than the electronic charge. A variational procedure is suggested in search for states of minimum charge, under the subsidiary quantum conditions on moMo/qo and so, i.e., by varying the profile of the electric space charge distribution.

  17. Phase space flow of particles in squeezed states

    NASA Technical Reports Server (NTRS)

    Ceperley, Peter H.

    1994-01-01

    The manipulation of noise and uncertainty in squeezed states is governed by the wave nature of the quantum mechanical particles in these states. This paper uses a deterministic model of quantum mechanics in which real guiding waves control the flow of localized particles. This model will be used to examine the phase space flow of particles in typical squeezed states.

  18. Equations of state and phase diagrams of hydrogen isotopes

    SciTech Connect

    Urlin, V. D.

    2013-11-15

    A new form of the semiempirical equation of state proposed for the liquid phase of hydrogen isotopes is based on the assumption that its structure is formed by cells some of which contain hydrogen molecules and others contain hydrogen atoms. The values of parameters in the equations of state of the solid (molecular and atomic) phases as well as of the liquid phase of hydrogen isotopes (protium and deuterium) are determined. Phase diagrams, shock adiabats, isentropes, isotherms, and the electrical conductivity of compressed hydrogen are calculated. Comparison of the results of calculations with available experimental data in a wide pressure range demonstrates satisfactory coincidence.

  19. Transitions of Spherical Thermohaline Circulation to Multiple Equilibria

    NASA Astrophysics Data System (ADS)

    Özer, Saadet; Şengül, Taylan

    2017-06-01

    The main aim of the paper is to investigate the transitions of the thermohaline circulation in a spherical shell in a parameter regime which only allows transitions to multiple equilibria. We find that the first transition is either continuous (Type-I) or drastic (Type-II) depending on the sign of the transition number. The transition number depends on the system parameters and l_c , which is the common degree of spherical harmonics of the first critical eigenmodes, and it can be written as a sum of terms describing the nonlinear interactions of various modes with the critical modes. We obtain the exact formulas of this transition number for l_c=1 and l_c=2 cases. Numerically, we find that the main contribution to the transition number is due to nonlinear interactions with modes having zero wave number and the contribution from the nonlinear interactions with higher frequency modes is negligible. In our numerical experiments we encountered both types of transition for Le<1 but only continuous transition for Le>1 . In the continuous transition scenario, we rigorously prove that an attractor in the phase space bifurcates which is homeomorphic to the 2l_c dimensional sphere and consists entirely of degenerate steady state solutions.

  20. Central State University: Phase I Report

    ERIC Educational Resources Information Center

    Ohio Board of Regents, 2012

    2012-01-01

    In December of 2011, a team of eight consultants authored a report to the Ohio Board of Regents and Central State University titled "Accentuating Strengths/Accelerating Progress (AS/AP)." AS/AP provided a road map for the administration, faculty, and staff of CSU to achieve the excellence it has sought under the leadership of President…

  1. Estimation of Fluid Properties and Phase Equilibria.

    ERIC Educational Resources Information Center

    Herskowitz, M.

    1985-01-01

    Describes a course (given to junior/senior students with strong background in thermodynamics and transport phenomena) that covers the theoretical and practical aspects of properties estimation. An outline for the course is included. (JN)

  2. Predictive thermochemistry and phase equilibria of slags

    NASA Astrophysics Data System (ADS)

    Barry, Thomas I.; Dinsdale, Alan T.; Gisby, John A.

    1993-04-01

    It is well understood that the efficient recovery of values by pyrometallurgical processing of ores requires control of the slag chemistry. In an effort to improve the understanding of slags, a thermodynamic database on subsystems of the CaO-MgO-Fe-O-Al2O3-SiO2 system has been generated through critical assessment of the literature. Data for connecting systems of specific industrial interest are being added. The data can be combined using well-established thermodynamic principles to make calculations on the multicomponent systems of practical interest. Following a description of the calculations, this article illustrates specific applications of thermodynamic modeling to the extraction of copper, nickel, and precious metals; zinc extraction; purification of pig iron; meltdown in nuclear reactors; hot corrosion; and pollution control.

  3. Estimation of Fluid Properties and Phase Equilibria.

    ERIC Educational Resources Information Center

    Herskowitz, M.

    1985-01-01

    Describes a course (given to junior/senior students with strong background in thermodynamics and transport phenomena) that covers the theoretical and practical aspects of properties estimation. An outline for the course is included. (JN)

  4. Vapor-liquid equilibria of binary and ternary mixtures of cyclohexane, 3-methyl-2-butanone, and octane at 101.3 kPa

    SciTech Connect

    Chen, C.C.; Tang, M.; Chen, Y.P.

    1996-05-01

    Vapor-liquid equilibria were measured at 101.3 kPa for the three binary and one ternary mixtures of cyclohexane, 3-methyl-2-butanone, and octane. The isobaric T-x-y data were reported, including an azeotropic point for the binary mixture cyclohexane + 3-methyl-2-butanone. The virial equation of state truncated after the second coefficient was used to calculate the vapor-phase fugacity coefficients. The Tsonopoulos correlation equation was applied to determine the second virial coefficients. Various activity coefficient models of the Wilson, the NRTL, and the UNIQUAC equations were used to correlate the binary experimental vapor-liquid equilibrium results. Optimally-fitted binary parameters of the activity coefficient models were obtained and those parameters of the NRTL model were employed to predict the ternary vapor-liquid equilibria. Satisfactory results were presented for the correlation and prediction of the vapor-liquid equilibrium data on binary and ternary mixtures.

  5. Gaussian cloning of coherent states with known phases

    SciTech Connect

    Alexanian, Moorad

    2006-04-15

    The fidelity for cloning coherent states is improved over that provided by optimal Gaussian and non-Gaussian cloners for the subset of coherent states that are prepared with known phases. Gaussian quantum cloning duplicates all coherent states with an optimal fidelity of 2/3. Non-Gaussian cloners give optimal single-clone fidelity for a symmetric 1-to-2 cloner of 0.6826. Coherent states that have known phases can be cloned with a fidelity of 4/5. The latter is realized by a combination of two beam splitters and a four-wave mixer operated in the nonlinear regime, all of which are realized by interaction Hamiltonians that are quadratic in the photon operators. Therefore, the known Gaussian devices for cloning coherent states are extended when cloning coherent states with known phases by considering a nonbalanced beam splitter at the input side of the amplifier.

  6. Noniterative reconstruction of tokamak equilibria

    NASA Astrophysics Data System (ADS)

    Rodrigues, Paulo; Bizarro, João P. S.

    2009-02-01

    Unlike iterative approaches, noniterative equilibria reconstruction schemes are designed to keep two measured internal profiles fixed along a given chord while solving a sequence of linear differential equations, providing a unique and asymptotic solution to the Grad-Shafranov (GS) equation directly in laboratory coordinates. A noniterative algorithm is extended to handle plasma configurations that are not symmetric with respect to the tokamak midplane and then used to compute an equilibrium solution from an actual experimental data set. A number of issues concerning how available experimental data can be handled and provided as input to the GS solver in practical situations are also discussed.

  7. Inefficiency of Nash Equilibria. I

    DTIC Science & Technology

    1982-03-12

    continuously for U’ near csEA a’ This also shows that for il close to , D6?’)(X) fl (IW’, f ) - * for a a hence we may assume U0 open.all * 6 A A Furthermore...34 Journal of Economic Theory 22 (1980), 363-376. 14] P. Dubey, A. as-Colell and M. Shubik, "Efficiency Properties of Strategic Market Games: An...Axiomatic Approach," Journal of Economic Theory 22 (1980), 339-362. [5] P. Dubey and J. D. Rogsvski, "Inefficiency of Nash Equilibria: II," forthcoming

  8. Implicit PIC Simulations of Magnetospheric Reconnection Initialized with Fully Kinetic Asymmetric Current-Sheet Equilibria

    NASA Astrophysics Data System (ADS)

    Newman, David L.; Goldman, Martin V.; Lapenta, Giovanni; Markidis, Stefano

    2013-10-01

    A family of one-dimensional kinetic current sheet equilibria has been developed in which the density difference across the sheet is maintained by ambipolar electric fields (with E perpendicular to J and B). These electric fields can form an effective potential barrier that allows particles of one species (e.g., electrons) with the same energy to have different phase-space densities on the two sides of the current sheet, thereby breaking the symmetry. Such solutions necessarily require the inclusion of non-Maxwellian features, and share characteristics with double layers and other nonlinear electrostatic structures. Implicit PIC simulations were initialized with the electron and ion distribution functions corresponding to specific solutions of this type and were found to behave as equilibria that are subject to an asymmetric tearing-mode-like instability. As expected, the instability growth rate increases as the width of the current sheet decreases. Imposing a weak perturbation on the equilibrium allows for a controlled study of the evolution of the asymmetric reconnecting plasma. Examples will be presented of the evolution for different initial states relevant to magnetospheric reconnection, including varying values of the guide magnetic field. Research supported by NSF and NASA.

  9. Multi-Phase Extraction: State-of-the-Practice

    EPA Pesticide Factsheets

    This report describes the state-of-the-practice for multi-phase extraction (MPE) of contaminated soil and groundwater, focusing primarily on the application and use of MPE at sites with halogenated volatile organic compounds (VOCs).

  10. Approximation of stochastic equilibria for dynamic systems with colored noise

    SciTech Connect

    Bashkirtseva, Irina

    2015-03-10

    We consider nonlinear dynamic systems forced by colored noise. Using first approximation systems, we study dynamics of deviations of stochastic solutions from stable deterministic equilibria. Equations for the stationary second moments of deviations of random states are derived. An application of the elaborated theory to Van der Pol system driven by colored noise is given. A dependence of the dispersion on the time correlation of the colored noise is studied.

  11. Dynamic equilibria of phases in the processes of the mechanosynthesis of an alloy with composition Fe72.6C24.5O1.1N1.8

    NASA Astrophysics Data System (ADS)

    Volkov, V. A.; El'kin, I. A.; Zagainov, A. V.; Protasov, A. V.; Elsukov, E. P.

    2014-06-01

    X-ray diffraction, Mössbauer spectroscopy, and measurements of the dynamic magnetic susceptibility have been used to investigate phase states of the Fe72.6C24.5O1.1N1.8 alloy at different stages of the mechanosynthesis (MS) in a planetary ball mill. The introduction of impurities of O and N into an Fe75C25-based alloy changes the sequence of the formation of phases during MS: instead of Fe3C, the Fe7C3 carbide is first to be formed. The processes of phase formation in the alloy preliminarily subjected to MS have unidirectional nature upon the continuation of the MS and upon annealings and are determined by the interaction of the alloy components with one another under the effect of the accumulated excess energy. The phase compositions of the MS alloys depend on the conditions of the dynamic equilibrium between the crystalline and amorphous phases.

  12. MHD equilibria with diamagnetic effects

    NASA Astrophysics Data System (ADS)

    Tessarotto, M.; Zorat, R.; Johnson, J. L.; White, R. B.

    1997-11-01

    An outstanding issue in magnetic confinement is the establishment of MHD equilibria with enhanced flow shear profiles for which turbulence (and transport) may be locally effectively suppressed or at least substantially reduced with respect to standard weak turbulence models. Strong flows develop in the presence of equilibrium E× B-drifts produced by a strong radial electric field, as well as due to diamagnetic contributions produced by steep equilibrium radial profiles of number density, temperature and the flow velocity itself. In the framework of a kinetic description, this generally requires the construction of guiding-center variables correct to second order in the relevant expansion parameter. For this purpose, the Lagrangian approach developed recently by Tessarotto et al. [1] is adopted. In this paper the conditions of existence of such equilibria are analyzed and their basic physical properties are investigated in detail. 1 - M. Pozzo, M. Tessarotto and R. Zorat, in Theory of fusion Plasmas, E.Sindoni et al. eds. (Societá Italiana di Fisica, Editrice Compositori, Bologna, 1996), p.295.

  13. Signaling equilibria in sensorimotor interactions.

    PubMed

    Leibfried, Felix; Grau-Moya, Jordi; Braun, Daniel A

    2015-08-01

    Although complex forms of communication like human language are often assumed to have evolved out of more simple forms of sensorimotor signaling, less attention has been devoted to investigate the latter. Here, we study communicative sensorimotor behavior of humans in a two-person joint motor task where each player controls one dimension of a planar motion. We designed this joint task as a game where one player (the sender) possesses private information about a hidden target the other player (the receiver) wants to know about, and where the sender's actions are costly signals that influence the receiver's control strategy. We developed a game-theoretic model within the framework of signaling games to investigate whether subjects' behavior could be adequately described by the corresponding equilibrium solutions. The model predicts both separating and pooling equilibria, in which signaling does and does not occur respectively. We observed both kinds of equilibria in subjects and found that, in line with model predictions, the propensity of signaling decreased with increasing signaling costs and decreasing uncertainty on the part of the receiver. Our study demonstrates that signaling games, which have previously been applied to economic decision-making and animal communication, provide a framework for human signaling behavior arising during sensorimotor interactions in continuous and dynamic environments.

  14. Oxygen and Bis(3',5')-cyclic Dimeric Guanosine Monophosphate Binding Control Oligomerization State Equilibria of Diguanylate Cyclase-Containing Globin Coupled Sensors.

    PubMed

    Burns, Justin L; Rivera, Shannon; Deer, D Douglas; Joynt, Shawnna C; Dvorak, David; Weinert, Emily E

    2016-12-06

    Bacteria sense their environment to alter phenotypes, including biofilm formation, to survive changing conditions. Heme proteins play important roles in sensing the bacterial gaseous environment and controlling the switch between motile and sessile (biofilm) states. Globin coupled sensors (GCS), a family of heme proteins consisting of a globin domain linked by a central domain to an output domain, are often found with diguanylate cyclase output domains that synthesize c-di-GMP, a major regulator of biofilm formation. Characterization of diguanylate cyclase-containing GCS proteins from Bordetella pertussis and Pectobacterium carotovorum demonstrated that cyclase activity is controlled by ligand binding to the heme within the globin domain. Both O2 binding to the heme within the globin domain and c-di-GMP binding to a product-binding inhibitory site (I-site) within the cyclase domain control oligomerization states of the enzymes. Changes in oligomerization state caused by c-di-GMP binding to the I-site also affect O2 kinetics within the globin domain, suggesting that shifting the oligomer equilibrium leads to broad rearrangements throughout the protein. In addition, mutations within the I-site that eliminate product inhibition result in changes to the accessible oligomerization states and decreased catalytic activity. These studies provide insight into the mechanism by which ligand binding to the heme and I-site controls activity of GCS proteins and suggests a role for oligomerization-dependent activity in vivo.

  15. Quantum phase estimation using path-symmetric entangled states

    NASA Astrophysics Data System (ADS)

    Lee, Su-Yong; Lee, Chang-Woo; Lee, Jaehak; Nha, Hyunchul

    2016-07-01

    We study the sensitivity of phase estimation using a generic class of path-symmetric entangled states |φ>|0> + |0>|φ>, where an arbitrary state |φ> occupies one of two modes in quantum superposition. With this generalization, we identify the fundamental limit of phase estimation under energy constraint that is characterized by the photon statistics of the component state |φ>. We show that quantum Cramer-Rao bound (QCRB) can be indefinitely lowered with super-Poissonianity of the state |φ>. For possible measurement schemes, we demonstrate that a full photon-counting employing the path-symmetric entangled states achieves the QCRB over the entire range [0, 2π] of unknown phase shift ϕ whereas a parity measurement does so in a certain confined range of ϕ. By introducing a component state of the form , we particularly show that an arbitrarily small QCRB can be achieved even with a finite energy in an ideal situation. This component state also provides the most robust resource against photon loss among considered entangled states over the range of the average input energy Nav > 1. Finally we propose experimental schemes to generate these path-symmetric entangled states for phase estimation.

  16. Quantum phase estimation using path-symmetric entangled states

    PubMed Central

    Lee, Su-Yong; Lee, Chang-Woo; Lee, Jaehak; Nha, Hyunchul

    2016-01-01

    We study the sensitivity of phase estimation using a generic class of path-symmetric entangled states |φ〉|0〉 + |0〉|φ〉, where an arbitrary state |φ〉 occupies one of two modes in quantum superposition. With this generalization, we identify the fundamental limit of phase estimation under energy constraint that is characterized by the photon statistics of the component state |φ〉. We show that quantum Cramer-Rao bound (QCRB) can be indefinitely lowered with super-Poissonianity of the state |φ〉. For possible measurement schemes, we demonstrate that a full photon-counting employing the path-symmetric entangled states achieves the QCRB over the entire range [0, 2π] of unknown phase shift ϕ whereas a parity measurement does so in a certain confined range of ϕ. By introducing a component state of the form , we particularly show that an arbitrarily small QCRB can be achieved even with a finite energy in an ideal situation. This component state also provides the most robust resource against photon loss among considered entangled states over the range of the average input energy Nav > 1. Finally we propose experimental schemes to generate these path-symmetric entangled states for phase estimation. PMID:27457267

  17. Investigation of Liquidus Temperatures and Phase Equilibria of Copper Smelting Slags in the FeO-Fe2O3-SiO2-CaO-MgO-Al2O3 System at PO2 10-8 atm

    NASA Astrophysics Data System (ADS)

    Henao, Hector M.; Nexhip, Colin; George-Kennedy, David P.; Hayes, P. C.; Jak, E.

    2010-08-01

    Copper concentrates and fluxes can contain variable levels of SiO2, CaO, and MgO in addition to main components Cu, Fe, and S. Metal recovery, slag tapping, and furnace wall integrity all are dependent on phase equilibria and other properties of the phases and are functions of slag composition and operational temperature. Optimal control of the slag chemistry in the copper smelting, therefore, is essential for high recovery and productivity; this, in turn, requires detailed knowledge of the slag phase equilibria. The present work provides new phase equilibrium experimental data in the FeO-Fe2O3-SiO2-CaO-MgO-Al2O3 system at oxygen partial pressure of 10-8 atm within the range of temperatures and compositions directly relevant to copper smelting. For the range of conditions relevant to the Kennecott Utah Copper (South Magna, UT) smelting furnace, it was confirmed experimentally that increasing concentrations of MgO or CaO resulted in significant decreases of the tridymite liquidus temperature and in changes in the position of the tridymite liquidus in the direction of higher silica concentration; in contrast, the spinel liquidus temperatures increase significantly with the increase of MgO or CaO. Olivine and clinopyroxene precipitates appeared at high MgO concentrations in the liquid slag. The liquidus temperature in the spinel primary phase field was expressed as a linear function of 1/(wt pctFe/wt pctSiO2), wt pctCaO, wt pctMgO, and wt pctAl2O3. The positions of each of the liquidus points (wt pctFe)/(wt pctSiO2) at a fixed temperatures in the tridymite primary phase field were expressed as linear functions of wt pctCaO, wt pctMgO, and wt pctAl2O3.

  18. Solid state photomultiplier for astronomy, phase 2

    NASA Technical Reports Server (NTRS)

    Besser, P. J.; Hays, K. M.; Laviolette, R. A.

    1989-01-01

    Epitaxial layers with varying donor concentration profiles were grown on silicon substrate wafers using chemical vapor deposition (CVD) techniques, and solid state photomultiplier (SSPM) devices were fabricated from the wafers. Representative detectors were tested in a low background photon flux, low temperature environment to determine the device characteristics for comparison to NASA goals for astronomical applications. The SSPM temperatures varied between 6 and 11 K with background fluxes in the range from less than 5 x 10 to the 6th power to 10 to the 13th power photons/square cm per second at wavelengths of 3.2 and 20 cm. Measured parameters included quantum efficiency, dark count rate and bias current. Temperature for optimal performance is 10 K, the highest ever obtained for SSPMs. The devices exhibit a combination of the lowest dark current and highest quantum efficiency yet achieved. Experimental data were reduced, analyzed and used to generate recommendations for future studies. The background and present status of the microscopic theory of SSPM operation were reviewed and summarized. Present emphasis is on modeling of the avalanche process which is the basis for SSPM operation. Approaches to the solution of the Boltzmann transport equation are described and the treatment of electron scattering mechanisms is presented. The microscopic single-electron transport theory is ready to be implemented for large-scale computations.

  19. Topological superconducting phase and Majorana bound states in Shiba chains

    NASA Astrophysics Data System (ADS)

    Pientka, Falko; Peng, Yang; Glazman, Leonid; von Oppen, Felix

    2015-12-01

    Chains of magnetic adatoms on a conventional superconducting substrate constitute a promising venue for realizing topological superconductivity and Majorana end states. Here, we give a brief overview over recent attempts to describe these systems theoretically, emphasizing how the topological phase emerges from the physics of individual magnetic impurities and their associated Shiba states.

  20. Equation of state and phase diagram of dense hydrogen

    NASA Technical Reports Server (NTRS)

    Kerley, G. I.

    1972-01-01

    The equation of state of hydrogen was calculated for specific volumes ranging from 0.01 to 0.0001 cm3/mole and for temperatures ranging from 200 to 1 million K. Three phases are considered: the molecular solid, the metallic solid and the fluid. Chemical equilibrium between molecules, atoms, ions and electrons is considered in calculating the properties of the fluid phase. Transitions between the three phases will be discussed. The triple point, where the three phases coexist, is calculated to occur at 2.3 Mbar and 1679 K. At higher temperatures and pressures, the molecular solid is unstable.