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1

Thermodynamic Properties of Supported Catalysts

The goals of this work were to develop Coulometric Titration as a method for characterizing the thermodynamic redox properties of oxides and to apply this technique to the characterization of ceria- and vanadia-based catalysts. The redox properties of ceria and vanadia are a major part of what makes these materials catalytically active but their properties are also dependent on their structure and the presence of other oxides. Quantifying these properties through the measurement of oxidation energetics was the goal of this work.

Gorte, Raymond J.

2014-03-26

2

The Thermodynamic Properties of Cubanite

NASA Technical Reports Server (NTRS)

CuFe2S3 exists in two polymorphs, a low-temperature orthorhombic form (cubanite) and a high-temperature cubic form (isocubanite). Cubanite has been identified in the CI-chondrite and Stardust collections. However, the thermodynamic properties of cubanite have neither been measured nor estimated. Our derivation of a thermodynamic model for cubanite allows constraints to be placed on the formation conditions. This data, along with the temperature constraint afforded by the crystal structure, can be used to assess the environments in which cubanite formation is (or is not) thermodynamically favored.

Berger, E. L.; Lauretta, D. S.; Keller, L. P.

2012-01-01

3

Inflight thermodynamic properties

NASA Technical Reports Server (NTRS)

The inflight thermodynamic parameters (temperature, pressure, and density) of the atmosphere are presented. Mean and extreme values of the thermodynamic parameters given here can be used in application of many aerospace problems, such as: (1) research and planning and engineering design of remote earth sensing systems; (2) vehicle design and development; and (3) vehicle trajectory analysis, dealing with vehicle thrust, dynamic pressure, aerodynamic drag, aerodynamic heating, vibration, structural and guidance limitations, and reentry analysis. Atmospheric density plays a very important role in most of the above problems. A subsection on reentry is presented, giving atmospheric models to be used for reentry heating, trajectory, etc., analysis.

Brown, S. C.; Daniels, G. E.; Johnson, D. L.; Smith, O. E.

1973-01-01

4

Thermodynamic properties of uranium dioxide

In order to provide reliable and consistent data on the thermophysical properties of reactor materials for reactor safety studies, this revision is prepared for the thermodynamic properties of the uranium dioxide portion of the fuel property section of the report Properties for LMFBR Safety Analysis. Since the original report was issued in 1976, there has been international agreement on a vapor pressure equation for the total pressure over UO/sub 2/, new methods have been suggested for the calculation of enthalpy and heat capacity, and a phase change at 2670 K has been proposed. In this report, an electronic term is used in place of the Frenkel defect term in the enthalpy and heat capacity equation and the phase transition is accepted.

Fink, J.K.; Chasanov, M.G.; Leibowitz, L.

1981-04-01

5

Advanced working fluids: Thermodynamic properties

NASA Astrophysics Data System (ADS)

Electrolytes are used as working fluids in gas fired heat pump chiller engine cycles. To find out which molecular parameters of the electrolytes impact on cycle performance, a molecular theory is developed for calculating solution properties, enthalpies, vapor-liquid equilibria, and engine cycle performance. Aqueous and ammoniac single and mixed salt solutions in single and multisolvent systems are investigated. An accurate correlation is developed to evaluate properties for concentrated electrolyte solutions. Sensitivity analysis is used to determine the impact of molecular parameters on the thermodynamic properties and cycle performance. The preferred electrolytes are of 1-1 valence type, small ion size, high molecular weight, and in strongly colligative cosolvent. The operating windows are determined for a number of absorption fluids of industrial importance.

Lee, Lloyd L.; Gering, Kevin L.

1990-10-01

6

Thermodynamic properties of adamantane revisited.

The heat capacity and parameters of the solid-to-solid phase transition of adamantane were measured in the temperature range from 80 to 370 K by use of adiabatic calorimetry. The thermodynamic functions for the compound in the crystalline and liquid states were calculated. The standard molar enthalpy of formation in the crystalline state for adamantane was obtained from combustion calorimetry by use of two different calorimeters. Available data on the enthalpy of combustion, saturated vapor pressure, and enthalpy of sublimation of adamantane were collected, analyzed, and selected. On the basis of spectroscopic data and results of quantum-chemical calculations, the ideal-gas properties for adamantane were calculated by a statistical thermodynamics method. PMID:21809832

Bazyleva, Ala B; Blokhin, Andrey V; Kabo, Gennady J; Charapennikau, Mikhail B; Emel'yanenko, Vladimir N; Verevkin, Sergey P; Diky, Vladimir

2011-08-25

7

Thermodynamic Properties of Dimethyl Carbonatea)

NASA Astrophysics Data System (ADS)

A thermodynamic property formulation for dimethyl carbonate has been developed with the use of available experimental thermodynamic property data. The equation of state was developed with multiproperty fitting methods involving pressure-density-temperature (p?T), heat capacity, vapor pressure, and saturated-liquid density data. The equation of state conforms to the Maxwell criterion for two-phase liquid-vapor equilibrium states, and is valid for temperatures from the triple-point temperature (277.06 ± 0.63) K to 600 K, for pressures up to 60 MPa, and for densities up to 12.12 mol dm-3. The extrapolation behavior of the equation of state at low and high temperatures and pressures is reasonable. The uncertainties (k = 2, indicating a 95% confidence level) of the equation of state in density are 0.05% for saturated-liquid states below 350 K, rising to 0.1% in the single phase between 278 K and 400 K at pressures up to 60 MPa. Due to the lack of reliable data outside this region, the estimated uncertainties increase to 0.5% to 1% in the vapor and critical regions. The uncertainties in vapor pressure are 0.6% from 310 K to 400 K, and increase to 1% at higher temperatures and to 2% at lower temperatures due to a lack of experimental data. The uncertainty in isobaric heat capacity and speed of sound in the liquid phase at saturation or atmospheric pressure is 0.5% from 280 K to 335 K. The uncertainties are higher for all properties in the critical region. Detailed comparisons between experimental and calculated data, and an analysis of the equation, have been performed.

Zhou, Yong; Wu, Jiangtao; Lemmon, Eric W.

2011-12-01

8

Tables of thermodynamic properties of sodium

The thermodynamic properties of saturated sodium, superheated sodium, and subcooled sodium are tabulated as a function of temperature. The temperature ranges are 380 to 2508 K for saturated sodium, 500 to 2500 K for subcooled sodium, and 400 to 1600 K for superheated sodium. Tabulated thermodynamic properties are enthalpy, heat capacity, pressure, entropy, density, instantaneous thermal expansion coefficient, compressibility, and thermal pressure coefficient. Tables are given in SI units and cgs units.

Fink, J.K.

1982-06-01

9

Thermodynamic properties of ferrocene dicarboxylic acid

NASA Astrophysics Data System (ADS)

The temperature dependence of the heat capacity of crystal ferrocene dicarboxylic acid is studied in a precision adiabatic vacuum calorimeter in the range of 8 to 350 K. Its standard thermodynamic functions are calculated in the range of T ? 0 to 350 K. The thermal and physical heat properties of ferrocene dicarboxylic acid are studied on a differential scanning calorimeter in the range of 260 to 573 K. The enthalpy of combustion for the investigated compound is measured in an isoperibol calorimeter. The standard thermodynamic functions of the formation of ferrocene dicarboxylic acid in the crystal state at 298.15 K are calculated.

Kozlova, M. S.; Markin, A. V.; Larina, V. N.; Letyanina, I. A.

2014-02-01

10

Thermodynamic properties of ammonia in the critical region

A theoretically based crossover model, which incorporates a crossover from singular thermodynamic behavior at the critical point to regular thermodynamic behavior far away from the critical point, is presented for the thermodynamic properties of ammonia. The equation is capable of representing the thermodynamic properties of ammonia between 398 and 500K in an appreciable range of densities around the critical density.

T. A. Edison; J. V. Sengers

1999-01-01

11

Thermodynamics and statistical mechanics. [thermodynamic properties of gases

NASA Technical Reports Server (NTRS)

The basic thermodynamic properties of gases are reviewed and the relations between them are derived from the first and second laws. The elements of statistical mechanics are then formulated and the partition function is derived. The classical form of the partition function is used to obtain the Maxwell-Boltzmann distribution of kinetic energies in the gas phase and the equipartition of energy theorem is given in its most general form. The thermodynamic properties are all derived as functions of the partition function. Quantum statistics are reviewed briefly and the differences between the Boltzmann distribution function for classical particles and the Fermi-Dirac and Bose-Einstein distributions for quantum particles are discussed.

1976-01-01

12

Thermodynamic properties for the alternative refrigerants

Models commonly used to calculate the thermodynamic properties of refrigerants are summarized. For pure refrigerants, the virial, cubic, Martin-Hou, Benedict-Webb-Rubin, and Helmholtz energy equations of state and the extended corresponding states model are discussed. High-accuracy formulations for 16 refrigerants are recommended. These models may be extended to mixtures through the use of mixing rules applied either to the parameters of

Mark O McLinden; Eric W Lemmon; Richard T Jacobsen

1998-01-01

13

The thermodynamic properties of thianthrene and phenoxathiin

Measurements leading to the calculation of the ideal-gas thermodynamic properties are reported for thianthrene (Chemical Abstracts registry number [92-85-3]) and phenoxathiin (registry number [262-20-41]). Experimental methods included combustion calorimetry, adiabatic heat-capacity calorimetry, vibrating-tube densitometry, comparative ebulliometry, inclined-piston gauge manometry, and differential-scanning calorimetry (d.s.c.). Critical properties were estimated for both materials based on the measurement results. Entropies, enthalpies, and Gibbs energies of formation were derived for the ideal gas for both compounds for selected temperatures between 298.15 K and 700 K. The property-measurement results reported here for thianthrene and phenoxathiin provide the first experimental gas-phase Gibbs energies of formation for tricyclic diheteroatom-containing molecules.

Steele, W.V.; Chirico, R.D.; Knipmeyer, S.E.; Nguyen, A.

1993-04-01

14

The thermodynamic properties of benzothiazole and benzoxazole

This research program, funded by the Department of Energy, Office of Fossil Energy, Advanced Extraction and Process Technology, provides accurate experimental thermochemical and thermophysical properties for key'' organic diheteroatom-containing compounds present in heavy petroleum feedstocks, and applies the experimental information to thermodynamic analyses of key hydrodesulfurization, hydrodenitrogenation, and hydrodeoxygenation reaction networks. Thermodynamic analyses, based on accurate information, provide insights for the design of cost-effective methods of heteroatom removal. The results reported here, and in a companion report to be completed, will point the way to the development of new methods of heteroatom removal from heavy petroleum. Measurements leading to the calculation of the ideal-gas thermodynamic properties are reported for benzothiazole and benzoxazole. Experimental methods included combustion calorimetry, adiabatic heat-capacity calorimetry, comparative ebulliometry, inclinded-piston gauge manometry, and differential-scanning calorimetry (d.s.c). Critical property estimates are made for both compounds. Entropies, enthalpies, and Gibbs energies of formation were derived for the ideal gas for both compounds for selected temperatures between 280 K and near 650 K. The Gibbs energies of formation will be used in a subsequent report in thermodynamic calculations to study the reaction pathways for the removal of the heteratoms by hydrogenolysis. The results obtained in this research are compared with values present in the literature. The failure of a previous adiabatic heat capacity study to see the phase transition in benzothiazole is noted. Literature vibrational frequency assignments were used to calculate ideal gas entropies in the temperature range reported here for both compounds. Resulting large deviations show the need for a revision of those assignments. 68 refs., 6 figs., 15 tabs.

Steele, W.V.; Chirico, R.D.; Knipmeyer, S.E.; Nguyen, A.

1991-08-01

15

Thermodynamic Properties of Actinides and Actinide Compounds

NASA Astrophysics Data System (ADS)

The necessity of obtaining accurate thermodynamic quantities for the actinide elements and their compounds was recognized at the outset of the Manhattan Project, when a dedicated team of scientists and engineers initiated the program to exploit nuclear energy for military purposes. Since the end of World War II, both fundamental and applied objectives have motivated a great deal of further study of actinide thermodynamics. This chapter brings together many research papers and critical reviews on this subject. It also seeks to assess, to systematize, and to predict important properties of the actinide elements, ions, and compounds, especially for species in which there is significant interest and for which there is an experimental basis for the prediction.

Konings, Rudy J. M.; Morss, Lester R.; Fuger, Jean

16

Thermodynamic properties of 3-dimensional quantum antiferromagnets

NASA Astrophysics Data System (ADS)

We present systematic calculations of thermal properties of 3-dimensional quantum antiferromagnets, in the thermodynamic limit, using series expansions. For this purpose, High Temperature Expansions (HTE) are supplemented by Numerical Linked Cluster (NLC) Expansions.footnotetextR. Applegate et al, Phys. Rev. Lett. 109, 097205 (2012); R. R. P. Singh and J. Oitmaa Phys. Rev. B 85, 144414 (2012); R. R. P. Singh and J. Oitmaa Phys. Rev. B 85, 104406 (2012). These expansions provide essentially exact calculations of thermodynamic properties of the system at (i) all fields at high temperatures and (ii) at all temperatures at high fields. In addition, we show that for classical exchange spin-ice model defined on the pyrochlore lattice, the first order NLC leads to the Pauling approximation, which gives even the zero-field ground state entropy to about one percent accuracy. Thus, these calculations are accurate over a wide parameter range. Results are presented and compared with a variety of experimental systems including pyrochlore materials Yb2Ti2O7 and Er2Ti2O7 and the Hyper Kagome material Na4Ir3O8

Singh, Rajiv R. P.; Oitmaa, Jaan; Gingras, Michel J. P.

2013-03-01

17

Prediction of thermodynamic properties of coal derivatives

The purpose of this research program is to understand the relationship between macroscopic thermodynamic properties and the various types of intermolecular forces. Since coal-derived liquids contain a wide variety of compounds, a theory capable of successfully predicting the thermophysical properties for coal processes must take into account the molecular shapes and all significant intermolecular forces: dispersion forces, anisotropic forces due to dipoles and quadrupoles, as well as Lewis acid-base interactions. We have developed the Acid-Base-Perturbed-Anisotropic-Chain Theory (ABPACT), a comprehensive theory that is capable of predicting the thermophysical properties for many systems where these different intermolecular forces are present. The ABPACT can treat non-polar compounds, polar compounds and compounds that associate through Lewis acid-base interactions. In addition to our theoretical work, we have used computer simulations to evaluate (and in some cases correct) the assumptions made in this theory. We also have conducted experiments to help us better understand the interplay of different kinds of interactions in multicomponent mixtures.

Donohue, M.D.

1990-09-01

18

Calculation of the standard molal thermodynamic properties of crystalline peptides

NASA Astrophysics Data System (ADS)

To augment the relatively sparse set of thermodynamic data available for high molecular weight biopolymers, group additivity algorithms have been developed to estimate the heat capacity power function coefficients and standard molal thermodynamic properties of crystalline peptides in the multitude of biogeochemical environments in which they are found. Group contributions representing the 20 common amino acids plus 5-hydroxylysine and 4-hydroxyproline for each coefficient and property were generated using the thermodynamic properties of crystalline amino acids, polypeptides and other organic compounds. These group contributions were in turn used to compute the thermodynamic properties of naturally occurring proteins that are found in a crystalline state in cells. The coefficients and properties of the model compounds, group contributions and proteins are tabulated. In a demonstration of the uncertainty of the thermodynamic properties of the groups generated in this study, experimentally determined heat capacities and entropies of crystalline homopolypeptides and proteins taken from the literature have been compared to estimates of these quantities. Additionally, standard molal volumes for 24 amino acids have been recalculated in light of inconsistencies in an earlier analysis, and the standard molal thermodynamic properties of aqueous and crystalline methionine at 25 °C and 0.1 MPa have been reassessed. Calculations of this kind can be carried out to thermodynamically describe the biogeochemical interactions throughout the broad range of environmental settings in which they are known to occur.

LaRowe, Douglas E.; Dick, Jeffrey M.

2012-03-01

19

Measurement of Thermodynamic Properties of Titanium Aluminum Alloys

NASA Technical Reports Server (NTRS)

This final report is a summary of the work done by Professor Mehrotra at NASA Lewis Research Center. He has worked extensively on the measurement of thermodynamic properties of titanium aluminum alloys over the past six years.

Mehrotra, Gopal

1995-01-01

20

Thermodynamic properties of UF6 at high temperatures

NASA Technical Reports Server (NTRS)

The equilibrium composition and the thermodynamic properties of the mixture resulting from the decomposition of uranium hexafluoride is calculated for temperatures ranging from 600 K to 4000 K at pressures from 0.01 atmospheres to 10 atmospheres.

Hassan, H. A.; Deese, J. E.

1974-01-01

21

Thermodynamic property determination in low gravity

NASA Technical Reports Server (NTRS)

Techniques for determining heat capacities and other properties of molten metals were investigated and critically evaluated. Precisely determining heat capacities calorimetrically in space poses several problems. The weight of a drop calorimeter block along with the necessity of obtaining a large number of data points tend to make traditional approaches appear infeasible. However, for many substances exhibiting sufficiently high thermal conductivities and with known emissivities, it appears possible to investigate their properties by observing the rate of cooling of a levitated sphere which is initially at a uniform temperature above the melting point. A special advantage of the levitation method is that considerable supercooling is expected, making the study of the heat capacities of molten metals both above and below their melting points possible.

Margrave, J. L.

1977-01-01

22

The thermodynamic properties of organic oxygen compounds

The principles of group additivity are used to compare a series of cyclic hydrocarbons with the corresponding oxygen-containing analogs. The strengths and limitations of the group-additivity method are demonstrated and recommendations are made for measurements essential to the improvement of the accuracy of the predicted properties. The ideal-gas enthalpies of formation and ideal-gas entropies (which are used in combination to

R. D. Chirico; W. V. Steele; A. Hossenlopp; A. Nguyen; D. G. Archer; M. M. Strube

1988-01-01

23

Thermodynamical properties of graphene in noncommutative phase-space

NASA Astrophysics Data System (ADS)

We investigated the thermodynamic properties of graphene in a noncommutative phase-space in the presence of a constant magnetic field. In particular, we determined the behaviour of the main thermodynamical functions: the Helmholtz free energy, the mean energy, the entropy and the specific heat. The high temperature limit is worked out and the thermodynamic quantities, such as mean energy and specific heat, exhibit the same features as the commutative case. Possible connections with the results already established in the literature are discussed briefly.

Santos, Victor; Maluf, R. V.; Almeida, C. A. S.

2014-10-01

24

Thermodynamical properties of graphene in noncommutative phase-space

We investigated the thermodynamic properties of graphene in a noncommutative phase-space in the presence of a constant magnetic field. In particular, we determined the behaviour of the main thermodynamical functions: the Helmholtz free energy, the mean energy, the entropy and the specific heat. The high temperature limit is worked out and the thermodynamic quantities, such as mean energy and specific heat, exhibit the same features as the commutative case. Possible connections with the results already established in the literature are discussed briefly.

Victor Santos; R. V. Maluf; C. A. S. Almeida

2014-01-31

25

A Theoretical Survey of DNA Oligomers Thermodynamic Properties

NASA Astrophysics Data System (ADS)

Central to numerous techniques of molecular biology, some ubiquitous as PCR and Southern blotting, is the design of oligonucleotide probes possessing specific thermodynamic properties. Calculations of oligonucleotide thermodynamics, based on the nearest-neighbor model, have become increasingly accurate and have been extended to include not only canonical duplexes but also duplexes with mismatches. Here we use validated theoretical methods to explore the general behavior of melting temperature (Tm), free energy, and hybridization propensity in response to changes in experimental conditions and sequence. Distributions of these thermodynamic quantities are presented for DNA sequences of 5 to 50 bases sampled from the human genome. The effects of concentrations (oligonucleotide, cations), temperature, sequence composition constrains, and introduction of mismatches are considered. Thermodynamic quantities were computed using specially built softwares to facilitate our length sampling strategy. Our results provide a general survey of typical and limiting thermodynamic values that will be useful for the wide range of applications that rely on DNA probe design.

Koehler, Ryan; Peyret, Nicolas

2002-08-01

26

Structural properties of nanoclusters: Energetic, thermodynamic, and kinetic effects

The structural properties of free nanoclusters are reviewed. Special attention is paid to the interplay of energetic, thermodynamic, and kinetic factors in the explanation of cluster structures that are actually observed in experiments. The review starts with a brief summary of the experimental methods for the production of free nanoclusters and then considers theoretical and simulation issues, always discussed in

Francesca Baletto; Riccardo Ferrando

2005-01-01

27

The thermodynamic properties of bis-(?5-cyclopentadienylirondicarbonyl)

NASA Astrophysics Data System (ADS)

The temperature dependence of the heat capacity of crystalline bis-(?5-cyclopentadienylirondicarbonyl) was studied over the temperature range 5-495 K in precision adiabatic vacuum and differential scanning calorimeters. The temperature dependence contained an anomaly (160-295 K) with a maximum at 250 K interpreted as a ? transition in the solid state. The fusion of the sample occurred at 435-491 K; it was accompanied by partial substance decomposition. The thermodynamic functions of crystalline bis-(?5-cyclopentadienylirondicarbonyl) were calculated from T?0 to 472.9 K. The enthalpy of combustion of the compound was determined in an isothermal calorimeter with a stationary bomb. The standard thermodynamic functions of its formation in the crystalline state at 298.15 K were calculated.

Kozlova, M. S.; Markin, A. V.; Larina, V. N.; Domracheva, L. G.; Sheiman, M. S.; Karyakin, N. V.

2008-12-01

28

NASA Glenn Coefficients for Calculating Thermodynamic Properties of Individual Species

NASA Technical Reports Server (NTRS)

This report documents the library of thermodynamic data used with the NASA Glenn computer program CEA (Chemical Equilibrium with Applications). This library, containing data for over 2000 solid, liquid, and gaseous chemical species for temperatures ranging from 200 to 20,000 K, is available for use with other computer codes as well. The data are expressed as least-squares coefficients to a seven-term functional form for C((sup o)(sub p)) (T) / R with integration constants for H (sup o) (T) / RT and S(sup o) (T) / R. The NASA Glenn computer program PAC (Properties and Coefficients) was used to calculate thermodynamic functions and to generate the least-squares coefficients. PAC input was taken from a variety of sources. A complete listing of the database is given along with a summary of thermodynamic properties at 0 and 298.15 K.

McBride, Bonnie J.; Zehe, Michael J.; Gordon, Sanford

2002-01-01

29

Thermodynamic properties of fluids from Fluctuation Solution Theory

Fluctuation Theory develops exact relations between integrals of molecular correlation functions and concentration derivatives of pressure and chemical potential. These quantities can be usefully correlated, particularly for mechanical and thermal properties of pure and mixed dense fluids and for activities of strongly nonideal liquid solutions. The expressions yield unique formulae for the desirable thermodynamic properties of activity and density. The molecular theory origins of the flucuation properties, their behavior for systems of technical interest and some of their successful correlations will be described. Suggestions for fruitful directions will be suggested.

O'Connell, J.P.

1990-01-01

30

Thermodynamic properties of fluids from Fluctuation Solution Theory

Fluctuation Theory develops exact relations between integrals of molecular correlation functions and concentration derivatives of pressure and chemical potential. These quantities can be usefully correlated, particularly for mechanical and thermal properties of pure and mixed dense fluids and for activities of strongly nonideal liquid solutions. The expressions yield unique formulae for the desirable thermodynamic properties of activity and density. The molecular theory origins of the flucuation properties, their behavior for systems of technical interest and some of their successful correlations will be described. Suggestions for fruitful directions will be suggested.

O`Connell, J.P.

1990-12-31

31

Computational Models of Thermodynamic Properties of Uranium Nitride

NASA Astrophysics Data System (ADS)

The structural, elastic, electronic, phonon and thermodynamic properties of uranium nitride (UN) have been systematically studied by density functional theory (DFT) calculations. The calculated electronic band structure shows that UN is a metallic phase. The ground state structural and elastic properties predicted by DFT agree well with experiments. The thermodynamic properties of UN are studied by quasiharmonic approximation by including both lattice vibrational and thermal electronic contributions to free energies. The calculated enthalpy, entropy, Gibbs energy and heat capacity show an excellent agreement with experimental results. The thermal electronic contribution due to 5f electrons of U is found to be critical to describe the free energy of UN due to its metallic character.

Mei, Zhi-Gang; Stan, Marius

2014-06-01

32

Thermodynamic properties of bulk and confined water.

The thermodynamic response functions of water display anomalous behaviors. We study these anomalous behaviors in bulk and confined water. We use nuclear magnetic resonance (NMR) to examine the configurational specific heat and the transport parameters in both the thermal stable and the metastable supercooled phases. The data we obtain suggest that there is a behavior common to both phases: that the dynamics of water exhibit two singular temperatures belonging to the supercooled and the stable phase, respectively. One is the dynamic fragile-to-strong crossover temperature (T(L) ? 225 K). The second, T* ? 315 ± 5 K, is a special locus of the isothermal compressibility K(T)(T, P) and the thermal expansion coefficient ?(P)(T, P) in the P-T plane. In the case of water confined inside a protein, we observe that these two temperatures mark, respectively, the onset of protein flexibility from its low temperature glass state (T(L)) and the onset of the unfolding process (T*). PMID:25399169

Mallamace, Francesco; Corsaro, Carmelo; Mallamace, Domenico; Vasi, Sebastiano; Vasi, Cirino; Stanley, H Eugene

2014-11-14

33

Thermodynamic and melting properties of RDX at elevated pressures

NASA Technical Reports Server (NTRS)

The laboratory set up for determination of melting and thermodynamic properties of RDX using a diamond anvil cell apparatus capable of pressures exceeding 10 kbar and 250 C is described. The slope of the melting temperature versus applied pressure curve for RDX, as determined in the diamond cell, was found to equal 4.09 + or - 0.6 C (kbar). The density of liquid RDX at its melting point was calculated from this slope to be approximately 1.63 gm/cu cm. Practical and theoretical considerations in using the diamond anvil cell to generate thermodynamic data on RDX are discussed.

Carlson, D. W.; Nauflett, G. W.; Brasch, J. W., Sr.; Austin, T. D.

1980-01-01

34

Thermodynamical property of entanglement entropy for excited states.

We argue that the entanglement entropy for a very small subsystem obeys a property which is analogous to the first law of thermodynamics when we excite the system. In relativistic setups, its effective temperature is proportional to the inverse of the subsystem size. This provides a universal relationship between the energy and the amount of quantum information. We derive the results using holography and confirm them in two-dimensional field theories. We will also comment on an example with negative specific heat and suggest a connection between the second law of thermodynamics and the strong subadditivity of entanglement entropy. PMID:23496702

Bhattacharya, Jyotirmoy; Nozaki, Masahiro; Takayanagi, Tadashi; Ugajin, Tomonori

2013-03-01

35

Thermodynamic properties and diffusion of water + methane binary mixtures

Thermodynamic and diffusion properties of water + methane mixtures in a single liquid phase are studied using NVT molecular dynamics. An extensive comparison is reported for the thermal pressure coefficient, compressibilities, expansion coefficients, heat capacities, Joule-Thomson coefficient, zero frequency speed of sound, and diffusion coefficient at methane concentrations up to 15% in the temperature range of 298–650 K. The simulations reveal a complex concentration dependence of the thermodynamic properties of water + methane mixtures. The compressibilities, heat capacities, and diffusion coefficients decrease with increasing methane concentration, whereas values of the thermal expansion coefficients and speed of sound increase. Increasing methane concentration considerably retards the self-diffusion of both water and methane in the mixture. These effects are caused by changes in hydrogen bond network, solvation shell structure, and dynamics of water molecules induced by the solvation of methane at constant volume conditions.

Shvab, I.; Sadus, Richard J., E-mail: rsadus@swin.edu.au [Centre for Molecular Simulation, Swinburne University of Technology, PO Box 218 Hawthorn, Victoria 3122 (Australia)

2014-03-14

36

Generalized thermodynamic and transport properties. I. Simple liquids

NASA Astrophysics Data System (ADS)

We propose a method by which the generalized transport properties and coefficients at all wavelengths and frequencies can be obtained by inversion of an exact kinetic equation. The necessary data are the density-density, energy-energy, and density-energy time correlation functions, which can be obtained by molecular-dynamics simulation. In addition, also the coupling between viscous stress tensor and energy flux vector can be obtained without approximation. This allows one to check the validity of the Markov assumption in a straightforward way. As a first test case, the theory is applied to liquid argon in two thermodynamic states. For this system, we calculate and discuss generalized thermodynamic (enthalpy, specific heats, and thermal expansion) and transport properties (longitudinal viscosity, thermal conductivity).

Bertolini, D.; Tani, A.

2011-03-01

37

Thermodynamic properties of massive dilaton black holes, 2

We numerically reanalyze static and spherically symmetric black hole solutions in an Einstein-Maxwell-dilaton system with a dilaton potential $m_{d}^{2}\\phi^{2}$. We investigate thermodynamic properties for various dilaton coupling constants and find that thermodynamic properties change at a critical dilaton mass $m_{d,crit}$. For $m_{d}\\geq m_{d,crit}$, the black hole becomes an extreme solution for a nonzero horizon radius $r_{h,ex}$ as the Reissner-Nordstr\\"om black hole. However, if $m_{d}$ is nearly equal to $m_{d,crit}$, there appears a solution of smaller horizon radius than $r_{h,ex}$. For $m_{d}

Tamaki, T

2002-01-01

38

Thermodynamic properties of materials derived from coal liquefaction

Few measurements of the thermodynamic properties of materials obtained from the liquefaction of coal have been reported. Because several sets of well-defined fractions of coal-derived materials existed that had been separated and characterized by the Characterization Branch of the Division of Processing and Thermodynamics of this Center, the expertise of the Thermodynamics Research Branch was utilized to measure enthalpies of combustion and heat capacities of these materials. The sets of fractions came from five sources: a synthetic crude oil derived from western Kentucky coal by the char-oil-energy development (COED) process, a synthetic crude oil derived from Utah A-seam coal by the COED process, material derived from West Virginia Pittsburgh seam coal by the Synthoil process, material derived from Illinois No. 6 coal by the H-Coal process and materials derived from subbituminous coal by the Conoco Colstrip zinc chloride hydrocracking process.

Smith, N.K.; Lee-Bechtold, S.H.; Good, W.D.

1980-01-01

39

Thermodynamic Properties of Ammonia–Water Mixtures for Power Cycles

Power cycles with ammonia–water mixtures as working fluids have been shown to reach higher thermal efficiencies than the traditional steam turbine (Rankine) cycle with water as the working fluid. Different correlations for the thermo-dynamic properties of ammonia–water mixtures have been used in studies of ammonia–water mixture cycles described in the literature. Four of these correlations are compared in this paper.

E. Thorin; C. Dejfors; G. Svedberg

1998-01-01

40

Thermodynamic and magnetocaloric properties of geometrically frustrated Ising nanoclusters

NASA Astrophysics Data System (ADS)

Thermodynamic and magnetocaloric properties of geometrically frustrated Ising spin clusters of selected shapes and sizes are studied by exact enumeration. In the ground state the magnetization and the entropy show step-wise variations with an applied magnetic field. The number of steps, their widths and heights depend on the cluster shape and size. While the character of the magnetization plateau heights is always increasing, the entropy is not necessarily decreasing function of the field, as one would expect. For selected clusters showing some interesting ground-state properties, the calculations are extended to finite temperatures by exact enumeration of densities of states in the energy-magnetization space. In zero field the focus is laid on a peculiar behavior of some thermodynamic quantities, such as the entropy, the specific heat and the magnetic susceptibility. In finite fields various thermodynamic functions are studied in the temperature-field parameter plane and particular attention is paid to the cases showing an enhanced magnetocaloric effect. The exact results on the finite clusters are compared with the thermodynamic limit behavior obtained from Monte Carlo simulations.

Žukovi?, M.

2015-01-01

41

Determining thermodynamic properties of molecular interactions from single crystal studies.

The concept of single crystals of macromolecules as thermodynamic systems is not a common one. However, it should be possible to derive thermodynamic properties from single crystal structures, if the process of crystallization follows thermodynamic rules. We review here an example of how the stabilizing potentials of molecular interactions can be measured from studying the properties of DNA crystals. In this example, we describe an assay based on the four-stranded DNA junction to determine the stabilizing potentials of halogen bonds, a class of electrostatic interactions, analogous to hydrogen bonds, that are becoming increasing recognized as important for conferring specificity in protein-ligand complexes. The system demonstrates how crystallographic studies, when coupled with calorimetric methods, allow the geometries at the atomic level to be directly correlated with the stabilizing energies of molecular interactions. The approach can be generally applied to study the effects of DNA sequence and modifications of the thermodynamic stability of the Holliday junction and, by inference, on recombination and recombination dependent processes. PMID:23933330

Vander Zanden, Crystal M; Carter, Megan; Ho, Pui Shing

2013-11-01

42

Coefficients for calculating thermodynamic and transport properties of individual species

NASA Technical Reports Server (NTRS)

Libraries of thermodynamic data and transport properties are given for individual species in the form of least-squares coefficients. Values of C(sup 0)(sub p)(T), H(sup 0)(T), and S(sup 0)(T) are available for 1130 solid, liquid, and gaseous species. Viscosity and thermal conductivity data are given for 155 gases. The original C(sup 0)(sub p)(T) values were fit to a fourth-order polynomial with integration constants for H(sup 0)(T) and S(sup 0)(T). For each species the integration constant for H(sup 0)(T) includes the heat of formation. Transport properties have a different functional form. The temperature range for most of the data is 300 to 5000 K, although some of the newer thermodynamic data have a range of 200 to 6000 K. Because the species are mainly possible products of reaction, the data are useful for chemical equilibrium and kinetics computer codes. Much of the data has been distributed for several years with the NASA Lewis equilibrium program CET89. The thermodynamic properties of the reference elements were updated along with about 175 species that involve the elements carbon, hydrogen, oxygen, and nitrogen. These sets of data will be distributed with the NASA Lewis personal computer program for calculating chemical equilibria, CETPC.

Mcbride, Bonnie J.; Gordon, Sanford; Reno, Martin A.

1993-01-01

43

Coefficients for calculating thermodynamic and transport properties of individual species

NASA Astrophysics Data System (ADS)

Libraries of thermodynamic data and transport properties are given for individual species in the form of least-squares coefficients. Values of C(sup 0)(sub p)(T), H(sup 0)(T), and S(sup 0)(T) are available for 1130 solid, liquid, and gaseous species. Viscosity and thermal conductivity data are given for 155 gases. The original C(sup 0)(sub p)(T) values were fit to a fourth-order polynomial with integration constants for H(sup 0)(T) and S(sup 0)(T). For each species the integration constant for H(sup 0)(T) includes the heat of formation. Transport properties have a different functional form. The temperature range for most of the data is 300 to 5000 K, although some of the newer thermodynamic data have a range of 200 to 6000 K. Because the species are mainly possible products of reaction, the data are useful for chemical equilibrium and kinetics computer codes. Much of the data has been distributed for several years with the NASA Lewis equilibrium program CET89. The thermodynamic properties of the reference elements were updated along with about 175 species that involve the elements carbon, hydrogen, oxygen, and nitrogen. These sets of data will be distributed with the NASA Lewis personal computer program for calculating chemical equilibria, CETPC.

McBride, Bonnie J.; Gordon, Sanford; Reno, Martin A.

1993-10-01

44

A thermodynamic approach to obtain materials properties for engineering applications

NASA Technical Reports Server (NTRS)

With the ever increases in the capabilities of computers for numerical computations, we are on the verge of using these tools to model manufacturing processes for improving the efficiency of these processes as well as the quality of the products. One such process is casting for the production of metals. However, in order to model metal casting processes in a meaningful way it is essential to have the basic properties of these materials in their molten state, solid state as well as in the mixed state of solid and liquid. Some of the properties needed may be considered as intrinsic such as the density, heat capacity or enthalpy of freezing of a pure metal, while others are not. For instance, the enthalpy of solidification of an alloy is not a defined thermodynamic quantity. Its value depends on the micro-segregation of the phases during the course of solidification. The objective of the present study is to present a thermodynamic approach to obtain some of the intrinsic properties and combining thermodynamics with kinetic models to estimate such quantities as the enthalpy of solidification of an alloy.

Chang, Y. Austin

1993-01-01

45

Structural and thermodynamics properties of organo-modified montmorillonite clay

NASA Astrophysics Data System (ADS)

Polymer clay nanocomposites (PCNs) have been seen as the most novel materials in engineering applications since they exhibit significant improvement in mechanical and physical properties. Indeed, with few amount of organoclay, PCNs exhibit enhanced mechanical, optical, thermal and liquid or gas barrier properties compared to pure polymers and to their counterpart microcomposites. Thus, organoclays are extensively used as precursors in the preparation of PCNs. They are the best candidate in reinforcing PCNs because of the lightweight and the high availability of clay minerals in the nature. However, structure and physical phenomena arising at molecular level in organoclays, and subsequently in PCNs, are not completely or difficultly accessible with existing experimental techniques. In this work, molecular dynamics (MD) simulation was conducted using the combination of two force fields (CLAYFF and CHARMM) to evaluate the thermodynamics and structural properties of organoclay such as heat capacities, isothermal bulk modulus, density, basal spacing and chains arrangement in the interlayer spacing. Our results regarding the basal spacing and density are in fairly good agreement with available experimental data. This allows us to validate the use of the two force fields to represent interactions in organoclays. The effect of the cation exchange capacity (CEC) on the basal spacing and the thermodynamics properties is assessed. We found, through our MD simulation, that the calculated isothermal bulk modulus is in good agreement with the density value of organoclays with two different CEC.

Anoukou, K.; Zaoui, A.; Zaïri, F.; Naït-Abdelaziz, M.; Gloaguen, J. M.

2015-01-01

46

Optical and thermodynamic property measurements of liquid metals and alloys

NASA Technical Reports Server (NTRS)

Optical properties and spectral emissivities of liquid silicon, titanium, niobium, and zirconium were investigated by HeNe laser polarimetry at 632.8 nm. The metals were of a high purity and, except for zirconium, clean. The more demanding environmental requirements for eliminating oxide or nitride phases from zirconium were not met. Containerless conditions were achieved by electromagnetic levitation and heating. CO2 laser beam heating was also used to extend the temperature range for stable levitation and to heat solid silicon to form the metallic liquid phase. Corrections to previously reported calorimetric measurements of the heat capacity of liquid niobium were derived from the measured temperature dependence of its spectral emissivity. Property measurements were obtained for supercooled liquid silicon and supercooling of liquid zirconium was accomplished. The purification of liquid metals and the extension of this work on liquids to the measurement of thermodynamic properties and phase equilibria are discussed.

Weber, J. K. R.; Krishnan, Shankar; Schiffman, Robert A.; Nordine, Paul C.

1991-01-01

47

ERIC Educational Resources Information Center

In this chapter on decisions made by federal and state courts during 1983 concerning school property it is noted that no new trends emerged during the year. Among the topics addressed are the extent of school board authority over property use and other property matters; the attachment and detachment of land from school district holdings; school…

Goldblatt, Steven M.

48

A family of bismuth ferrites (BFO), including Bi2Fe4O9, BiFeO3, and Bi25FeO39 with different morphologies, has been prepared by the hydrothermal method assisted by different alkaline mineralizers. X-ray diffraction refinement calculations are carried out to study the crystal structures of bismuth ferrites. A thermodynamic calculation based on the dissolution-precipitation model was carried out to analyze the hydrothermal synthesis of BFO powders. Magnetic measurements of the obtained bismuth ferrites show different magnetic properties from 5 K to 350 K. PMID:22630029

Du, Yi; Cheng, Zhenxiang; Yu, Zhenwei; Dou, Shi Xue; Wang, Xiaolin; Liu, L Q

2012-02-01

49

This work has considered the intrinsic influence of bond energy on the macroscopic, thermodynamic, and mechanical properties of crystalline materials. A general criterion is proposed to evaluate the properties of nanocrystalline materials. The interrelation between the thermodynamic and mechanical properties of nanomaterials is presented and the relationship between the variation of these properties and the size of the nanomaterials is explained. The results of our work agree well with thermodynamics, molecular dynamics simulations, and experimental results. This method is of significance in investigating the size effects of nanomaterials and provides a new approach for studying their thermodynamic and mechanical properties. PMID:25288913

2014-01-01

50

To look for high energy density materials (HEDM), the relationships between the structures and the performances of polynitroadamantanes (PNAs) were studied. The assigned infrared spectra of PNAs obtained at the density functional theory (DFT) B3LYP/6-31G level were used to compute the thermodynamic properties on the basis of the principle of statistical thermodynamics. The thermodynamic properties are linearly related with the number of nitro groups as well as with the temperatures. Detonation properties of PNAs were evaluated by using the Kamlet-Jacobs equation based on the calculated densities and heats of formation for titled compounds, and it is found that only when the number of nitro groups of PNA is equal to or more than eight can it be possible for PNAs to be used as HEDMs. The relative stabilities of PNAs were studied by the pyrolysis mechanism using the UHF-PM3 method. The homolysis of the C-NO2 bond is predicted to be the initial step of thermal decomposition. The activation energies (Ea) for the homolysis decrease with the number of nitro groups being increased on the whole. The stability order of dinitroadamantane isomers derived from the interactions among nitro groups is consistent with what is determined by Ea. The relations between the Ea's and the electronic structure parameters were discussed. In combination with the stability, PNA (1,2,3,4,5,6,7,8,9,10-) is recommended as the target of HEDM with insensitivity. PMID:16331911

Xu, Xiao Juan; Xiao, He Ming; Gong, Xue Dong; Ju, Xue Hai; Chen, Zhao Xu

2005-12-15

51

Thermodynamic properties of pulverized coal during rapid heating devolatilization processes

Knowledge of the thermodynamic and morphological properties of coal associated with rapid heating decomposition pathways is essential to progress in coal utilization technology. Specifically, knowledge of the heat of devolatilization, surface area and density of coal as a function of rank characteristics, temperature and extent of devolatilization in the context of rapid heating conditions is required both, for the fundamental determination of kinetic parameters of coal devolatilization, and to refine existing devolatilization sub-models used in comprehensive coal combustion codes. The objective of this research is to obtain data on the thermodynamic properties and morphology of coal under conditions of rapid heating. Specifically, the total heat of devolatilization, external surface area, BET surface area and true density will be measured for representative coal samples. In addition, for one coal, the contribution of each of the following components to the overall heat of devolatilization will be measured: the specific heat of coal/char during devolatilization, the heat of thermal decomposition of the coal, the specific heat capacity of tars, and the heat of vaporization of tars. Calibration of the heated grid calorimeter (Task 2) was completed this reporting period. Several refinements to the heated grid apparatus have been implemented which allow quantitative determination of sample heat capacity at high heating rates.

Proscia, W.M.; Freihaut, J.D.

1993-03-01

52

Vibrational and thermodynamic properties of transition-metal nanoclusters

NASA Astrophysics Data System (ADS)

The knowledge of the vibrational spectrum of a cluster, which is the fingerprint of its structure, is necessary for the development of thermodynamics of clusters (melting, heat capacity, solid-solid structural transitions) and for the understanding of experimental vibrational spectra. In summary, the full vibrational spectrum of NiN and CuN nanoclusters with N from 2 to 150 atoms has been determined using the analytical expression of the embedded-atom method (EAM) for the force-constant tensor for the first time. In the determination of the spectra we have employed the global-minimum structures obtained in our previous unbiased EAM studies (see e.g. Physical Review B, 2004; 2006). Furthermore, using those spectra and the superposition approximation, the thermodynamic properties of the clusters have been calculated quantum mechanically, including their heat capacity and solid-solid transition temperatures for several structural changes in the Ni and Cu clusters. Both the vibrational spectrum and the thermodynamic functions show strong cluster-size effects. We emphasized that our approach is general. It is based only on the (common) EAM form of the total energy and applicable to many other many-body potentials.

Grigoryan, Valeri G.; Springborg, Michael

2013-03-01

53

Thermodynamic properties of pulverized coal during rapid heating devolatilization processes

The thermodynamic properties of coal under conditions of rapid heating have been determined using a combination of UTRC facilities including a proprietary rapid heating rate differential thermal analyzer (RHR-DTA), a microbomb calorimeter (MBC), an entrained flow reactor (EFR), an elemental analyzer (EA), and a FT-IR. The total heat of devolatilization, was measured for a HVA bituminous coal (PSOC 1451D, Pittsburgh No. 8) and a LV bituminous coal (PSOC 1516D, Lower Kittaning). For the HVA coal, the contributions of each of the following components to the overall heat of devolatilization were measured: the specific heat of coal/char during devolatilization, the heat of thermal decomposition of the coal, the specific heat capacity of tars, and the heat of vaporization of tars. Morphological characterization of coal and char samples was performed at the University of Pittsburgh using a PC-based image analysis system, BET apparatus, helium pcynometer, and mercury porosimeter. The bulk density, true density, CO{sub 2} surface area, pore volume distribution, and particle size distribution as a function of extent of reaction are reported for both the HVA and LV coal. Analyses of the data were performed to obtain the fractal dimension of the particles as well as estimates for the external surface area. The morphological data together with the thermodynamic data obtained in this investigation provides a complete database for a set of common, well characterized coal and char samples. This database can be used to improve the prediction of particle temperatures in coal devolatilization models. Such models are used both to obtain kinetic rates from fundamental studies and in predicting furnace performance with comprehensive coal combustion codes. Recommendations for heat capacity functions and heats of devolatilization for the HVA and LV coals are given. Results of sample particle temperature calculations using the recommended thermodynamic properties are provided.

Proscia, W.M.; Freihaut, J.D. [United Technologies Research Center, E. Hartford, CT (United States); Rastogi, S.; Klinzing, G.E. [Univ. of Pittsburg, PA (United States)

1994-07-01

54

NASA Technical Reports Server (NTRS)

The two most common approaches used to formulate thermodynamic properties of pure substances are fundamental (or characteristic) equations of state (Helmholtz and Gibbs functions) and a piecemeal approach that is described in Adebiyi and Russell (1992). This paper neither presents a different method to formulate thermodynamic properties of pure substances nor validates the aforementioned approaches. Rather its purpose is to present a method to generate property tables from existing property packages and a method to facilitate the accurate interpretation of fluid thermodynamic property data from those tables. There are two parts to this paper. The first part of the paper shows how efficient and usable property tables were generated, with the minimum number of data points, using an aerospace industry standard property package. The second part describes an innovative interpolation technique that has been developed to properly obtain thermodynamic properties near the saturated liquid and saturated vapor lines.

Nguyen, Huy H.; Martin, Michael A.

2004-01-01

55

ms2: A molecular simulation tool for thermodynamic properties

NASA Astrophysics Data System (ADS)

This work presents the molecular simulation program ms2 that is designed for the calculation of thermodynamic properties of bulk fluids in equilibrium consisting of small electro-neutral molecules. ms2 features the two main molecular simulation techniques, molecular dynamics (MD) and Monte-Carlo. It supports the calculation of vapor-liquid equilibria of pure fluids and multi-component mixtures described by rigid molecular models on the basis of the grand equilibrium method. Furthermore, it is capable of sampling various classical ensembles and yields numerous thermodynamic properties. To evaluate the chemical potential, Widom's test molecule method and gradual insertion are implemented. Transport properties are determined by equilibrium MD simulations following the Green-Kubo formalism. ms2 is designed to meet the requirements of academia and industry, particularly achieving short response times and straightforward handling. It is written in Fortran90 and optimized for a fast execution on a broad range of computer architectures, spanning from single processor PCs over PC-clusters and vector computers to high-end parallel machines. The standard Message Passing Interface (MPI) is used for parallelization and ms2 is therefore easily portable to different computing platforms. Feature tools facilitate the interaction with the code and the interpretation of input and output files. The accuracy and reliability of ms2 has been shown for a large variety of fluids in preceding work. Program summaryProgram title:ms2 Catalogue identifier: AEJF_v1_0 Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AEJF_v1_0.html Program obtainable from: CPC Program Library, Queen's University, Belfast, N. Ireland Licensing provisions: Special Licence supplied by the authors No. of lines in distributed program, including test data, etc.: 82 794 No. of bytes in distributed program, including test data, etc.: 793 705 Distribution format: tar.gz Programming language: Fortran90 Computer: The simulation tool ms2 is usable on a wide variety of platforms, from single processor machines over PC-clusters and vector computers to vector-parallel architectures. (Tested with Fortran compilers: gfortran, Intel, PathScale, Portland Group and Sun Studio.) Operating system: Unix/Linux, Windows Has the code been vectorized or parallelized?: Yes. Message Passing Interface (MPI) protocol Scalability. Excellent scalability up to 16 processors for molecular dynamics and >512 processors for Monte-Carlo simulations. RAM:ms2 runs on single processors with 512 MB RAM. The memory demand rises with increasing number of processors used per node and increasing number of molecules. Classification: 7.7, 7.9, 12 External routines: Message Passing Interface (MPI) Nature of problem: Calculation of application oriented thermodynamic properties for rigid electro-neutral molecules: vapor-liquid equilibria, thermal and caloric data as well as transport properties of pure fluids and multi-component mixtures. Solution method: Molecular dynamics, Monte-Carlo, various classical ensembles, grand equilibrium method, Green-Kubo formalism. Restrictions: No. The system size is user-defined. Typical problems addressed by ms2 can be solved by simulating systems containing typically 2000 molecules or less. Unusual features: Feature tools are available for creating input files, analyzing simulation results and visualizing molecular trajectories. Additional comments: Sample makefiles for multiple operation platforms are provided. Documentation is provided with the installation package and is available at http://www.ms-2.de. Running time: The running time of ms2 depends on the problem set, the system size and the number of processes used in the simulation. Running four processes on a "Nehalem" processor, simulations calculating VLE data take between two and twelve hours, calculating transport properties between six and 24 hours.

Deublein, Stephan; Eckl, Bernhard; Stoll, Jürgen; Lishchuk, Sergey V.; Guevara-Carrion, Gabriela; Glass, Colin W.; Merker, Thorsten; Bernreuther, Martin; Hasse, Hans; Vrabec, Jadran

2011-11-01

56

NASA Technical Reports Server (NTRS)

Thermodynamic and transport combustion properties were calculated for a wide range of conditions for the reaction of hydrocarbons with air. Three hydrogen-carbon atom ratios (H/C = 1.7, 2.0, 2.1) were selected to represent the range of aircraft fuels. For each of these H/C ratios, combustion properties were calculated for the following conditions: Equivalence ratio: 0, 0.25, 0.5, 0.75, 1.0, 1.25 Water - dry air mass ratio: 0, 0.03 Pressure, kPa: 1.01325, 10.1325, 101.325, 1013.25, 5066.25 (or in atm: 0.01, 0.1, 1, 10, 50) Temperature, K: every 10 degrees from 200 to 900 K; every 50 degrees from 900 to 3000 K Temperature, R: every 20 degrees from 360 to 1600 R; very 100 degrees from 1600 to 5400 R. The properties presented are composition, density, molecular weight, enthalphy, entropy, specific heat at constant pressure, volume derivatives, isentropic exponent, velocity of sound, viscosity, thermal conductivity, and Prandtl number. Property tables are based on composites that were calculated by assuming both: (1) chemical equilibrium (for both homogeneous and heterogeneous phases) and (2) constant compositions for all temperatures. Properties in SI units are presented in this report for the Kelvin temperature schedules.

Gordon, S.

1982-01-01

57

Molecular dynamics calculation of thermodynamic properties of iron solidification

NASA Astrophysics Data System (ADS)

The aim of this study is to identify the best available inter-atomic potentials for molecular dynamics (MD) calculation of solidification of iron and then to use the best potential to calculate thermodynamic properties such as equilibrium melting temperature, enthalpy, heat capacity and solid-liquid interfacial free energy. Our study reveals that embedded atom method (EAM) potential developed by Ackland et al. [2004 J. Phys.: Condens Matter. 16 S2629] appears to be the most accurate model for MD simulation of iron solidification. Simulations with the above EAM model predict the equilibrium melting temperature of iron is 1790K, the solid-liquid interfacial energy 214 mJ/m2. The difference with the experimental data is 1.2%, and 4.9% respectively.

Liu, J.; Dong, H. B.

2012-07-01

58

A note on electrical and thermodynamic properties of Isolated Horizon

The electrical laws and Carnot cycle of Isolated Horizon (IH) are investigated in this paper. We establish the Ohm's law and Joule's law of an Isolated Horizon, and find that the conceptual picture of black holes (Membrane Paradigm) can also apply to this kind of quasi-local black holes. We also investigate the geometrical properties near a non-rotating IH, and find that under the first-order approximation of r, there exist a Killing vector and a Hamiltonian conjugate to it, so this vector is a physical observer. We calculate the energy as measured at infinity of a particle at rest outside a non-rotating IH, and use this result to construct a reversible Carnot cycle with the Isolated Horizon as a cold reservoir, which confirms the thermodynamic nature of Isolated Horizon.

Gerui Chen; Xiaoning Wu; Sijie Gao

2014-10-27

59

Electronic and thermodynamic properties of ?-Pu2O3

NASA Astrophysics Data System (ADS)

Based on density functional theory+U calculations and the quasi-annealing simulation method, we obtain the ground electronic state for ?-Pu2O3 and present its phonon dispersion curves as well as various thermodynamic properties, which have seldom been theoretically studied because of the huge unit cell. We find that the Pu-O chemical bonding is weaker in ?-Pu2O3 than in fluorite PuO2, and subsequently a frequency gap appears between oxygen and plutonium vibration density of states. Based on the calculated Helmholtz free energies at different temperatures, we further study the reaction energies for Pu oxidation, PuO2 reduction, and transformation between PuO2 and ?-Pu2O3. Our reaction energy results are in agreements with available experiment. And it is revealed that high temperature and insufficient oxygen environment are in favor of the formation of ?-Pu2O3.

Lu, Yong; Yang, Yu; Zheng, Fawei; Zhang, Ping

2014-08-01

60

Thermodynamic properties of liquid Au–Bi–Sn alloys

The thermodynamic properties of the liquid ternary Au–Bi–Sn alloys were determined using an electromotive force (EMF) method with an eutectic mixture of (KCl + LiCl) as liquid electrolyte. The cell arrangement was: W, Sn ( l ) / KCl – LiCl – SnCl 2 / Au – Bi – Sn ( l ) , W. The measurements were carried out over the temperature range from 723 K to 973 K. The compositions investigated were situated on three different cross-sections with a constant ratio of Au:Bi = 2:1, 1:1, and 1:2. The partial Gibbs free energies of Sn in liquid Au–Bi–Sn alloys were determined as a function of concentration and temperature. The integral Gibbs free energy and the integral enthalpy at T = 800 K were calculated by the Gibbs–Duhem integration. The ternary interaction parameters were evaluated using the Redlich–Kister–Muggianu polynomial.

Guo, Zhongnan; Yuan, Wenxia; Hindler, Michael; Mikula, Adolf

2012-01-01

61

Thermodynamic properties of Rashba spin-orbit-coupled Fermi gas

NASA Astrophysics Data System (ADS)

We investigate the thermodynamic properties of a superfluid Fermi gas subject to Rashba spin-orbit coupling and effective Zeeman field. We adopt a T -matrix scheme that takes beyond-mean-field effects, which are important for strongly interacting systems, into account. We focus on the calculation of two important quantities: the superfluid transition temperature and the isothermal compressibility. Our calculation shows very distinct influences of the out-of-plane and the in-plane Zeeman fields on the Fermi gas. We also confirm that the in-plane Zeeman field induces a Fulde-Ferrell superfluid below the critical temperature and an exotic finite-momentum pseudogap phase above the critical temperature.

Zheng, Zhen; Pu, Han; Zou, Xubo; Guo, Guangcan

2014-12-01

62

Thermodynamic properties of chlorite and berthierine derived from calorimetric measurements

NASA Astrophysics Data System (ADS)

In the context of the deep waste disposal, we have investigated the respective stabilities of two iron-bearing clay minerals: berthierine ISGS from Illinois [USA; (Al0.975FeIII0.182FeII1.422Mg0.157Li0.035Mn0.002)(Si1.332Al0.668)O5(OH)4] and chlorite CCa-2 from Flagstaff Hill, California [USA; (Si2.633Al1.367)(Al1.116FeIII0.215Mg2.952FeII1.712Mn0.012Ca0.011)O10(OH)8]. For berthierine, the complete thermodynamic dataset was determined at 1 bar and from 2 to 310 K, using calorimetric methods. The standard enthalpies of formation were obtained by solution-reaction calorimetry at 298.15 K, and the heat capacities were measured by heat-pulse calorimetry. For chlorite, the standard enthalpy of formation is measured by solution-reaction calorimetry at 298.15 K. This is completing the entropy and heat capacity obtained previously by Gailhanou et al. (Geochim Cosmochim Acta 73:4738-4749, 2009) between 2 and 520 K, by using low-temperature adiabatic calorimetry and differential scanning calorimetry. For both minerals, the standard entropies and the Gibbs free energies of formation at 298.15 K were then calculated. An assessment of the measured properties could be carried out with respect to literature data. Eventually, the thermodynamic dataset allowed realizing theoretical calculations concerning the berthierine to chlorite transition. The latter showed that, from a thermodynamic viewpoint, the main factor controlling this transition is probably the composition of the berthierine and chlorite minerals and the nature of the secondary minerals rather than temperature.

Blanc, Philippe; Gailhanou, Hélène; Rogez, Jacques; Mikaelian, Georges; Kawaji, Hitoshi; Warmont, Fabienne; Gaboreau, Stéphane; Grangeon, Sylvain; Grenèche, Jean-Marc; Vieillard, Philippe; Fialips, Claire I.; Giffaut, Eric; Gaucher, Eric C.; Claret, F.

2014-09-01

63

The thermodynamic properties of 2,3-benzothiophene

Upgrading of heavy fossil fuels is normally done by hydrotreating in the presence of catalysts at 5 to 15 MPa pressure of hydrogen and 575 to 700 K. The efficient use of expensive hydrogen in this process is essential to the economic viability of alternative fuel sources (heavy petroleum, tar sands, shale oil, and the products of the liquefaction of coal). 2,3-Benzothiophene is widely used as a model compound in catalyst-comparison and kinetic studies of the hydrodesulfurization (HDS) mechanism. To perform a thermodynamic analysis of the 2,3-benzothiophene/hydrogen reaction network at the process temperatures, Gibbs energies of reaction at those high temperatures are required for the molecules involved. Measurements leading to the calculation of the ideal-gas thermodynamic properties for 2,3-benzothiophene are reported. Experimental methods included adiabatic heat-capacity calorimetry, comparative ebulliometry, inclined-piston gauge manometry, and differential-scanning calorimetry (d.s.c.). The critical temperature and critical density were determined with the d.s.c., and the critical pressure was derived. Entropies, enthalpies, and Gibbs energies of formation were derived for the ideal gas for selected temperatures between 260 K and 750 K. These values were derived by combining the reported measurements with values published previously for the enthalpy of combustion, the enthalpy of fusion, and the absolute entropy and enthalpy of the liquid at the triple-point temperature. Measured and derived quantities were compared with available literature values. 55 refs., 6 figs., 13 tabs.

Chirico, R.D.; Knipmeyer, S.E.; Nguyen, A.; Steele, W.V.

1991-01-01

64

The thermodynamic properties of hydrated -Al2O3 nanoparticles

In this paper we report a combined calorimetric and inelastic neutron scattering (INS) study of hydrated -Al2O3 ( -alumina) nanoparticles. These complementary techniques have enabled a comprehensive evaluation of the thermodynamic properties of this technological and industrially important metal oxide to be achieved. The isobaric heat capacity (Cp) data presented herein provide further critical insights into the much-debated chemical composition of -alumina nanoparticles. Furthermore, the isochoric heat capacity (Cv) of the surface water, which is so essential to the stability of all metal-oxides at the nanoscale, has been extracted from the high-resolution INS data and differs significantly from that of ice Ih due to the dominating influence of strong surface-water interactions. This study also encompassed the analysis of four -alumina samples with differing pore diameters [4.5 (1), 13.8 (2), 17.9 (3), and 27.2 nm (4)], and the results obtained allow us to unambiguously conclude that the water content and pore size have no influence on the thermodynamic behaviour of hydrated -alumina nanoparticles.

Spencer, Elinor [Virginia Polytechnic Institute and State University] [Virginia Polytechnic Institute and State University; Huang, Baiyu [Brigham Young University, Provo] [Brigham Young University, Provo; Parker, Stewart F. [ISIS Facility, Rutherford Appleton Laboratory (ISIS)] [ISIS Facility, Rutherford Appleton Laboratory (ISIS); Kolesnikov, Alexander I [ORNL] [ORNL; Ross, Dr. Nancy [Virginia Polytechnic Institute and State University] [Virginia Polytechnic Institute and State University; Woodfield, Brian [Brigham Young University, Provo] [Brigham Young University, Provo

2013-01-01

65

Thermodynamic and Structural Properties of Metallic Glasses and Supercooled Liquids

NASA Astrophysics Data System (ADS)

It is demonstrated, both theoretically and numerically, that the Gibbs-Bogoliubov (GB) thermodynamic variational calculations, developed originally for equilibrium systems, can be applied to a metastable thermodynamic system provided the structure of the chosen reference system has the same main features as the metastable system under consideration. It appears that the Einstein model, which properly contains the basic glass characteristics, can be used as a reference system for metallic glasses and that the hard sphere model, which properly includes the basic liquid properties, can be used as a reference system for supercooled metallic liquids. The results for the thermodynamic quantities, calculated for the glass states of Mg_3Ca _7 and Al and for the supercooled liquid states of Mg_3Ca_7, Ti_ {66}V_{34}, In and V are in a good agreement with those of computer and laboratory experiments. Also, the investigation of the GB variational calculations for the behavior of the heat capacity at constant pressure for supercooled liquid Rb suggests that supercooled liquids can be divided into two regions: the undercooled region and the hypercooled region, in which the structure of the liquids may differ. Next, in order to study the topological structure of supercooled liquids and glasses, molecular-dynamics simulations with a damped force method are performed to model the liquids and glasses in a sample of 150 Mg atoms and 350 Ca atoms. The techniques of pair analysis and steepest descent minimization with the conjugate gradient method are used to analyze the structural properties for the supercooled liquids and glasses. Not only are the usual Frank-Kasper polyhedra with coordination number 14 -16 and Bernal "hole" polyhedra with coordination number 10 detected, but also fourteen other kinds of defective icosahedra are identified. Especially, the number of the defective icosahedra defined by eight 1551 pairs, two 1661 pairs and two 1441 pairs is greater than that of Frank -Kasper or that of Bernal polyhedra, and is next to the number of icosahedra. On average, 61% of the atoms are in icosahedra and 32% atoms are in defective icosahedra at T = 100 K. The correlation between the energies and populations of the different kinds of pairs is explained. These results strongly support the physical picture of liquids and glasses being a disordered, entangled array of +72 ^circ and -72^ circ disclination lines in an icosahedral medium. Further, we prove that W_6 is a standard gauge of icosahedral order for a variety of defective icosahedra. (Abstract shortened by UMI.).

Qi, Dewei

66

Thermodynamic and structural properties of metallic glasses and supercooled liquids

NASA Astrophysics Data System (ADS)

It is demonstrated, both theoretically and numerically, that the Gibbs-Bogoliubov (GB) thermodynamic variational calculations, developed originally for equilibrium systems, can be applied to a metastable thermodynamic system provided the structure of the chosen reference system has the same main features as the metastable system under consideration. It appears that the Einstein model, which properly contains the basic glass characteristics, can be used as a reference system for metallic glasses and that the hard sphere model, which properly includes the basic liquid properties, can be used as a reference system for supercooled metallic liquids. The results for the thermodynamic quantities, calculated for the glass states of Mg3Ca7 and Al and for the supercooled liquid states of Mg3Ca7, Ti66V34, In, and V are in a good agreement with those of computer and laboratory experiments. Also, the investigation of the GB variational calculations for the behavior of the heat capacity at constant pressure for supercooled liquid Rb suggests that supercooled liquids can be divided into two regions: the undercooled region and the hypercooled region, in which the structure of the liquids may differ. Next, in order to study the topological structure of supercooled liquids and glasses, molecular-dynamics simulations with a damped force method are performed to model the liquids and glasses in a sample of 150 Mg atoms and 350 Ca atoms. The techniques of pair analysis and steepest descent minimization with the conjugate gradient method are used to analyze the structural properties for the supercooled liquids and glasses. Not only are the usual Frank-Kasper polyhedra with coordination number 14-16 and Bernal 'hole' polyhedra with coordination number 10 detected, but also fourteen other kinds of defective icosahedra are identified. Especially, the number of the defective icosahedra defined by eight 1551 pairs, two 1661 pairs and two 1441 pairs is greater than that of Frank-Kasper or that of Bernal polyhedra, and is next to the number of icosahedra. On average, 61 percent of the atoms are in icosahedra and 32 percent atoms are in defective icosahedra at T = 100 K. The correlation between the energies and populations of the different kinds of pairs is explained. These results strongly support the physical picture of liquids and glasses being a disordered, entangled array of +72 deg and -72 deg disclination lines in an icosahedral medium. Further, it is proved that W(sub 6). is a standard gauge of icosahedral order for a variety of defective icosahedra.

Qi, Dewei

67

Electronic, mechanical, and thermodynamic properties of americium dioxide

NASA Astrophysics Data System (ADS)

By performing density functional theory (DFT) +U calculations, we systematically study the electronic, mechanical, tensile, and thermodynamic properties of AmO2. It is found that the chemical bonding character in AmO2 is similar to that in PuO2, with smaller charge transfer and stronger covalent interactions between americium and oxygen atoms. The stress-strain relationship of AmO2 is examined along the three low-index directions, showing that the [1 0 0] and [1 1 1] directions are the strongest and weakest tensile directions, respectively, but the theoretical tensile strengths of AmO2 are smaller than those of PuO2. The phonon dispersion curves of AmO2 are calculated and the heat capacities as well as lattice expansion curve are subsequently determined. The lattice thermal conductivity of AmO2 is further evaluated and compared with attainable experiments. Our present work integrally reveals various physical properties of AmO2 and can be referenced for technological applications of AmO2 based materials.

Lu, Yong; Yang, Yu; Zheng, Fawei; Wang, Bao-Tian; Zhang, Ping

2013-10-01

68

Thermodynamic properties and structural stability of thorium dioxide.

Using density functional theory (DFT) calculations, we have systematically investigated the thermodynamic properties and structural stabilities of thorium dioxide (ThO(2)). Based on the calculated phonon dispersion curves, we have calculated the thermal expansion coefficient, bulk modulus, and heat capacities at different temperatures for ThO(2) under the quasi-harmonic approximation. All the results are in good agreement with corresponding experiments proving the validity of our methods. Our theoretical studies can aid a clearer understanding of the thermodynamic behaviors of ThO(2) at different temperatures. In addition, we have also studied possible defect formations and diffusion behaviors of helium in ThO(2), to discuss its structural stability. It is found that in intrinsic ThO(2) without any Fermi energy shifts, the interstitial Th(i)(4+) defect rather than oxygen or thorium vacancies, interstitial oxygen, or any kinds of Frenkel pairs, is the most probable to form with an energy release of 1.74 eV. However, after upshifting the Fermi energy, the formation of the other defects also becomes possible. Regarding helium diffusion, we find that only through the thorium vacancy can it occur with the small energy barrier of 0.52 eV. Otherwise, helium atoms can hardly incorporate or diffuse in ThO(2). Our results indicate that upward shifting of the Fermi energy of ThO(2) should be prevented to avoid the formation of thorium vacancies so as to avert helium caused damage. PMID:22555111

Lu, Y; Yang, Y; Zhang, P

2012-06-01

69

NASA Technical Reports Server (NTRS)

Accurate numerical prediction of high-temperature, chemically reacting flowfields requires a knowledge of the physical properties and reaction kinetics for the species involved in the reacting gas mixture. Assuming an 11-species air model at temperatures below 30,000 degrees Kelvin, SPECIES (Computer Codes for the Evaluation of Thermodynamic Properties, Transport Properties, and Equilibrium Constants of an 11-Species Air Model) computes values for the species thermodynamic and transport properties, diffusion coefficients and collision cross sections for any combination of the eleven species, and reaction rates for the twenty reactions normally occurring. The species represented in the model are diatomic nitrogen, diatomic oxygen, atomic nitrogen, atomic oxygen, nitric oxide, ionized nitric oxide, the free electron, ionized atomic nitrogen, ionized atomic oxygen, ionized diatomic nitrogen, and ionized diatomic oxygen. Sixteen subroutines compute the following properties for both a single species, interaction pair, or reaction, and an array of all species, pairs, or reactions: species specific heat and static enthalpy, species viscosity, species frozen thermal conductivity, diffusion coefficient, collision cross section (OMEGA 1,1), collision cross section (OMEGA 2,2), collision cross section ratio, and equilibrium constant. The program uses least squares polynomial curve-fits of the most accurate data believed available to provide the requested values more quickly than is possible with table look-up methods. The subroutines for computing transport coefficients and collision cross sections use additional code to correct for any electron pressure when working with ionic species. SPECIES was developed on a SUN 3/280 computer running the SunOS 3.5 operating system. It is written in standard FORTRAN 77 for use on any machine, and requires roughly 92K memory. The standard distribution medium for SPECIES is a 5.25 inch 360K MS-DOS format diskette. The contents of the diskettes are compressed using the PKWARE archiving tools. The utility to unarchive the files, PKUNZIP.EXE, is included. This program was last updated in 1991. SUN and SunOS are registered trademarks of Sun Microsystems, Inc.

Thompson, R. A.

1994-01-01

70

Investigation of thermodynamic properties of metal-oxide catalysts

NASA Astrophysics Data System (ADS)

An apparatus for Coulometric Titration was developed and used to measure the redox isotherms (i.e. oxygen fugacity P(O2) vs oxygen stoichiometry) of ceria-zirconia solid solutions, mixed oxides of vanadia, and vanadia supported on ZrO2. This data was used to correlate the redox thermodynamics of these oxides to their structure and catalytic properties. From the redox isotherms measured between 873 K and 973 K, the differential enthalpies of oxidation (DeltaH) for Ce0.81Zr0.19O 2.0 and Ce0.25Zr0.75O2.0 were determined, and they were found to be independent of extent of reduction or composition of the solid solution. They were also lower than DeltaH for ceria, which explains the better redox properties of ceria-zirconia solid solutions. The oxidation was driven by entropy in the low reduction region, and a structural model was proposed to explain the observed entropy effects. Redox isotherms were also measured for a number of bulk vanadates between 823 K and 973 K. DeltaG, DeltaH and DeltaS were reported for V 2O5, Mg3(VO4)2, CeVO 4 and ZrV2O7 along with DeltaG values for AlVO 4, LaVO4, CrVO4. V2O5 and ZrV2O7, which were the only oxides having V-O-V bonds, showed a two-step transition of vanadium for V+3?V +4 and V+4?V+5 equilibrium in the redox isotherms. The other oxides, all of which have only M-O-V (M=cation other than V), showed a direct one-step transition, V+3?V +5. The nature of the M-atom also influenced the P(O2) at which the V+3?V+5 transition occurs. Redox isotherms at 748 K were measured for vanadia supported on ZrO 2; with two different vanadia loadings corresponding to isolated vanadyls and polymeric vanadyls. The isotherm for the sample with isolated vanadyls showed a single-step transition, similar to the one seen in bulk vanadates with M-O-V linkages, while no such one-step transition was observed in the isotherm of the other sample. To study the affect of the varying redox properties of the vanadium-based catalysts on oxidation rates, kinetic studies were performed for methanol and propane oxidation reactions on some of these catalysts. The results suggested that there was no effect of thermodynamic properties of these catalysts on the rates of these oxidation reactions.

Shah, Parag Rasiklal

71

Thermodynamic properties of liquid ³3He-?4He mixtures between 0.15 K and 1.8 K

Thermodynamic property relations for liquid ³3He-?4He mixtures between temperatures of 0.15 K and 1.8 K are determined. The relations are valid over the entire concentration range. Thermodynamic properties are first ...

Chaudhry, Gunaranjan

2009-01-01

72

Thermodynamic and transport properties of air/water mixtures

NASA Technical Reports Server (NTRS)

Subroutine WETAIR calculates properties at nearly 1,500 K and 4,500 atmospheres. Necessary inputs are assigned values of combinations of density, pressure, temperature, and entropy. Interpolation of property tables obtains dry air and water (steam) properties, and simple mixing laws calculate properties of air/water mixture. WETAIR is used to test gas turbine engines and components operating in relatively humid air. Program is written in SFTRAN and FORTRAN.

Fessler, T. E.

1981-01-01

73

Thermodynamic properties of holographic multiquark and the multiquark star

NASA Astrophysics Data System (ADS)

We study thermodynamic properties of the multiquark nuclear matter. The dependence of the equation of state on the colour charges is explored both analytically and numerically in the limits where the baryon density is small and large at fixed temperature between the gluon deconfinement and chiral symmetry restoration. The gravitational stability of the hypothetical multiquark stars are discussed using the Tolman-Oppenheimer-Volkoff equation. Since the equations of state of the multiquarks can be well approximated by different power laws for small and large density, the content of the multiquark stars has the core and crust structure. We found that most of the mass of the star comes from the crust region where the density is relatively small. The mass limit of the multiquark star is determined as well as its relation to the star radius. For typical energy density scale of 10 GeV/fm3, the converging mass and radius of the hypothetical multiquark star in the limit of large central density are approximately 2.6 - 3.9 solar mass and 15-27 km. The adiabatic index and sound speed distributions of the multiquark matter in the star are also calculated and discussed. The sound speed never exceeds the speed of light and the multiquark matters are thus compressible even at high density and pressure.

Burikham, P.; Hirunsirisawat, E.; Pinkanjanarod, S.

2010-06-01

74

Thermodynamic Properties of Polypeptide Chains. Parallel Tempering Monte Carlo Simulations

NASA Astrophysics Data System (ADS)

A coarse-grained model of polypeptide chains was designed and studied. The chains consisted of united atoms located at the position of alpha carbons and the coordinates of these atoms were restricted to a [310] type lattice. Two kinds of amino acids residues were defined: hydrophilic and hydrophobic ones. The sequence of the residues was assumed to be characteristic for alpha -helical proteins (the helical septet). The force field used consisted of the long-range contact potential between residues and the local potential preferring conformational states, which were characteristic for alpha -helices. In order to study the thermodynamics of our model we employed the Multi-histogram method combined with the Parallel Tempering (the Replica Exchange) Monte Carlo sampling scheme. The optimal set of temperatures for the Parallel Tempering simulations was found by an iterative procedure. The influence of the temperature and the force field on the properties of coil-to-globule transition was studied. It was shown that this method can give more precise results when compared to Metropolis and Replica Exchange methods.

Sikorski, A.; Gront, D.

2007-05-01

75

Thermodynamic and electromagnetic properties of the Penson-Kolb model

NASA Astrophysics Data System (ADS)

We study thermodynamic and electromagnetic properties of the Penson-Kolb model, i.e., the tight-binding model with the pair-hopping interaction J, and analyze the effects of phase fluctuations on the s-wave superconductivity in this system. The evolution of the critical fields, the coherence length, the Ginzburg ratio, and the London penetration depth ? with particle concentration n and pairing strength is determined at T=0 for d-dimensional hypercubic lattices d=2 (SQ) and d=3 (SC). Within the Kosterlitz-Thouless scenario the critical temperatures Tc are calculated for d=2 SQ lattice and compared with the ones from BCS-HFA Tp. The results show a substantial enhancement of the gap to critical temperature ratio due to the phase fluctuations as well as a separation of the energy scales for the pair formation (~kBTp) and the phase coherence (~kBTc). The Uemura type plots, i.e., the Tc vs ?-2(0) plots, are obtained both as a function of n and as a function of pairing strength. The results are compared with those found earlier for the attractive Hubbard model.

Czart, W. R.; Robaszkiewicz, S.

2001-09-01

76

Thermodynamic properties of the lithium bromide + diethanolamine + water system

Thermodynamic properties (solubility, vapor pressure, density, viscosity, and heat capacity) of the lithium bromide + diethanolamine + water system (LiBr/(HOCH{sub 2}CH{sub 2}){sub 2}NH, mass ratio = 3.5) were measured as a possible new working fluid for absorption heat pumps. Solubility was measured by the visual polythermal method in the temperature range from 281.75 to 338.954 K and vapor pressure by the boiling point method from 329.15 to 401.25 K. Density and viscosity were measured by using a set of hydrometers and five pieces of Ubbelohde-type capillary viscometers in the temperature range from 283.15 to 343.15 K. Heat capacity was measured by using an isoperibol solution calorimeter in the temperature range from 283.15 to 333.15 K. Each measured data set was correlated with a proper equation, and all the correlation results showed good agreement between measured and calculated values.

Park, Y.; Kim, J.S.; Lee, H. [Korea Advanced Inst. of Science and Technology, Taejon (Korea, Republic of). Dept. of Chemical Engineering

1997-12-31

77

Molecular Dynamics Simulation of Thermodynamic Properties in Uranium Dioxide

In the present study, we investigated the thermodynamic properties of uranium dioxide (UO2) by molecular dynamics (MD) simulations. As for solid UO2, the lattice parameter, density, and enthalpy obtained by MD simulations were in good agreement with existing experimental data and previous theoretical predictions. The calculated thermal conductivities matched the experiment results at the midtemperature range but were underestimated at very low and very high temperatures. The calculation results of mean square displacement represented the stability of uranium at all temperatures and the high mobility of oxygen toward 3000 K. By fitting the diffusivity constant of oxygen with the Vogel-Fulcher-Tamman law, we noticed a secondary phase transition near 2006.4 K, which can be identified as a ‘‘strong’’ to ‘‘fragile’’ supercooled liquid or glass phase transition in UO2. By fitting the oxygen diffusion constant with the Arrhenius equation, activation energies of 2.0 and 2.7 eV that we obtained were fairly close to the recommended values of 2.3 to 2.6 eV. Xiangyu Wang, Bin Wu, Fei Gao, Xin Li, Xin Sun, Mohammed A. Khaleel, Ademola V. Akinlalu and Li Liu

Wang, Xiangyu; Wu, Bin; Gao, Fei; Li, Xin; Sun, Xin; Khaleel, Mohammad A.; Akinlalu, Ademola V.; Liu, L.

2014-03-01

78

THERMODYNAMIC PROPERTIES OF SEA-SALTAEROSOLS A. C. Tridico and I. N. Tang

, (he hygroscopic properties of aerosolparticles generated from filtered sea-water sampleswere studiedBNL- 63377 [Abstract] THERMODYNAMIC PROPERTIES OF SEA-SALTAEROSOLS A. C. Tridico and I. N. Tang,FL Oct. 14-18, 1996 ABSTRACT The thennodynamic properties of mixed salt microdropletsrepresentativeof sea

79

Thermodynamic properties of UF sub 6 measured with a ballistic piston compressor

NASA Technical Reports Server (NTRS)

From experiments performed with a ballistic piston compressor, certain thermodynamic properties of uranium hexafluoride were investigated. Difficulties presented by the nonideal processes encountered in ballistic compressors are discussed and a computer code BCCC (Ballistic Compressor Computer Code) is developed to analyze the experimental data. The BCCC unfolds the thermodynamic properties of uranium hexafluoride from the helium-uranium hexafluoride mixture used as the test gas in the ballistic compressor. The thermodynamic properties deduced include the specific heat at constant volume, the ratio of specific heats for UF6, and the viscous coupling constant of helium-uranium hexafluoride mixtures.

Sterritt, D. E.; Lalos, G. T.; Schneider, R. T.

1973-01-01

80

NASA Technical Reports Server (NTRS)

A FORTRAN IV computer program for the calculation of the thermodynamic and transport properties of complex mixtures is described. The program has the capability of performing calculations such as:(1) chemical equilibrium for assigned thermodynamic states, (2) theoretical rocket performance for both equilibrium and frozen compositions during expansion, (3) incident and reflected shock properties, and (4) Chapman-Jouguet detonation properties. Condensed species, as well as gaseous species, are considered in the thermodynamic calculation; but only the gaseous species are considered in the transport calculations.

Svehla, R. A.; Mcbride, B. J.

1973-01-01

81

Thermodynamic and rheological properties of hard sphere dispersions

NASA Astrophysics Data System (ADS)

We investigate the thermodynamic and rheological properties of hard sphere dispersions with colloidal poly-(methyl methacrylate) particles grafted with a layer of poly-(12-hydroxy stearic acid) (PMMA-PHSA). These spheres are index-matched in a mixture of tetralin and decalin and the absorption of tetralin into the PMMA core is determined with light scattering. The effective hard sphere volume fraction is set by the disorder-order transition, thereby accounting for the polymer layer, any swelling due to the solvent, and polydispersity. The equation of state for the fluid phase, extracted from the equilibrium sediment with x-ray densitometry, conforms to the Carnahan-Starling equation. However, the osmotic pressure of the crystalline phase lies slightly above that calculated for a single FCC crystal. Likewise the high shear viscosity of the fluid compares well with other hard sphere dispersions, but the low shear viscosity for PMMA-PHSA hard spheres exceeds those for polystyrene and silica hard spheres. Our low shear viscosities are consistent with other PMMA-PHSA data after rescaling for both the polymer layer thickness and polydispersity. We use simple models and molecular dynamics simulations to determine that the higher osmotic pressure in the crystalline phase is a direct effect of polydispersity. Polydispersity appears to lower the crystalline close packed volume fraction. The random close packing is almost independent of polydispersity. We measure the high frequency shear modulus and dynamic viscosity for our PMMA-PHSA crystals by detecting the resonant response to oscillatory forcing with a novel dynamic light scattering scheme. The resonant response for colloidal crystals formed in normal and microgravity environments were similar, indicating that the bulk rheological properties are unaffected within experimental error by differing crystal structure and crystallite size. Our high frequency shear modulus seem reasonable, lying close to predictions for the static modulus of hard sphere crystals, whereas our high frequency dynamic viscosity seem high, exceeding measurements on the high frequency dynamic viscosity for metastable fluids. The measurements are in the linear regime for the shear modulus but may not be for the dynamic viscosity, which may explain our anomalously high dynamic viscosity.

Phan, See-Eng

1998-09-01

82

In thiswork we present the development of a method for the prediciton of finite temperature elastic and thermodynamic properties of cubic, non-magnetic unary and binary metals from first principles calculations. Vibrational, electronic...

Williams, Michael Eric

2009-05-15

83

The structural, dynamical, and thermodynamic properties of different carbon allotropes are computed using a combination of ab-initio methods: density-functional theory for total-energy calculations and density-functional ...

Mounet, Nicolas (Nicolas Frank)

2005-01-01

84

WETAIR: A computer code for calculating thermodynamic and transport properties of air-water mixtures

NASA Technical Reports Server (NTRS)

A computer program subroutine, WETAIR, was developed to calculate the thermodynamic and transport properties of air water mixtures. It determines the thermodynamic state from assigned values of temperature and density, pressure and density, temperature and pressure, pressure and entropy, or pressure and enthalpy. The WETAIR calculates the properties of dry air and water (steam) by interpolating to obtain values from property tables. Then it uses simple mixing laws to calculate the properties of air water mixtures. Properties of mixtures with water contents below 40 percent (by mass) can be calculated at temperatures from 273.2 to 1497 K and pressures to 450 MN/sq m. Dry air properties can be calculated at temperatures as low as 150 K. Water properties can be calculated at temperatures to 1747 K and pressures to 100 MN/sq m. The WETAIR is available in both SFTRAN and FORTRAN.

Fessler, T. E.

1979-01-01

85

NASA Technical Reports Server (NTRS)

The availability and proper utilization of fluid properties is of fundamental importance in the process of mathematical modeling of propulsion systems. Real fluid properties provide the bridge between the realm of pure analytiis and empirical reality. The two most common approaches used to formulate thermodynamic properties of pure substances are fundamental (or characteristic) equations of state (Helmholtz and Gibbs functions) and a piecemeal approach that is described, for example, in Adebiyi and Russell (1992). This paper neither presents a different method to formulate thermodynamic properties of pure substances nor validates the aforementioned approaches. Rather its purpose is to present a method to be used to facilitate the accurate interpretation of fluid thermodynamic property data generated by existing property packages. There are two parts to this paper. The first part of the paper shows how efficient and usable property tables were generated, with the minimum number of data points, using an aerospace industry standard property package (based on fundamental equations of state approach). The second part describes an innovative interpolation technique that has been developed to properly obtain thermodynamic properties near the saturated liquid and saturated vapor lines.

Nguyen, Huy H.; Martin, Michael A.

2003-01-01

86

Transport and thermodynamic properties of iron-based superconductors

NASA Astrophysics Data System (ADS)

Iron-based superconductors (FeSCs) are a novel family of high-temperature superconductors. The rich phase diagrams exhibited by these compounds under various doping regimes, their multi-band electronic structure, the high superconducting critical temperature with exotic realization of order parameters, all contribute to this system being of considerable theoretical interest. In this Thesis, we report on our past work aimed at addressing possible signatures of the exotic superconducting (SC) order parameters (OPs), the coexistence with spin-density wave (SDW) phase, and fluctuations effects, as reflected in various transport or thermodynamic properties of these materials. We present a theoretical description of the differential conductance of point contacts between a normal metal and a multi-band superconductor with s+/--wave symmetry. We demonstrate that the interband impurity scattering broadens the coherent peak near the superconducting gap and significantly reduces its height even at relatively low scattering rates for an extended s+/--wave gap. Our mean-field treatment of the zero-temperature London penetration depth of a clean multi-band superconductor in the case when both SC and SDW orders coexist shows that the supefluid density closely follows the evolution of the superconducting order parameter as doping is increased, saturating to a BCS value in the pure superconducting state. Furthermore, a strong anisotropic in-pane penetration depth is shown to be induced by the SDW order. Beyond mean-field level, however, the monotonic behavior of both penetration depth, and specific heat jump is modified into a sharp peak near the tetracritical point - a point of intersection of four phase transition lines. We show that in the case of specific heat jump, this effect originates from thermal fluctuations of the SDW OP near the tetracritical point. Thermal fluctuations result in a power-law dependence of the specific heat jump fluctuation correction that is stronger than the contribution of mass renormalization due to quantum fluctuations of SDW in the vicinity of the putative critical point beneath the superconducting dome.

Kuzmanovski, Dushko

87

Thermodynamic and transport property modeling in super critical water

Supercritical water oxidation (SCWO) is a thermally-based, remediation and waste-treatment process that relies on unique property changes of water when water is heated and pressurized above its critical point. Above its ...

Kutney, Michael C. (Michael Charles)

2005-01-01

88

EquilTheTA: Thermodynamic and transport properties of complex equilibrium plasmas

NASA Astrophysics Data System (ADS)

EquilTheTA (EQUILibrium for plasma THErmodynamics and Transport Applications) is a web-based software which calculates chemical equilibrium product concentrations from any set of reactants and determines thermodynamic and transport properties for the product mixture in wide temperature and pressure ranges. The program calculates chemical equilibrium by using a hierarchical approach, thermodynamic properties and transport coefficients starting from recent and accurate databases of atomic and molecular energy levels and collision integrals. In the calculations, Debye length and cut-off are consistently updated and virial corrections (up to third order) can be considered. Transport coefficients are calculated by using high order approximations of the Chapman-Enskog method.

Colonna, G.; D'Angola, A.

2012-11-01

89

Two-Fluid Theory and Thermodynamic Properties of Liquid Mixtures: General Theory

The two-fluid theory of binary mixtures postulates that the extensive thermodynamic properties of a binary mixture may be expressed by the contributions of two hypothetical fluids that mix ideally. This postulate, coupled with an expression for the partition function of the hypothetical fluid, permits evaluation of the properties of binary liquid mixtures by using only two adjustable binary parameters. Particular

V. Brandani; J. M. Prausnitz

1982-01-01

90

Elastic and thermodynamic properties of AVO 3 (A=Sr, Pb) perovskites

NASA Astrophysics Data System (ADS)

We have investigated the elastic and thermodynamic properties for the perovskite type metavanadate SrVO 3 and the multiferroic PbVO 3, probably for the first time by the means of a Modified Rigid Ion Model (MRIM). We present the elastic constants ( C11,C12,C44) and other elastic properties like Bulk modulus ( B), Young?s modulus ( E), shear modulus ( G), Poisson?s ratio ( ?) and wave velocity ( ?l, ?s, ?m). Besides we have reported the thermodynamic properties molecular force constant ( f), Reststrahlen frequency ( ?), cohesive energy ( ?), Debye temperature ( ?D) and Gruneisen parameter ( ?). We have also computed the variation of heat capacity ( CP) and there by volume thermal expansion coefficient ( ?) in a wide temperature range. We found that the computed properties reproduce well with the available data in literature. To our knowledge some of the properties are reported for the first time.

Parveen, Atahar; Gaur, N. K.

2012-02-01

91

Thermodynamic and Structural Properties of Metallic Glasses and Supercooled Liquids

It is demonstrated, both theoretically and numerically, that the Gibbs-Bogoliubov (GB) thermodynamic variational calculations, developed originally for equilibrium systems, can be applied to a metastable thermodynamic system provided the structure of the chosen reference system has the same main features as the metastable system under consideration. It appears that the Einstein model, which properly contains the basic glass characteristics, can

Dewei Qi

1991-01-01

92

Generalizing thermodynamic properties of bulk single-walled carbon nanotubes

NASA Astrophysics Data System (ADS)

The enthalpy and Gibbs free energy thermodynamical potentials of single walled carbon nanotubes were studied of all types (armchairs, zig-zags, chirals (n>m), and chiral (n

Rodriguez, Kenneth R.; Malone, Marvin A.; Nanney, Warren A.; A. Maddux, Cassandra J.; Coe, James V.; Martínez, Hernán L.

2014-12-01

93

The thermodynamic properties of organic oxygen compounds: Topical report

The principles of group additivity are used to compare a series of cyclic hydrocarbons with the corresponding oxygen-containing analogues. The strengths and limitations of the group-additivity method are demonstrated and recommendations are made for measurements essential to the improvement of the accuracy of the predicted properties. The ideal-gas enthalpies of formation and ideal-gas entropies (which are used in combination to

R. D. Chirico; W. V. Steele; A. Hossenlopp; A. Nguyen; D. G. Archer; M. M. Strube

1988-01-01

94

Thermodynamical properties of dark energy with the equation of state $% ?=?_{0}+?_{1}z$

The thermodynamical properties of dark energy are usually investigated with the equation of state $\\omega =\\omega_{0}+\\omega_{1}z$. Recent observations show that our universe is accelerating, and the apparent horizon and the event horizon vary with redshift $z$. When definitions of the temperature and entropy of a black hole are used to the two horizons of the universe, we examine the thermodynamical properties of the universe which is enveloped by the apparent horizon and the event horizon respectively. We show that the first and the second laws of thermodynamics inside the apparent horizon in any redshift are satisfied, while they are broken down inside the event horizon in some redshift. Therefore, the apparent horizon for the universe may be the boundary of thermodynamical equilibrium for the universe like the event horizon for a black hole.

Yongping Zhang; Ze-Long Yi; Tong-Jie Zhang; Wenbiao Liu

2007-09-18

95

EOS, thermodynamic, and structural-mechanical properties of intermetallic compounds

This is the final report of a three-year, Laboratory-Directed Research and Development (LDRD) project at Los Alamos National Laboratory (LANL). Several classes of binary intermetallic compounds have important potential application as high temperature structural materials because of their high melting temperature, low density, and high strength, but their use is limited by their poor low temperature ductility and fracture toughness. The goal of this project was to further the development of techniques for performing ab-initio calculations of the electronic, structural, and elastic properties of these materials in an investigation of the relation between structure, composition, and mechanical properties of intermetallics. Materials properties to be addressed in these calculations included the equation of state (EOS), defect structure energetics, and elastic constants and phonons. Major accomplishments included calculations of stacking fault and twin energies in layered TiAl, structural stability in binary and ternary Ti-Al-Nb compounds, and point defect energies and elastic moduli of Laves phase intermetallics.

Wills, J.M.; Straub, G.; Albers, R.C.

1998-12-31

96

NASA Astrophysics Data System (ADS)

The structural, electronic, thermoelectric and thermodynamic properties of ternary half-Heusler compound YPdSb are investigated using the first principle calculations. It is found that YPdSb is an indirect semiconductor. The calculated band gap is 0.161 eV with spin-orbital coupling including and 0.235 eV without spin-orbital coupling including, respectively. The electronic transport properties are obtained via Boltzman transport theory. The predicted Seebeck coefficient is 240 ?V/K and the thermoelectric performance can be optimized by n-type doping at room temperature. Moreover, the lattice dynamical results regarding the phonon dispersion curves, phonon density of states and thermodynamic properties are reported. Thermodynamics (heat capacity and Debye temperature) as well as mean phonon free path and the thermal conductivity in a temperature range of 0-300 K are determined.

Kong, Fanjie; Hu, Yanfei; Hou, Haijun; Liu, Yanhua; Wang, Baolin; Wang, Lili

2012-12-01

97

The P-V-T equation of state and thermodynamic properties of liquid iron

NASA Astrophysics Data System (ADS)

equation of state (EoS) and thermodynamic properties of non-magnetic liquid iron were investigated from energy (E)-pressure (P)-volume (V)-temperature (T) relationships calculated by means of ab initio molecular dynamics simulations at 60-420 GPa and 4000-7000 K. Its internally consistent thermodynamic and elastic properties, in particular, density, adiabatic bulk modulus, and P wave velocity, were then analyzed. Compared to the seismological data of the Earth's outer core, pure liquid iron is found to have an 8-10% larger density and 3-10% larger bulk modulus than the Earth's values. Results also show that the P wave velocity of liquid iron has marginal temperature dependence as the bulk sound velocity of solid iron. The new EoS model and thermodynamic properties of liquid iron may serve as fundamental data for the thermochemical modeling of the Earth's core.

Ichikawa, Hiroki; Tsuchiya, Taku; Tange, Yoshinori

2014-01-01

98

NASA Technical Reports Server (NTRS)

The computer codes developed provide data to 30000 K for the thermodynamic and transport properties of individual species and reaction rates for the prominent reactions occurring in an 11-species nonequilibrium air model. These properties and the reaction-rate data are computed through the use of curve-fit relations which are functions of temperature (and number density for the equilibrium constant). The curve fits were made using the most accurate data believed available. A detailed review and discussion of the sources and accuracy of the curve-fitted data used herein are given in NASA RP 1232.

Thompson, Richard A.; Lee, Kam-Pui; Gupta, Roop N.

1990-01-01

99

A Helmholtz Free Energy Formulation of the Thermodynamic Properties of the Mixture {Water + Ammonia}

A thermodynamic model incorporating a fundamental equation of state for the Helmholtz free energy of the mixture {water+ammonia} is presented which covers the thermodynamic space between the solid–liquid–vapor boundary and the critical locus. It is also valid in the vapor and liquid phases for pressures up to 40 MPa. It represents vapor–liquid equilibrium properties with an uncertainty of ±0.01 in

Reiner Tillner-Roth; Daniel G. Friend

1998-01-01

100

Thermodynamic properties of sophocarpine and oxysophocarpine alkaloids in aqueous glucose solutions

NASA Astrophysics Data System (ADS)

Sophocarpine and oxysophocarpine's dissolution in aqueous glucose solutions were studied by a microcalorimetry method. The measured integral and differential heat of dissolution was used to build equations of the solute and the heat, so that dissolution thermodynamic equations, ?sol H m were achieved, which reveals the relationship between the substances structure and the thermodynamic properties. The current study provides theoretical bases for clinical applications of them.

Li, Zongxiao; Zhao, Weiwei; Pu, Xiaohua

2012-04-01

101

Comparison of the National Institute of Standards and Technology’s Standard Reference Material 720 certificate values for heat capacity with those obtained from recent experimental determinations indicated the possibility of a systematic error in the certificate values. Selected experimental determinations of enthalpy increments and heat capacities were fitted in order to obtain a representation of the thermodynamic properties of ?-Al2O3, a

Donald G. Archer

1993-01-01

102

The thermodynamic behavior and spin dynamics of the colossal magnetoresistive (CMR) perovskites of general formula La(1-x)(A)xMn(1-y)(B)yO3 (where A is an alkaline earth, and B = Al, In) have been studied in order to evidence the effect of composition and the influence of nanocrystallinity on the thermodynamic and magnetic characteristics. By using electron paramagnetic resonance (EPR) spectroscopy, the behavior of the exchange coupling integral (J) between Mn spins and the polaron activation energy (Ea) have been investigated. The thermodynamic properties represented by the relative partial molar free energies, enthalpies and entropies of oxygen dissolution in the perovskite phase, as well as the equilibrium partial pressures of oxygen have been obtained by using solid electrolyte electrochemical cells method. The influence of the oxygen stoichiometry change on the thermodynamic properties was examined using the data obtained by a coulometric titration technique coupled with measurements of the electromotive force (EMF). The results were correlated with the average Mn valence values as determined by redox titration. The properties of the rare-earth manganites are strongly affected by the A- and B-site substitution and by the oxygen nonstoichiometry. New features related to the modifications in properties connected with the nanocrystalline state were evidenced. The correlation existing between the magnetic and thermodynamic characteristics were discussed in relation to significant changes in the overall concentration of defects. PMID:18464427

Tanasescu, Speranta; Maxim, Florentina; Teodorescu, Florina; Giurgiu, Liviu

2008-02-01

103

Exploring the effect of anharmonicity of molecular vibrations on thermodynamic properties

NASA Astrophysics Data System (ADS)

Thermodynamic properties of selected small and medium size molecules were calculated using harmonic and anharmonic vibrational frequencies. Harmonic vibrational frequencies were obtained by normal mode analysis, whereas anharmonic ones were calculated using the vibrational self-consistent field (VSCF) method. The calculated and available experimental thermodynamic data for zero point energy, enthalpy, entropy, and heat capacity are compared. It is found that the anharmonicity and coupling of molecular vibrations can play a significant role in predicting accurate thermodynamic quantities. Limitations of the current VSCF method for low frequency modes have been partially removed by following normal mode displacements in internal, rather than Cartesian, coordinates.

Njegic, Bosiljka; Gordon, Mark S.

2006-12-01

104

Exploring the effect of anharmonicity of molecular vibrations on thermodynamic properties.

Thermodynamic properties of selected small and medium size molecules were calculated using harmonic and anharmonic vibrational frequencies. Harmonic vibrational frequencies were obtained by normal mode analysis, whereas anharmonic ones were calculated using the vibrational self-consistent field (VSCF) method. The calculated and available experimental thermodynamic data for zero point energy, enthalpy, entropy, and heat capacity are compared. It is found that the anharmonicity and coupling of molecular vibrations can play a significant role in predicting accurate thermodynamic quantities. Limitations of the current VSCF method for low frequency modes have been partially removed by following normal mode displacements in internal, rather than Cartesian, coordinates. PMID:17176129

Njegic, Bosiljka; Gordon, Mark S

2006-12-14

105

The Extended Thermodynamic Properties of Taub-NUT/Bolt-AdS spaces

We investigate the extended thermodynamic properties of higher-dimensional Taub-NUT/Bolt-AdS spaces where a cosmological constant is treated as a pressure. We find a general form for thermodynamic volumes of Taub-NUT/Bolt-AdS black holes for arbitrary dimensions. Interestingly, it is found that the Taub-NUT-AdS metric has a thermodynamically stable range when the total number of dimensions is a multiple of 4 (4, 8, 12, ...). We also explore their phase structure and find the first order phase transition holds for higher-dimensional cases.

Chong Oh Lee

2014-08-09

106

Thermodynamic properties of almandine-grossular garnet solid solutions

The mixing properties of Fe3Al2Si3O12-Ca3Al2Si3O12 garnet solid solutions have been studied in the temperature range 850–1100° C. The experimental method involves measuring the composition of garnet in equilibrium with an assemblage in which the activity of the Ca3Al2Si3O12 component is fixed. Experiments on the assemblage garnet solid solution, anorthite, Al2SiO5 polymorph and quartz at known pressure and temperature fix the

G. Cressey; R. Schmid; B. J. Wood

1978-01-01

107

Structure-property maps and optimal inversion in configurational thermodynamics

NASA Astrophysics Data System (ADS)

Cluster expansions of first-principles density-functional databases in multicomponent systems are now used as a routine tool for the prediction of zero- and finite-temperature physical properties. The ability of producing large databases of various degrees of accuracy, i.e., high-throughput calculations, makes pertinent the analysis of error propagation during the inversion process. This is a very demanding task as both data and numerical noise have to be treated on equal footing. We have addressed this problem by using an analysis that combines the variational and evolutionary approaches to cluster expansions. Simulated databases were constructed ex professo to sample the configurational space in two different and complementary ways. These databases were in turn treated with different levels of both systematic and random numerical noise. The effects of the cross-validation level, size of the database, type of numerical imprecisions on the forecasting power of the expansions were extensively analyzed. We found that the size of the database is the most important parameter. Upon this analysis, we have determined criteria for selecting the optimal expansions, i.e., transferable expansions with constant forecasting power in the configurational space (a structure-property map). As a by-product, our study provides a detailed comparison between the variational cluster expansion and the genetic-algorithm approaches.

Arnold, Björn; Díaz Ortiz, Alejandro; Hart, Gus L. W.; Dosch, Helmut

2010-03-01

108

An Equation of State for the Thermodynamic Properties of Cyclohexane

NASA Astrophysics Data System (ADS)

An equation of state for cyclohexane has been developed using the Helmholtz energy as the fundamental property with independent variables of density and temperature. Multi-property fitting technology was used to fit the equation of state to data for p?T, heat capacities, sound speeds, virial coefficients, vapor pressures, and saturated densities. The equation of state was developed to conform to the Maxwell criteria for two-phase vapor-liquid equilibrium states, and is valid from the triple-point temperature to 700 K, with pressures up to 250 MPa and densities up to 10.3 mol dm-3. In general, the uncertainties (k = 2, indicating a level of confidence of 95%) in density for the equation of state are 0.1% (liquid and vapor) up to 500 K, and 0.2% above 500 K, with higher uncertainties within the critical region. Between 283 and 473 K with pressures lower than 30 MPa, the uncertainty is as low as 0.03% in density in the liquid phase. The uncertainties in the speed of sound are 0.2% between 283 and 323 K in the liquid, and 1% elsewhere. Other uncertainties are 0.05% in vapor pressure and 2% in heat capacities. The behavior of the equation of state is reasonable within the region of validity and at higher and lower temperatures and pressures. A detailed analysis has been performed in this article.

Zhou, Yong; Liu, Jun; Penoncello, Steven G.; Lemmon, Eric W.

2014-12-01

109

Precise thermodynamic properties for natural waters covering only the limnological range

Dissolved salts affect the thermodynamic properties of lake waters. Equations are given to calculate the following properties over the range of 0-0.6 salinity, 0/sup 0/-30/sup 0/C, and 0-180 bars: density, thermal expansibility, temperature of maximum density, maximum density and minimum specific volume, isothermal compressibility, specific heat at constant pressure, specific heat at constant volume, sound speed, adiabatic compressibility, freezing point, adiabatic temperature gradient, and static stability.

Chen, C.T.A.; Millero, F.J.

1986-05-01

110

Thermodynamic Properties for A Drop-in Refrigerant R-SP34E

NASA Astrophysics Data System (ADS)

Although a transition into several promising HFC alternative refrigerants and their mixtures from conventional CFC and/or HCFC refrigerants is steadily in progress, there still remains a niche to pursue a drop-in refrigerant in some limited engineering applications where the advantage of retrofitting can be emphasized.R-SP34E is one of such drop-in refrigerants to complement R-12 which is a ternary mixture refrigerant consisted of R-134a with minor fractions of propane and ethanol. In this paper, the fundamental thermodynamic properties such as VLE properties and gas-phase PVT properties of R-SP34E are presented. This paper reports the first sets of measured data including 7 dew-and bubble-point pressures and 73 gas-phase PVT properties in the extensive range of temperatures 300-380 K, pressures 0.1-5.2 MPa, and densities up to around the critical density, obtained by employing the Burnett apparatus. In order to complement and confirm the reliability of the measurements, thermodynamic models including a dew-point pressure correlation and a truncated virial equation of state were originally developed in this study. The models were confirmed to exhibit not only excellent reproducibility of the measurements but also the thermodynamic consistency regarding the temperature dependence of the second and third virial coefficients and derived properties such as specific heats or speed of sound. By presenting the reliable thermodynamic model, a systematic information about the thermodynamic properties of R-SP34E is provided in this paper.

Kayukawa, Yohei; Hondo, Takashi; Watanabe, Koichi

111

A thermodynamic model of thermal end elastic properties of curium

NASA Astrophysics Data System (ADS)

A self-consistent thermodynamic model of curium is developed. In the framework of this model the temperature dependencies of heat capacity, coefficient of thermal expansion, bulk modulus and Debye temperature of Cm are calculated. It is shown that the phonon anharmonicity of Cm is weaker than in the case of Np and ?-Pu, but stronger than in lanthanides.

Povzner, A. A.; Filanovich, A. N.; Oskina, V. A.

2013-11-01

112

NASA Astrophysics Data System (ADS)

The thermodynamic scaling of molecular dynamic properties of rotation and thermodynamic parameters in a nematic phase was investigated by a molecular dynamic simulation using the Gay-Berne potential. A master curve for the relaxation time of flip-flop motion was obtained using thermodynamic scaling, and the dynamic property could be solely expressed as a function of TV^{? _? }, where T and V are the temperature and volume, respectively. The scaling parameter ?? was in excellent agreement with the thermodynamic parameter ?, which is the logarithm of the slope of a line plotted for the temperature and volume at constant P2. This line was fairly linear, and as good as the line for p-azoxyanisole or using the highly ordered small cluster model. The equivalence relation between ? and ?? was compared with results obtained from the highly ordered small cluster model. The possibility of adapting the molecular model for the thermodynamic scaling of other dynamic rotational properties was also explored. The rotational diffusion constant and rotational viscosity coefficients, which were calculated using established theoretical and experimental expressions, were rescaled onto master curves with the same scaling parameters. The simulation illustrates the universal nature of the equivalence relation for liquid crystals.

Satoh, Katsuhiko

2013-08-01

113

The Problem of Counting the Number of Molecules and Calculating Thermodynamic Properties.

ERIC Educational Resources Information Center

Presents an experimental approach to illustrate that the thermodynamic properties of a system can be considered as the average of mechanical variables. Discusses the Knudsen effusion method to count the number of molecules, vapor pressure, the piezoelectric effect, the experimental setup, and sample experimental results. (JRH)

Torres, Luis Alfonso; And Others

1995-01-01

114

Hypothetical Thermodynamic Properties. Subcooled Vaporization Enthalpies and Vapor Pressures and liquid vapor pressures from T ) 298.15 K to T ) 510 K of a series of polyaromatic hydrocarbons have been of a thermochemical cycle, and agreement is within the combined experimental uncertainties. Vapor pressures

Chickos, James S.

115

Hypothetical Thermodynamic Properties. Subcooled Vaporization Enthalpies and Vapor Pressures The vaporization enthalpies and vapor pressures of the liqiud phase from T ) 298.15 K to T ) 500 K of a series in the literature was measured on a hydrated form. Vapor pressures and normal boiling temperatures for the liquid

Chickos, James S.

116

Thermodynamic properties of the fcc Ising antiferromagnet obtained from precision density of states May 2006 We calculate the density of states for the face-centered-cubic fcc Ising model with nearest of the fcc Ising antiferromagnet has been a long-standing problem in statistical physics, dating back to1

Ryan, Dominic

117

Nano, Quantum, and Statistical Mechanics and Thermodynamics: Data and Property Calculation Websites

NSDL National Science Digital Library

This collection of links provides access to web sites associated with nano, quantum, and statistical mechanics and thermodynamics. The links are arranged by type: data sites, calculation/program download sites, organizations involved with data compilation and property calculation, and bibliographies.

118

Thermodynamic properties of some perovskite type oxides used as SOFC cathode materials

The solid-oxide electrolyte galvanic cells method has been employed in order to obtain the thermodynamic properties of some perovskite-type materials based on lanthanum strontium manganite and lanthanum strontium ferrite manganite. The relative partial molar free energies, enthalpies and entropies of oxygen dissolution in the perovskite phase, as well as the partial pressures of oxygen have been obtained in the temperature

S. Tanasescu; N. D. Totir; D. I. Marchidan

1999-01-01

119

Thermodynamic properties of 1,1-difluoroethane (R152a) in the critical region

In this paper we present a theoretically based crossover model, that is capable of representing the thermodynamic properties of R 152a in a large range of temperatures and densities around the critical point. It includes the singular asymptotic behavior in the vicinity of the critical point and crosses over to regular analytic behavior far away from the critical point. The

A. van Pelt; J. V. Sengers

1995-01-01

120

The thermodynamic properties of Davydov-Scott's protein model in thermal bath

The thermodynamic properties of Davydov-Scott monomer contacting with thermal bath is investigated using Lindblad open quantum system formalism. The Lindblad equation is investigated through path integral method. It is found that the environmental effects contribute destructively to the specific heat, and large interaction between amide-I and amide-site is not preferred for a stable Davydov-Scott monomer.

Sulaiman, A; Alatas, H; Handoko, L T; 10.1142/9789814335614_0072

2011-01-01

121

The structural, electronic, thermoelectric and thermodynamic properties of ternary half-Heusler compound YPdSb are investigated using the first principle calculations. It is found that YPdSb is an indirect semiconductor. The calculated band gap is 0.161 eV with spin-orbital coupling including and 0.235 eV without spin-orbital coupling including, respectively. The electronic transport properties are obtained via Boltzman transport theory. The predicted Seebeck coefficient is 240 {mu}V/K and the thermoelectric performance can be optimized by n-type doping at room temperature. Moreover, the lattice dynamical results regarding the phonon dispersion curves, phonon density of states and thermodynamic properties are reported. Thermodynamics (heat capacity and Debye temperature) as well as mean phonon free path and the thermal conductivity in a temperature range of 0-300 K are determined. - Graphical Abstract: (a) The dependence of the Seebeck coefficient on chemical potential at 300 K. (b) The dependence of the thermopower factor on chemical potential at 300 K. Highlights: Black-Right-Pointing-Pointer The Seebeck coefficient and the thermopower factor are calculated. Black-Right-Pointing-Pointer The lattice dynamics and thermodynamic properties are obtained.

Kong, Fanjie, E-mail: fanjiekong@gmail.com [Department of Physics, Yancheng Institute of Technology, Jiangsu 224051 (China)] [Department of Physics, Yancheng Institute of Technology, Jiangsu 224051 (China); Hu, Yanfei [School of Science, Sichuan University of Science and Engineering, Zigong 643000 (China)] [School of Science, Sichuan University of Science and Engineering, Zigong 643000 (China); Hou, Haijun [School of Materials Science and Engineering, Yancheng Institute of Technology, Jiangsu 224051 (China)] [School of Materials Science and Engineering, Yancheng Institute of Technology, Jiangsu 224051 (China); Liu, Yanhua [School of information engineering, Yancheng Institute of Technology, Jiangsu 224051 (China)] [School of information engineering, Yancheng Institute of Technology, Jiangsu 224051 (China); Wang, Baolin [Department of Physics, Yancheng Institute of Technology, Jiangsu 224051 (China)] [Department of Physics, Yancheng Institute of Technology, Jiangsu 224051 (China); Wang, Lili [Computer Application Institute of CAEP, Academy of Engineering Physics of China, Mianyang 621900 (China)] [Computer Application Institute of CAEP, Academy of Engineering Physics of China, Mianyang 621900 (China)

2012-12-15

122

NIST Standard Reference Database 23 NIST Reference Fluid Thermodynamic and Transport Properties--

#12;NIST Standard Reference Database 23 NIST Reference Fluid Thermodynamic and Transport Properties (NIST) uses its best efforts to deliver a high quality copy of the Database and to verify that the data or omissions in the Database. Â©2007 copyright by the U.S. Secretary of Commerce on behalf of the United States

Magee, Joseph W.

123

: Ab initio and molecular dynamics study Zhong-Li Liu* and Jie-Hui Yang College of Physics and Electric molecular dynamics simulations have been performed to study the structural and thermodynamic propertiesPHYSICAL REVIEW B 83, 144113 (2011) Structural and thermodynamic properties of compressed palladium

AlfÃ¨, Dario

124

Thermodynamic critical and geometrical properties of charged BTZ black hole

The heat capacities and the electric capacitances of charged Banados-Teitelboim-Zanelli (BTZ) black hole are first calculated. By using the equilibrium fluctuation theory of thermodynamics the second-order moments in three different ensembles are obtained, and it is found that in the microcanonical ensemble the extremal charged BTZ black hole is a critical point of the second-order phase transition. The critical exponents associated with some response coefficients satisfy the scaling law of the first kind and the effective spatial dimension is determined to be one from the scaling law of the second kind. The Ricci curvature scalar associated with the Ruppeiner thermodynamic metric is calculated, which suggests also that the effective spatial dimension of the charged BTZ black hole is one.

Wei Yihuan [Department of Physics, Bohai University, Jinzhou 121000, Liaoning (China)

2009-07-15

125

Thermodynamic Properties of 4f- and 5f-SHELL Metals at Finite Temperatures:

NASA Astrophysics Data System (ADS)

The thermodynamic properties of 4f- and 5f-shell metals have been studied at high temperatures using mean-field potential approach. The MFP seen by the lattice ion is constructed in terms of the total energy-volume relation using local pseudopotentials due to Pandya et al. [Physica B 307, 138 (2001)]. We have calculated static compression, shock-wave compression, volume thermal expansion, isothermal and adiabatic bulk moduli (BT and BS), specific heats (CV and CP), thermodynamic Grüneisen parameter (?th), anharmonic contribution to the specific heat and temperature along shock Hugoniot for 4f (?-Ce)- and 5f (fcc-Th)-shell metals. The results are well compared with the other theoretical and experimental findings, which ensure the use of pseudopotentials for studying thermodynamic properties at higher temperatures in case of lanthanides and actinides.

Bhatt, N. K.; Vyas, P. R.; Jani, A. R.; Gohel, V. B.

126

Thermodynamic properties of uranium in Ga-In based alloys

NASA Astrophysics Data System (ADS)

Activity of uranium was determined in gallium, indium and gallium-indium eutectic (21.8 wt.% In) based alloys between 573 and 1073 K employing the electromotive force method. In two-phase U-Ga-In alloys, uranium forms the intermetallic compound UGa3. Activity coefficients and solubility of uranium in Ga-In eutectic were also determined in the same temperature range. Partial thermodynamic functions of ?-U in saturated alloys with gallium, indium and Ga-In eutectic were calculated.

Volkovich, V. A.; Maltsev, D. S.; Yamshchikov, L. F.; Melchakov, S. Yu; Shchetinskiy, A. V.; Osipenko, A. G.; Kormilitsyn, M. V.

2013-07-01

127

The thermodynamic properties of 2-methylaniline and trans-(R,S)- decahydroquinoline

Measurements leading to the calculation of the ideal-gas thermodynamic properties for 2-methylaniline and trans-(R,S)-decahydroquinoline are reported. Experimental methods included combustion calorimetry, adiabatic heat-capacity calorimetry, comparative ebulliometry, inclined-piston gauge manometry, and differential-scanning calorimetry (dsc). Entropies, enthalpies, and Gibbs energies of formation were derived for the ideal gas at selected temperatures for both compounds. Critical properties were determined for 2-methylaniline with the dsc. Measured combustion enthalpies, vapor pressures, critical properties, and ideal-gas entropies were compared with estimated and experimental literature values. 59 refs., 7 figs., 15 tabs.

Steele, W.V.; Chirico, R.D.; Nguyen, A.; Knipmeyer, S.E.

1990-02-01

128

Thermodynamic and material properties of charge-stabilized colloidal crystals

NASA Astrophysics Data System (ADS)

We describe direct space imaging measurements of elastic properties evident at the surface faces of face-centered cubic crystals of polystyrene sulfate spheres suspended in clean water at and near the melting point. The crystals' bulk modulus emerges from measurements of the static structure factor. To measure the shear phonon dispersion, and extract a shear modulus, we develop the theory of direct imaging phonon spectroscopy for colloidal crystals. We then discuss our use of high resolution digital video microscopy to follow the emergence and evolution of order during a nonequilibrium phase transition in a geometrically confined charge-stabilized colloidal suspension. The equilibrium configuration for the spheres in this system is a two-layer square lattice, equivalent to two layers of a body-centered cubic (BCC) crystal, which upon shear melting rapidly crystallizes to a buckled single-layer triangular lattice, and subsequently undergoes a martensitic phase transition back to the two-layer square lattice. Finally, we report direct crystallographic studies of bidisperse suspensions of polystyrene sulfonate spheres mixed in the 1:1 and 1:13 stoichiometries. These portions of the binary phase diagram are extraordinarily rich and include ordered, fluid, glassy and phase separated structures, and transitions among these phases are driven by varying kappasp{-1} (screening length) and phi (volume fraction) for a given value of the size ratio.

Weiss, Jessica Ann

129

Thermodynamic properties of ZrSiO4 polymorphs from DFT based ab initio phonon calculations

NASA Astrophysics Data System (ADS)

Zircon and Reidite are the polymorphs of ZrSiO4 minerals that are natural hosts of various radioactive elements in the crust of the earth. Its high permittivity also makes it a promising material for the gate dielectric material in metal-oxide semiconductors. Knowledge of the thermodynamic properties at high temperature and high is very important to consider its application as an effective natural storage for the radioactive wastes and high technology ceramics. These properties are thoroughly studied both computationally and experimentally for zircon, while significantly less attention was paid to reidite in the literature. We report studies of thermodynamic properties of Zircon and Reidite from phonon spectra calculations using ab initio based periodic density-functional theory (DFT) calculations. Various thermodynamic properties such as free energy, internal energy, entropy, enthalpy, heat capacity and thermal displacement as a function of temperature are calculated. Phoon dispersion curves and density of states are calculated and compared with the experimental data. Calculated bulk properties agree very well with the experimental data in the literature.

Du, Jincheng; Chaudhari, Mrunal

2011-03-01

130

The thermodynamic properties of 2-amino-ethylphosphonic acid

+ . 07 - 1. 94 + . 08 15 8 5 5 4 - 30. 7 + . 2 ? 32. 0 + . 1 33. 3 + . 2 - 34. 4 + . 2 - 35. 9 + . 3 36 TABLE VII Thermodynamic Functions for pK of 2-Aminoethylphosphonic Acid Temperature pK T 0 -1 0 aHT, Kca1 mol aS& , eu 0 25 C 35'C.... 3 - 7. 5) for pK 2 solutions, acidic (1. 6 - 2. 7) for pKl solut1ons, and basic (9. 8 - 11. 5) for pK3 solutions. The plot of pK versus l/T produced a smooth curve for pKl, 0 pK 2, and pK3, as shown 1n Figures 5 through 7, respectively (pages 30...

Unruh, Stephen George Walter

2012-06-07

131

Fragility of polymeric liquids: Correlation between thermodynamic and dynamic properties

The effect of polymer structure on fragility was determined by relating the apparent fragility to the relaxation response, heat capacity, and thermal expansion. For the 14 polymers studied, the fragility estimates based on the relaxation behavior (log a{sub T}) correlated well with the thermodynamic estimates of {Delta}C{sub p}/M{sub o}, and {Delta}{alpha}. In general, polymers with less sterically hindered repeat unit structures exhibited strong behavior. Polymers with sterically hindered backbones containing oxygen or ringed structures in the backbone were consistently fragile using log a{sub T}, {Delta}C{sub p}/M{sub o}, and {Delta}{alpha} as measures of fragility. On the other hand, using C{sub p}{sup 1}/C{sub p}{sup g} as a fragility criterion resulted in very different fragility classifications.

Colucci, D.M.; McKenna, G.B. [National Inst. of Standards and Technology, Gaithersburg, MD (United States). Polymers Div.

1997-12-31

132

Metastable Solution Thermodynamic Properties and Crystal Growth Kinetics

NASA Technical Reports Server (NTRS)

The crystal growth rates of NH4H2PO4, KH2PO4, (NH4)2SO4, KAl(SO4)2 central dot 12H2O, NaCl, and glycine and the nucleation rates of KBr, KCl, NaBr central dot 2H2O, (NH4)2Cl, and (NH4)2SO4 were expressed in terms of the fundamental driving force of crystallization calculated from the activity of supersaturated solutions. The kinetic parameters were compared with those from the commonly used kinetic expression based on the concentration difference. From the viewpoint of thermodynamics, rate expressions based on the chemical potential difference provide accurate kinetic representation over a broad range of supersaturation. The rates estimated using the expression based on the concentration difference coincide with the true rates of crystallization only in the concentration range of low supersaturation and deviate from the true kinetics as the supersaturation increases.

Kim, Soojin; Myerson, Allan S.

1996-01-01

133

Thermodynamic properties of mesoscale convective systems observed during BAMEX

Dropsonde observations from the Bow-echo and Mesoscale convective vortex EXperiment (BAMEX) are used to document the spatio-temporal variability of temperature, moisture and wind within mesoscale convective systems (MCSs). Onion type sounding structures are found throughout the stratiform region of MCSs but the temperature and moisture variability is large. Composite soundings were constructed and statistics of thermodynamic variability were generated within each sub-region of the MCS. The calculated air vertical velocity helped identify subsaturated downdrafts. We found that lapse rates within the cold pool varied markedly throughout the MCS. Layered wet bulb potential temperature profiles seem to indicate that air within the lowest several km comes from a variety of source regions. We also found that lapse rate transitions across the 0 C level were more common than isothermal, melting layers. We discuss the implications these findings have and how they can be used to validate future high resolution numerical simulations of MCSs.

Correia, James; Arritt, R.

2008-11-01

134

Evaluation of phosphate thermodynamic properties for spent electrolyte recycle

NASA Astrophysics Data System (ADS)

Adaptation of the phosphate conversion technique was undertaken and evaluated for application to the recycle process of the spent electrolyte generated from metal electrorefining process. In order to confirm the conversion behaviors of fission product (FP) chlorides to the phosphates, conversion experiments were carried out for some alkali metal, alkaline earth metals and rare-earth elements and their results were compared with that of thermodynamic calculations of previous study [I. Amamoto, H. Kofuji, M. Myochin et al., in: Proceedings of Global 2007, Boisi, Idaho, USA, 2007]. Among these elements, rare-earth chlorides were converted into phosphates and Cs was not, according to the prediction by the calculation. As for alkaline earth metals, their equilibrium constants were nearly 1 based on the results of the calculations, the conversion reactions were difficult to occur. In addition, it was clarified that phosphates were thermally unstable, easily to decompose at higher temperature, through the measurements of their heat flow and vapor pressure.

Kofuji, Hirohide; Amamoto, Ippei; Yasumoto, Masaru; Sasaki, Kazuya; Myochin, Munetaka; Terai, Takayuki

2009-06-01

135

Thermodynamic properties of some metal oxide-zirconia systems

NASA Technical Reports Server (NTRS)

Metal oxide-zirconia systems are a potential class of materials for use as structural materials at temperatures above 1900 K. These materials must have no destructive phase changes and low vapor pressures. Both alkaline earth oxide (MgO, CaO, SrO, and BaO)-zirconia and some rare earth oxide (Y2O3, Sc2O3, La2O3, CeO2, Sm2O3, Gd2O3, Yb2O3, Dy2O3, Ho2O3, and Er2O3)-zirconia system are examined. For each system, the phase diagram is discussed and the vapor pressure for each vapor species is calculated via a free energy minimization procedure. The available thermodynamic literature on each system is also surveyed. Some of the systems look promising for high temperature structural materials.

Jacobson, Nathan S.

1989-01-01

136

Ab initio study of the thermodynamic properties and the phonon calculations of Zircon and Reidite

NASA Astrophysics Data System (ADS)

Zircon and Reidite are the polymorphs of Zirconium Silicate which find its importance geologically, because of its natural hosting to various radioactive elements in the crust of the earth. High permittivity also makes it a promising material for the gate dielectric material in metal-oxide semiconductors. Knowledge of the thermodynamic properties and the phonon based calculations is very critical to understand the high temperature and high pressure properties in order to consider its application as an effective natural storage for the radioactive wastes. These properties are thoroughly studied both computationally and experimentally for zircon, while significantly less attention was paid to reidite in the literature. The thermodynamic properties and phonon calculations of Zircon and Reidite were studied using ab initio based periodic density-functional theory (DFT) based calculations using the generalized gradient approximation (GGA). Various properties such as free energy, internal energy, entropy, heat capacity and thermal displacement as a function of temperature is calculated using the PHONON software. Various phonon based density of states and dispersion curves are calculated and compared with the experimental data. No first principles based computational results were reported up to now. Calculated bulk properties agree very well with the experimental data in the literature.

Chaudhari, Mrunalkumar; Du, Jincheng

2011-03-01

137

Study of Thermodynamical Properties of Polyvinyl Acetate in Tetrahydrofuran

NASA Astrophysics Data System (ADS)

The propagation of ultrasonic waves and the measurement of their velocity in solutions form an important tool for the evaluation of various acoustical and thermodynamical parameters which give an insight into the nature of miscibility and molecular interactions in polymer solutions. In the present study, the ultrasonic velocity, density, viscosity measurements have been made in 0.1 M solution using pulse echo overlap technique at 293 K at the different concentrations of polyvinyl acetate in tetrahydrofuran. Thermo-acoustical parameters viz., adiabatic compressibility, molar sound velocity, molar compressibility, expansion coefficient, acoustic impedance, van der Waals' constant and internal pressure have been computed from the experimental data. The nature of polymer/solvent interaction and the effect of concentration on the molecular interaction are studied. The nonlinear variations of polyvinyl acetate in tetrahydrofuran have been studied. The variation of ultrasonic velocity and other thermo-acoustical parameters shows nonlinear increase or decrease with molar concentration which suggest semi-compatibility of the polymer in the given solvent.

Tabhane, Priyanka V.; Chimankar, Omprakash P.; Tabhane, Vilas A.

2012-10-01

138

Vibrational and thermodynamic properties of orthorhombic CaSnO3 from DFT and DFPT calculations

NASA Astrophysics Data System (ADS)

Density functional theory (DFT) and density functional perturbation theory (DFPT) calculations were used to investigate the vibrational and thermodynamic properties of orthorhombic stannate CaSnO3 compound. Our approach was based on the generalized gradient approximation with dispersion correction (GGA+D), considering the norm-conserved pseudopotentials. The phonon dispersion relation as well as theoretical peaks of the infrared (IR) and Raman spectrum in the frequency range of 100-800 cm-1 was analyzed and assigned. The thermodynamic potentials and the specific heat at constant volume of the CaSnO3 compound are also calculated, whose dependence with the temperature are discussed.

Moreira, E.; Barboza, C. A.; Albuquerque, E. L.; Fulco, U. L.; Henriques, J. M.; Araújo, A. I.

2015-02-01

139

Thermodynamic properties of liquid Au-Cu-Sn alloys determined from electromotive force measurements.

The thermodynamic properties of the ternary Au-Cu-Sn system were determined with the electromotive force (EMF) method using a liquid electrolyte. Three different cross-sections with constant Au:Cu ratios of 3:1, 1:1, and 1:3 were applied to measure the thermodynamic properties of the ternary system in the temperature range between the liquidus temperature of the alloys and 1023 K. The partial free energies of Sn in liquid Au-Cu-Sn alloys were obtained from EMF data. The integral Gibbs free energy and the integral enthalpy at 900 K were calculated by Gibbs-Duhem integration. The ternary interaction parameters were evaluated using the Redlich-Kister-Muggianu polynomial. PMID:22039311

Guo, Zhongnan; Hindler, Michael; Yuan, Wenxia; Mikula, Adolf

2011-10-20

140

LDA+ U calculation of structural and thermodynamic properties of Ce2O3

NASA Astrophysics Data System (ADS)

We investigated the structure and thermodynamic properties of the hexagonal Ce2O3 by using LDA+ U scheme in the frame of density functional theory (DFT), together with the quasi-harmonic Debye model. The obtained lattice constants, bulk modulus, and the insulating gap agree well with the available experimental data. We successfully yielded the temperature dependence of bulk modulus, volume, thermal expansion coefficient, Debye temperature, specific heat as well as the entropy at different U values. It is found that the introduction of the U value cannot only correct the calculation of the structure but also improve the accurate description of the thermodynamic properties of Ce2O3. When U = 6 eV the calculated volume (538 Bohr3) at 300 K agrees well with the experimental value (536 Bohr3). The calculated entropy curve becomes more and more close to the experimental curve with the increasing U value.

Zhu, Bo; Cheng, Yan; Niu, Zhen-Wei; Zhou, Meng; Gong, Min

2014-08-01

141

We report the results of our first-principles calculations of structural stability, mechanical, magnetic, and thermodynamic properties for ?-M(23)C(6) (M = Fe, Cr) compounds with each of the four metal Wyckoff sites being occupied in turn by Fe. The thermodynamic properties and the temperature dependence of the mechanical behavior of ?-M(23)C(6) compounds are investigated based on the quasi-harmonic Debye model. The results show that the thermodynamic properties of ?-M(23)C(6) (M = Fe, Cr) compounds are more dependent on the position of Fe atoms than the amount of Fe. PMID:23172712

Han, J J; Wang, C P; Liu, X J; Wang, Y; Liu, Zi-Kui

2012-12-19

142

NASA Astrophysics Data System (ADS)

We report the results of our first-principles calculations of structural stability, mechanical, magnetic, and thermodynamic properties for ?-M23C6 (M = Fe, Cr) compounds with each of the four metal Wyckoff sites being occupied in turn by Fe. The thermodynamic properties and the temperature dependence of the mechanical behavior of ?-M23C6 compounds are investigated based on the quasi-harmonic Debye model. The results show that the thermodynamic properties of ?-M23C6 (M = Fe, Cr) compounds are more dependent on the position of Fe atoms than the amount of Fe.

Han, J. J.; Wang, C. P.; Liu, X. J.; Wang, Y.; Liu, Zi-Kui

2012-12-01

143

Accuracy Based Generation of Thermodynamic Properties for Light Water in RELAP5-3D

RELAP5-3D interpolates to obtain thermodynamic properties for use in its internal calculations. The accuracy of the interpolation was determined for the original steam tables currently used by the code. This accuracy evaluation showed that the original steam tables are generally detailed enough to allow reasonably accurate interpolations in most areas needed for typical analyses of nuclear reactors cooled by light water. However, there were some regions in which the original steam tables were judged to not provide acceptable accurate results. Revised steam tables were created that used a finer thermodynamic mesh between 4 and 21 MPa and 530 and 640 K. The revised steam tables solved most of the problems observed with the original steam tables. The accuracies of the original and revised steam tables were compared throughout the thermodynamic grid.

Cliff B. Davis

2010-09-01

144

Viscosity and thermodynamic properties of QGP in relativistic heavy-ion collisions

We study the viscosity and thermodynamic properties of QGP at RHIC by employing the recently extracted equilibrium distribution\\u000a functions from two hot QCD equations of state of O(g\\u000a 5) and O(g\\u000a 6ln?(1\\/g)), respectively. After obtaining the temperature dependence of the energy density and the entropy density, we focus our attention\\u000a on the determination of the shear viscosity for a rapidly

Vinod Chandraaand; V. Ravishankar

2009-01-01

145

NASA Technical Reports Server (NTRS)

A virial equation of state for nitrogen was determined by use of newly measured speed-of-sound data and existing pressure-density-temperature data in a multiproperty-fitting technique. The experimental data taken were chosen to optimize the equation of state for a pressure range of 0 to 10 atm and for a temperature range of 60 to 350 K. Comparisons are made for thermodynamic properties calculated both from the new equation and from existing equations of state.

Younglove, B.; Mccarty, R. D.

1979-01-01

146

A model is developed for the thermodynamic properties of Fe2+-Mg2+-aluminate-titanate-ferrite spinels of space group Fd3m. The model incorporates an expression for the configurational entropy of mixing which accounts for long-range order over tetrahedral and octahedral sites. Short-range order or departures from cubic symmetry are not considered. The non-configurational Gibbs energy is formulated as a second degree Taylor expansion in six

Richard O. Sack; Mark S. Ghiorso

1991-01-01

147

First-principles and classical molecular dynamics simulations have been performed to study the structural and thermodynamic properties of Pd under pressure. By comparing the Gibbs free energy, in the quasiharmonic approximation (QHA), of the face-centered cubic (fcc) phase with those of the hexagonal-close-packed (hcp) and body-centered-cubic (bcc) phases we found that the fcc phase is stable up to 500 GPa and

Zhong-Li Liu; Jie-Hui Yang; Ling-Cang Cai; Fu-Qian Jing; Dario Alfè

2011-01-01

148

The thermodynamic properties of hot nuclei are described within the canonical and microcanonical ensemble approaches. These approaches are derived based on the solutions of the BCS and self-consistent quasiparticle random-phase approximation at zero temperature embedded into the canonical and microcanonical ensembles. The results obtained agree well with the recent data extracted from experimental level densities by the Oslo group for {sup 94}Mo, {sup 98}Mo, {sup 162}Dy, and {sup 172}Yb nuclei.

Hung, N. Quang [Center for Nuclear Physics, Institute of Physics, Hanoi (Viet Nam); Dang, N. Dinh [Theoretical Nuclear Physics Laboratory, RIKEN Nishina Center for Accelerator-Based Science, 2-1 Hirosawa, Wako City, 351-0198 Saitama (Japan); Institute for Nuclear Science and Technique, Hanoi (Viet Nam)

2010-10-15

149

Quartz: heat capacities from 340 to 1000 K and revised values for the thermodynamic properties.

New heat-capacity data for quartz have been measured over the T interval 340-1000 K by differential scanning calorimetry. The data were combined with recent heat-content and heat-capacity data to provide a significantly revised set of thermodynamic properties for alpha -quartz and to resolve the problem of disparate heat-content and heat-capacity data for alpha - and beta -quartz.-J.A.Z.

Hemingway, B.S.

1987-01-01

150

The stoichiometry and thermodynamic properties of As (III) hydroxide complexes were determined from both solubility and Raman spectroscopic measurements. Arsenolite, claudetite, and orpiment solubilities were measured at temperatures to 250 and 300 °C, respectively, in acid solutions (pH < 6) at the saturated vapor pressure of the system. Raman spectroscopic measurements were performed on As2O3-H2O solutions (0.02 ? As ?

Gleb Pokrovski; Robert Gout; Jacques Schott; Alexandre Zotov; Jean-Claude Harrichoury

1996-01-01

151

Thermodynamic properties of strongly coupled plasma in the presence of an external magnetic field

NASA Astrophysics Data System (ADS)

Thermodynamic properties of a Yukawa system consisting of dust particles in plasma are studied in the presence of an external magnetic field. It is assumed that dust particles interact with each other by a modified potential in the presence of a magnetic field. A molecular dynamics code is developed to calculate this internal energy for the entire system. Based on the values of the internal energy given by the code, the Helmholtz free energy and pressure are calculated for the system.

Begum, M.; Baruah, S.; Das, N.

2014-07-01

152

Thermodynamic and thermophysical properties of organic working fluids for Rankine-cycle engines

Refrigerants, especially the halocarbon compounds R-11, R-113 and R-114, are the most suitable organic working fluids for the majority of operational Rankine-cycle engines utilising low grade heat sources. Thus, the quick and accurate evaluation of the thermodynamic and thermo-physical properties of these refrigerants is desirable for the analytical prediction of the performances of individual components of such a Rankine-cycle engine,

O. Badr; P. W. OCallaghan; S. D. Probert

1985-01-01

153

Thermodynamical properties of small superconductors with a fixed number of particles

NASA Astrophysics Data System (ADS)

The variation after projection approach is applied for the first time to the Richardson pairing Hamiltonian to describe the thermodynamics of small superconductors with a fixed number of particles. The minimization of the free energy is made by a direct diagonalization of the entropy. The variation after projection applied at finite temperature provides a perfect reproduction of the exact canonical properties of odd or even systems from very low to high temperatures.

Gambacurta, Danilo; Lacroix, Denis

2012-04-01

154

Structural and Thermodynamic Properties of Amyloid-? Peptides: Impact of Fragment Size

NASA Astrophysics Data System (ADS)

Alzheimer's disease is a progressive neurodegenerative disease whose physiological characteristics include the accumulation of amyloid-containing deposits in the brain and consequent synapse and neuron loss. Unfortunately, most widely used drugs for the treatment can palliate the outer symptoms but cannot cure the disease itself. Hence, developing a new drug that can cure it. Most recently, the ``early aggregation and monomer'' hypothesis has become popular and a few drugs have been developed based on this hypothesis. Detailed understanding of the amyloid-? peptide structure can better help us to determine more effective treatment strategies; indeed, the structure of Amyloid has been studied extensively employing experimental and theoretical tools. Nevertheless, those studies have employed different fragment sizes of Amyloid and characterized its conformational nature in different media. Thus, the structural properties might be different from each other and provide a reason for the existing debates in the literature. Here, we performed all-atom MD simulations and present the structural and thermodynamic properties of A?1-16, A?1-28, and A?1-42 in the gas phase and in aqueous solution. Our studies show that the overall structures, secondary structures, and the calculated thermodynamic properties change with increasing peptide size. In addition, we find that the structural properties of those peptides are different from each other in the gas phase and in aqueous solution.

Kitahara, T.; Wise-Scira, O.; Coskuner, O.

2010-10-01

155

Thermodynamic and electron transport properties of the argon and argon-hydrogen plasmas have been calculated under the local thermodynamic equilibrium conditions in temperature range of 10 000-40 000 K over the wide range of pressures. Electronic excitation affects strongly these properties especially at high pressures. The inclusion of electronically excited states (EES) in relevant partition function influences the internal contribution to frozen and total specific heat for argon and argon-hydrogen plasma and it has been observed that although the total specific heat of argon plasma is less than that of hydrogen plasma, yet its internal contribution is more. Compensation between different contributions to total specific heat (by including and neglecting EES) occurring in hydrogen plasmas at low pressures has not been observed in argon and argon-hydrogen plasmas. As electron transport properties strongly depend upon the degree of ionization, therefore larger relative errors are found for these properties with and without EES, and in contrast to hydrogen plasma there exist a dominance of electron-atom cross section at low temperatures and EES dominance at intermediate temperatures.

Singh, Kuldip; Singh, Gurpreet; Sharma, Rohit [Department of Physics, Guru Nanak Dev University, Amritsar 143005 (India)

2010-07-15

156

Free energy of formation of Mo2C and the thermodynamic properties of carbon in solid molybdenum

NASA Technical Reports Server (NTRS)

As part of a study of the thermodynamical properties of interstitial elements in refractory metals, the free energy of formation of Mo2C is determined, and the thermodynamical properties of C in solution in solid Mo evaluated. The activity of C in the two-phase region Mo + Mo2C is obtained from the C content of iron rods equilibrated with metal + carbide powder mixtures. The free energy of formation of alpha-Mo2C is determined from the activity data. The thermodynamic properties of C in the terminal solid solution are calculated from available data on the solid solubility of C in Mo. Lattice distortion due to misfit of the C atoms in the interstitial sites appears to play a significant role in determining the thermodynamic properties of C in solid Mo.

Seigle, L. L.; Chang, C. L.; Sharma, T. P.

1979-01-01

157

NASA Astrophysics Data System (ADS)

A new thermodynamic analysis has been performed on experimental thermophysical and phase diagram data of (Mg,Fe)2SiO_4 olivine, wadsleyite and ringwoodite solid solutions. The analysis demonstrates that large inconsistencies exist in the V- P- T data of wadsleyite and ringwoodite. It has been suggested in recent literature that a hydration effect is able to explain the large differences in volume measured by several independent groups of investigators [1,2]. However, this hydration effect does not explain the combination of a large measured volume associated with a large measured bulk modulus for a number of experimental V- P- T data sets [3-7]. We show the effects of the inconsistencies on the calculated phase diagram, bulk sound velocities and other thermodynamic properties. We have applied our thermodynamic analysis to iron rich compositions at pressure/temperature/iron content conditions representative for the mantles of Earth and Mars. For these conditions a strong compositional effect on thermodynamic properties in two- phase regions is observed from our thermodynamic model. This compositional effect is associated with the slopes of two- phase boundaries in pressure- composition and temperature- composition phase diagrams leading to a change up to 100% or more for specific thermodynamic properties thermal expansivity ? , specific heat cP and bulk modulus kS. The amplitude of the anomalies increases with iron content larger than 10%. These anomalous two-phase zones, where olivine transforms to ringwoodite via wadsleyite, cover a pressure range of about 5 GPa. In the Earth's mantle transition zone these two-phase zones therefore occupy a depth range of some 150 km and the impact of these strong variations in ? and cP on mantle dynamics may be limited. Planet Mars with its weaker gravity field and reduced pressure gradient is an environment more susceptible to the impact of these two-phase compositional effects, even more so since the iron content of the Martian mantle is likely about twice as high as for Earth's mantle. We will show preliminary results of convection modeling including these effects for both Earth and Mars like conditions. Putting the variations in thermophysical properties in perspective we can say that at conditions prevailing in the Martian mantle, the V- P- T inconsistencies affect thermodynamic properties in two- phase regions by about 7%. This is substantially less than the mentioned variations up to 100%, due to the composition effect. On the other hand differences between properties computed with several modern thermodynamic databases amount to about 30%. [1] Smyth JR, Holl CM, Frost DJ, Jacobsen SD, Langenhorst F, McCammon CA (2003), Am. Miner. 88, 1402-1407. [2] Inoue T, Tanimoto Y, Irifune T, Suzuki T, Fukui H and Ohtaka O (2004), Physics Earth Planet. Int., in press. [3] Hazen RM Zhang J and Ko J (1990), Phys. Chem. Miner., 17, 416-419. [4] Hazen RM, Downs RT, Finger LW and Ko J (1993), Am. Miner. 78, 1320-1323. [5] Fei Y, Mao HK, Shu J, Parthasarathy, Bassett WA and Ko J (1992), J. Geophys. Res. 97, 4489-4495. [6] Meng Y et al., J. Geophys. Res. 98, 22199-22207. [7] Meng Y, Fei Y, Weidner DJ, Gwanmesia GD and Hu J (1994), Phys. Chem. Minerals 21, 407-412.

Jacobs, M. H.; de Jong, B. H.; Matas, J.; van den Berg, A. P.

2004-12-01

158

Improved relationships for the thermodynamic properties of carbon phases at detonation conditions

NASA Astrophysics Data System (ADS)

Accurate volumetric and heat capacity relationships have been developed for graphite and diamond carbon forms for use with the Jaguar thermochemical equilibrium program for the calculation of the detonation properties of explosives. Available experimental thermodynamic properties and Hugoniot values have been analyzed to establish the equations of state for the carbon phases. The diamond-graphite transition curve results from the equality of the chemical potentials of the phases. The resulting relationships are utilized to examine the actual phase behaviour of carbon under shock conditions. The existence of metastable carbon states is established by analyses of Hugoniot data for hydrocarbons and explosives at elevated temperatures and pressures. The accuracy of the resulting relationships is demonstrated by comparisons for several properties, including the Hugoniot behaviour of oxygen-deficient explosives at overdriven conditions.

Stiel, L. I.; Baker, E. L.; Murphy, D. J.

2014-05-01

159

NASA Astrophysics Data System (ADS)

The new simple semi empirical equation of state for description of P-?-T data of "normal" substances was specified. New equation of state has 10 individual adjustable coefficients and it describes thermal properties of gas, liquid and fluid in the main with the accuracy within the error of experimental data, except of critical region. The caloric properties and the speed of sound of argon, nitrogen and carbon dioxide were calculated with the help of known thermodynamic equations and in general divergences between calculated and tabular caloric data do not exceed the experimental error. New equation can be used for engineering calculations at the deficit of experimental data, especially on the caloric properties of substances.

Kaplun, Alexander; Meshalkin, Arkadiy

2014-08-01

160

Thermodynamic properties of Al, Ni, NiAl, and Ni3Al from first-principles calculations

Thermodynamic properties of Al, Ni, NiAl, and Ni3Al from first-principles calculations Y. Wang *, Z The thermodynamic properties of Al, Ni, NiAl, and Ni3Al were studied using the first-principles approach. The 0-K of )1.6 J/mol/K for NiAl and )1.2 J/mol/K for Ni3Al. For Ni, the inclusion of thermal electronic

Chen, Long-Qing

161

Quantum topological method studies on the thermodynamic properties of polychlorinated phenoxazines

NASA Astrophysics Data System (ADS)

The novel quantum topological indices PY1,2 were derived from molecular structure combined with the effect of atom space, the character of bonding atoms (such as equilibrium electro-negativity) and the branching effect between the atoms. The quantitative structure-property relationships (QSPRs) were proposed between PY1,2 and the thermodynamic properties (?fH?, ?fG? and ?fGR?) of phenoxazine (Phx) and 135 kinds of polychlorinated phenoxazines (PCPXs), by Multiple linear regression (MLR) analysis method. The high-quality prediction models were evidenced by the correlation coefficient R, the standard error of estimate S, the Fisher statistic value and the cross-validated correlation coefficient RCV. With the new QSPR model, we are able to predict a wide range of thermodynamic properties of an extensive number of molecules. And the model is statistically significant and shows good stability for data variation as tested by the leave-one-out cross-validation (LOO-CV).

Xiao, Fangzhu; Peng, Guowen; Nie, Changming; Wu, Yaxin; Dai, Yimin

2014-09-01

162

Intermolecular potentials and the accurate prediction of the thermodynamic properties of water

The ability of intermolecular potentials to correctly predict the thermodynamic properties of liquid water at a density of 0.998 g/cm{sup 3} for a wide range of temperatures (298–650 K) and pressures (0.1–700 MPa) is investigated. Molecular dynamics simulations are reported for the pressure, thermal pressure coefficient, thermal expansion coefficient, isothermal and adiabatic compressibilities, isobaric and isochoric heat capacities, and Joule-Thomson coefficient of liquid water using the non-polarizable SPC/E and TIP4P/2005 potentials. The results are compared with both experiment data and results obtained from the ab initio-based Matsuoka-Clementi-Yoshimine non-additive (MCYna) [J. Li, Z. Zhou, and R. J. Sadus, J. Chem. Phys. 127, 154509 (2007)] potential, which includes polarization contributions. The data clearly indicate that both the SPC/E and TIP4P/2005 potentials are only in qualitative agreement with experiment, whereas the polarizable MCYna potential predicts some properties within experimental uncertainty. This highlights the importance of polarizability for the accurate prediction of the thermodynamic properties of water, particularly at temperatures beyond 298 K.

Shvab, I.; Sadus, Richard J., E-mail: rsadus@swin.edu.au [Centre for Molecular Simulation, Swinburne University of Technology, PO Box 218, Hawthorn, Victoria 3122 (Australia)

2013-11-21

163

Thermodynamic and structural properties of phospholipid langmuir monolayers on hydrosol surfaces.

Measurements of Langmuir pressure/area isotherms, rheology, grazing incidence X-ray diffraction (GIXD), and grazing incidence diffuse X-ray scattering out of the specular plane (GIXOS) have been used to investigate the influence of a hydrosol containing charged mineral nanoparticles on the thermodynamic and structural properties of a DPPC monolayer. The mineral adsorption layer that is formed via electrostatic interaction underneath the lipid layer alters the thermodynamic properties of the phospholipid monolayer in terms of maximal achievable compression, compressibility, and phase behavior. Modifications appear in the latter case as a coolinglike effect. Rheology measurements of the bulk viscoelastic properties revealed a stabilizing effect of the transient bulk network on the surfactant layer. The lipid chain lattice is found to be reorganized and adapted to the internal atomic structure of the mineral particles. A model for the superposition of Bragg rods from the lipid chains and the minerals is applied to separate these scattering contributions. In the vicinity of the mineral particles, the (2) reflection for DPPC on a liquid substrate was found, indicating strongly suppressed fluctuations at the surface. An estimation of the Debye-Waller factor associated with the lipid layer organization is used to quantify the damping of fluctuations within the lipid matrix due to the rigidifying and stabilizing effect of the mineral particles. PMID:16042465

Wiegart, Lutz; Struth, Bernd; Tolan, Metin; Terech, Pierre

2005-08-01

164

Thermodynamic properties of a geothermal working fluid; 90% isobutane-10% isopentane: Final report

We present tables of thermodynamic properties, and dew and bubble properties, of a mixture of 90 mol % isobutane and 10 mol % isopentane, a working fluid in a binary geothermal power cycle. The tables are generated by a formulation of the Helmholtz free energy, in which the mixture properties are mapped onto the known properties of pure isobutane by means of the principle of generalized corresponding states. The data base for the Helmholtz free energy formulation is new. We report data obtained in three different apparatus: critical-line and isopentane vapor pressure data obtained in a visual cell; vapor-liquid equilibria data obtained in a mercury-operated variable-volume cell; and pressure-volume-temperature data for the 90 mol %-10 mol % mixture obtained in a semi-automated Burnett-isochoric apparatus. The principles of the methods, and estimates of the reliability, are discussed and all experimental data are compared with the surface. The results are tables of specific volume, enthalpy, entropy, specific heat and density and temperature derivatives of the pressure at 10 K temperature increments from 240 to 600 K along isobars from 0.01 to 20 MPa. Separate tables are prepared from the dew and bubble properties of the 90-10 mixture. Estimates of the effects of isomeric impurity of isobutane are given in graphical form.

Gallagher, J.S.; Linsky, D.; Morrison, G.; Levelt Sengers, J.M.H.

1987-04-01

165

Study of thermodynamic properties of liquid binary alloys by a pseudopotential method

NASA Astrophysics Data System (ADS)

On the basis of the Percus-Yevick hard-sphere model as a reference system and the Gibbs-Bogoliubov inequality, a thermodynamic perturbation method is applied with the use of the well-known model potential. By applying a variational method, the hard-core diameters are found which correspond to a minimum free energy. With this procedure, the thermodynamic properties such as the internal energy, entropy, Helmholtz free energy, entropy of mixing, and heat of mixing are computed for liquid NaK binary systems. The influence of the local-field correction functions of Hartree, Taylor, Ichimaru-Utsumi, Farid-Heine-Engel-Robertson, and Sarkar-Sen-Haldar-Roy is also investigated. The computed excess entropy is in agreement with available experimental data in the case of liquid alloys, whereas the agreement for the heat of mixing is poor. This may be due to the sensitivity of the latter to the potential parameters and dielectric function.

Vora, Aditya M.

2010-11-01

166

NASA Astrophysics Data System (ADS)

We have systematically studied the thermodynamic properties of a two-dimensional half-filled SU (2 N ) Hubbard model on a square lattice by using the determinant quantum Monte Carlo method. The entropy-temperature relation, the isoentropy curve, and the probability distribution of the on-site occupation number are calculated in both SU(4) and SU(6) cases, which exhibit prominent features of the Pomeranchuk effect. We analyze these thermodynamic behaviors based on energy scales in the density and spin channels. In the density channel, the interaction strength that marks the crossover from the weak to strong interaction regimes increases with the number of fermion components. In the spin channel, increasing the number of fermion components enhances quantum spin fluctuations, which is shown in the simulations of uniform spin susceptibilities and antiferromagnetic structure factors.

Zhou, Zhichao; Cai, Zi; Wu, Congjun; Wang, Yu

2014-12-01

167

Thermodynamic properties of antiperovskite MgCNi3 in superconducting phase

NASA Astrophysics Data System (ADS)

The aim of the present work is to explore the physical properties of the transition-metal based antiperovskite MgCNi3 in superconducting state. In particular, the critical value of the Coulomb pseudopotential and temperature dependence of the energy gap, specific heat, thermodynamic critical field and London penetration depth are theoretically analyzed within the framework of the Eliashberg formalism. Moreover, we determined the dimensionless ratios which are related to the above thermodynamic functions: 2 ? (0) /kBTC = 4.19, ?C (TC) /CN (TC) = 2.27 and TCCN (TC) /HC2 (0) = 0.141. Our calculations show that obtained results significantly diverge from the values predicted by the BCS model due to the strong-coupling corrections and retardation effect existing in investigated antiperovskite.

Szcz??niak, R.; Durajski, A. P.; Herok, ?.

2015-02-01

168

In this study, we use solubility and drop-solution calorimetry measurements to determine the thermodynamic properties of the uranyl phosphate phases autunite, uranyl hydrogen phosphate, and uranyl orthophosphate. Conducting the solubility measurements from both supersaturated and undersaturated conditions and under different pH conditions rigorously demonstrates attainment of equilibrium and yields well-constrained solubility product values. We use the solubility data and the calorimetry data, respectively, to calculate standard-state Gibbs free energies of formation and standard-state enthalpies of formation for these uranyl phosphate phases. Combining these results allows us also to calculate the standard-state entropy of formation for each mineral phase. The results from this study are part of a combined effort to develop reliable and internally consistent thermodynamic data for environmentally relevant uranyl minerals. Data such as these are required to optimize and quantitatively assess the effect of phosphate amendment remediation technologies for uranium contaminated systems. PMID:19848155

Gorman-Lewis, Drew; Shvareva, Tatiana; Kubatko, Karrie-Ann; Burns, Peter C; Wellman, Dawn M; Mcnamara, Bruce; Szymanowski, Jennifer E S; Navrotsky, Alexandra; Fein, Jeremy B

2009-10-01

169

In 1995, the International Association for the Properties of Water and Steam (IAPWS) adopted a new formulation called “The IAPWS Formulation 1995 for the Thermodynamic Properties of Ordinary Water Substance for General and Scientific Use”, which we abbreviate to IAPWS-95 formulation or IAPWS-95 for short. This IAPWS-95 formulation replaces the previous formulation adopted in 1984. This work provides information on

W. Wagner; A. Pruß

1999-01-01

170

Thermodynamic Properties of Rock-Forming Garnets: How Well Known are They?

NASA Astrophysics Data System (ADS)

Garnet is an important rock-forming mineral whose geological occurrence is widespread. The silicate garnets (E3G2Si3O12) show extensive compositional variability and the various end-members are stable over an enormous range of rock compositions and pressure and temperature conditions. Extensive geothermometry and geobarometry studies involving garnet have been made. Thus, much research has been done to determine garnet's thermodynamic properties. There are now several internally consistent mineralogical thermodynamic databases and their use is widespread. It is common belief in some/many circles that the present databases represent "the final word" on thermodynamic properties at least in terms of most end-member silicates. The question arises - How true is this assumption in the case of garnet? We have been and are presently engaged in investigating the thermodynamic properties of garnet, where volumetric properties and heat-capacity behavior play a central role. The volumes of the various end-member garnets are now known precisely. Only secondary effects arising from extra minor components (e.g., OH-,Fe3+,Mn3+) have yet to be worked out exactly. In terms of heat capacity Cp behavior, new calorimetric data allow improved understanding. Low T calorimetric measurements on spessartine were made recently and show that previous estimates for S° were in error (Dachs et al. 2009). New unpublished calorimetric results on grossular appear to have resolved long-standing uncertainty regarding its precise S° value. S° for silica-free hydrogrossular has also been determined for the first time. Cp measurements are now focusing on almandine and here low T electronic and magnetic properties must be considered. One can conclude that Cp, S°, ?H°f, V and ?G°f for the common silicate garnet end-members are now well determined to about 1000 K. Cp behavior above roughly 1000 K is less certain for some garnets (e.g., almandine, spessartine). What about thermodynamic behavior of garnet solid solutions? Here, there is much less is known (Geiger 1999). The precise mixing behavior of most garnet binaries, for example, is not understood. An exception is the pyrope-grossular binary, which has now been investigated numerous times and some consensus on its mixing properties now exist. In a related area, crystal-chemical investigations are providing good insight on possible macroscopic thermodynamic mixing behavior. Here, for example, low temperature synchrotron measurements on line broadening of powder diffraction lines give the first quantitative lattice-strain determinations on a solid solution (Dapiaggi et al. 20005). The asymmetric nature of the mixing functions ?Hex, ?Sex, and ?Vex can be explained via strain and local Ca/Mg-O bond behavior. Another area needing further investigation is short-range order. 29Si NMR spectroscopic study of synthetic Py-Gr garnets indicates that some short-range Ca-Mg order may be present. Bosenick et al. (1999) estimate that configurational entropy effects of about 2 J/mole.K may result at T > 1000 °C. It remains to be determined, however, what the structural state is at lower temperatures of 600 to 900 °C. The degree of short-range order could be substantial in metamorphic garnet solid solutions.

Geiger, C. A.; Dachs, E.

2011-12-01

171

Catalytic hydrodenitrogenation (HDN) is a key step in upgrading processes for conversion of heavy petroleum, shale oil, tar sands, and the products of the liquefaction of coal to economically viable products. This research program provides accurate experimental thermochemical and thermophysical properties for key organic nitrogen-containing compounds present in the range of alternative feedstocks, and applies the experimental information to thermodynamic analyses of key HDN reaction networks. This report is the first in a series that will lead to an analysis of a three-ring HDN system; the carbazole/hydrogen reaction network. 2-Aminobiphenyl is the initial intermediate in the HDN pathway for carbazole, which consumes the least hydrogen possible. Measurements leading to the calculation of the ideal-gas thermodynamic properties for 2-aminobiphenyl are reported. Experimental methods included combustion calorimetry, adiabatic heat-capacity calorimetry, comparative ebulliometry, inclined-piston gauge manometry, and differential-scanning calorimetry (d.s.c). Entropies, enthalpies, and Gibbs energies of formation were derived for the ideal gas for selected temperatures between 298.15 K and 820 K. The critical temperature and critical density were determined for 2-aminobiphenyl with the d.s.c., and the critical pressure was derived. The Gibbs energies of formation are used in thermodynamic calculations to compare the feasibility of the initial hydrogenolysis step in the carbazole/H{sub 2} network with that of its hydrocarbon and oxygen-containing analogous; i.e., fluorene/H{sub 2} and dibenzofuran/H{sub 2}. Results of the thermodynamic calculations are compared with those of batch-reaction studies reported in the literature. 57 refs., 8 figs., 18 tabs.

Steele, W.V.; Chirico, R.D.; Knipmeyer, S.E.; Nguyen, A.

1990-12-01

172

Emergence of equilibrium thermodynamic properties in quantum pure states. I. Theory

Investigation on foundational aspects of quantum statistical mechanics recently entered a renaissance period due to novel intuitions from quantum information theory and to increasing attention on the dynamical aspects of single quantum systems. In the present contribution a simple but effective theoretical framework is introduced to clarify the connections between a purely mechanical description and the thermodynamic characterization of the equilibrium state of an isolated quantum system. A salient feature of our approach is the very transparent distinction between the statistical aspects and the dynamical aspects in the description of isolated quantum systems. Like in the classical statistical mechanics, the equilibrium distribution of any property is identified on the basis of the time evolution of the considered system. As a consequence equilibrium properties of quantum system appear to depend on the details of the initial state due to the abundance of constants of the motion in the Schroedinger dynamics. On the other hand the study of the probability distributions of some functions, such as the entropy or the equilibrium state of a subsystem, in statistical ensembles of pure states reveals the crucial role of typicality as the bridge between macroscopic thermodynamics and microscopic quantum dynamics. We shall consider two particular ensembles: the random pure state ensemble and the fixed expectation energy ensemble. The relation between the introduced ensembles, the properties of a given isolated system, and the standard quantum statistical description are discussed throughout the presentation. Finally we point out the conditions which should be satisfied by an ensemble in order to get meaningful thermodynamical characterization of an isolated quantum system.

Fresch, Barbara; Moro, Giorgio J. [Department of Chemical Science, University of Padova, Via Marzolo 1, Padova 35131 (Italy)

2010-07-21

173

Background Gram-negative bacteria use periplasmic-binding proteins (bPBP) to transport nutrients through the periplasm. Despite immense diversity within the recognized substrates, all members of the family share a common fold that includes two domains that are separated by a conserved hinge. The hinge allows the protein to cycle between open (apo) and closed (ligated) conformations. Conformational changes within the proteins depend on a complex interplay of mechanical and thermodynamic response, which is manifested as an increase in thermal stability and decrease of flexibility upon ligand binding. Results We use a distance constraint model (DCM) to quantify the give and take between thermodynamic stability and mechanical flexibility across the bPBP family. Quantitative stability/flexibility relationships (QSFR) are readily evaluated because the DCM links mechanical and thermodynamic properties. We have previously demonstrated that QSFR is moderately conserved across a mesophilic/thermophilic RNase H pair, whereas the observed variance indicated that different enthalpy-entropy mechanisms allow similar mechanical response at their respective melting temperatures. Our predictions of heat capacity and free energy show marked diversity across the bPBP family. While backbone flexibility metrics are mostly conserved, cooperativity correlation (long-range couplings) also demonstrate considerable amount of variation. Upon ligand removal, heat capacity, melting point, and mechanical rigidity are, as expected, lowered. Nevertheless, significant differences are found in molecular cooperativity correlations that can be explained by the detailed nature of the hydrogen bond network. Conclusion Non-trivial mechanical and thermodynamic variation across the family is explained by differences within the underlying H-bond networks. The mechanism is simple; variation within the H-bond networks result in altered mechanical linkage properties that directly affect intrinsic flexibility. Moreover, varying numbers of H-bonds and their strengths control the likelihood for energetic fluctuations as H-bonds break and reform, thus directly affecting thermodynamic properties. Consequently, these results demonstrate how unexpected large differences, especially within cooperativity correlation, emerge from subtle differences within the underlying H-bond network. This inference is consistent with well-known results that show allosteric response within a family generally varies significantly. Identifying the hydrogen bond network as a critical determining factor for these large variances may lead to new methods that can predict such effects. PMID:18700034

Livesay, Dennis R; Huynh, Dang H; Dallakyan, Sargis; Jacobs, Donald J

2008-01-01

174

Thermodynamic properties and oxygen stoichiometry of Ba2Cu3O5 + ?

NASA Astrophysics Data System (ADS)

The thermodynamic properties and oxygen stoichiometry of Ba2Cu3O5 + ? are studied by means of the electromotive force (EMF) with a fluoride electrolyte, dissolution calorimetry, and thermogravimetry. It is shown that the temperature dependence of the Gibbs energy of the formation of barium cuprate from simple oxides and oxygen in the temperature range of 860-1120 K can be described by the polynomial ?f, ox G ?(Ba2Cu3O5 + ?) ± 0.1 (kJ/mol) = -291.78 + 1.127 T - 0.13207 Tln T (kJ/mol).

Kovba, M. L.; Tiflova, L. A.; Istomin, S. Ya.; Skolis, Yu. Ya.; Monaenkova, A. S.

2014-03-01

175

Viscosity and thermodynamic properties of QGP in relativistic heavy ion collisions

We study the viscosity and thermodynamic properties of QGP at RHIC by employing the recently extracted equilibrium distribution functions from two hot QCD equations of state of $O(g^5)$ and $O(g^6\\ln(1/g))$ respectively. After obtaining the temperature dependence of energy density, and entropy density, we focus our attention on the determination of shear viscosity for a rapidly expanding interacting plasma, as a function of temperature. We find that interactions significantly decrease the shear viscosity. They decrease the viscosity to entropy density ratio, $\\eta/{\\mathcal S}$ as well.

Vinod Chandra; V. Ravishankar

2008-05-30

176

The magnetic and thermodynamic properties of a spin-2 Heisenberg ferromagnetic system

NASA Astrophysics Data System (ADS)

The magnetic and thermodynamic properties such as the magnetization, internal energy, specific heat and susceptibility of spin-2 Heisenberg ferromagnetic system on a square lattice are studied by using Green's function technique. Without including the next nearest neighbor interaction, one doesn't observe the second-order phase transitions. We found that only when the next nearest neighbor interaction is greater than the nearest neighbor interaction, the second-order phase transitions exist for the small single-ion anisotropy values. Indeed, in the case of negative anisotropy which corresponds to first-order phase transitions, the energies have discontinuities. At the same time, the specific heat shows two peaks.

Mert, Gülistan

2015-01-01

177

Thermodynamic properties of NiS melts between 700° and 1100°c

The vapor pressure of sulfur over Ni-S melts of various compositions was calculated from the equilibrium weight of the melt\\u000a in gas streams of known H2S-H2 composition. The Gibbs-Duhem equation was used to calculate the activity of nickel and other thermodynamic properties. For\\u000a the reaction: 3Ni(S) + S2(g) ? Ni3S2(l) the suggested free energy rslationship is: ?G = -57,910 +

M. Nagamori; T. R. Ingraham

1970-01-01

178

Calculating the thermodynamic properties of aqueous solutions of alkali metal carboxylates

NASA Astrophysics Data System (ADS)

A modified Robinson-Stokes equation with terms that consider the formation of ionic hydrates and associates is used to describe thermodynamic properties of aqueous solutions of electrolytes. The model is used to describe data on the osmotic coefficients of aqueous solutions of alkali metal carboxylates, and to calculate the mean ionic activity coefficients of salts and excess Gibbs energies. The key contributions from ionic hydration and association to the nonideality of solutions is determined by analyzing the contributions of various factors. Relations that connect the hydration numbers of electrolytes with the parameters of the Pitzer-Mayorga equation and a modified Hückel equation are developed.

Rudakov, A. M.; Sergievskii, V. V.; Zhukova, T. V.

2014-06-01

179

We study the finite-temperature properties of two-component fermionic atoms trapped in a two-dimensional (2D) optical lattice. We apply the self-energy functional approach to the 2D Hubbard model with a harmonic-trapping potential, and systematically investigate the thermodynamic properties of this system. We find that entropy and grand potential provide evidence of a crossover between the Mott-insulating and the metallic phases at certain temperatures. In addition, we find that entropy exhibits a cusplike anomaly at lower temperatures, suggesting a second- or higher-order antiferromagnetic transition. We estimate the antiferromagnetic transition temperatures, and clarify how the trapping potential affects this magnetic transition.

Inaba, Kensuke; Yamashita, Makoto [NTT Basic Research Laboratories, NTT Corporation, Atsugi 243-0198, Japan and Japan Science and Technology Agency, CREST, Chiyoda-ku, Tokyo 102-0075 (Japan)

2010-06-15

180

Thermodynamic properties of some S = 1 soliton-bearing and Haldane-like systems

NASA Astrophysics Data System (ADS)

The numerical finite-size technique has been applied to study thermodynamic properties of the S = 1 quasi-one-dimensional magnets CsNiF 3, (CH 3) 4NNiBr 3 (TMNB), (CH 3) 4NNiCl 3 (TMNC) and CsNiCl 3, the latter showing the Haldane gap. The length of chains has been extended up to N ? 8 and the successful fitting procedure has been performed to match the parameters of the easy-plane Heisenberg model with single-ion anisotropy. The quantitative agreement with experiment has been found both for the zero-field and the field-dependent properties. An attempt to apply the renormalization-group approach is also put forward for CsNiCl 3.

Kamieniarz, G.; Gerling, R. W.; Campana, L. S.; Caramico D'Auria, A.; Esposito, F.; Esposito, U.

1992-02-01

181

Pairing and thermodynamics properties of finite-systems with fixed number of particles

NASA Astrophysics Data System (ADS)

A canonical description of the thermodynamical pairing properties of small systems is achieved by using the Variation After Projection approach at finite temperature. The minimization of the free energy is made by a direct evaluation of the energy and full diagonalization of the entropy. We use the Richardson - pairing model whose exact solution allows to study the reliability of different approaches. We show that the Projection After Variation approach, that is usually performed at zero temperature with rather good success, provides a quite poor description at finite temperature. On the contrary, the Variation After Projection applied at finite temperature provides a perfect reproduction of the exact canonical properties of odd or even systems from very low to high temperature.

Gambacurta, D.; Lacroix, D.

2012-12-01

182

Thermodynamics and Structural Properties of the High Density Gaussian Core Model

We numerically study thermodynamic and structural properties of the one-component Gaussian core model (GCM) at very high densities. The solid-fluid phase boundary is carefully determined. We find that the density dependence of both the freezing and melting temperatures obey the asymptotic relation, $\\log T_f$, $\\log T_m \\propto -\\rho^{2/3}$, where $\\rho$ is the number density, which is consistent with Stillinger's conjecture. Thermodynamic quantities such as the energy and pressure and the structural functions such as the static structure factor are also investigated in the fluid phase for a wide range of temperature above the phase boundary. We compare the numerical results with the prediction of the liquid theory with the random phase approximation (RPA). At high temperatures, the results are in almost perfect agreement with RPA for a wide range of density, as it has been already shown in the previous studies. In the low temperature regime close to the phase boundary line, although RPA fails to describe the structure factors and the radial distribution functions at the length scales of the interparticle distance, it successfully predicts their behaviors at shorter length scales. RPA also predicts thermodynamic quantities such as the energy, pressure, and the temperature at which the thermal expansion coefficient becomes negative, almost perfectly. Striking ability of RPA to predict thermodynamic quantities even at high densities and low temperatures is understood in terms of the decoupling of the length scales which dictate thermodynamic quantities from the interparticle distance which dominates the peak structures of the static structure factor due to the softness of the Gaussian core potential.

Atsushi Ikeda; Kunimasa Miyazaki

2011-04-18

183

A new application for two-dimensional (2D) materials is emulsification, where they can serve as ultrathin platelike interfacial stabilizers in two-liquid systems. We present a first detailed thermodynamic analysis of atomically thin 2D materials at organic-aqueous liquid-liquid interfaces and derive expressions for the transfer free energies of emulsion stabilization that account for material geometry, van der Waals transparency or opacity, and variable hydrophobicity. High mass potency is shown to be an intrinsic property of the 2D geometry, which at the atomically thin limit places every atom in contact with both liquid phases, resulting in unit atom efficiency. The thermodynamic model successfully predicts that graphene oxide but not pristine graphene has a favorable hydrophobic-hydrophilic balance for oil-water emulsion stabilization. Multilayer tiling is predicted to occur by the passivation of droplet surface patches left uncovered by packing inefficiencies in the first monolayer, and complete multilayer coverage is confirmed by cryogenic scanning electron microscopy. The molecular barrier function of graphene interfacial films causes a significant suppression of dispersed-phase evaporation rates with potential applications in controlled release. Finally, these emulsions can be used as templates for creating solid graphene foams or graphene microsacks filled with lipophilic cargos. Emerging 2D materials are promising as dispersants or emulsifiers where high mass potency and multifunctional properties are desired. PMID:24625132

Creighton, Megan A; Ohata, Yuzo; Miyawaki, Jin; Bose, Arijit; Hurt, Robert H

2014-04-01

184

Heat shock protein A6, also known as HSP70B', is a member of the Hsp70 family of molecular chaperones. Under stressed conditions, the level of HSPA6 increases substantially, and the protein has been targeted as a biomarker of cellular stress in several studies. We report the spectroscopic and thermodynamic properties of Arabian camel species cHSPA6, determined by measurement of intrinsic and extrinsic fluorescence emission, and use of far-UV circular dichroism and dynamic multimode spectroscopy. Our results showed that cHSPA6 has similar binding affinity for both ATP and ADP (K D = ~50 nM). Binding of ATP and ADP reduced the surface hydrophobicity of the protein, and slightly altered its secondary structure, suggesting localized conformational rearrangement after ATP or ADP binding. Dynamic multimode spectroscopy revealed that cHSPA6 unfolds through three transitions with melting points (T m) of 42.3 ± 0.2, 61.3 ± 0.1, and 81.2 ± 0.2 °C. To the best of the author's knowledge, and literature search, this is the first report of the spectroscopic and thermodynamic properties of the Arabian camel heat shock protein. PMID:25395330

Malik, Ajamaluddin; Haroon, Abuzar; Jagirdar, Haseeb; Alsenaidy, Abdulrahman M; Elrobh, Mohamed; Khan, Wajahatullah; Alanazi, Mohammed S; Bazzi, Mohammad D

2015-02-01

185

The thermodynamic properties to 700 K of naphthalene and 2,7-dimethylnaphthalene

Measurements leading to the calculation of the ideal-gas thermodynamic properties are reported for naphthalene and 2,7-dimethylnaphthalene. Experimental methods included adiabatic heat-capacity calorimetry, vibrating-tube densitometry, comparative ebulliometry, and differential-scanning calorimetry (d.s.c.). The critical temperature and critical density were determined experimentally for each compound and the critical pressures were derived from fitting procedures. Vapor-pressure measurements reported in the literature were compared with the results obtained in this research. Enthalpies of vaporization and sublimation were derived from the experimental measurements and compared with literature results. New self-consistent equations for the variation of sublimation pressure with temperature for naphthalene and 2,7-dimethylnaphthalene were derived. Literature values for entropies and enthalpies of the liquid phases and energies of combustion were combined with the present results to derive entropies, enthalpies, and Gibbs energies of formation for the ideal gases for selected temperatures between 298.15 K and 700 K. The ideal-gas properties for naphthalene were compared with values obtained using statistical mechanics with various fundamental vibrational frequency assignments available in the literature. A scheme to estimate the ideal-gas thermodynamic functions for alkylnaphthalenes was updated. The barrier to methyl-group rotation in 2,7-dimethylnaphthalene was shown to be of the same order of magnitude as that published for toluene. Values for ideal-gas entropies for 2-methylnaphthalene in the temperature range 300 K to 700 K were estimated.

Chirico, R.D.; Knipmeyer, S.E.; Nguyen, A.; Steele, W.V.

1993-08-01

186

Magneto-elastic effects and thermodynamic properties of ferromagnetic hcp Co

NASA Astrophysics Data System (ADS)

Using first principles projector augmented wave (PAW) potential method, the magneto-elastic effects and thermodynamic properties of ferromagnetic hcp Cobalt at high pressure and temperature are investigated. The calculated elastic constants from PBE+U method demonstrate a noticeable improvement with regard to experimental data. Various physical quantities under high pressure also present significant improvements, such as the bulk modulus, shear modulus, Young's modulus, Debye temperature, various sound velocities and the normalized acoustic velocities in the meridian plane. That is due to the fact that Cobalt system possesses large correlation effects. Meanwhile, the phonon dispersion curves are in excellent agreement with experimental data. It is not observed any anomaly or instability under compression. However, according to the E2g-phonon frequencies, the obtained pressure variation of C44 elastic modulus also suggests that the system has miraculous magneto-elastic effects. Moreover, the pressure and temperature dependence of thermodynamic properties are derived within the quasi-harmonic approximation for the first time. The obtained Grüneisen ratio, Anderon-Grüneisen parameter and the volume dependence of Grüneisen ratio display manifestly temperature and pressure dependences.

Kuang, Fang-Guang; Kuang, Xiao-Yu; Kang, Shu-Ying; Mao, Ai-Jie

2014-05-01

187

Atomistic modeling of thermodynamic properties of Pu-Ga alloys based on the Invar mechanism

NASA Astrophysics Data System (ADS)

We present an atomistic model that accounts for a range of anomalous thermodynamic properties of the fcc ? phase of Pu-Ga alloys in terms of the Invar mechanism. Two modified embedded atom method potentials are employed to represent competing electronic states in ?-Pu, each of which has an individual configuration dependence as well as distinct interactions with gallium. Using classical Monte Carlo simulations, we compute the temperature dependence of various thermodynamic properties for different dilute gallium concentrations. The model reproduces the observed effects of excessive volume reduction along with a rapid shift in thermal expansion from negative to positive values with increasing gallium concentration. It also predicts progressive stiffening upon dilute-gallium alloying, while the calculated thermal softening is nearly independent of the gallium concentration in agreement with resonant ultrasound spectroscopy measurements in the literature. Analysis of the local structure predicted by the model indicates that the distribution of the gallium atoms is not completely random in the ? phase due to the presence of short-range order associated with the Invar mechanism. This effect is consistent with the nanoscale heterogeneity in local gallium concentration which is observed in recent extended x-ray absorption fine structure spectroscopy experiments. Implications of the Invar effect for phase stability and physical interpretations of the two states are also discussed.

Lee, Tongsik; Taylor, Christopher D.; Lawson, A. C.; Conradson, Steven D.; Chen, Shao Ping; Caro, A.; Valone, Steven M.; Baskes, Michael I.

2014-05-01

188

NASA Astrophysics Data System (ADS)

First-principles and classical molecular dynamics simulations have been performed to study the structural and thermodynamic properties of Pd under pressure. By comparing the Gibbs free energy, in the quasiharmonic approximation (QHA), of the face-centered cubic (fcc) phase with those of the hexagonal-close-packed (hcp) and body-centered-cubic (bcc) phases we found that the fcc phase is stable up to 500 GPa and 5000 K. The predicted high-temperature elastic constants of fcc Pd agree well with experiments. The phonon dispersion curves are obtained at various pressures. In contrast with experiments we did not observe any phonon anomalies in Pd. We reproduced the thermodynamic properties of Pd accurately by taking into account the electron and phonon contributions to the free energy of Pd. The obtained thermal expansion coefficient, Hugoniot curves, and specific heat capacity compare well with experiments. In particular, the excellent agreement of the thermal expansion coefficients with experiment supports the validity of the QHA for Pd at high temperatures. Our QHA-based Hugoniot curves also show good agreement with experiments and our dynamic shock simulations. Shocks along [100] produced a melting temperature with a superheating of 18.3% at 226 GPa, compared with our high-pressure melting curve of Pd from coexistence-phase simulations based on an embedded atom model.

Liu, Zhong-Li; Yang, Jie-Hui; Cai, Ling-Cang; Jing, Fu-Qian; Alfè, Dario

2011-04-01

189

Evaluation of the thermodynamic properties of hydrated metal oxide nanoparticles by INS techniques

In this contribution we will present a detailed methodology for the elucidation of the following aspects of the thermodynamic properties of hydrated metal oxide nanoparticles from high-resolution, low-temperature inelastic neutron scattering (INS) data: (i) the isochoric heat capacity and entropy of the hydration layers both chemi- and physisorbed to the particle surface; (ii) the magnetic contribution to the heat capacity of the nanoparticles. This will include the calculation of the vibrational density of states (VDOS) from the raw INS spectra, and the subsequent extraction of the thermodynamic data from the VDOS. This technique will be described in terms of a worked example namely, cobalt oxide (Co3O4 and CoO). To complement this evaluation of the physical properties of metal oxide nanoparticle systems, we will emphasise the importance of high-resolution, high-energy INS for the determination of the structure and dynamics of the water species, namely molecular (H2O) and dissociated water (OH, hydroxyl), confined to the oxide surfaces. For this component of the chapter we will focus on INS investigations of hydrated isostructural rutile (a-TiO2) and cassiterite (SnO2) nanoparticles. We will complete this discussion of nanoparticle analysis by including an appraisal of the INS instrumentation employed in such studies with particular focus on TOSCA [ISIS, Rutherford Appleton Laboratory (RAL), U.K.] and the newly developed spectrometer SEQUOIA [SNS, Oak Ridge National Laboratory (ORNL), U.S.A].

Spencer, Elinor [Virginia Polytechnic Institute and State University] [Virginia Polytechnic Institute and State University; Ross, Dr. Nancy [Virginia Polytechnic Institute and State University] [Virginia Polytechnic Institute and State University; Parker, Stewart F. [ISIS Facility, Rutherford Appleton Laboratory (ISIS)] [ISIS Facility, Rutherford Appleton Laboratory (ISIS); Kolesnikov, Alexander I [ORNL] [ORNL

2013-01-01

190

NASA Astrophysics Data System (ADS)

Understanding protein folding confined by surfaces is important for both biological sciences and the development of nanomaterials. In this work, we study the properties of a confined HP model protein by three different types of surfaces, namely, surfaces that attract: (a) all monomers; (b) only P monomers; and (c) only H monomers. The thermodynamic and structural quantities, such as the specific heat, number of surface contacts, and number of hydrophobic pairs, are obtained by using Wang-Landau sampling. The conformational "transitions", specifically, the debridging process and hydrophobic core formation, can be identified based on an analysis of these quantities. We found that these transitions take place at different temperatures, and the ground state configurations show variations in structural properties when different surface type is used. These scenarios are confirmed by snapshots of typical states of the systems. From our study, we conclude that the thermodynamics of these transitions and the structural changes depend on the combined actions of both the composition of the H monomers and the P monomers in the HP chain and the surface types.

Pattanasiri, Busara; Li, Ying Wai; Landau, David P.; Wüst, Thomas; Triampo, Wannapong

2013-08-01

191

NASA Astrophysics Data System (ADS)

We calculate for the first time the equation of state and other thermodynamic properties of the planar square-well dumbbell (SWD) fluid. The SWD molecule consists of two fused hard discs of diameter ?, separated by a reduced separation L*=L/? with attractive annuli of outer radii, K? around each hard disc. Monte Carlo simulations were carried out over a range of densities and temperatures for two choices of potential width and several molecular elongations. In particular, we concentrated on states with the molecular elongation parameter, L*=0.3 and the potential-width parameter, K=1.5. In this article we concentrate on analytic representations of the thermodynamic behavior of the SWD fluid. The second virial coefficients of the SWD system are calculated by a part analytic/part numerical procedure. The free energy expansion coefficients are calculated up to third order. Convergence of the perturbation expansion based on the hard-dumbbell fluid is examined and shown to be very satisfactory. A generalization of the quasichemical (QCA) coordination number model for the SWD fluid is proposed. The equation of state and energy derived from this model, compared with the simulation results, show that the QCA model represents well the simulated properties of the SWD at low density but fails at high density.

Bra?ka, A. C.; Heyes, D. M.

1993-12-01

192

NASA Astrophysics Data System (ADS)

In this dissertation it is shown how quantum and statistical mechanical computational techniques can be combined in order to make possible the calculation of thermodynamic properties for solid-state binary substitutional alloy phases from first principles, i.e., from a knowledge of only basic crystallographic information and the atomic numbers of the alloy constituents. The framework which is discussed here for performing such calculations is based on the formalism of cluster expansions. Using this formalism the statistical mechanical problem of computing substitutional alloy thermodynamic properties can be reduced to that of solving a generalized Ising model. It is shown how the parameters describing atomic interactions in such an Ising model can be derived with the structure inversion method from the results of quantum mechanical calculations of zero-temperature total energies for a number of ordered stoichiometric alloy compounds sharing a common underlying parent structure. Once the parameters in the generalized Ising model have been derived, alloy thermodynamic properties can be calculated by a variety of statistical mechanical techniques. In the work presented here the quantum and statistical mechanical calculations have been performed using the linear muffin-tin orbital and cluster variation methods, respectively. These computational methods are both described in some detail. The formalism and computational techniques mentioned in the previous paragraph are applied to the study of alloy phase stability in the Ti-Al and Cd-Mg systems. For Cd -Mg an effort is made to determine the relative magnitudes of the contributions to the alloy free energy arising from configurational disorder, structural relaxations, as well as vibrational and electronic excitations. It is shown that when all of these different contributions to the free energy are included, the calculated solid-state portion of the composition-temperature phase diagram for the Cd -Mg system is in excellent agreement with experimental measurements. For the Ti-Al system, the thermodynamic stability of phases with fcc- and hcp-based crystal structures is studied. It is shown that the complexity of the Ti-Al phase diagram can be understood as being the result of a very close competition between stable and metastable ordered phases in this system.

Asta, Mark David

193

NASA Astrophysics Data System (ADS)

The temperature dependences of the heat capacities of carbosilane dendrimers of the third and sixth generations with ethyleneoxide terminal groups are examined for the first time by means of precision adiabatic vacuum calorimetry at temperatures between 6.5 and 350 K. In this temperature range, physical transformations are observed and their standard thermodynamic characteristics are determined and discussed. The standard thermodynamic functions are calculated per nominal mole of a chosen unit using the obtained experimental data: C° p ( T), H°( T) - H°(0), S°( T) - S°(0), and G°( T) - H°(0) in the interval T ? 0 to 350 K, and the standard entropies of formation at T = 298.15 K. The low-temperature ( T ? 50 K) heat capacity is analyzed using the Debye theory of specific heat and a multifractal model. The values of fractal dimension D are also determined, and conclusions on the investigated structures' topology are drawn. The corresponding thermodynamic properties of the studied dendrimers are compared as well.

Smirnova, N. N.; Markin, A. V.; Letyanina, I. A.; Sologubov, S. S.; Novozhilova, N. A.; Tatarinova, E. A.; Muzafarov, A. M.

2014-05-01

194

NASA Astrophysics Data System (ADS)

The following dissertation is an account of my research in the Mandelshtam group at UC Irvine beginning in the Fall of 2006 and ending in the Summer of 2011. My general area of study falls within the realm of equilibrium quantum statistical mechanics, a discipline which attempts to relate molecular-scale properties to time averaged, macroscopic observables. The major tools used herein are the Variational Gaussian Wavepacket (VGW) approximation for quantum calculations, and Monte-Carlo methods, particularly parallel tempering, for global optimization and the prediction of equilibrium thermodynamic properties. Much of my work used these two methods to model both small and bulk systems at equilibrium where quantum effects are significant. All the systems considered are characterized by inter-molecular van der Waals forces, which are weak but significant electrostatic attractions between atoms and molecules and posses a 1/r6 dependence. The research herein begins at the microscopic level, starting with Lennard-Jones (LJ) clusters, then later shifts to the macroscopic for a study involving bulk para-hydrogen. For the LJ clusters the structural transitions induced by a changing deBoer parameter, ?, a measure of quantum delocalization of the constituent particles, are investigated over a range of cluster sizes, N. From the data a "phase" diagram as a function of ? and N is constructed, which depicts the structural motifs favored at different size and quantum parameter. Comparisons of the "quantum induced" structural transitions depicted in the latter are also made with temperature induced transitions and those caused by varying the range of the Morse potential. Following this, the structural properties of binary para-Hydrogen/ ortho-Deuterium clusters are investigated using the VGW approximation and Monte-Carlo methods within the GMIN framework. The latter uses the "Basin-Hopping" algorithm, which simplifies the potential energy landscape, and coupled with the VGW approximation, an efficient and viable method for predicting equilibrium quantum mechanical properties is demonstrated. In the next chapter my contribution to the numerical implementation of the Thermal Gaussian Molecular Dynamics (TGMD) method is discussed. Within TGMD, a mapping of a quantum system to a classical is performed by means of an effective Hamiltonian, H eff, which is computed within the VGW framework. Using the classical dynamical equations of motion with Heff, the properties of a quantum system can be modeled within a classical framework. After this, the bulk system of fluid para-Hydrogen is investigated using the VGW in the NPT ensemble in an attempt to derive the thermodynamic properties at the phase transition and construct the equation of state. The dissertation then concludes with a discussion on the adaptation of the VGW methodology to any molecular system.

Deckman, Jason

195

Thermodynamic properties and entropy scaling law for diffusivity in soft spheres.

The purely repulsive soft-sphere system, where the interaction potential is inversely proportional to the pair separation raised to the power n, is considered. The Laplace transform technique is used to derive its thermodynamic properties in terms of the potential energy and its density derivative obtained from molecular dynamics simulations. The derived expressions provide an analytic framework with which to explore soft-sphere thermodynamics across the whole softness-density fluid domain. The trends in the isochoric and isobaric heat capacity, thermal expansion coefficient, isothermal and adiabatic bulk moduli, Grüneisen parameter, isothermal pressure, and the Joule-Thomson coefficient as a function of fluid density and potential softness are described using these formulas supplemented by the simulation-derived equation of state. At low densities a minimum in the isobaric heat capacity with density is found, which is a new feature for a purely repulsive pair interaction. The hard-sphere and n = 3 limits are obtained, and the low density limit specified analytically for any n is discussed. The softness dependence of calculated quantities indicates freezing criteria based on features of the radial distribution function or derived functions of it are not expected to be universal. A new and accurate formula linking the self-diffusion coefficient to the excess entropy for the entire fluid softness-density domain is proposed, which incorporates the kinetic theory solution for the low density limit and an entropy-dependent function in an exponential form. The thermodynamic properties (or their derivatives), structural quantities, and diffusion coefficient indicate that three regions specified by a convex, concave, and intermediate density dependence can be expected as a function of n, with a narrow transition region within the range 5 < n < 8. PMID:25122250

Pieprzyk, S; Heyes, D M; Bra?ka, A C

2014-07-01

196

Prediction of the thermodynamic properties of aqueous metal complexes to 1000°C and 5 kb

NASA Astrophysics Data System (ADS)

A large number of aqueous metal complexes contribute significantly to hydrothermal, metamorphic, and magmatic processes in the crust of the Earth. Nevertheless, relatively few thermodynamic data other than dissociation constants ( K) for a few dozen of these complexes have been determined experimentally at elevated temperatures and pressures. The calculations summarized below are intended to supplement these experimental data by providing interim predictions of the thermodynamic properties of supercritical aqueous metal complexes using the revised HKF (Helgeson et al., 1981) equations of state for aqueous species (Tanger and Helgeson, 1988; Shock et al., 1992) and correlations among equations of state parameters and standard partial molal properties at 25°C and 1 bar (Shock and Helgeson, 1988, 1990; Shock et al., 1989). These equations and correlations permit retrieval of the conventional standard partial molal entropies ( overlineS0), volumes ( overlineV0), and heat capacities ( overlineCP0) of aqueous metal complexes at 25°C and 1 bar from published values of log K in the supercritical region and the limited number of experimental dissociation constants available in the literature over relatively short ranges of elevated temperature at PSAT ( PSAT and SAT are used in the present communication to refer to pressures corresponding to liquid-vapor equilibrium for the system H 2O, except at temperatures <100°C, where they refer to the reference pressure of 1 bar). The standard partial molal properties computed in this way can then be used to generate corresponding values of ? overlineS0, ? overlineV0, and ? overlineCP0 of association, which for similar complexes correlate linearly with overlineS0, overlineV0 and overlineCP0, respectively, of the constituent cations and ligands at 25°C and 1 bar. Generalizing these correlations and combining them with the equations of state permits prediction of the temperature and pressure dependence of log K and other thermodynamic properties of a large number of aqueous metal complexes. As a consequence, it is possible to retrieve values of log K at 25°C and 1 bar from the results of hydrothermal experiments at higher temperatures and pressures or to predict values of log K at hydrothermal conditions when no experimental data are available at temperatures and pressures above 25°C and l bar. Such predictions can be made for temperatures and pressures from 0°C and 1 bar to 1000°C and 5000 bars.

Sverjensky, D. A.; Shock, E. L.; Helgeson, H. C.

1997-04-01

197

The thermodynamical properties of dark energy are usually investigated with the equation of state {omega}={omega}{sub 0}+{omega}{sub 1}z. Recent observations show that our Universe is accelerating, and the apparent horizon and the event horizon vary with redshift z. Because definitions of the temperature and entropy of a black hole are used to describe the two horizons of the Universe, we examine the thermodynamical properties of the Universe, which is enveloped by the apparent horizon and the event horizon, respectively. We show that the first and the second laws of thermodynamics inside the apparent horizon in any redshift are satisfied, while they are broken down inside the event horizon in some redshifts. Therefore, the apparent horizon for the Universe may be the boundary of thermodynamical equilibrium for the Universe like the event horizon for a black hole.

Zhang Yongping; Yi Zelong; Zhang Tongjie; Liu Wenbiao [Department of Physics, Institute of Theoretical Physics, Beijing Normal University, Beijing, 100875 (China); Department of Astronomy, Beijing Normal University, Beijing, 100875 (China); Department of Astronomy, Beijing Normal University, Beijing, 100875 (China); Kavli Institute for Theoretical Physics China, Institute of Theoretical Physics, Chinese Academy of Sciences (KITPC/ITP-CAS), P.O. Box 2735, Beijing, 100080 (China); Department of Physics, Institute of Theoretical Physics, Beijing Normal University, Beijing, 100875 (China)

2008-01-15

198

NASA Astrophysics Data System (ADS)

A midpoint method is introduced to calculate the chiral phase transition and thermodynamic properties in the Nambu-Jona-Lasinio (NJL) model with two flavors (u,d). The constituent quark mass, the pressure, the energy density, and the entropy are calculated in the mean-field approximation using the midpoint technique. The phase transition was found to be crossover for all values of bare quark mass. The effect of finite temperature and chemical potential on the thermodynamic properties is studied. A comparison with other models is presented. In addition, the advantages of the midpoint technique are discussed. In conclusion, the midpoint technique successfully predicts the phase transition and thermodynamic properties with a good accuracy for numerical integrals.

Abu-Shady, M.

2014-09-01

199

Quantum and Thermodynamic Properties of Spontaneous and Low-Energy Induced Fission of Nuclei

It is shown that A. Bohr's concept of transition fission states can be matched with the properties of Coriolis interaction if an axisymmetric fissile nucleus near the scission point remains cold despite a nonadiabatic character of nuclear collective deformation motion. The quantum and thermodynamic properties of various stages of binary and ternary fission after the descent of a fissile nucleus from the outer saddle point are studied within quantum-mechanical fission theory. It is shown that two-particle nucleon-nucleon correlations--in particular, superfluid correlations--play an important role in the formation of fission products and in the classification of fission transitions. The distributions of thermalized primary fission fragments with respect to spins and their projections onto the symmetry axis of the fissile nucleus and fission fragments are constructed, these distributions determining the properties of prompt neutrons and gamma rays emitted by these fragments. A new nonevaporation mechanism of third-particle production in ternary fission is proposed. This mechanism involves transitions of third particles from the cluster states of the fissile-nucleus neck to high-energy states under effects of the shake-off type that are due to the nonadiabatic character of nuclear collective deformation motion.

Kadmensky, S.G. [Voronezh State University, Universitetskaya pl. 1, Voronezh, 394693 (Russian Federation)

2005-12-01

200

Magnetic and thermodynamic properties of Americium-II: An Ab Initio Study

NASA Astrophysics Data System (ADS)

Hybrid density functional theory based method has been used to study the structural, magnetic, electronic, and thermodynamic properties of Americium-II. Non-magnetic, ferromagnetic (FM), and anti-ferromagnetic (AFM) configurations without and with spin-orbit coupling (SOC) have been considered. The experimental NM ground state configuration is indeed obtained for Am-II at a level of 40% HF exchange with SOC and the computed structural properties and electronic density of states are in good agreement with experimental observations. The importance of SOC is found to be significant. The phonon related properties of Am-II are presented for the NM ground state configuration and the computed heat capacity and entropy are in good agreement with the experimental measurements. The lattice constant, bulk modulus, heat capacity, and entropy of Am-II are predicted to be 9.44 a.u., 21.7 GPa, 24.3 JK-1mol-1, and 55.7 JK-1mol-1, respectively.

Wang, Jianguang; Ma, Li; Ray, Asok

2011-03-01

201

Mechanical, electronic, optical, thermodynamic properties and superconductivity of ScGa3

NASA Astrophysics Data System (ADS)

The rare occurrence of type-I superconductivity in binary system ScGa3 has experimentally been shown recently. In the present paper we study the electronic, optical, thermodynamic properties and some aspects of superconductivity of this compound using first-principles calculations. The mechanical properties like elastic constants, bulk modulus, shear modulus, Pugh's ductility index, Young's modulus, Poisson's ratio, elastic anisotropy factor, Peierls stress are calculated for the first time. The material is anisotropic and brittle. Electronic band structure, density of states, Fermi surfaces and bonding nature have also been studied. The optical functions are estimated and discussed for the first time. The high reflectivity is found in the ultraviolet regions up to ~13 eV and thus ScGa3 can serve as a possible shielding material for ultraviolet radiation. Thermal effects on some macroscopic properties of ScGa3 are predicted using the quasi-harmonic Debye model and phonon approximation in the temperature and hydrostatic pressure in the ranges of 0-1000 K and 0-40 GPa, respectively. The calculated electron-phonon coupling constant ?=0.52 yields Tc=2.6 K, which is in very good agreement with the experimentally observed value. The value of the coupling constant and the Ginzburg-Landau parameter (?=0.09) indicate that the compound is a weak-coupled type-I rare binary BCS superconductor.

Parvin, F.; Hossain, M. A.; Ali, M. S.; Islam, A. K. M. A.

2015-01-01

202

Phonon densities of states and related thermodynamic properties of high temperature ceramics.

Structural components and semiconductor devices based on silicon nitride, aluminum nitride and gallium nitride are expected to function more reliably at elevated temperatures and at higher levels of performance because of the strong atomic bonding in these materials. The degree of covalency, lattice specific heat, and thermal conductivity are important design factors for the realization of advanced applications. We have determined the phonon densities of states of these ceramics by the method of neutron scattering. The results provide a microscopic interpretation of the mechanical and thermal properties. Moreover, experimental data of the static, structures, and dynamic excitations of atoms are essential to the validation of interparticle potentials employed for molecular-dynamics simulations of high-temperature properties of multi-component ceramic systems. We present an overview of neutron-scattering investigations of the atomic organization, phonon excitations, as well as calculations of related thermodynamic properties of Si{sub 3}N{sub 4}, {beta}-sialon, AlN and GaN. The results are compared with those of the oxide analogs such as SiO{sub 2} and Al{sub 2}O{sub 3}.

Loong, C.-K.

1998-08-28

203

The purpose of this research program is to understand the relationship between macroscopic thermodynamic properties and the various types of intermolecular forces. Since coal-derived liquids contain a wide variety of compounds, a theory capable of successfully predicting the thermophysical properties for coal processes must take into account the molecular shapes and all significant intermolecular forces: dispersion forces, anisotropic forces due to dipoles and quadrupoles, as well as Lewis acid-base interactions. We have developed the Acid-Base-Perturbed-Anisotropic-Chain Theory (ABPACT), a comprehensive theory that is capable of predicting the thermophysical properties for many systems where these different intermolecular forces are present. The ABPACT can treat non-polar compounds, polar compounds and compounds that associate through Lewis acid-base interactions. In addition to our theoretical work, we have used computer simulations to evaluate (and in some cases correct) the assumptions made in this theory. We also have conducted experiments to help us better understand the interplay of different kinds of interactions in multicomponent mixtures.

Donohue, M.D.

1990-09-01

204

NASA Astrophysics Data System (ADS)

The structural and elastic properties of RuN2 were investigated through the first-principles calculation using generalized gradient approximation (GGA) and local density approximation (LDA) within the plane-wave pseudopotential density functional theory. The obtained equilibrium structure and mechanical properties are in excellent agreement with other theoretical results. Then we compared the elastic modulus of RuN2 with several other isomorphic noble metal nitrides. Results show that RuN2 can nearly rival with OsN2 and IrN2, which indicate RuN2 is a potentially ultra-incompressible and hard material. By the elastic stability criteria, it is predicted that RuN2 is stable in our calculations (0-100 GPa). The calculated B/G ratios indicate that RuN2 possesses brittle nature at 0 GPa and when the pressure increases to 13.4 GPa (for LDA) or 20.8 GPa (for GGA), it begins to prone to ductility. Through the quasi-harmonic Debye model, we also investigated the thermodynamic properties of RuN2.

Dong, Bing; Zhou, Xiao-Lin; Liu, Ke; Chang, Jing

2014-08-01

205

Short-Range Order Effects on the Thermodynamic Properties of the Ni3Al Alloy

NASA Astrophysics Data System (ADS)

The reasons for the substantial changes induced by disorder in the thermodynamic properties of the Ni3Al alloy still remain controversial. While several computational studies have found a significant increase in both vibrational entropy and volume as the alloy becomes disordered, there is also evidence that these properties remain unchanged upon disordering. In this work, we present a computational study of the excess vibrational entropy and excess volume of the disordered Ni3Al alloy, in which, we focused on the interplay between short-range order and long-range order effects on these properties. Using the Simulated Annealing optimization technique, we obtained several structures that exhibit no long- range order, but have different degrees of short-range order. Excess vibrational entropies were computed using an empirical potential, while excess volumes were obtained using both: an empirical potential and ab initio techniques. Our calculations indicate that, both excess vibrational entropy and excess volume are substantially reduced in alloys that have no long-range order but have some degree of local order. Both methodologies used to model the alloy give rise to similar results for the excess volume, indicating that the short-range effects are not an artifact of how the system is modelled.

Antonelli, Alex; Meirelles, Bernardo; Miranda, Caetano

2006-03-01

206

The main purpose of our investigation is to achieve better insight into the electrophoretic and thermodynamic properties of protein-coated biomaterial particles. Many academic studies have been performed to understand the complex phenomena of microscopic biomaterial particles as a function of ionic strength, pH and temperature. By electrophoretic measurements of biomaterial particles, the surface structures of it can be analysed with a suitable model. Therefore, the zeta potential measurements are useful to know the effects of adsorbed BSA concentration upon the electrophoretic properties of bioceramics and bioglasses. Unexpectedly, the zeta potential of the BSA-coated biomaterials exhibits a local minimum as the concentrations of adsorbed BSA increases. Apparently, the structures of the attached BSA layer on the biomaterial particles play a significant role. In an attempt to elaborate the phenomenon observed, a model for proteins, which composes two BSA sublayers with different structures and properties, is proposed. Also, the association or equilibrium constant were determined and represented the isotherm curves in function of the zeta potential measurements. PMID:12775905

Sánchez-Muñoz, Orlando L; Nordström, Egon G; Prérez-Hernández, Ever

2003-01-01

207

Advanced working fluids: Thermodynamic properties. Final report, 1 December 1987-30 November 1989

Electrolytes are used as working fluids in gas-fired heat pump-chiller engine cycles. To find out which molecular parameters of the electrolytes impact on cycle performance, a molecular theory, the EXP-MSA correlation, is developed for calculating solution properties, enthalpies, vapor-liquid equilibria, and engine cycle performance. Aqueous and ammoniac single and mixed salt solutions in single and multisolvent systems are investigated. The outcomes are: (1) an accurate correlation is developed to evaluate properties for concentrated electrolyte solutions (e.g., for aqueous LiBr to 19 molal); (2) sensitivity analysis is used to determine the impact of molecular parameters on the thermodynamic properties and cycle performance. The preferred electrolytes are of 1-1 valence type, small ion size, high molecular weight, and in a strongly colligative cosolvent; (3) the abilities of correlation on single-effect and double-effect engine cycles are demonstrated; (4) the operating windows are determined for a number of absorption fluids of industrial importance.

Lee, L.L.; Gering, K.L.

1990-09-01

208

A theoretical investigation on structural and thermodynamic properties of 11-type iron-based superconductor FeSe at high pressure and high temperature was performed by employing the first-principles method based on the density functional theory. Some structural parameters of FeSe in both tetragonal and hexagonal phases are reported. According to the fourth-order Birch-Murnaghan equation of states, the transition pressure P(t) of FeSe from the PbO-type phase to the NiAs-type phase was determined. The calculated results are found to be in good agreement with the available experimental data. Based on the quasi-harmonic Debye model, the pressure and temperature dependence of the thermodynamic properties for hexagonal phase FeSe were investigated. Our theoretical calculations suggest that the pressure and temperature have significant effects on the heat capacity, vibrational internal energy, vibrational entropy, vibrational Helmholtz free energy, thermal expansion coefficient and Debye temperature. Even though few theoretical reports on the structural properties of FeSe are found in the current literature, to our knowledge, this is a novel theoretical investigation on the structural and thermodynamic properties of FeSe at high temperature. We hope that the theoretical results reported here can give more insight into the structural and thermodynamic properties of other iron-based superconductors at high temperature. PMID:22790848

Lu, Cheng; Yang, Xing-Qiang; Zhu, Chun-Ye; Kuang, Xiao-Yu

2012-08-28

209

NASA Astrophysics Data System (ADS)

It is of interest to predict the thermodynamic properties and phase behavior of a substance from quantum-chemical calculations of intermolecular interaction energies followed by molecular simulations. However, while quantum-chemical methods can be quite accurate, they do not provide an exact solution to Schrödinger's equation (excluding full CI) and additional errors arise when fitting energies to analytic potential functions. The purpose of this communication is to provide an understanding and quantification of the sensitivity of the calculated properties to changes (or uncertainties) in different parts of the potential function. For this purpose, Gibbs ensemble Monte Carlo simulations were used to determine the effects on phase behavior of small perturbations to various regions of the model Lennard-Jones 12-6 potential. The results indicate that repulsive energies play a limited role in determining the phase behavior and critical properties, while the attractive energies strongly affect the critical temperature, critical pressure, saturation densities, and vapor pressure. The critical density is most strongly affected by the location at which the potential is zero. However, when the phase behavior and second virial coefficient are scaled by the critical properties calculated for each potential, the results obey a corresponding states relation. These results are used to understand and predict variations in the calculated phase behavior for intermolecular potentials obtained using various strategies to fit ab initio-calculated interaction energies. The knowledge obtained is used to provide accurate predictions for neon based on quantum-chemical energies and a recommended fitting strategy. We also show that three-body nonadditivity effects are largely unimportant for neon.

Garrison, Stephen L.; Sandler, Stanley I.

2002-12-01

210

NASA Technical Reports Server (NTRS)

Equilibrium thermodynamic properties for pure ammonia were generated for a range of temperature from 500 to 50,000 K and pressure from 0.01 to 40 MN/sq m and are presented in tabulated and graphical form. Properties include pressure, temperature, density, enthalpy, speed of sound, entropy, molecular-weight ratio, specific heat at constant pressure, specific heat at constant volume, isentropic exponent, and species mole fractions. These properties were calculated by the method which is based on minimization of the Gibbs free energy. The data presented herein are for an 18-species ammonia model. Heats of formation and spectroscopic constants used as input data are presented. Comparison of several thermodynamic properties calculated with the present program and a second computer code is performed for a range of pressure and for temperatures up to 30,000 K.

Simmonds, A. L.; Miller, C. G., III; Nealy, J. E.

1976-01-01

211

Thermodynamic and Kinetic Properties of Metal Hydrides from First-Principles Calculations

NASA Astrophysics Data System (ADS)

In an effort to minimize the worldwide dependence on fossil fuels, much research has focused on the development of hydrogen fuel cell vehicles. Among the many challenges currently facing the transition to such an alternative energy economy is the storage of hydrogen in an economical and practical way. One class of materials that has presented itself as a possible candidate is solid metal hydrides. These materials chemically bind hydrogen and on heating, release the gas which can then be used to generate power as needed for the vehicle. In order to meet guidelines that have been set for such a storage system, hydrogen must be released rapidly in a narrow temperature range of -40 to 80°C with all reactions being reversible. This sets both thermodynamic and kinetic requirements for the design of candidate metal hydrides. First-principles calculations are well-suited for the task of exploring reactions involving metal hydrides. Here, density-functional theory is used to calculate properties of these materials at the quantum mechanical level of accuracy. In particular, three systems have been investigated: 1. Li-Mg-N-H. Reactions between all known compounds in this system are systematically investigated in order to predict thermodynamically allowed reactions that release hydrogen. The properties of these reactions are compared to the requirements set for hydrogen storage systems. Additionally, ground-state structures are predicted for Li2Mg(NH)2 and Li 4Mg(NH)3. 2. Na-Al-H. The kinetics of mass transport during the (de)hydrogenation of the well-known metal hydride NaAlH4 are investigated. A model is developed to study the flux of native defects through phases involved in these reactions. Since it is also known that titanium is an effective catalyst for both dehydrogenation and rehydrogenation, the effect of Ti substitution in bulk lattices on the kinetics of mass transport is investigated. Results are compared to experiments in order to determine if mass transport represents the rate-limiting process during de- or rehydrogenation and what the effect of Ti may be. 3. Si-H. Properties of the recently synthesized compound SiH4(H 2)2 are investigated. Under high pressures, hydrogen binding to SiH4 exhibits characteristics of both physical and chemical bonds. A ground-state structure is predicted for this phase and the vibrational and bonding properties are investigated in order to determine the origin of the unusual binding between H2 and SiH4.

Michel, Kyle Jay

212

Mint leaves were dried by three different types of dryers, namely; tray, freeze and distributed (indirect)-type solar dryer. Sorption isotherms of fresh, solar, tray and freeze dried mint were determined at temperatures of 15 °C, 25 °C and 35 °C over a range of relative humidities (10-90%). The effect of drying method on the water sorption isotherms of dried mint samples was evaluated. Experimental data were used to determine the best models for predicting the moisture sorption content of mint. Among nine sorption models tested, Peleg, GAB, Lewicki and modified Mizrahi equations gave the best fit to experimental data. The sorption data were analyzed for determination of monolayer moisture content, density of sorbed water, number of adsorbed monolayers, percent bound water, and surface area of adsorbance. The experimental data were also used to determine some thermodynamic properties of mint. PMID:23904652

Dalg?ç, Ali Co?kun; Pekmez, Hatice; Beliba?l?, Kadir Bülent

2012-08-01

213

NASA Astrophysics Data System (ADS)

The thermodynamic and conformational properties of catenated double-ring A-B copolymer melts are investigated through lattice Monte Carlo simulations. The topological constraint on the catenated copolymers is shown to suppress demixing of A and B monomers. This action results in their order-to-disorder transition (ODT) at an increased segregation level and the lamellae below ODT with reduced order, when compared to diblock copolymers of linear or single-ring topology. The A and B rings are pulled closer by catenation in the copolymer, which leads to its smaller gyration radius, lamellar domain spacing, and distance between mass centers of the two rings than for the diblock copolymers. With increasing segregation tendencies, the gyration radii of the A rings of the catenated copolymers stretch along the direction normal to lamellae, while the A-block conformations of the single-ring copolymers change their shapes from ellipsoid to sphere.

Sun, Dachuan; Cho, Junhan

2014-12-01

214

NASA Technical Reports Server (NTRS)

Results of calculations to determine thermodynamic, transport, and flow properties of combustion product gases are presented. The product gases are those resulting from combustion of methane-air-oxygen and methane-oxygen mixtures. The oxygen content of products resulting from the combustion of methane-air-oxygen mixtures was similiar to that of air; however, the oxygen contained in products of methane-oxygen combustion ranged from 20 percent by volume to zero for stoichiometric combustion. Calculations were made for products of reactant mixtures with fuel percentages, by mass, of 7.5 to 20. Results are presented for specific mixtures for a range of pressures varying from 0.0001 to 1,000 atm and for temperatures ranging from 200 to 3,800 K.

Klich, G. F.

1976-01-01

215

NASA Astrophysics Data System (ADS)

First principles calculations are performed to investigate the elastic anisotropy and thermodynamic properties of the recently synthesized iron tetraboride (FeB4) under high pressure and high temperature. The obtained normalized crystal parameters dependence of the resulting pressure are in excellent agreement with experimental data. Young's modulus and shear modulus as a function of crystal orientations have been systematically investigated. The obtained results reveal that the FeB4 exhibits a pronounced elastic anisotropy and it is stiffest along [110] and the most compliant along [100] in response to tension or compression loading. Using a set of total energy versus volume obtained with the first-principles calculations, the quasiharmonic Debye model is applied to the study of the thermal and vibrational effects. The dependences of Debye temperature, Grüneisen parameter, heat capacity, and expansion coefficient on the temperature and pressure are systematically explored in the whole pressure range from 0 to 30 GPa and temperature range from 0 to 1800 K.

Zhang, Meiguang; Yan, Haiyan

2014-06-01

216

NASA Astrophysics Data System (ADS)

Different theoretical approaches for the thermodynamic properties and the equation of state for multicomponent mixtures of nonadditive hard spheres in d dimensions are presented in a unified way. These include the theory by Hamad, our previous formulation, the original MIX1 theory, a recently proposed modified MIX1 theory, as well as a nonlinear extension of the MIX1 theory proposed in this paper. Explicit expressions for the compressibility factor, Helmholtz free energy, and second, third, and fourth virial coefficients are provided. A comparison is carried out with recent Monte Carlo data for the virial coefficients of asymmetric mixtures and with available simulation data for the compressibility factor, the critical consolute point, and the liquid-liquid coexistence curves. The merits and limitations of each theory are pointed out.

Santos, Andrés; López de Haro, Mariano; Yuste, Santos B.

2010-05-01

217

Quantum phase transition and thermodynamic properties of a fourfold magnetic periodic system

NASA Astrophysics Data System (ADS)

Based on the experimental synthesis of organic compound verdazyl radical ?-3-(2,6-dichlorophenyl)-1,5-diphenylverdazyl, consisting of four antiferromagnetic couplings, we study the magnetic properties and thermodynamic behaviors for different antiferromagnetic interactions using Green’s function theory. Under different fields, there are five regimes containing two gapless phases and three magnetization plateaus (M=0, 1/2 and saturated magnetization) distinguished by four critical lines, which are evidenced by the two-site entanglement entropy and closely related to the energy spectra. In addition, we calculate the susceptibility and specific heat, to demonstrate the low-lying excitations at low temperatures. It will provide guidance for us to synthesize varieties of unconventional magnetic materials, and stimulate future studies on quantum spin systems.

Wang, Shuling; Li, Ruixue; Ding, Linjie; Fu, Hua-Hua; Zhu, Si-cong; Ni, Yun; Meng, Yan; Yao, Kailun

2014-12-01

218

Ab initio calculation of the thermodynamic properties of InSb under intense laser irradiation

In this paper, phonon spectra of InSb at different electronic temperatures are presented. Based on the phonon dispersion relationship, we further perform a theoretical investigation of the thermodynamic properties of InSb under intense laser irradiation. The phonon entropy, phonon heat capacity, and phonon contribution to Helmholtz free energy and internal energy of InSb are calculated as functions of temperature at different electronic temperatures. The abrupt change in the phonon entropy- temperature curve from T{sub e} = 0.75 to 1.0 eV provides an indication of InSb undergoing a phase transition from solid to liquid. It can be considered as a collateral evidence of non-thermal melting for InSb under intense electronic excitation effect.

Feng, ShiQuan; Cheng, XinLu [Institute of Atomic and Molecular Physics, Sichuan University, Chengdu 610065 (China) [Institute of Atomic and Molecular Physics, Sichuan University, Chengdu 610065 (China); Key Laboratory of High Energy Density Physics and Technology of Ministry of Education, Sichuan University, Chengdu, 610064 (China); Zhao, JianLing [Institute of Atomic and Molecular Physics, Sichuan University, Chengdu 610065 (China)] [Institute of Atomic and Molecular Physics, Sichuan University, Chengdu 610065 (China); Zhang, Hong [College of Physical Science and Technology, Sichuan University, Chengdu 610065 (China)] [College of Physical Science and Technology, Sichuan University, Chengdu 610065 (China)

2013-07-28

219

NASA Technical Reports Server (NTRS)

Equilibrium thermodynamic properties for pure carbon dioxide are presented in tabulated and graphical form for temperatures from 100 K to 25,000 K and pressures from 40 mN/sq m to 1 GN/sq m. Properties include pressure, temperature, density, enthalpy, speed of sound, entropy, molecular weight ratio, specific heat at constant pressure, specific heat at constant volume, isentropic exponent, and species mole fractions.

Miller, C. G., III; Wilder, S. E.

1976-01-01

220

We present an analysis of the nonequilibrium thermodynamics and, mainly, a response function theory for the study of optical properties in ultrafast-spectroscopy pump-probe experiments. These experiments give rise to the formation of a photoinjected plasma in semiconductors in far-from-equilibrium conditions. The dissipative processes that evolve in this medium greatly influence optical and transport properties. The theory is centred on the

Áurea R. Vasconcellos; Roberto Luzzi; Justino R. Madureira

2000-01-01

221

The present paper presents the computational implementation of the indus- trial formulation of the thermodynamic properties of water at liquid and steam phases, proposed by the International Association for the Properties of Water and Steam, known as IAPWS-IF97. The validity field extends over to temperatures T between 0ºC and 800°C, for pressures p up to 100 MPa. Temperature T, specific

J. G. Fonseca Jr; P. S. Schneider

2004-01-01

222

The work on this project was initiated on September 1, 1989. The project consisted of three different tasks. 1. A thermodynamic model to predict VLE and calorimetric properties of coal liquids. 2. VLE measurements at high temperature and high pressure for coal model compounds and 3. Chromatographic characterization of coal liquids for distribution of heteroatoms. The thermodynamic model developed is an extension of the previous model developed for VLE of coal derived fluids (DOE Grant no. FG22-86PC90541). The model uses the modified UNIFAC correlation for the liquid phase. Some unavailable UNIFAC interactions parameters have been regressed from experimental VLE and excess enthalpy data. The model is successful in predicting binary VLE and excess enthalpy data. Further refinements of the model are suggested. An apparatus for the high pressure high temperature VLE data measurements has been built and tested. Tetralin-Quinoline is the first binary system selected for data measurements. The equipment was tested by measuring 325{degree}C isotherm for this system and comparing it with literature data. Additional isotherms at 350{degree}C and 370{degree}C have been measured. The framework for a characterization procedure for coal derived liquids has been developed. A coal liquid is defined by a true molecular weight distribution and distribution of heteroatoms as a function of molecular weights. Size exclusions liquid chromatography, elemental analysis and FTIR spectroscopy methods are used to obtain the molecular weight and hetroatom distributions. Further work in this area should include refinements of the characterization procedure, high temperature high pressure VLE data measurements for selective model compound binary systems, and improvement of the thermodynamic model using the new measured data and consistent with the developments in the characterization procedure.

Kabadi, V.N.

1992-10-01

223

NASA Astrophysics Data System (ADS)

Based on the tensor network state representation, we develop a nonlinear dynamic theory, coined network contractor dynamics (NCD), to explore the thermodynamic properties of two-dimensional quantum lattice models. By invoking the rank-1 decomposition in the multilinear algebra, the NCD scheme makes the contraction of the tensor network of the partition function be realized through a contraction of a local tensor cluster with vectors on its boundary. An imaginary-time-sweep algorithm for implementation of the NCD method is proposed for practical numerical simulations. We benchmark the NCD scheme on the square Ising model, which shows great accuracy. Also, the results on the spin-1/2 Heisenberg antiferromagnet on a honeycomb lattice are disclosed to be in good agreement with the quantum Monte Carlo calculations. The quasientanglement entropy S, Lyapunov exponent ILya, and loop character Iloop are introduced within the dynamic scheme, which are found to display “nonlocality” near the critical point, and can be applied to determine the thermodynamic phase transitions of both classical and quantum systems.

Ran, Shi-Ju; Xi, Bin; Liu, Tao; Su, Gang

2013-08-01

224

Atmospheric amines - Part II. Thermodynamic properties and gas/particle partitioning

NASA Astrophysics Data System (ADS)

Amines enter the atmosphere from a wide range of sources, but relatively little is known about their atmospheric behavior, especially their role in gas/particle partitioning. In Part I of this work ( Ge et al., 2011) a total of 154 amines, 32 amino acids and urea were identified as occurring in the atmosphere, based upon a survey of the literature. In this work we compile data for the thermodynamic properties of the amines which control gas/particle partitioning (Henry's Law constant, liquid vapor pressure, acid dissociation constant, activity coefficient and solubility in water), and also estimate the solid/gas dissociation constants of their nitrate and chloride salts. Prediction methods for boiling point, liquid vapor pressure, acid dissociation constant and the solubility of the amines in water are evaluated, and used to estimate values of the equilibrium constants where experimental data are lacking. Partitioning of amines into aqueous aerosols is strongly dependent upon pH and is greatest for acidic aerosols. For several common amines the tendency to partition to the particle phase is similar to or greater than that of ammonia. Our results are presented as tables of values of thermodynamic equilibrium constants, which are also incorporated into the Extended Aerosol Inorganics Model ( E-AIM, http://www.aim.env.uea.ac.uk/aim/aim.php) to enable gas/aerosol partitioning and other calculations to be carried out.

Ge, Xinlei; Wexler, Anthony S.; Clegg, Simon L.

2011-01-01

225

High-Precision Thermodynamic and Critical Properties from Tensor Renormalization-Group Flows

NASA Astrophysics Data System (ADS)

The recently developed tensor renormalization-group (TRG) method [1] provides a highly precise technique for deriving thermodynamic and critical properties of lattice Hamiltonians. The TRG is a local coarse-graining transformation, with the elements of the tensor at each lattice site playing the part of the interactions that undergo the renormalization-group flows. These tensor flows are directly related [2] to the phase diagram structure of the infinite system, with each phase flowing to a distinct surface of fixed points. Fixed-point analysis and summation along the flows give the critical exponents, as well as thermodynamic functions along the entire temperature range. Thus, for the ferromagnetic triangular lattice Ising model, the free energy is calculated to better than 10-5 along the entire temperature range. Unlike previous position-space renormalization-group methods, the truncation (of the tensor index range D) in this general method converges under straightforward and systematic improvements. Our best results are easily obtained with D=24, corresponding to 4624-dimensional renormalization-group flows. [1] M. Levin and C.P. Nave, Phys. Rev. Lett. 99, 120601 (2007). [2] M. Hinczewski and A.N. Berker, arXiv:0709.2803v1 [cond-mat.stat-mech], Phys. Rev. E, in press.

Hinczewski, Michael; Berker, A. Nihat

2008-03-01

226

Thermodynamic properties of 9-methylcarbazole and 1,2,3,4-tetrahydro-9-methylcarbazole

Removal of carbazole and its derivatives from heavy petroleum has proved to be particularly difficult using present technology. Studies have shown carbazole and its alkyl-homologs are the dominant nitrogen-containing components in clarified slurry oils, thereby indicating their low reactivity and/or formation during cat-cracking processes. The results reported here will point the way to the development of new methods of nitrogen removal from carbazole and its derivatives. Measurements leading to the calculation of the ideal-gas thermodynamic properties are reported for 9-methylcarbazole and 1,2,3,4-tetrahydro-9-methylcarbazole. For studies on 1,2,3,4-tetrahydro-9-methylcarbazole experimental methods included combustion calorimetry, adiabatic heat-capacity calorimetry, vibrating-tube densitometry, comparative ebulliometry, inclined-piston gauge manometry, and differential-scanning calorimetry (d.s.c.). Adiabatic heat-capacity and combustion calorimetric studies were reported previously for 9-methylcarbazole. Vapor pressures by comparative ebulliometry and inclined-piston gauge manometry, and heat-capacities for the liquid phase by d.s.c. are reported here. Entropies, enthalpies, and Gibbs energies of formation were derived for the ideal gas for both compounds for selected temperatures between 298.15 K and near 700 K. The Gibbs energies of formation will be used in a subsequent report in thermodynamic calculations to study the reaction pathway of the initial hydrogenation step in the carbazole/H{sub 2} hydrodenitrogenation network. 52 refs., 9 figs., 15 tabs.

Steele, W.V.; Knipmeyer, S.E.; Nguyen, A.; Chirico, R.D.

1991-04-01

227

Understanding of protein structure and stability gained to date has been acquired through investigations made under dilute conditions where total macromolecular concentration never surpasses 10 g l?1. However, biological macromolecules are known to evolve and function under crowded intracellular environments that comprises of proteins, nucleic acids, ribosomes and carbohydrates etc. Crowded environment is known to result in altered biological properties including thermodynamic, structural and functional aspect of macromolecules as compared to the macromolecules present in our commonly used experimental dilute buffers (for example, Tris HCl or phosphate buffer). In this study, we have investigated the thermodynamic and structural consequences of synthetic crowding agent (Ficoll 70) on three different proteins (Ribonuclease-A, lysozyme and holo ?-lactalbumin) at different pH values. We report here that the effect of crowding is protein dependent in terms of protein thermal stability and structure. We also observed that the structural characteristics of the denatured state determines if crowding will have an effect or not on the protein stability. PMID:24265729

Mittal, Shruti; Singh, Laishram Rajendrakumar

2013-01-01

228

The thermodynamic properties of hydrated ?-Al{sub 2}O{sub 3} nanoparticles

In this paper we report a combined calorimetric and inelastic neutron scattering (INS) study of hydrated ?-Al{sub 2}O{sub 3} (?-alumina) nanoparticles. These complementary techniques have enabled a comprehensive evaluation of the thermodynamic properties of this technological and industrially important metal oxide to be achieved. The isobaric heat capacity (C{sub p}) data presented herein provide further critical insights into the much-debated chemical composition of ?-alumina nanoparticles. Furthermore, the isochoric heat capacity (C{sub v}) of the surface water, which is so essential to the stability of all metal-oxides at the nanoscale, has been extracted from the high-resolution INS data and differs significantly from that of ice?Ih due to the dominating influence of strong surface-water interactions. This study also encompassed the analysis of four ?-alumina samples with differing pore diameters [4.5 (1), 13.8 (2), 17.9 (3), and 27.2 nm (4)], and the results obtained allow us to unambiguously conclude that the water content and pore size have no influence on the thermodynamic behaviour of hydrated ?-alumina nanoparticles.

Spencer, Elinor C.; Ross, Nancy L. [Department of Geosciences, Virginia Tech, Blacksburg, Virginia 24061 (United States)] [Department of Geosciences, Virginia Tech, Blacksburg, Virginia 24061 (United States); Huang, Baiyu; Woodfield, Brian F. [Department of Chemistry and Biochemistry, Brigham Young University, Provo, Utah 84602 (United States)] [Department of Chemistry and Biochemistry, Brigham Young University, Provo, Utah 84602 (United States); Parker, Stewart F. [ISIS Facility, STFC Rutherford Appleton Laboratory, Chilton, Didcot, Oxon OX11 0QX (United Kingdom)] [ISIS Facility, STFC Rutherford Appleton Laboratory, Chilton, Didcot, Oxon OX11 0QX (United Kingdom); Kolesnikov, Alexander I. [Chemical and Engineering Materials Division, Oak Ridge National Laboratory, P.O. Box 2008, Oak Ridge, Tennessee 37831 (United States)] [Chemical and Engineering Materials Division, Oak Ridge National Laboratory, P.O. Box 2008, Oak Ridge, Tennessee 37831 (United States)

2013-12-28

229

On the thermodynamic properties of the Rb3C60 superconductor

NASA Astrophysics Data System (ADS)

The thermodynamic properties of the superconducting state in Rb3C60 fulleride have been studied in the framework of the Migdal-Eliashberg approach. In the first step, the high physical value of the Coulomb pseudopotential has been predicted (?C?=0.33), which corresponds to the screened Coulomb potential UC=0.61 eV. Next, the temperature dependence of the order parameter and the wave function renormalization factor has been calculated. On the basis of the obtained results, the ratio of the energy gap to the critical temperature (R??2?(0)/kBTC), the ratio of the specific heat jump to the normal state specific heat (RC??CTC/CNTC), and the parameter connected with the thermodynamic critical field (RH?TCCNTC/HC2(0)) have been estimated. It has been shown that the above parameters significantly differ from the BCS predictions: R?=4.06,RC=2.15, and RH=0.145. Finally, the temperature dependence of the electron effective mass (me?) has been presented; me? assumes maximum at the critical temperature: 2.27me, where me denotes the electron band mass. In the paper, the obtained theoretical results have been also compared with the experimental data.

Szcze&?acute; niak, R.; Durajski, A. P.; Pach, P. W.

2014-05-01

230

Thermodynamic and mechanical properties of crystalline CoSb3: A molecular dynamics simulation study

NASA Astrophysics Data System (ADS)

Molecular dynamics simulations have been performed to study the fundamental thermodynamic and mechanical properties of single-crystalline skutterudite CoSb3 in the nanometric scale. The several interesting thermodynamic predictions, including linear thermal expansion coefficient, specific heat capacity, thermal conductivity, and temperature dependence of elastic constants, show excellent agreement with data available in the literature. The classic mechanical tests of uniaxial tension and compression are performed respectively at constant temperatures. The CoSb3 single-crystal exhibits nonlinear elastic response during the deformation process and the sustainable stress is very high, demonstrating its outstanding stability. An interesting phenomenon occurs at compression that the stress-strain curve undergoes a transition. The cause of the transition is an atomic reconstruction, which is observed and interpreted on the basis of interatomic interactions. Both of the failure patterns under tension and compression reveal brittleness of the material. The increasing of temperature would result in a linear degradation of the effective Young's modulus and ultimate strength, but its effect on Poisson's ratio is negligible. The results provide the groundwork for future studies of service behavior of the skutterudites-based thermoelectric devices.

Yang, Xu-qiu; Zhai, Peng-cheng; Liu, Li-sheng; Zhang, Qing-jie

2011-06-01

231

First principles calculation of thermodynamic properties of NaAlSi ternary

NASA Astrophysics Data System (ADS)

PbFCl-type NaAlSi ternary is a corrosion compound found in aluminum, which is used as a sealing material in sodium sulfur battery. To understand and control the corrosion process, it is important to predict its quantitative properties. In this study, a first-principles calculation has been carried out to calculate its equilibrium lattice parameters, bulk modulus and pressure derivative of bulk modulus by both all-electron full-potential linear augmented plane wave scheme and pseudopotential plane wave scheme within the generalized gradient approximation. The theoretical results show good agreement with the available experimental data. The thermodynamic properties, including the specific heat capacity and entropy with pressure up to 9 GPa, have been investigated for the first time by coupling of density functional perturbation theory and quasiharmonic approximation. The volume and linear thermal expansion coefficients were estimated and the results show that the linear thermal expansion on c-axis is nearly twice as large as that on a-axis within the calculated temperature.

Qin, Jining; Lu, Weijie; Zhang, Di; Fan, Tongxiang

2012-01-01

232

Ab initio studies of thermodynamic and electronic properties of phosphorene nanoribbons

NASA Astrophysics Data System (ADS)

We present a density functional theory study of the thermodynamic and electronic properties of phosphorene nanoribbons. We consider a variety of terminations and reconstructions of ribbon edges, both with and without hydrogen passivation, and calculate an ab intio phase diagram that identifies energetically preferred edges as a function of temperature and hydrogen partial pressure. These studies are also accompanied by detailed electronic structure calculations from which we find that ribbons with hydrogenated edges are typically direct gap semiconductors with fundamental gaps that are in excess of phosphorene, the gaps varying inversely with ribbon width. In contrast, ribbons with bare or partially passivated edges either have metallic edges or are semiconducting with band gaps that are smaller than those of their hydrogenated counterparts due to the appearance of midgap edge states. Overall, our studies provide a basis for tailoring the electronic properties of phosphorene nanoribbons by controlling the edge termination via processing conditions (temperature and hydrogen partial pressure) as well as by confinement of carriers via control over ribbon width.

Ramasubramaniam, Ashwin; Muniz, Andre R.

2014-08-01

233

Factors controlling thermodynamic properties at the nanoscale: Ab initio study of Pt nanoparticles

NASA Astrophysics Data System (ADS)

We analyze via density-functional-theory calculations how factors such as size, shape, and hydrogen passivation influence the bond lengths, vibrational density of states (VDOS), and thermodynamic quantities of 0.8-1.7 nm diameter Pt nanoparticles (NPs), whose shape was previously characterized via extended X-ray absorption fine structure spectroscopy (EXAFS) [1]. For a given shape, unsupported NPs display increasingly broader bond-length distributions with decreasing size. Since the VDOS is remarkably non-Debye-like (even for the largest NPs), the VDOS and the thermal properties are not correlated as they are in the bulk. Generally, the fundamental vibrational frequency of a NP is associated with the shape and decreases with increasing size, as in macroscopic systems. Not surprisingly, we find that the frequency of this fundamental mode largely characterizes the thermal properties. We demonstrate that the qualitative difference between the atomic mean-square-displacement and the corresponding mean bond-projected bond-length fluctuations should be taken into account when interpreting the Debye-Waller factor of NPs measured by X-ray (or neutron) scattering or EXAFS. We find that in H-passivated Pt NPs, H desorption with increasing temperature explains the appearance of negative thermal expansion.[4pt] [1] B. Roldan Cuenya, et al. (2011), preprint available

Shafai, Ghazal; Alcantara Ortigoza, Marisol; Rahman, Talat S.

2012-02-01

234

Structural and thermodynamic properties of Fe{sub 1.12}Te with multiple phase transitions

The parent compound of iron chalcogenide superconductors, Fe{sub 1+y}Te, with a range of excess Fe concentrations exhibits intriguing structural and magnetic properties. Here, the interplay of magnetic and structural properties of Fe{sub 1.12}Te single crystals have been probed by low-temperature synchrotron X-ray powder diffraction, magnetization, and specific heat measurements. Thermodynamic measurements reveal two distinct phase transitions, considered unique to samples possessing excess Fe content in the range of 0.11?y?0.13. On cooling, an antiferromagnetic transition, T{sub N}?57?K is observed. A closer examination of powder diffraction data suggests that the transition at T{sub N} is not purely magnetic, but accompanied by the commencement of a structural phase transition from tetragonal to orthorhombic symmetry. This is followed by a second prominent first-order structural transition at T{sub S} with T{sub S}

Cherian, Dona, E-mail: donacherian@physics.iisc.ernet.in; Elizabeth, Suja [Department of Physics, Indian Institute of Science, Bangalore 560012 (India); Rößler, S.; Koz, C.; Schwarz, U.; Wirth, S. [Max Planck Institute for Chemical Physics of Solids, Nöthnitzer Straße 40, 01187 Dresden (Germany); Tsirlin, A. A. [Max Planck Institute for Chemical Physics of Solids, Nöthnitzer Straße 40, 01187 Dresden (Germany); National Institute of Chemical Physics and Biophysics, 12618 Tallinn (Estonia)

2014-03-28

235

First-principles investigation on the elastic stability and thermodynamic properties of Ti2SC

NASA Astrophysics Data System (ADS)

Using Vanderbilt-type plane-wave ultrasoft pseudopotentials within the generalized gradient approximation (GGA) in the frame of density functional theory (DFT), we have investigated the crystal structures, elastic, and thermodynamic properties for Ti2SC under high temperature and high pressure. The calculated pressure dependence of the lattice volume is in excellent agreement with the experimental results. The calculated structural parameter of the Ti atom experienced a subtle increase with applied pressures and the increase suspended under higher pressures. The elastic constants calculations demonstrated that the crystal lattice is still stable up to 200 GPa. Investigations on the elastic properties show that the c axis is stiffer than the a axis, which is consistent with the larger longitudinal elastic constants (C33, C11) relative to transverse ones (C44, C12, C13). Study on Poisson's ratio confirmed that the higher ionic or weaker covalent contribution in intra-atomic bonding for Ti2SC should be assumed and the nature of ionic increased with pressure. The ratio (B/G) of bulk (B) and shear (G) moduli as well as B/C44 demonstrated the brittleness of Ti2SC at ambient conditions and the brittleness decreased with pressure. Moreover, the isothermal and adiabatic bulk moduli displayed opposite temperature dependence under different pressures. Again, we observed that the Debye temperature and Grüneisen parameter show weak temperature dependence relative to the thermal expansion coefficient, entropy, and heat capacity, from which the pressure effects are clearly seen.

Yang, Ze-Jin; Guo, Yun-Dong; Linghu, Rong-Feng; Cheng, Xin-Lu; Yang, Xiang-Dong

2012-05-01

236

NASA Astrophysics Data System (ADS)

Community databases such as EarthChem, LEPR, and AMCSD both increase demand for quantitative petrological tools, including thermodynamic models like the MELTS family of algorithms, and are invaluable in development of such tools. The need to extend existing solid solution models to include minor components such as Cr and Na has been evident for years but as the number of components increases it becomes impossible to completely separate derivation of end-member thermodynamic data from calibration of solution properties. In Hamecher et al. (2012; 2013) we developed a calibration scheme that directly interfaces with a MySQL database based on LEPR, with volume data from AMCSD and elsewhere. Here we combine that scheme with a Bayesian approach, where independent constraints on parameter values (e.g. existence of miscibility gaps) are combined with uncertainty propagation to give a more reliable best-fit along with associated model uncertainties. We illustrate the scheme with a new model of molar volume for (Ca,Fe,Mg,Mn,Na)3(Al,Cr,Fe3+,Fe2+,Mg,Mn,Si,Ti)2Si3O12 cubic garnets. For a garnet in this chemical system, the model molar volume is obtained by adding excess volume terms to a linear combination of nine independent end-member volumes. The model calibration is broken into three main stages: (1) estimation of individual end-member thermodynamic properties; (2) calibration of standard state volumes for all available independent and dependent end members; (3) fitting of binary and mixed composition data. For each calibration step, the goodness-of-fit includes weighted residuals as well as ?2-like penalty terms representing the (not necessarily Gaussian) prior constraints on parameter values. Using the Bayesian approach, uncertainties are correctly propagated forward to subsequent steps, allowing determination of final parameter values and correlated uncertainties that account for the entire calibration process. For the aluminosilicate garnets, optimal values of the bulk modulus and its pressure derivative are obtained by fitting published compression data using the Vinet equation of state, with the Mie-Grüneisen-Debye thermal pressure formalism to model thermal expansion. End-member thermal parameters are obtained by fitting volume data while ensuring that the heat capacity is consistent with the thermodynamic database of Berman and co-workers. For other end members, data for related compositions are used where such data exist; otherwise ultrasonic data or density functional theory results are taken or, for thermal parameters, systematics in cation radii are used. In stages (2) and (3) the remaining data at ambient conditions are fit. Using this step-wise calibration scheme, most parameters are modified little by subsequent calibration steps but some, such as the standard state volume of the Ti-bearing end member, can vary within calculated uncertainties. The final model satisfies desired criteria and fits almost all the data (more than 1000 points); only excess parameters that are justified by the data are activated. The scheme can be easily extended to calibration of end-member and solution properties from experimental phase equilibria. As a first step we obtain the internally consistent standard state entropy and enthalpy of formation for knorringite and discuss differences between our results and those of Klemme and co-workers.

Antoshechkina, P. M.; Wolf, A. S.; Hamecher, E. A.; Asimow, P. D.; Ghiorso, M. S.

2013-12-01

237

A comprehensive review of the thermodynamic properties of the oxide compounds of the lanthanide and actinide elements is presented. The available literature data for the solid, liquid, and gaseous state have been analysed and recommended values are presented. In case experimental data are missing, estimates have been made based on the trends in the two series, which are extensively discussed.

Konings, Rudy J. M., E-mail: rudy.konings@ec.europa.eu; Beneš, Ondrej; Kovács, Attila; Manara, Dario; Sedmidubský, David [European Commission, Joint Research Centre, Institute for Transuranium Elements, P.O. Box 2340, 76125 Karlsruhe (Germany); Gorokhov, Lev; Iorish, Vladimir S.; Yungman, Vladimir; Shenyavskaya, E.; Osina, E. [Joint Institute for High Temperatures, Russian Academy of Sciences, 13-2 Izhorskaya Street, Moscow 125412 (Russian Federation)

2014-03-15

238

Molecular simulation of thermodynamic and transport properties for the H2O+NaCl system.

Molecular dynamics and Monte Carlo simulations have been carried out to obtain thermodynamic and transport properties of the binary mixture H2O+NaCl at temperatures from T = 298 to 473 K. In particular, vapor pressures, liquid densities, viscosities, and vapor-liquid interfacial tensions have been obtained as functions of pressure and salt concentration. Several previously proposed fixed-point-charge models that include either Lennard-Jones (LJ) 12-6 or exponential-6 (Exp6) functional forms to describe non-Coulombic interactions were studied. In particular, for water we used the SPC and SPC/E (LJ) models in their rigid forms, a semiflexible version of the SPC/E (LJ) model, and the Errington-Panagiotopoulos Exp6 model; for NaCl, we used the Smith-Dang and Joung-Cheatham (LJ) parameterizations as well as the Tosi-Fumi (Exp6) model. While none of the model combinations are able to reproduce simultaneously all target properties, vapor pressures are well represented using the SPC plus Joung-Cheathem model combination, and all LJ models do well for the liquid density, with the semiflexible SPC/E plus Joung-Cheatham combination being the most accurate. For viscosities, the combination of rigid SPC/E plus Smith-Dang is the best alternative. For interfacial tensions, the combination of the semiflexible SPC/E plus Smith-Dang or Joung-Cheatham gives the best results. Inclusion of water flexibility improves the mixture densities and interfacial tensions, at the cost of larger deviations for the vapor pressures and viscosities. The Exp6 water plus Tosi-Fumi salt model combination was found to perform poorly for most of the properties of interest, in particular being unable to describe the experimental trend for the vapor pressure as a function of salt concentration. PMID:25527948

Orozco, Gustavo A; Moultos, Othonas A; Jiang, Hao; Economou, Ioannis G; Panagiotopoulos, Athanassios Z

2014-12-21

239

In this study, we use solubility and oxide melt solution calorimetry measurements to determine the thermodynamic properties of the uranyl phosphate phases autunite (abbreviated: CaUP), uranyl hydrogen phosphate (HUP), and uranyl orthophosphate (UP). Solubility measurements from both supersaturated and undersaturated conditions, as well as under different pH conditions, rigorously demonstrate attainment of equilibrium and yield well-constrained solubility product values of -48.36 (-0.03 /+ 0.03), -13.17 (-0.11 / +0.07), and -49.36 (-0.04 / +0.02) for CaUP, HUP, and UP, respectively. We use the solubility data to calculate standard state Gibbs free energies of formation for all phases (-7630.61 ± 9.69, -3072.27 ± 4.76, and -6138.95 ± 12.24 kJ mol-1 for CaUP, HUP, and UP, respectively), and calorimetry data to calculate standard state enthalpies of formation of -3223.22 ± 4.00 and -7001.01 ± 15.10 kJ mol-1 for HUP and UP, respectively. Combining these results allows us also to calculate the standard state entropies of formation of -506.54 ± 10.48 and -2893.12 ± 19.44 kJ mol-1 K-1 for HUP and UP phases, respectively. The results from this study are part of a combined effort to develop reliable and internally consistent thermodynamic data for environmentally relevant uranyl minerals. Data such as these are required in order to optimize and quantitatively assess the effect of phosphate amendment remediation technologies for uranium contaminated systems.

Gorman-Lewis, Drew; Shareva, Tatiana; kubatko, Karrie-Ann; burns, Peter; Wellman, Dawn M.; McNamara, Bruce K.; szymanowski, jennifer; Navrotsky, Alexandra; Fein, Jeremy B.

2009-10-01

240

Experimental Study of the Thermodynamic Properties of Diethyl Ether (DEE) at Saturation

NASA Astrophysics Data System (ADS)

The isochoric heat capacities {({C_{V1}^' ,{C_{V1}^'',{C_{V2}^',{C_{V2}^'')}, saturation densities ({? _S^' and ({?_S^'')}), vapor pressures ( P S), thermal-pressure coefficients {?_V=left({partial P/partial T}right)_V}, and first temperature derivatives of the vapor pressure ? S = (d P S/d T) of diethyl ether (DEE) on the liquid-gas coexistence curve near the critical point have been measured with a high-temperature and high-pressure nearly constant-volume adiabatic piezo-calorimeter. The measurements of {({C_{V1}^' ,{C_{V1}^'',{C_{V2}^',{C_{V2}^'')} were made in the liquid and vapor one- and two-phase regions along the coexistence curve. The calorimeter was additionally supplied with a calibrated extensometer to accurately and simultaneously measure the PVT, C V VT, and thermal-pressure coefficient, ? V , along the saturation curve. The measurements were carried out in the temperature range from 416 K to 466.845 K (the critical temperature) for 17 liquid and vapor densities from 212.6 kg · m-3 to 534.6 kg · m-3. The quasi-static thermo- (reading of PRT, T - ? plot) and baro-gram (readings of the tensotransducer, P - ? plot) techniques were used to accurately measure the phase-transition parameters ( P S , ? S , T S) and ? V . The total experimental uncertainty of density ( ? S), pressure ( P S), temperature ( T S), isochoric heat capacities {({C_{V1}^' ,{C_{V1}^'',{C_{V2}^',{C_{V2}^'')}, and thermal-pressure coefficient, ? V , were estimated to be 0.02 % to 0.05 %, 0.05 %, 15 mK, 2 % to 3 %, and 0.12 % to 1.5 %, respectively. The measured values of saturated caloric {({C_{V1}^' ,{C_{V1}^'',{C_{V2}^',{C_{V2}^'')} and saturated thermal ( P S, ? S, T S) properties were used to calculate other derived thermodynamic properties C P , C S, W, K T , P int, ? H vap, and {left({partial V/partial T}right)_P^' of DEE near the critical point. The second temperature derivatives of the vapor pressure, (d2 P S/d T 2), and chemical potential, (d2 ?/d T 2), were also calculated directly from the measured one- and two-phase liquid and vapor isochoric heat capacities {({C_{V1}^' ,{C_{V1}^'',{C_{V2}^',{C_{V2}^'')} near the critical point. The derived values of (d2 P S/d T 2) from calorimetric measurements were compared with values calculated from vapor-pressure equations. The measured and derived thermodynamic properties of DEE near the critical point were interpreted in terms of the "complete scaling" theory of critical phenomena. In particular, the effect of a Yang-Yang anomaly of strength R ? on the coexistence-curve diameter behavior near the critical point was studied. Extended scaling-type equations for the measured properties P S ( T), ? S ( T), and {({C_{V1}^' ,{C_{V1}^'',{C_{V2}^',{C_{V2}^'')} as a function of temperature were developed.

Polikhronidi, N. G.; Abdulagatov, I. M.; Batyrova, R. G.; Stepanov, G. V.; Ustuzhanin, E. E.; Wu, J. T.

2011-03-01

241

Thermodynamic properties of Pt nanoparticles: Size, shape, support, and adsorbate effects

NASA Astrophysics Data System (ADS)

This study presents a systematic investigation of the thermodynamic properties of free and ?-Al2O3-supported size-controlled Pt nanoparticles (NPs) and their evolution with decreasing NP size. A combination of in situ extended x-ray absorption fine-structure spectroscopy (EXAFS), ex situ transmission electron microscopy (TEM) measurements, and NP shape modeling revealed (i) a cross over from positive to negative thermal expansion with decreasing particle size, (ii) size- and shape-dependent changes in the mean square bond-projected bond-length fluctuations, and (iii) enhanced Debye temperatures (?D, relative to bulk Pt) with a bimodal size-dependence for NPs in the size range of ˜0.8-5.4 nm. For large NP sizes (diameter d >1.5 nm) ?D was found to decrease toward ?D of bulk Pt with increasing NP size. For NPs ? 1 nm, a monotonic decrease of ?D was observed with decreasing NP size and increasing number of low-coordinated surface atoms. Our density functional theory calculations confirm the size- and shape-dependence of the vibrational properties of our smallest NPs and show how their behavior may be tuned by H desorption from the NPs. The experimental results can be partly attributed to thermally induced changes in the coverage of the adsorbate (H2) used during the EXAFS measurements, bearing in mind that the interaction of the Pt NPs with the stiff, high-melting temperature ?-Al2O3 support may also play a role. The calculations also provide good qualitative agreement with the trends in the mean square bond-projected bond-length fluctuations measured via EXAFS. Furthermore, they revealed that part of the ?D enhancement observed experimentally for the smallest NPs (d ? 1 nm) might be assigned to the specific sensitivity of EXAFS, which is intrinsically limited to bond-projected bond-length fluctuations.

Roldan Cuenya, B.; Alcántara Ortigoza, M.; Ono, L. K.; Behafarid, F.; Mostafa, S.; Croy, J. R.; Paredis, K.; Shafai, G.; Rahman, T. S.; Li, L.; Zhang, Z.; Yang, J. C.

2011-12-01

242

Path Integral Monte Carlo Calculations of Thermodynamic Properties of Dense Hydrogen-Helium Plasma

NASA Astrophysics Data System (ADS)

In this work we present new results of ab initio/ calculations of thermodynamic properties of dense hydrogen-helium plasma with helium concentration corresponding to that in the higher layers of the Jovian atmosphere at temperatures from 10^4 K to 2.10^5 K and electron particle densities from 10^20 to 10^24 cm-3. The calculations were made by path-integral Monte Carlo method in a cubical cell using periodic boundary conditions. To correctly take into account exchange effects at high values of the degeneracy parameter we used a special correcting procedure. At temperature higher than 5.10^4 K the calculation results are practically coincides with computations by the equation of state based on the chemical plasma model. However at temperatures 10^4 and 2.10^4 K in the density range from 0.5 to 5 g/cm^3 we found a phase transition region positioned in a good agreement with other theories and the experimentally revealed region of the sharp electrical conductivity rise. Along the isotherm 10^4 K in the density range from 0.01 to 0.2 g/cm^3 we found one more region of bad convergence to the equilibrium state. We also present first simulation results for helium plasma in comparison with other models and experimental data. The authors are grateful to the Russian Science support foundation for financial support of the work.

Filinov, Vladimir; Levashov, Pavel; Bonitz, Michael; Fortov, Vladimir

2005-07-01

243

Magnetic, electrical and thermodynamic properties of RE 8Pd 24In

NASA Astrophysics Data System (ADS)

Investigations of magnetic, transport and thermodynamic properties of RE 8Pd 24In (RE=Pr, Nd, Gd, Tb, Dy, Ho, Er and Tm) are reported through measurements of X-ray diffraction, electrical resistivity ( ?(T)), magnetic susceptibility ( ?(T)), magnetization ( ?(?0H)) and heat capacity ( Cp(T)). These ternary compounds have the cubic AuCu 3-type structure. Compounds with RE=Gd and Tb order antiferromagnetically (AF) and exhibit magnetic transitions observed in their ?(T) and Cp(T). ?(T) results for the Gd and Tb compounds indicate a minimum above the magnetic phase transition temperature TN, and an increase in ?(T) upon further cooling as a precursor of AF order at lower temperatures. ?(T) data at high temperatures follow the Curie-Weiss relation for all compounds and give effective moment values close to those expected for the free RE 3+-ion. Enhanced values of the electronic contribution to the heat capacity were observed for Gd 8Pd 24In and Tb 8Pd 24In.

Tchoula Tchokonté, M. B.; de V. du Plessis, P.; Kaczorowski, D.; Strydom, A. M.

2010-12-01

244

A status is presented of the development during FY2002 of a database for physical properties models for the simulation of the treatment of Sodium-Bearing Waste (SBW) at the Idaho National Engineering and Environmental Laboratory. An activity coefficient model is needed for concentrated, aqueous, multi-electrolyte solutions that can be used by process design practitioners. Reasonable first-order estimates of activity coefficients in the relevant media are needed rather than an incremental improvement in theoretical approaches which are not usable by practitioners. A comparison of the Electrolyte Non-Random Two-Liquid (ENRTL) and Pitzer ion-interaction models for the thermodynamic representation of SBW is presented. It is concluded that Pitzer's model is superior to ENRTL in modeling treatment processes for SBW. The applicability of the Pitzer treatment to high concentrations of pertinent species and to the determination of solubilities and chemical equilibria is addressed. Alternate values of Pitzer parameters for HCl, H2SO4, and HNO3 are proposed, applicable up to 16m, and 12m, respectively. Partial validation of the implementation of Pitzer's treatment within the commercial process simulator ASPEN Plus was performed.

Nichols, T.T.; Taylor, D.D.

2002-07-18

245

Thermodynamic Properties of He Gas in the Temperature Range 4.2-10 K

NASA Astrophysics Data System (ADS)

The thermodynamic properties of He gas are investigated in the temperature-range 4.2-10 K, with special emphasis on the second virial coefficient in both the classical and quantum regimes. The main input in computing the quantum coefficient is the `effective' phase shifts. These are calculated within the framework of the Galitskii-Migdal-Feynman (GMF) formalism, using the HFDHE2 and Sposito potentials. The virial equation of state is constructed. Extensive calculations are carried out for the pressure-volume-temperature (P-V-T) behavior, as well as chemical potential, and nonideality of the system. The following results are obtained. First, the validity of the GMF formalism for the present system is demonstrated beyond any doubt. Second, the boiling point (phase-transition point) of He gas is determined from the P-V behavior using the virial equation of state, its value being closest than all previous results to the experimental value. Third, the chemical potential is evaluated from the quantum second virial coefficient. It is found that increases (becomes less negative) as the temperature decreases or the number density n increases. Further, shows no sensitivity to the differences between the potentials used up to n = 10 m. Finally, the compressibility Z is computed and discussed as a measure of the nonideality of the system.

Mosameh, S. M.; Sandouqa, A. S.; Ghassib, H. B.; Joudeh, B. R.

2014-05-01

246

JavaScript Programs To Calculate Thermodynamic Properties Using Cubic Equations of State

NASA Astrophysics Data System (ADS)

Cubic equations of state are widely used by chemists and chemical engineers to predict the thermodynamic properties of both pure substances and mixtures. In particular, they enable predictions concerning the temperature and pressure at which vapor liquid equilibrium occurs. In this article, two JavaScript programs are described. The first program gives students the choice of five different cubic equations of state and performs calculations for pure substances. The second program predicts vapor liquid equilibrium for binary mixtures using a choice of three modern equations of state and the van der Waals mixing rules. There are three advantages to using JavaScript and a Web interface for these programs. Firstly, the program contains online theory so that, rather than just calculating the parameter, the program explains how the calculation is being performed. Secondly, virtually all students are familiar with how forms work when they are used on Web pages and so they find the program straightforward to use. Thirdly, the Web interface means that it is easy for a student to vary a parameter and observe its influence on the answer or to repeat a calculation using a different equation of state.

Barrie, Patrick J.

2005-06-01

247

In this work, some thermodynamic properties of poly (cyclohexyl methacrylate) were studied by inverse gas chromatography (IGC). For this purpose, the polymeric substance was coated on Chromosorb W and which was filled into a glass column. The retention times (t(r)) of the probes were determined from the interactions of poly (cyclohexyl methacrylate) with n-pentane, n-hexane, n-heptane, n-octane, n-decane, methanol, ethanol, 2-propanol, butanol, acetone, ethyl methyl ketone, benzene, toluene and o-xylene by IGC technique. Then, the specific volume (Vg(0)) was determined for each probe molecule. By using (1/T; lnVg(0)) graphics, the glass transition temperature of poly (cyclohexyl methacrylate) was found to be 373 K. The adsorption heat under the glass transition temperature (deltaH(a)), and partial molar heat of sorption above the glass transition (deltaH1(S)), partial molar free energy of sorption (deltaG1(S)) and partial molar entropy of sorption (deltaS1(S)) belonging to sorption for every probe were calculated. The partial molar heat of mixing at infinite dilution (deltaH1(infinity)), partial molar free energy of mixing at infinite dilution (deltaG1(infinity)), Flory-Huggins interaction parameter (chi12(infinity)) and weight fraction activity coefficient (a1/w1)(infinity) values of polymer-solute systems were calculated at different column temperatures. The solubility parameters (delta2) of the polymer were obtained by IGC technique. PMID:25255568

Kaya, Ismet; Pala, Cigdem Yigit

2014-07-01

248

The water flow across porous, semipermeable membranes associated with osmosis and filtration under a variety of conditions is analysed and compared to macromolecular diffusion across free-liquid boundaries, diffusion and sedimentation in the ultracentrifuge, and tracer diffusion of water. This study establishes that osmosis can be explained in terms of the irreversible thermodynamics of diffusion. For macromolecular osmotically active solutes in the semidilute concentration regime the water flows across semipermeable porous membranes are interpreted in terms of a rate-limiting solute-solvent exchange layer that exists on the solution side of the membrane adjacent to the membrane pore; both osmosis and filtration will be governed by these exchange layers. These exchange layers also yield unique properties of their constituent molecules in systems where there is osmotic equilibration between solutions of different solutes. This study also establishes the need to consider the internal osmotic pressure of membranes in the pressure balance associated with the flow across the membrane. The complex situation of partially permeable membranes is analysed for the simple case where there are no mechanical gradients and there is only one osmotically active solution that creates a rate-limiting exchange layer. This treatment predicts that the flow will be governed primarily by the osmotic pressure difference associated with the partitioning of the solute at the membrane-solution interface. PMID:8072300

Comper, W D

1994-06-21

249

NASA Astrophysics Data System (ADS)

Today first principles calculations in mineral physics play a fundamental role in understanding of the Earth. They complement experiments by expanding the pressure and temperature range for which properties can be obtained and provide access to atomic scale phenomena. Since the wealth of predictive first principles results can hardly be communicated in printed form, we have developed online applications where published results can be reproduced/verified online and extensive unpublished results can be generated in customized form. So far these applications have included thermodynamics properties of end-member phases and thermal elastic properties of end-member phases and few solid solutions. Extension of this software infrastructure to include other properties is in principle straightforward. This contribution will review the nature of results that can be generated (methods, thermodynamics domain, list of minerals, properties, etc) and nature of the software infrastructure. These applications are part of a more extensive cyber-infrastructure operating in the XSEDE - the VLab Science Gateway [1]. [1] https://www.xsede.org/web/guest/gateways-listing Research supported by NSF grants ATM-0428744 and EAR-1047629.

Wentzcovitch, R. M.; Da Silveira, P. R.; Wu, Z.; Yu, Y.

2013-12-01

250

NASA Astrophysics Data System (ADS)

The structural, phonon, and thermodynamic properties of the cubic hbox {CeO}2 are investigated from first-principles calculations. The calculated lattice parameters, bulk modulus, and phonon dispersion curves are in agreement with available experimental data and other calculations. It is shown that the local density approximation (LDA)+U method is more suitable for describing the properties of hbox {CeO}2 compared with the LDA method. The pressure and temperature dependences of the specific heat, Debye temperature, and the thermal expansion coefficient are successfully obtained from the Debye-Grüneisen model by combining with the phonon density of states.

Niu, Zhen-Wei; Cheng, Yan; Zhang, Huai-Yong; Ji, Guang-Fu

2014-08-01

251

NASA Astrophysics Data System (ADS)

We calculated the phase diagram of up to 15 GPa and 2,000 K and investigated the thermodynamic properties of the high-pressure phases. The investigated phases include the berlinite, moganite-like, , and phases . The computational methods used include density functional theory, density functional perturbation theory, and the quasiharmonic approximation. The investigated thermodynamic properties include the thermal equation of state, isothermal bulk modulus, thermal expansivity, and heat capacity. With increasing pressure, the ambient phase berlinite transforms to the moganite-like phase, and then to the and phases, and further to the phase. The stability fields of the and phases are similar in pressure but different in temperature, as the phase is stable at low temperatures, whereas the phase is stable at high temperatures. All of the phase relationships agree well with those obtained by quench experiments, and they support the stabilities of the moganite-like, , and phases, which were not observed in room-temperature compression experiments.

Wang, Riping; Kanzaki, Masami

2015-01-01

252

NASA Technical Reports Server (NTRS)

The evaluation of the thermodynamic properties of a gas mixture can be performed using a generalized correlation which makes use of the second virial coefficient. This coefficient is based on statistical mechanics and is a function of temperature and composition, but not of pressure. The method provides results accurate to within 3 percent for gases which are nonpolar or only slightly polar. When applied to highly polar gases, errors of 5 to 10 percent may result. For gases which associate, even larger errors are possible. The sequences of calculations can be routinely programmed for a digital computer. The thermodynamic properties of a mixture of neon, argon and ethane were calculated by such a program. The result will be used for the design of the gas replenishment system for the Energetic Gamma Ray Experiment Telescope.

Colon, G.

1981-01-01

253

Results of ab initio molecular orbital (MO) calculations provide a basis for the interpretation of structural and thermodynamic properties of crystals, glasses, and melts containing tetrahedrally coordinated Si, Al, and B. Calculated and experimental tetrahedral atom-oxygen (TO) bond lengths are in good agreement and the observed average SiO and AlO bond lengths remain relatively constant in crystalline, glassy, and molten

A. Navrotsky; K. L. Geisinger; P. McMillan; G. V. Gibbs

1985-01-01

254

This article describes a new method for estimating the thermodynamic properties of asphaltenes. To illustrate this methodology, we used a computer assisted structure elucidation software (SIGNATURE) to generate an ensemble of 10 isomers for Arabian Light (AL) asphaltenes compatible with (i) analytical data from elemental analysis, FT-IR spectroscopy, 1-D H\\/C solution NMR and vapor pressure osmometry and (ii) literature data

Mamadou S. Diallo; Alejandro Strachan; Jean-Loup Faulon; William A. Goddard III

2004-01-01

255

The structural, electronic, optical and thermodynamic properties of Mg1-xSrxO ternary alloys in NaCl structures at various Sr concentrations are presented. The calculations were performed using the full potential linearized augmented plane wave (FP-LAPW) method within the density functional theory (DFT) in the local density approximation (LDA) and two developed refinements, namely the generalized gradient approximation (GGA) of Perdew et al

M. Labidi; S. Labidi; S. Ghemid; H. Meradji; F. El Haj Hassan

2010-01-01

256

National Institute of Standards and Technology Data Gateway

SRD 10 NIST/ASME Steam Properties Database (PC database for purchase) Based upon the International Association for the Properties of Water and Steam (IAPWS) 1995 formulation for the thermodynamic properties of water and the most recent IAPWS formulations for transport and other properties, this updated version provides water properties over a wide range of conditions according to the accepted international standards.

257

NASA Astrophysics Data System (ADS)

A brief review is presented for the pre-history and discovery of fullerenes. Single-site potentials with parameters proposed by Girifalco was used to describe the interactions of the fullerene molecules C70 and C96. We present theoretical model for calculating the thermodynamic properties of liquid for both C70 and C96 by means of an improved equation of state (EOS), in which the particles are interacting via pair wise interaction composed of suitable linear combination of three Yukawa functions (3YK). The proposed equation of state provides a powerful mathematical formalism for the Helmholtz free energy and the pressure within the series mean-spherical approximation (SMSA) which are the basic ingredients to compute the liquid-vapour coexistence curve of C70 and C96 as well as the other thermodynamic properties for the bulk liquid and the vapour phases. The comparisons with Gibbs ensemble Monte Carlo (GEMC) simulations and the self-consistent Ornstein-Zernike approximation (SCOZA) were carried out. The estimated critical parameters for both C70 and C96 are TC = 2176 K, ?C = 0.44 nm-3, PC = 51.64 bars and TC = 2477 K, ?C = 0.32 nm-3, PC = 44.28 bars respectively. It is to be noted that the obtained results of the thermodynamic properties along the binodal curves of C70 and C96 are exhibit interesting features.

Khedr, M. Bahaa; Osman, S. M.

2011-10-01

258

EFFECT OF HEATING RATE ON THE THERMODYNAMIC PROPERTIES OF PULVERIZED COAL

This final technical report describes work performed under DOE Grant No. DE-FG22-96PC96224 during the period September 24, 1996 to September 23, 1999 which covers the entire performance period of the project. During this period, modification, alignment, and calibration of the measurement system, measurement of devolatilization time-scales for single coal particles subjected to a range of heating rates and temperature data at these time-scales, and analysis of the temperature data to understand the effect of heating rates on coal thermal properties were carried out. A new thermodynamic model was developed to predict the heat transfer behavior for single coal particles using one approach based on the analogy for thermal property of polymers. Results of this model suggest that bituminous coal particles behave like polymers during rapid heating on the order of 10{sup 4}-10{sup 5} K/s. At these heating rates during the early stages of heating, the vibrational part of the heat capacity of the coal molecules appears to be still frozen but during the transition from heat-up to devolatilization, the heat capacity appears to attain a sudden jump in its value as in the case of polymers. There are a few data available in the coal literature for low heating rate experiments (10{sup 2}-10{sup 3} K/s) conducted by UTRC, our industrial partner, in this project. These data were obtained for a longer heating duration on the order of several seconds as opposed to the 10 milliseconds heating time of the single particle experiments discussed above. The polymer analogy model was modified to include longer heating time on the order of several seconds to test these data. However, the model failed to predict these low heating rate data. It should be noted that UTRC's work showed reasonably good agreement with Merrick model heat capacity predictions at these low heating rates, but at higher heating rates UTRC observed that coal thermal response was heat flux dependent. It is concluded that at combustion level heating rates (10{sup 4}-10{sup 5} K/s) coal structural changes are delayed and attendant increases in heat capacity and thermal conductivity are pushed to higher temperatures or require significant hold times to become manifest.

Ramanathan Sampath

2000-01-01

259

NASA Astrophysics Data System (ADS)

The garnet class of phases is extremely broad in terms of composition and structural properties. Garnet is found in nature and various synthetic garnet phases have a number of important technical applications. There exist the rock-forming silicate garnets that are so widespread geologically. An additional class is given by the so-called "hydrogarnets" in which the tetrahedral site (Wyckoff position 24d) is empty. At relatively low temperatures there is complete solid solution between Ca3Al2Si3O12 and Ca3Al2H12O12, for example. The substitution mechanism can be written as O4H4 \\lrarr SiO4. The latter, pure OH-containing end-member, which has not been found in nature, is termed katoite/hydrogrossular. Its structure has been investigated by various workers by X-ray and neutron diffraction and by proton NMR, IR and Raman spectroscopic methods. At ambient conditions the structure has the "standard" garnet cubic symmetry of Ia-3d. At high pressures, and possibly at low temperatures, a different structure may occur. We measured the low temperature IR spectra and heat capacity of katoite in order to understand its structural, crystal-chemical and thermophysical properties. A sample of Ca3Al2H12O12 was synthesized hydrothermally in Au capsules at 250 °C and 3 kb water pressure. X-ray powder measurements show that about 98-99% katoite was obtained. Powder IR spectra were recorded between 298 K and 10 K. The measured spectra are considerably different in the high wavenumber region, where O-H stretching modes occur, between 298 K and 10 K. At room temperature the IR-active O-H band located around 3662 cm-1 is broad and it narrows and shifts to higher wavenumbers and also develops structure below about 80 K. Concomitantly, additional weak intensity O-H bands located around 3600 cm-1 begin to appear and they become sharper and increase in intensity with further decreases in temperature down to 10 K. The spectra indicate that the vibrational behavior of individual OH groups and their collective interactions measurably affect the lattice dynamic (i.e. thermodynamic) behavior. The low temperature heat capacity behavior was investigated with a commercially designed relaxation calorimeter between 5 and 300 K on a mg-sized sample. The heat capacity data are well behaved at T < 300 K and show a monotonic decrease in magnitude with decreasing temperature. A standard third-law entropy value of So = 421.7 ± 1.6 J/mol·K was calculated. Using this new calorimetric-based So value and published standard enthalpy of formation data for katoite, a calorimetric-based Gibbs free energy of formation at 298 K can be obtained as ?G°f = -5021.2 kJ/mol. The Cp data show no evidence for any phase transition as possibly expected by the change in OH-mode behavior with decreasing temperature. We have no explanation for the appearance of the additional modes. It is worth noting that the katoite crystal structure in terms of lattice dynamic or thermodynamic behavior should be thought of having OH groups and not O4H4 clusters or polyhedral units as is often written in the literature. The single crystallographic OH group in katoite shows very weak, if any, hydrogen bonding and the H atoms have large amplitudes of vibration. The weak H bonding controls the nature of low energy OH-related vibrations and this leads to its large So value.

Geiger, C. A.; Dachs, E.

2012-04-01

260

Thermodynamic and mechanical properties of copper precipitates in ?-iron from atomistic simulations

NASA Astrophysics Data System (ADS)

Precipitate hardening is commonly used in materials science to control strength by acting on the number density, size distribution, and shape of solute precipitates in the hardened matrix. The Fe-Cu system has attracted much attention over the last several decades due to its technological importance as a model alloy for Cu steels. In spite of these efforts several aspects of its phase diagram remain unexplained. Here we use atomistic simulations to characterize the polymorphic phase diagram of Cu precipitates in body-centered cubic (BCC) Fe and establish a consistent link between their thermodynamic and mechanical properties in terms of thermal stability, shape, and strength. The size at which Cu precipitates transform from BCC to a close-packed 9R structure is found to be strongly temperature dependent, ranging from approximately 4 nm in diameter (˜2700atoms) at 200 K to about 8 nm (˜22800atoms) at 700 K. These numbers are in very good agreement with the interpretation of experimental data given Monzen [Philos. Mag. APMAADG0141-861010.1080/01418610008212077 80, 711 (2000)]. The strong temperature dependence originates from the entropic stabilization of BCC Cu, which is mechanically unstable as a bulk phase. While at high temperatures the transition exhibits first-order characteristics, the hysteresis, and thus the nucleation barrier, vanish at temperatures below approximately 300 K. This behavior is explained in terms of the mutual cancellation of the energy differences between core and shell (wetting layer) regions of BCC and 9R nanoprecipitates, respectively. The proposed mechanism is not specific for the Fe-Cu system but could generally be observed in immiscible systems, whenever the minority component is unstable in the lattice structure of the host matrix. Finally, we also study the interaction of precipitates with screw dislocations as a function of both structure and orientation. The results provide a coherent picture of precipitate strength that unifies previous calculations and experimental observations.

Erhart, Paul; Marian, Jaime; Sadigh, Babak

2013-07-01

261

Background Urease, one of the highly efficient known enzymes, catalyzes the hydrolysis of urea into ammonia and carbon dioxide. The present study aimed to extract urease from pea seeds (Pisum Sativum L). The enzyme was then purified in three consequence steps: acetone precipitation, DEAE-cellulose ion-exchange chromatography, and gel filtration chromatography (Sephacryl S-200 column). Results The purification fold was 12.85 with a yield of 40%. The molecular weight of the isolated urease was estimated by chromatography to be 269,000 Daltons. Maximum urease activity (190 U/g) was achieved at the optimum conditions of 40°C and pH of 7.5 after 5 min of incubation. The kinetic parameters, K m and V max , were estimated by Lineweaver-Burk fits and found to be 500 mM and 333.3 U/g, respectively. The thermodynamic constants of activation, ?H, E a , and ?S, were determined using Arrhenius plot and found to be 21.20 kJ/mol, 23.7 kJ/mol, and 1.18 kJ/mol/K, respectively. Conclusions Urease was purified from germinating Pisum Sativum L. seeds. The purification fold, yield, and molecular weight were determined. The effects of pH, concentration of enzyme, temperature, concentration of substrate, and storage period on urease activity were examined. This may provide an insight on the various aspects of the property of the enzyme. The significance of extracting urease from different sources could play a good role in understanding the metabolism of urea in plants. PMID:25065975

2014-01-01

262

NSDL National Science Digital Library

For engineering graduates entering the job market, experience with appropriate computational tools and techniques is increasingly necessary. Therefore, the University of Alabama's Mechanical Engineering Department is introducing students to computational problem solving earlier in their college careers by developing Microsoft Excel-based modules to be used as teaching tools in the sophomore and junior-level thermodynamics and heat transfer courses. The MS Excel package was chosen as a software platform for this purpose because of its ubiquitous nature and its ability to utilize Visual Basic for Applications (VBA) macros in a spreadsheet format. In the sophomore-level thermodynamics course, much of the class material focuses on the properties of steam and ideal gases. Therefore, a suite of Microsoft Excel functions to compute steam and ideal gas properties and assist in analyzing properties of states and processes has been developed. A number of Excel packages that pertained to the computation of steam properties were already available in the public domain. In a companion paper1, these packages were compared and Magnus Holmgrens Xsteam functions were chosen as a starting point for the current project.

Huguet, Jesse; Taylor, Robert; Woodbury, Keith

2011-05-09

263

NASA Astrophysics Data System (ADS)

In this study the pseudo-potential method is used to investigate the structural, electronic, and thermodynamic properties of ZnO1?xSx semiconductor materials. The results show that the electronic properties are found to be improved when calculated by using LDA + U functional as compared with local density approximation (LDA). At various concentrations the ground-state properties are determined for bulk materials ZnO, ZnS, and their tertiary alloys in cubic zinc-blende phase. From the results, a minor difference is observed between the lattice parameters from Vegard's law and other calculated results, which may be due to the large mismatch between lattice parameters of binary compounds ZnO and ZnS. A small deviation in the bulk modulus from linear concentration dependence is also observed for each of these alloys. The thermodynamic properties, including the phonon contribution to Helmholtz free energy ?F, phonon contribution to internal energy ?E, and specific heat at constant-volume CV, are calculated within quasi-harmonic approximation based on the calculated phonon dispersion relations.

Muhammad, Zafar; Shabbir, Ahmed; Shakil, M.; A. Choudhary, M.

2014-10-01

264

Unified approach to electronic, thermodynamical, and transport properties of Fe3Si and Fe3Al alloys

NASA Astrophysics Data System (ADS)

The electronic, thermodynamical, and transport properties of ordered Fe3X (X =Al,Si) alloys are studied from first principles. We present here a unified approach to the phase stability, the estimate of the Curie temperature, the temperature dependence of sublattice magnetizations, magnon spectra, the spin-stiffnesses, and residual resistivities. An important feature of the present study is that all calculated physical properties are determined in the framework of the same first-principles electronic structure model combined with the effective Ising and Heisenberg Hamiltonians used for study of the thermodynamical properties of alloys. Curie temperatures, spin-stiffnesses, and magnon spectra are determined using the same calculated exchange integrals. Finally, the transport properties are calculated using the linear-response theory. Our theoretical estimates compare well with available experimental data. In particular, calculations predict (in agreement with experiment) the ordered D03 phase as the ground-state alloy structure, demonstrate that a correct relation of Curie temperatures of Fe3Al/Fe3Si alloys can be obtained only by going beyond a simple mean-field approximation, provide reasonable estimates of spin-stiffnesses, and give resistivities compatible with structural disorder observed in the experiment. Although the calculated temperature dependences of the Fe magnetization on different sublattices are similar, they nevertheless deviate more than in the experiment, and we discuss a possible origin.

Kudrnovský, J.; Drchal, V.; Bergqvist, L.; Rusz, J.; Turek, I.; Újfalussy, B.; Vincze, I.

2014-10-01

265

The thermodynamic properties of 4,5,9,10-tetrahydropyrene and 1,2,3,6,7,8-hexahydropyrene

Measurements leading to the calculation of the ideal-gas thermodynamic properties are reported for 4,5,9,10-tetrahydropyrene and 1,2,3,6,7,8-hexahydropyrene. Experimental methods included combustion calorimetry, adiabatic heat-capacity calorimetry, vibrating-tube densitometry, comparative ebulliometry, inclined-piston gauge manometry, and differential-scanning calorimetry (d.s.c.). Critical properties were estimated for both materials based on the measurement results. Entropies, enthalpies, and Gibbs energies of formation were derived for the ideal gases for selected temperatures between 380 K and 700 K. The property-measurement results reported here for 4,5,9,10-tetrahydropyrene and 1,2,3,6,7,8-hexahydropyrene are the first for these important intermediates in the pyrene/H{sub 2} hydrogenation reaction network.

Chirico, R.D.; Knipmeyer, S.E.; Nguyen, A.; Smith, N.K.; Steele, W.V.

1992-12-01

266

NASA Astrophysics Data System (ADS)

This work is devoted to analyze the relation between the thermodynamic properties of a confined fluid and the shape of its confining vessel. Recently, new insights in this topic were found through the study of cluster integrals for inhomogeneous fluids that revealed the dependence on the vessel shape of the low density behavior of the system. Here, the statistical mechanics and thermodynamics of fluids confined in wedges or by edges is revisited, focusing on their cluster integrals. In particular, the well known hard sphere fluid, which was not studied in this framework so far, is analyzed under confinement and its thermodynamic properties are analytically studied up to order two in the density. Furthermore, the analysis is extended to the confinement produced by a corrugated wall. These results rely on the obtained analytic expression for the second cluster integral of the confined hard sphere system as a function of the opening dihedral angle 0 < ? < 2?. It enables a unified approach to both wedges and edges.

Urrutia, Ignacio

2014-12-01

267

This work is devoted to analyze the relation between the thermodynamic properties of a confined fluid and the shape of its confining vessel. Recently, new insights in this topic were found through the study of cluster integrals for inhomogeneous fluids that revealed the dependence on the vessel shape of the low density behavior of the system. Here, the statistical mechanics and thermodynamics of fluids confined in wedges or by edges is revisited, focusing on their cluster integrals. In particular, the well known hard sphere fluid, which was not studied in this framework so far, is analyzed under confinement and its thermodynamic properties are analytically studied up to order two in the density. Furthermore, the analysis is extended to the confinement produced by a corrugated wall. These results rely on the obtained analytic expression for the second cluster integral of the confined hard sphere system as a function of the opening dihedral angle 0 < ? < 2?. It enables a unified approach to both wedges and edges. PMID:25554179

Urrutia, Ignacio

2014-12-28

268

Cardiolipins (CLs) are important biologically for their unique role in biomembranes that couple phosphorylation and electron transport like bacterial plasma membranes, chromatophores, chloroplasts and mitochondria. CLs are often tightly coupled to proteins involved in oxidative phosphorylation. The first step in understanding the interaction of CL with proteins is to obtain the pure CL structure, and the structure of mixtures of CL with other lipids. In this work we use a variety of techniques to characterize the fluid phase structure, material properties and thermodynamics of mixtures of dimyristoylphosphatidylcholine (DMPC) with tetramyristoylcardiolipin (TMCL), both with 14-carbon chains, at several mole percentages. X-ray diffuse scattering was used to determine structure, including bilayer thickness and area/lipid, the bending modulus, KC, and Sxray, a measure of chain orientational order. Our results reveal that TMCL thickens DMPC bilayers at all mole percentages, with a total increase of ~6 Å in pure TMCL, and increases AL from 64 Å2 (DMPC at 35°C) to 109 Å2 (TMCL at 50°C). KC increases by ~50%, indicating that TMCL stiffens DMPC membranes. TMCL also orders DMPC chains by a factor of ~2 for pure TMCL. Coarse grain molecular dynamics simulations confirm the experimental thickening of 2 Å for 20 mol% TMCL and locate the TMCL headgroups near the glycerol-carbonyl region of DMPC; i.e., they are sequestered below the DMPC phosphocholine headgroup. Our results suggest that TMCL plays a role similar to cholesterol in that it thickens and stiffens DMPC membranes, orders chains, and is positioned under the umbrella of the PC headgroup. CL may be necessary for hydrophobic matching to inner mitochondrial membrane proteins. Differential scanning calorimetry, Sxray and CGMD simulations all suggest that TMCL does not form domains within the DMPC bilayers. We also determined the gel phase structure of TMCL, which surprisingly displays diffuse X-ray scattering, like a fluid phase lipid. AL = 40.8 Å2 for the ½TMCL gel phase, smaller than the DMPC gel phase with AL = 47.2 Å2, but similar to AL of DLPE = 41 Å2, consistent with untilted chains in gel phase TMCL. PMID:24378240

Boscia, Alexander L.; Treece, Bradley W.; Mohammadyani, Dariush; Klein-Seetharaman, Judith; Braun, Anthony R.; Wassenaar, Tsjerk A.; Klösgen, Beate; Tristram-Nagle, Stephanie

2014-01-01

269

NASA Astrophysics Data System (ADS)

The rheological and thermodynamic properties of silicate melts control fluid-dynamics of transport, eruption style and rates of physico-chemical processes (degassing and crystallization) in natural magmas. In this study we investigated the effect of H2O and CO2 on the liquid viscosity and heat capacity on several multicomponent systems. Measurements were conducted on four series of melts, obtained by remelting and homogenization of natural pantelleritic (Khaggiar dome, Pantelleria), trachytic (Agnano Monte Spina eruption, Phlegrean Fields), latitic (Fondo Riccio eruption, Phlegrean Fields) and trachybasaltic (Etna 1992 eruption) magmas. CO2 or H2O synthesis experiments were conducted in piston cylinder apparatus. The volatile -bearing samples were measured with a differential scanning calorimeter (DSC) and a vertical dilatometer (micropenetration technique). Water and CO2 content were measured by Karl Fisher Titration and FTIR spectroscopy. Compositions were analyzed over a range of water contents up to 5.3 wt% and CO2 content up to 4000 ppm. Viscosity ranged from 108 to 1013 Pa s with decreasing temperature from 630 to 1100 K. Viscosity is strongly affected by H2O and CO2. The effect of CO2 on viscosity appears to be a function of speciation and chemical composition. The heat capacity of glasses and liquids and the glass transition interval were also investigated. Base chemical composition have a strong influences on Tg: high alkali contents can lower Tg of low NBO/T liquids. This behavior is demonstrated by Pantellerite samples. Glass transition temperatures are also strongly affected by H2O and CO2. The CO2 effect, such as water, is to decrease Tg and it appears to be a function of chemical composition. We present data for partial molar CpH2Omol and CpOH- and derive a simple expression to evaluate the relative contributions of different H-bearing species to the total heat capacity of hydrous melts. Experimental viscosity and calorimetric data were fitted according to the Adam and Gibbs theory in which configurational entropy (Sconf) is the main factor controlling the viscosity of melts. From calorimetric measurements, and assuming that the vibrational contribution to the liquid Cp remains constant above Tg, we determined the configurational contribution to Cpliq and thus calculated the variation of the Sconf as a function of T, H2O and CO2 content in the liquid state. Combining viscosity measurements with the configurational entropies for our liquids, we parameterized the variation of viscosity as a function of temperature and volatiles content within the framework of the Adam and Gibbs theory of structural relaxation.

Di Genova, D.; Romano, C.; Alletti, M.; Behrens, H.; Scaillet, B.

2011-12-01

270

Rational design of ion force fields based on thermodynamic solvation properties

NASA Astrophysics Data System (ADS)

Most aqueous biological and technological systems contain solvated ions. Atomistic explicit-water simulations of ionic solutions rely crucially on accurate ionic force fields, which contain most commonly two adjustable parameters: the Lennard-Jones diameter and the interaction strength. Assuming these parameters to be properly optimized, the plethora of parameters one finds in the literature for one and the same ion is surprising. In principle, the two parameters should be uniquely determined by matching two ionic properties obtained for a particular water model and within a given simulation protocol with the corresponding experimental observables. Traditionally, ion parameters were chosen in a somewhat unsystematic way to reproduce the solvation free energy and to give the correct ion size when compared with scattering results. Which experimental observable one chooses to reproduce should in principle depend on the context within which the ionic force field is going to be used. In the present work we suggest to use the solvation free energy in conjunction with the solvation entropy to construct thermodynamically sound force fields for the alkali and halide ions for the simulation of ion-specific effects in aqueous environment. To that end we determine the solvation free energy and entropy of both cations and anions in the entire relevant parameter space. As an independent check on the quality of the resulting force fields we also determine the effective ionic radius from the first peak of the radial ion-water distribution function. Several difficulties during parameter optimization are discussed in detail. (i) Single-ion solvation depends decisively on water-air surface properties, which experimentally becomes relevant when introducing extrathermodynamic assumptions on the hydronium (H3O+) solvation energy. Fitting ion pairs circumvents this problem but leaves the parameters of one reference ion (here we choose chloride) undetermined. (ii) For the halides the problem is almost underdetermined, i.e., there is a whole set of degenerate parameters that equally well describe, e.g., chloride and bromide ions. (iii) For the heavy cations the problem is overdetermined, i.e., no combination of Lennard-Jones parameters is able to reproduce simultaneously energy and entropy of solvation. We discuss various possibilities to deal with these problems and finally present an optimized force field for the halide anions that reproduces the free energy and the entropy of solvation. For the alkali metal cations there is no unambiguous choice of parameters. Therefore, we give three different parameter sets for every ion with a small, intermediate, or large Lennard-Jones interaction strength, where the Lennard-Jones diameters are optimized to reproduce the solvation free energy. The ionic radius is reproduced with acceptable accuracy by this optimization strategy, meaning that the proposed force fields are reliable beyond the target observables (i.e., free energy and entropy of solvation).

Horinek, Dominik; Mamatkulov, Shavkat I.; Netz, Roland R.

2009-03-01

271

NASA Astrophysics Data System (ADS)

Anisotropy and temperature dependence of structural, thermodynamic and elastic properties of crystalline cellulose I? were computed with first-principles density functional theory (DFT) and a semi-empirical correction for van der Waals interactions. Specifically, we report the computed temperature variation (up to 500 K) of the monoclinic cellulose I? lattice parameters, constant pressure heat capacity, Cp, entropy, S, enthalpy, H, the linear thermal expansion components, ?i, and components of the isentropic and isothermal (single crystal) elastic stiffness matrices, CijS (T) and CijT (T) , respectively. Thermodynamic quantities from phonon calculations computed with DFT and the supercell method provided necessary inputs to compute the temperature dependence of cellulose I? properties via the quasi-harmonic approach. The notable exceptions were the thermal conductivity components, ?i (the prediction of which has proven to be problematic for insulators using DFT) for which the reverse, non-equilibrium molecular dynamics approach with a force field was applied. The extent to which anisotropy of Young's modulus and Poisson's ratio is temperature-dependent was explored in terms of the variations of each with respect to crystallographic directions and preferred planes containing specific bonding characteristics (as revealed quantitatively from phonon force constants for each atomic pair, and qualitatively from charge density difference contours). Comparisons of the predicted quantities with available experimental data revealed reasonable agreement up to 500 K. Computed properties were interpreted in terms of the cellulose I? structure and bonding interactions.

Dri, Fernando L.; Shang, ShunLi; Hector, Louis G., Jr.; Saxe, Paul; Liu, Zi-Kui; Moon, Robert J.; Zavattieri, Pablo D.

2014-12-01

272

In this paper, we describe the analysis of the thermodynamic properties of cryogenic hydrogen using classical molecular dynamics (MD) and path integral MD (PIMD) method to understand the effects of the quantum nature of hydrogen molecules. We performed constant NVE MD simulations across a wide density–temperature region to establish an equation of state (EOS). Moreover, the quantum effect on the difference of molecular mechanism of pressure–volume–temperature relationship was addressed. The EOS was derived based on the classical mechanism idea only using the MD simulation results. Simulation results were compared with each MD method and experimental data. As a result, it was confirmed that although the EOS on the basis of classical MD cannot reproduce the experimental data of saturation property of hydrogen in the high-density region, the EOS on the basis of PIMD well reproduces those thermodynamic properties of hydrogen. Moreover, it was clarified that taking quantum effects into account makes the repulsion force larger and the potential well shallower. Because of this mechanism, the intermolecular interaction of hydrogen molecules diminishes and the virial pressure increases.

Nagashima, H., E-mail: nagashima@nanoint.ifs.tohoku.ac.jp [School of Engineering, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577 (Japan); Tsuda, S. [Department of Mechanical Systems Engineering, Shinshu University, Nagano 380-8553 (Japan)] [Department of Mechanical Systems Engineering, Shinshu University, Nagano 380-8553 (Japan); Tsuboi, N. [Department of Mechanical and Control Engineering, Kyushu Institute of Technology, Kitakyushu 804-8550 (Japan)] [Department of Mechanical and Control Engineering, Kyushu Institute of Technology, Kitakyushu 804-8550 (Japan); Koshi, M. [Graduate School of Environment and Information Science, Yokohama National University, Yokohama 240-8501 (Japan)] [Graduate School of Environment and Information Science, Yokohama National University, Yokohama 240-8501 (Japan); Hayashi, K. A. [Department of Mechanical Engineering, Aoyama Gakuin University, Sagamihara 229-8558 (Japan)] [Department of Mechanical Engineering, Aoyama Gakuin University, Sagamihara 229-8558 (Japan); Tokumasu, T. [Institute of Fluid Science, Tohoku University, Sendai 980-8577 (Japan)] [Institute of Fluid Science, Tohoku University, Sendai 980-8577 (Japan)

2014-04-07

273

NASA Astrophysics Data System (ADS)

In this paper, a theoretical method has been introduced for developing the crossover Peng-Robinson (CPR) equation of state (EoS) which incorporates the non-classical scaling laws asymptotically near the critical point into a classical analytic equation further away from the critical point. The CPR EoS has been adopted to describe the thermodynamic properties of some pure fluids (normal alkanes from methane to n-butane and carbon dioxide) such as density, saturated pressure, isochoric heat capacity and speed of sound. Unlike the original method for the crossover transformation made by Chen et al. (Phys Rev A 42:4470-4484, 1990), we have proposed a procedure which adding an additional term into the crossover transformation to obtain the thermophysical properties at the critical point more exactly. It is shown that this new crossover method yields a satisfactory representation of the thermodynamic properties close to the critical point for pure fluids relative to the original PR EoS.

Behnejad, Hassan; Cheshmpak, Hashem; Jamali, Asma

2015-01-01

274

NASA Astrophysics Data System (ADS)

Amylose, a major component of starch, is one of the most important biopolymers, being mainly associated with the pharmacological and food industries. Although widely studied, a complete control and understanding of the physical properties of amylose is still lacking. It is well known that structure and phase transition are important aspects of the functionality of biopolymers since they influence physical attributes such as appearance, digestibility, water holding capacity, etc. In the past, we have studied polyethylene phase composition by DSC in a very slow temperature (T) ramp (1K/h) and have demonstrated the presence and importance of short-range order on the polymer and its characteristics. In this study, we evaluated the phase composition of potato amylose and associated the thermodynamic properties with the presence of short-range order. Two methods were correlated, DSC (in a 1K/h T-ramp) and FTIR as a function of temperature, also in a 1K/h T-ramp. The effects of the various phases on thermodynamic properties such as gelation and enzyme or chemical resistance are discussed.

Bernazzani, Paul; Delmas, Genevieve

1998-03-01

275

The influence of 3d-metal alloy additions on the elastic and thermodynamic properties of CuPd3

NASA Astrophysics Data System (ADS)

Embedded-atom method (EAM) potentials are used to investigate the effects of alloying (e.g. 3d-metals) on the trends of elastic and thermodynamic properties for CuPd3 alloy. Our calculated lattice parameter, cohesive energy, and elastic constants of CuPd3 are consistent with the available experimental and theoretical data. The results of elastic constants indicate that all these alloys are mechanically stable. Further mechanical behavior analysis shows that the additions of Cr, Fe, Co, and Ni could improve the hardness of CuPd3 while V could well increase its ductility. Moreover, in order to evaluate the thermodynamic contribution of 3d-metals, the Debye temperature, phonon density of states, and vibrational entropy for CuMPd6 alloy are also investigated.

Huang, Shuo; Zhang, Chuan-Hui; Sun, Jing; Shen, Jiang

2013-08-01

276

Thermodynamic properties of carbon in b.c.c. and f.c.c. iron-silicon-carbon solid solutions.

NASA Technical Reports Server (NTRS)

The equilibrium between hydrogen-methane gas mixtures and Fe-Si-C solid solutions has been investigated both as a function of temperature and carburizing gas composition. The thermodynamic properties of the carbon atoms in both b.c.c. and f.c.c. solid solution have been derived from the equilibrium measurements. The results found have been compared with those of earlier investigations and with the predictions of recent theoretical models on ternary solid solutions containing both substitutional and interstitial solute atoms.

Chraska, P.; Mclellan, R. B.

1971-01-01

277

A Monte Carlo simulation is carried out to study thermodynamic properties of Cu-Au alloys using a face-centered-cubic (fcc) lattice-gas model. To obtain quantitatively accurate results, a Finnis-Sinclair-type potential, which has been widely used for molecular dynamics (MD) simulations, is employed. To overcome some shortcomings of lattice-gas models such as neglecting vibrational entropy, the potential is mapped onto the fcc lattice using the renormalization technique. The renormalized potential gives an improved Cu-Au phase diagram compared to the original MD potential applied directly on the lattice. PMID:15267866

Sahara, Ryoji; Ichikawa, Hiroshi; Mizuseki, Hiroshi; Ohno, Kaoru; Kubo, Hiroshi; Kawazoe, Yoshiyuki

2004-05-15

278

First-principles investigation of the elastic and thermodynamic properties of ReC2 (Re = Ho, Nd, Pr)

NASA Astrophysics Data System (ADS)

The elastic and thermodynamic properties of ReC2 (Re = Ho, Nd, Pr) have been investigated by using the first-principles density functional theory within the generalized gradient approximation. The computed lattice constants of ReC2 are in agreement with the experimental data. The calculated elastic constants reveal that all compounds are mechanically stable. The shear modulus, Young's modulus, Poisson's ratio ?, the ratio B/G, shear anisotropy and elastic anisotropy are also calculated. Finally, the Vicker hardness, Debye temperature, melting point and thermal conductivity have been predicted.

Huang, Wen; Chen, Haichuan

2015-01-01

279

On thermodynamic and dielectric properties of PbHPO4 and PbHAsO4 crystals

NASA Astrophysics Data System (ADS)

Thermodynamic and dielectric properties of PbHPO4 and PbHAsO4 crystals are studied using the pseudo-spin model for proton subsystem within a two-particle cluster approximation neglecting the proton tunneling on hydrogen bonds. Temperature dependence of spontaneous polarization, heat capacity, static dielectric permittivity and dielectric dispersion in wide frequency range is calculated for both compounds in two structural phases. At a proper set of model parameters, a good quantitative description of the corresponding experimental data is obtained.

Zachek, I. R.; Shchur, Ya.; Levitskii, R. R.; Bilenka, O. B.

2014-11-01

280

NASA Astrophysics Data System (ADS)

The thermodynamic and thermo-elastic properties of ductility intermetallic compounds DyCu with B2 structure are investigated with molecular dynamics. The calculated structural properties are in reasonable agreement with the available experimental and previously calculated data. At 300 K, the heat capacity of DyCu is 23.93 J mol-1 K-1. At the whole range 0-900 K, the elastic constants decrease with increasing temperature, and satisfy the stability criterions for DyCu compound. The value of B/G ratio for DyCu is greater than 1.75 implying the DyCu intermetallics are ductile, and increases with elevating temperature. Our results mean that the ductility of DyCu can be improved by increasing temperature.

Wu, Yurong; Xu, Longshan; Hu, Wangyu

2015-02-01

281

NASA Astrophysics Data System (ADS)

The phonon and thermodynamic properties of aluminum-rare-earth (AlRE, RE = Y, Gd, Pr, Yb) intermetallics with B2-type structure are investigated by performing density functional theory and density functional perturbation theory calculations within the quasiharmonic approximation. The phonon spectra and phonon density of states, including the phonon partial density of states and total density of states, are discussed. Our results demonstrate that the density of states is mostly composed of Al states at high frequency. The temperature dependences of various quantities such as thermal expansion, heat capacities at constant volume and pressure, the isothermal bulk modulus and the entropy are obtained. The electronic contribution to specific heat is discussed, and the present results show that the thermal electronic excitation affecting the thermal properties is inessential.

Wang, Rui; Wang, Shaofeng; Wu, Xiaozhi; Lan, Mingjian; Song, Tingting

2012-03-01

282

Impact of aerosols and atmospheric thermodynamics on cloud properties within the climate system

019287. 1. Introduction [2] Maritime low clouds, denoted hereafter as stratus, reduce the Earth's energy emission and the reflection of solar radiation [Hartmann et al., 1992]. This large impact of stratus properties of stratus. [3] Stratus amount is, in particular, positively correlated with lower

Pielke, Roger A.

283

Lead-free solder alloys: Thermodynamic properties of the (Au + Sb + Sn) and the (Au + Sb) system

The thermodynamic properties of liquid (Au–Sb–Sn) alloys were studied with an electromotive force (EMF) method using the eutectic mixture of KCl/LiCl with addition of SnCl2 as a liquid electrolyte. Activities of Sn in the liquid alloys were measured at three cross-sections with constant molar ratios of Au:Sb = 2:1, 1:1, and 1:2 with tin in the concentration range between 5 at.% and 90 at.% from the liquidus of the samples up to 1073 K. The integral Gibbs excess energies and the integral enthalpies at 873 K were calculated by Gibbs–Duhem integration. Additionally liquid Au–Sb alloys have been measured at 913 K with the EMF method as no reliable data for the Gibbs excess energies have been found in literature. The eutectic mixture of KCl/LiCl with addition of SbCl3 has been used as an electrolyte for the measurements. The Gibbs excess energies from the (Au + Sb) system were necessary for the integration of the thermodynamic properties of the ternary (Au + Sb + Sn) system. PMID:24926101

Hindler, Michael; Guo, Zhongnan; Mikula, Adolf

2012-01-01

284

Lead-free solder alloys: Thermodynamic properties of the (Au + Sb + Sn) and the (Au + Sb) system.

The thermodynamic properties of liquid (Au-Sb-Sn) alloys were studied with an electromotive force (EMF) method using the eutectic mixture of KCl/LiCl with addition of SnCl2 as a liquid electrolyte. Activities of Sn in the liquid alloys were measured at three cross-sections with constant molar ratios of Au:Sb = 2:1, 1:1, and 1:2 with tin in the concentration range between 5 at.% and 90 at.% from the liquidus of the samples up to 1073 K. The integral Gibbs excess energies and the integral enthalpies at 873 K were calculated by Gibbs-Duhem integration. Additionally liquid Au-Sb alloys have been measured at 913 K with the EMF method as no reliable data for the Gibbs excess energies have been found in literature. The eutectic mixture of KCl/LiCl with addition of SbCl3 has been used as an electrolyte for the measurements. The Gibbs excess energies from the (Au + Sb) system were necessary for the integration of the thermodynamic properties of the ternary (Au + Sb + Sn) system. PMID:24926101

Hindler, Michael; Guo, Zhongnan; Mikula, Adolf

2012-12-01

285

NASA Astrophysics Data System (ADS)

The structural, electronic, optical and thermodynamic properties of Mg1-xSrxO ternary alloys in NaCl structures at various Sr concentrations are presented. The calculations were performed using the full potential linearized augmented plane wave (FP-LAPW) method within the density functional theory (DFT) in the local density approximation (LDA) and two developed refinements, namely the generalized gradient approximation (GGA) of Perdew et al (1996 Phys. Rev. Lett. 77 3865) for the structural properties and Engel and Vosko (1993 Phys. Rev. B 47 13164) for the band structure calculations. Deviation of the lattice constants from Vegard's law and the bulk modulus from the linear concentration dependence (LCD) were observed for the alloys. The microscopic origins of the gap bowing were explained by using the approach of Bernard and Zunger (1986 Phys. Rev. Lett. 34 5982). The refractive index and optical dielectric constant for the alloys of interest were calculated by using different models. In addition, the thermodynamic stability of the alloys was investigated by calculating the critical temperatures of alloys.

Labidi, M.; Labidi, S.; Ghemid, S.; Meradji, H.; El Haj Hassan, F.

2010-10-01

286

NASA Astrophysics Data System (ADS)

First-principles calculations are used to investigate the mechanical and thermodynamic properties of cubic YH2 at different pressures and temperatures. The generalized gradient approximation (GGA) with Perdew-Burke-Ernzerhof (PBE) method is used to describe the exchange-correlation energy in the present work. The calculated equilibrium lattice constant a and bulk modulus B are in good accordance with the available experimental values. According to the Born-Huang criteria for mechanical stability, elastic constants are calculated from the strain-induced stress method in a pressure range from 0 to 67.1 GPa. Isotropic wave velocities and sound velocities are discussed in detail. It is found that the Debye temperature decreases monotonically with the increase of pressure and that YH2 has low anisotropy in both longitudinal and shear-wave velocities. The calculated elastic anisotropic factors indicate that YH2 has low anisotropy at zero pressure and that its elastic anisotropy increases as pressure increases. Through the quasi-harmonic Debye model, in which phononic effects are considered, the thermodynamic properties of YH2, such as the relations of (V-V0)/V0 to the temperature and the pressure, the dependences of heat capacity Cv and thermal expansion coefficient ? on temperature and pressure ranging from 0 to 2400 K and from 0 to 65 GPa, respectively, are also discussed.

Li, Zhen-Li; Cheng, Xin-Lu

2014-04-01

287

Knowledge of the thermodynamic and morphological properties of coal associated with rapid heating decomposition pathways is essential to progress in coal utilization technology. Specifically, knowledge of the heat of devolatilization, surface area and density of coal as a function of rank characteristics, temperature and extent of devolatilization in the context of rapid heating conditions is required both, for the fundamental determination of kinetic parameters of coal devolatilization, and to refine existing devolatilization sub-models used in comprehensive coal combustion codes. The objective of this research is to obtain data on the thermodynamic properties and morphology of coal under conditions of rapid heating. Specifically, the total heat of devolatilization, external surface area, BET surface area and true density will be measured for representative coal samples. In addition, for one coal, the contribution of each of the following components to the overall heat of devolatilization will be measured: the specific heat of coal/char during devolatilization, the heat of thermal decomposition of the coal, the specific heat capacity of tars, and the heat of vaporization of tars. Calibration of the heated grid calorimeter (Task 2) was completed this reporting period. Several refinements to the heated grid apparatus have been implemented which allow quantitative determination of sample heat capacity at high heating rates.

Proscia, W.M.; Freihaut, J.D.

1993-03-01

288

Kinetic and Statistical Thermodynamical Package (KiSThelP) is a cross-platform free open-source program developed to estimate molecular and reaction properties from electronic structure data. To date, three computational chemistry software formats are supported (Gaussian, GAMESS, and NWChem). Some key features are: gas-phase molecular thermodynamic properties (offering hindered rotor treatment), thermal equilibrium constants, transition state theory rate coefficients (transition state theory (TST), variational transition state theory (VTST)) including one-dimensional (1D) tunnelling effects (Wigner, and Eckart) and Rice-Ramsperger-Kassel-Marcus (RRKM) rate constants, for elementary reactions with well-defined barriers. KiSThelP is intended as a working tool both for the general public and also for more expert users. It provides graphical front-end capabilities designed to facilitate calculations and interpreting results. KiSThelP enables to change input data and simulation parameters directly through the graphical user interface and to visually probe how it affects results. Users can access results in the form of graphs and tables. The graphical tool offers customizing of 2D plots, exporting images and data files. These features make this program also well-suited to support and enhance students learning and can serve as a very attractive courseware, taking the teaching content directly from results in molecular and kinetic modelling. PMID:24190715

Canneaux, Sébastien; Bohr, Frédéric; Henon, Eric

2014-01-01

289

Cements are being considered for sealing boreholes, shafts, and tunnels in nuclear waste repositories. The phases which will be stable in the long run are those which have the lowest free energies under repository conditions. In order to identify these phases, the relevant thermodynamic literature has been reviewed and evaluated, and some calculations of thermodynamic properties have been made for plausible repository conditions. Best values of heats, entropies, and free energies of formation are presented for calcium silicates, aluminates, and ferrites. Data for C-S-H gel are presented, considering the gel to have a composition of Ca/sub 3/Si/sub 2/O/sub 7/.3H/sub 2/O, and compared to the data for comparable crystalline phases. Equations and thermodynamic properties, including temperature dependence, are given for the hydration of cement components. Calculations for specific reactions show that hydration of tricalcium silicate should produce hillebrandite, 2CaO.SiO/sub 2/.1.17H/sub 2/O; the presence of excess silica should make higher-silica phases such as hillebrandite, tobermorite, or others more stable. The equilibrium between tobermorite, 5CaO.6SiO/sub 2/.5.5H/sub 2/O, and xonotlite, 6CaO.6SiO/sub 2/.H/sub 2/O, was calculated. Calculations of free energy of reaction of aqueous ions with tricalcium aluminate to form salts show that under normal atmospheric pressure and temperature Friedel's salt, the tricalcium aluminate monochloride hydrate, is stable both in typical brines and in a basalt groundwater. Similarly, in a brine from Los Medanos in the Delaware Basin of New Mexico, the tricalcium aluminate trisulfate-hydrate ettringite is stable with respect to tricalcium aluminate and to tricalcium aluminate monosulfate hydrate, but not with respect to hydrogarnet (tricalcium aluminate hexahydrate). 3 figures, 23 tables.

Sarkar, A.K.; Barnes, M.W.; Roy, D.M.

1982-09-01

290

NASA Astrophysics Data System (ADS)

The structural, electronic thermodynamic and thermal properties of BaxSr1-xTe ternary mixed crystals have been studied using the ab initio full-potential linearized augmented plane wave (FP-LAPW) method within density functional theory (DFT). In this approach, the Perdew-Burke-Ernzerhof-generalized gradient approximation (PBE-GGA) was used for the exchange-correlation potential. Moreover, the recently proposed modified Becke Johnson (mBJ) potential approximation, which successfully corrects the band-gap problem was also used for band structure calculations. The ground-state properties are determined for the cubic bulk materials BaTe, SrTe and their mixed crystals at various concentrations (x = 0.25, 0.5 and 0.75). The effect of composition on lattice constant, bulk modulus and band gap was analyzed. Deviation of the lattice constant from Vegard's law and the bulk modulus from linear concentration dependence (LCD) were observed for the ternary BaxSr1-xTe alloys. The microscopic origins of the gap bowing were explained by using the approach of Zunger and co-workers. On the other hand, the thermodynamic stability of these alloys was investigated by calculating the excess enthalpy of mixing, ?Hm as well as the phase diagram. It was shown that these alloys are stable at high temperature. Thermal effects on some macroscopic properties of BaxSr1-xTe alloys were investigated using the quasi-harmonic Debye model, in which the phononic effects are considered.

Chelli, S.; Meradji, H.; Amara Korba, S.; Ghemid, S.; El Haj Hassan, F.

2014-12-01

291

THE ELASTIC AND THERMODYNAMIC PROPERTIES OF Lu DOPED ScVO3

NASA Astrophysics Data System (ADS)

We have investigated the elastic, cohesive and thermal properties of (Lu, Sc) VO3 and Sc1-xLuxVO3(0.6 ? x ? 0.9) perovskites by means of a modified rigid ion model (MRIM). The variation of specific heat is determined following the temperature driven structural phase transitions. Also, the effect of lattice distortions on the elastic and thermal properties of the present pure and doped vanadates has been studied by an atomistic approach. The calculated bulk modulus (BT), reststrahlen frequency (?0), cohesive energy (?), Debye temperature (?D) and Gruneisen parameter (?) reproduce well with the corresponding experimental data. The specific heat results can further be improved by including the magnetic ordering contributions to the specific heat.

Parveen, Atahar; Gaur, N. K.

2012-12-01

292

Structural, thermodynamic, mechanical, and magnetic properties of FeW system

NASA Astrophysics Data System (ADS)

The Fe-W system is systematically investigated through a combined use of first-principles calculation, cluster expansion, special quasirandom structures, and experiments. It is revealed that the ferromagnetic state of BCC Fe-W solid solution has lower heat of formation than its nonmagnetic state within the entire composition range, and intermetallic ?-Fe2W and ?-Fe7W6 phases are energetically favorable with negative heats of formation. Calculations also show that the Fe-W solid solution has much lower coefficient of thermal expansion than its mechanical mixture, and that the descending sequence of temperature-dependent elastic moduli of each Fe-W solid solution is E > G > B. Moreover, magnetic state should have an important effect on mechanical properties of Fe-W phases, and electronic structures can provide a deeper understanding of various properties of Fe-W. The derived results agree well with experimental observations, and can clarify two experimental controversies regarding structural stability and magnetic property of Fe-W phases in the literature.

Ren, Q. Q.; Fan, J. L.; Han, Y.; Gong, H. R.

2014-09-01

293

NASA Astrophysics Data System (ADS)

Molecular dynamics simulations are performed with a new ab initio neon—neon pair potential for pressures between 20 and 1000 MPa and temperatures between 100 and 600 K in the supercritical phase as well as for a point in the liquid phase of neon. Many properties, such as the pair distribution function g, the enthalpy H, the internal energy U, the molar heat capacities CV,m and CP,m, the speed of sound c, the adiabetic and isothermal compressibilities ? S and ? T, the thermal pressure coefficient ? V, the differential Joule-Thompson coefficient ?, the self-diffusion coefficient D, the thermal conductivity ? and the shear viscosity ?, are calculated and compared to the values obtained with a previous ab initio potential, to see the influence of the improvement in the quantum chemical calculation of the potential curve on the different properties. The typical deviations from experimental values, where available, are below 5% in the supercritical state. For several properties where experimental data are not available the calculated values give reliable predictions. For the liquid the errors are much larger, partially due to quantum effects, but probably also due to the stronger influence of the neglected many-body interactions and of the remaining errors in the two-particle potential.

Eggenberger, Rolf; Huber, Hanspeter; Welker, Marc

1994-10-01

294

NASA Astrophysics Data System (ADS)

The equilibrium compositions and thermodynamic properties of SF6–Cu mixtures with copper proportions up to 50% are calculated as a function of temperature from 300 to 30?000?K and pressure from 0.01 to 1.0?MPa. The condensed phases and Debye–Hückel corrections are both taken into account. The influences of condensed phases, Debye–Hückel corrections, copper proportions and gas pressures on the composition and/or thermodynamic properties are discussed in detail under various conditions. Some results are tabulated for the modelling of SF6 arc plasmas contaminated by Cu.

Rong, Mingzhe; Zhong, Linlin; Cressault, Yann; Gleizes, Alain; Wang, Xiaohua; Chen, Feng; Zheng, Hao

2014-11-01

295

NASA Astrophysics Data System (ADS)

A versatile code DLAYZ based on collisional-radiative model is developed for investigating the population kinetics and radiative properties of plasmas in non-local thermodynamic equilibrium. DLAYZ is implemented on the detailed level accounting (DLA) approach and can be extended to detailed configuration accounting (DCA) and hybrid DLA/DCA approaches. The code can treat both steady state and time-dependent problems. The implementation of the main modules of DLAYZ is discussed in detail including atomic data, rates, population distributions and radiative properties modules. The complete set of basic atomic data is obtained using relativistic quantum mechanics. For dense plasmas, the basic atomic data with plasma screening effects can be obtained. The populations are obtained by solving the coupled rate equations, which are used to calculate the radiative properties. A parallelized version is implemented in the code to treat the large-scale rate equations. Two illustrative examples of a steady state case for carbon plasmas and a time-dependent case for the relaxation of a K-shell excited argon are employed to show the main features of the present code.

Gao, Cheng; Zeng, Jiaolong; Li, Yongqiang; Jin, Fengtao; Yuan, Jianmin

2013-09-01

296

Thermodynamic and kinetic properties of the Li-graphite system from first-principles calculations

We present an ab initio study of the thermodynamics and kinetics of Li [subscript x]C[subscript 6], relevant for anode Li intercalation in rechargeable Li batteries. In graphite, the interlayer interactions are dominated ...

Ceder, Gerbrand

297

A comprehensive investigation of the structural, elastic, and thermodynamic properties for Laves-phases ZrZn{sub 2} and HfZn{sub 2} are conducted using density functional total energy calculations combined with the quasi-harmonic Debye model. The optimized lattice parameters of ZrZn{sub 2} and HfZn{sub 2} compare well with available experimental values. We estimated the mechanical behaviors of both compounds under compression, including mechanical stability, Young's modulus, Poisson's ratio, ductility, and anisotropy. Additionally, the thermodynamic properties as a function of pressure and temperature are analyzed and found to be in good agreement with the corresponding experimental data.

Sun, Na; Zhang, Xinyu, E-mail: jiaqianqin@gmail.com; Ning, Jinliang; Zhang, Suhong; Liang, Shunxing; Ma, Mingzhen; Liu, Riping [State Key Laboratory of Metastable Materials Science and Technology, Yanshan University, Qinhuangdao 066004 (China); Qin, Jiaqian, E-mail: jiaqianqin@gmail.com [Metallurgy and Materials Science Research Institute, Chulalongkorn University, Bangkok 10330 (Thailand)

2014-02-28

298

NASA Astrophysics Data System (ADS)

The authors report calculations of the intermolecular potential of mean force (PMF) in the case of the host-guest interaction. The host-guest system is defined by a water soluble calixarene and a cation. With an organic cation such as the tetramethylammonium cation, the calixarene forms an insertion complex, whereas with the Lanthane cation, the supramolecular assembly is an outer-sphere complex. The authors apply a modified free energy perturbation method and the force constraint technique to establish the PMF profiles as a function of the separation distance between the host and guest. They use the PMF profile for the calculation of the absolute thermodynamic properties of association that they compare to the experimental values previously determined. They finish by giving some structural features of the insertion and outer-sphere complexes at the Gibbs free energy minimum.

Ghoufi, Aziz; Malfreyt, Patrice

2006-12-01

299

It is generally accepted that current technologies for capturing CO{sub 2} are still too energy intensive. Hence, there is a critical need for development of new materials that can capture CO{sub 2} reversibly with acceptable energy costs. Accordingly, solid sorbents have been proposed to be used for CO{sub 2} capture applications through a reversible chemical transformation. By combining thermodynamic database mining with first principles density functional theory and phonon lattice dynamics calculations, a theoretical screening methodology to identify the most promising CO{sub 2} sorbent candidates from the vast array of possible solid materials has been proposed and validated. The calculated thermodynamic properties of different classes of solid materials versus temperature and pressure changes were further used to evaluate the equilibrium properties for the CO{sub 2} adsorption/desorption cycles. According to the requirements imposed by the pre- and post- combustion technologies and based on our calculated thermodynamic properties for the CO{sub 2} capture reactions by the solids of interest, we were able to screen only those solid materials for which lower capture energy costs are expected at the desired pressure and temperature conditions. These CO{sub 2} sorbent candidates were further considered for experimental validations. In this presentation, we first introduce our screening methodology with validating by solid dataset of alkali and alkaline metal oxides, hydroxides and bicarbonates which thermodynamic properties are available. Then, by studying a series of lithium silicates, we found that by increasing the Li{sub 2}O/SiO{sub 2} ratio in the lithium silicates their corresponding turnover temperatures for CO{sub 2} capture reactions can be increased. Compared to anhydrous K{sub 2}CO{sub 3}, the dehydrated K{sub 2}CO{sub 3}?1.5H{sub 2}O can only be applied for post-combustion CO{sub 2} capture technology at temperatures lower than its phase transition (to anhydrous phase) temperature, which depends on the CO{sub 2} pressure and the steam pressure with the best range being PH{sub 2}O?1.0 bar. Above the phase-transition temperature, the sorbent will be regenerated into anhydrous K{sub 2}CO{sub 3}. Our theoretical investigations on Na-promoted MgO sorbents revealed that the sorption process takes place through formation of the Na{sub 2}Mg(CO{sub 3}){sub 2} double carbonate with better reaction kinetics over porous MgO, that of pure MgO sorbent. The experimental sorption tests also indicated that the Na-promoted MgO sorbent has high reactivity and capacity towards CO{sub 2} sorption and can be easily regenerated either through pressure or temperature swing processes.

Duan, Yuhua; Luebke, David; Pennline, Henry; Li, Liyu; King, David; Zhang; Keling; Zhao; Lifeng; Xiao, Yunhan

2012-01-01

300

NASA Astrophysics Data System (ADS)

The formation of intrinsic vacancy defects in barium hafnate, BaHfO3 and their corresponding electronic structures have been investigated using first-principles calculations. The thermodynamics of pristine and vacancy defects containing barium hafnate have been analyzed. Formation energies for neutral and fully charged Ba, Hf and O vacancies have been evaluated for determining their stability with respect to different chemical environments. From the calculated electronic structure and density of states, it is found that cation deficient barium hafnate is hole-doped, while the incorporation of oxygen vacancy retains the insulating nature of this material. The defect reaction energies for partial and full Schottky reactions are also computed, which controls the properties of non-stoichiometric barium hafnate.

Alay-e-Abbas, S. M.; Shaukat, A.

2014-10-01

301

The formation of intrinsic vacancy defects in barium hafnate, BaHfO3 and their corresponding electronic structures have been investigated using first-principles calculations. The thermodynamics of pristine and vacancy defects containing barium hafnate have been analyzed. Formation energies for neutral and fully charged Ba, Hf and O vacancies have been evaluated for determining their stability with respect to different chemical environments. From the calculated electronic structure and density of states, it is found that cation deficient barium hafnate is hole-doped, while the incorporation of oxygen vacancy retains the insulating nature of this material. The defect reaction energies for partial and full Schottky reactions are also computed, which controls the properties of non-stoichiometric barium hafnate. PMID:25300032

Alay-e-Abbas, S M; Shaukat, A

2014-10-29

302

Iron monosilicides (FeSi) is an important material with very interesting properties that can be harnessed for technological applications. Our attention has been drawn to the so-called first principle study of the electronic and thermodynamic properties of B2-FeSi by Zhao et al. (Physica B 406 (2011) 363-367) using pseudopotential plane wave method. They reported that FeSi in B2 phase is a

E. C. Ekuma

2011-01-01

303

NASA Technical Reports Server (NTRS)

Reaction rate coefficients and thermodynamic and transport properties are provided for the 11-species air model which can be used for analyzing flows in chemical and thermal nonequilibrium. Such flows will likely occur around currently planned and future hypersonic vehicles. Guidelines for determining the state of the surrounding environment are provided. Approximate and more exact formulas are provided for computing the properties of partially ionized air mixtures in such environments.

Gupta, Roop N.; Yos, Jerrold M.; Thompson, Richard A.

1989-01-01

304

A modified Benedict–Webb–Rubin (MBWR) equation of state has been developed for R152a (1,1-difluoroethane). The correlation is based on a selection of available experimental thermodynamic property data. Single-phase pressure–volume–temperature (PVT), heat capacity, and sound speed data, as well as second virial coefficient, vapor pressure, and saturated liquid and saturated vapor density data, were used with multi-property linear least-squares fitting to determine

Stephanie L. Outcalt; Mark O. McLinden

1996-01-01

305

Analysis of elevated temperature data for thermodynamic properties of selected radionuclides

This report is a review of chemical thermodynamic data for Ni, Zr, Tc, U, Np, Pu and Am in aqueous solutions at elevated temperatures. Thermodynamic data for aqueous reactions over the temperature range 20-150{degrees}C are needed for geochemical modeling studies of the Yucca Mountain Project. The present review is focused on the aqueous complexes relevant to expected conditions in the Yucca Mountain region: primarily the hydroxide, carbonate, sulfate and fluoride complexes with the metal ions. Existing thermodynamic data are evaluated, and means of extrapolating 25{degrees}C data to the temperatures of interest are discussed. There will be a separate review of solubility data for relevant Ni, Zr, Tc, Np, Pu and Am compounds.

Wruck, D.A.; Palmer, C.E.A.

1997-08-01

306

Screened-exchange electronic structures and thermodynamic properties of the cubic perovskite BiAlO3

NASA Astrophysics Data System (ADS)

The screened exchange local density approximation (sX-LDA) hybrid functional within the pseudopotential plane wave method is performed to improve the electronic structures of cubic BiAlO3 and its thermodynamic properties are investigated using the density functional perturbation theory (DFPT). The equilibrium lattice constant of cubic BiAlO3 is 3.67 Å which is applied to calculate its electronic structures. The calculated sX-LDA electronic structures are compared to standard generalized gradient approximation (GGA) approach. It is found that BiAlO3 is an indirect band gap material at M(1/2,1/2,0)-X(0,0,1/2) point with the gap value of 1.84, and 3.43 eV for GGA, and sX-LDA calculations, respectively. The linear response method is employed in order to calculate the phonon dispersion relations and phonon density of states. The predicted thermodynamic quantities, specific heat and Debye temperature, of cubic perovskite BiAlO3 are also reported.

Poopanya, Piyawong; Yangthaisong, Anucha

2013-06-01

307

NASA Technical Reports Server (NTRS)

A computer program, GASP, has been written to calculate the thermodynamic and transport properties of argon, carbon dioxide, carbon monoxide, fluorine, methane, neon, nitrogen, and oxygen. GASP accepts any two of pressure, temperature, or density as input. In addition, entropy and enthalpy are possible inputs. Outputs are temperature, density, pressure, entropy, enthalpy, specific heats, expansion coefficient, sonic velocity, viscosity, thermal conductivity, and surface tension. A special technique is provided to estimate the thermal conductivity near the thermodynamic critical point. GASP is a group of FORTRAN subroutines. The user typically would write a main program that invoked GASP to provide only the described outputs. Subroutines are structured so that the user may call only those subroutines needed for his particular calculations. Allowable pressures range from 0.l atmosphere to 100 to l,000 atmospheres, depending on the fluid. Similarly, allowable pressures range from the triple point of each substance to 300 degrees K to 2000 degrees K, depending on the substance. The GASP package was developed to be used with heat transfer and fluid flow applications. It is particularly useful in applications of cryogenic fluids. Some problems associated with the liquefication, storage, and gasification of liquefied natural gas and liquefied petroleum gas can also be studied using GASP. This program is written in FORTRAN IV for batch execution and is available for implementation on IBM 7000 series computers. GASP was developed in 1971.

Hendricks, R. C.

1994-01-01

308

Hydrogen bonding and thermodynamic properties of ( R, S)- and ( R)-alanine-based selector

NASA Astrophysics Data System (ADS)

We report on structural investigation of homochiral and heterochiral alanine-based selector 4-butylamino- N-[1-(3,5-dimethyl-phenylcarbamoyl)-ethyl]-3,5-dinitrobenzamide ( I) preformed by X-ray structure analysis and thermo-optical analysis. The topologies of hydrogen bonding of racemate crystals and the homochiral crystals are significantly different and affect their thermodynamic stabilities. The heterochiral rac- I crystal is characterized by high temperature and entropy fusion due to the compact packing of the molecules of opposite chirality (hydrogen bonded RS pairs). On the contrary, packing of homochiral molecules is less compact and crystals reveal low thermodynamic stability related to conformational flexibility.

Gazi? Smilovi?, Ivana; Mol?anov, Krešimir; Vinkovi?, Vladimir; Koji?-Prodi?, Biserka; Lesac, Andreja

2010-09-01

309

Properties of hadronic systems according to the non-extensive self-consistent thermodynamics

NASA Astrophysics Data System (ADS)

The non-extensive self-consistent theory describing the thermodynamics of hadronic systems at high temperatures is used to derive some thermodynamical quantities, as pressure, entropy, speed of sound and trace-anomaly. The calculations are free of fitting parameters, and the results are compared to lattice QCD calculations, showing a good agreement between theory and data up to temperatures around 175 MeV. Above this temperature the effects of a singularity in the partition function at To = 192 MeV results in a divergent behaviour in respect with the lattice calculation.

Deppman, A.

2014-11-01

310

Thermodynamical properties of planetary fluid envelopes Valerio Lucarini [v.lucarini@reading.ac.uk

on the possibility of defining a baroclinic heat engine extracting work from the meridional heat flux scale heat flux. Observational estimates of the climatology of the thermodynamical bounds are derived. The approximate formula of the material entropy production is verified and used for studying the global

311

Modeling of Thermodynamic Properties and Phase Equilibria for the Cu-Mg Binary System

, respectively. The zero-Kelvin enthalpies of formation for the intermediate compounds, Cu2Mg-C15 (cF24) and Cu reports of heat capacity and enthalpy of mixing, indicating a more self-consistent thermodynamic formation and glass forming ability.[5] While alloys exhibiting promising glass formation tendency

Chen, Long-Qing

312

THERMODYNAMIC PROPERTIES OF MAGNESIUM OXIDE AND BERYLLIUM OXIDE FROM 298 TO 1200 K

As a step in developing new standards of high-temperature heat capacity ; and in determining accurate thermodynamic data for simple substances, the ; enthalpy (heat content) relative to 273 deg K, of high purity fused magnesium ; oxide, MgO, and of sintered beryllium oxide, BeO, was measured up to 1,173 deg K. ; A Bunsen ice calorimeter and the drop

Andrew C. Victor; Thomas B. Douglas

1963-01-01

313

Thermodynamic bounds and general properties of optimal efficiency and power in linear responses

NASA Astrophysics Data System (ADS)

We study the optimal exergy efficiency and power for thermodynamic systems with an Onsager-type "current-force" relationship describing the linear response to external influences. We derive, in analytic forms, the maximum efficiency and optimal efficiency for maximum power for a thermodynamic machine described by a N ×N symmetric Onsager matrix with arbitrary integer N. The figure of merit is expressed in terms of the largest eigenvalue of the "coupling matrix" which is solely determined by the Onsager matrix. Some simple but general relationships between the power and efficiency at the conditions for (i) maximum efficiency and (ii) optimal efficiency for maximum power are obtained. We show how the second law of thermodynamics bounds the optimal efficiency and the Onsager matrix and relate those bounds together. The maximum power theorem (Jacobi's Law) is generalized to all thermodynamic machines with a symmetric Onsager matrix in the linear-response regime. We also discuss systems with an asymmetric Onsager matrix (such as systems under magnetic field) for a particular situation and we show that the reversible limit of efficiency can be reached at finite output power. Cooperative effects are found to improve the figure of merit significantly in systems with multiply cross-correlated responses. Application to example systems demonstrates that the theory is helpful in guiding the search for high performance materials and structures in energy researches.

Jiang, Jian-Hua

2014-10-01

314

Correlation corrections to the thermodynamic properties of spin asymmetric QGP matter

We calculate the free energy, entropy and pressure of QGP at finite temperature and density with a given fraction of spin-up and spin-down quarks using MIT bag model with corrections upto ${\\cal O} (g^4 \\ln g^2)$. The expressions for the specific heat, spin susceptibility in terms of Fermi momentum and temperature are derived. The effects of interaction between the quarks on the properties of the QGP phase are also investigated. Within our phenomenological model, we estimate the transition temperature $T_c$ by constructing the phase boundary between the hadronic phase to the QGP phase. Finally, we compute the equation of state of QGP and see the effects of temperature and density on the equation of state.

Pal, Kausik

2014-01-01

315

Anharmonicity, mechanical instability, and thermodynamic properties of the Cr-Re ?-phase.

Using density-functional theory in combination with the direct force method and molecular dynamics we investigate the vibrational properties of a binary Cr-Re ?-phase. In the harmonic approximation, we have computed phonon dispersion curves and density of states, evidencing structural and chemical effects. We found that the ?-phase is mechanically unstable in some configurations, for example, when all crystallographic sites are occupied by Re atoms. By using a molecular-dynamics-based method, we have analysed the anharmonicity in the system and found negligible effects (~0.5 kJ/mol) on the Helmholtz energy of the binary Cr-Re ?-phase up to 2000 K (~0.8T(m)). Finally, we show that the vibrational contribution has significant consequences on the disordering of the ?-phase at high temperature. PMID:24735300

Palumbo, Mauro; Fries, Suzana G; Pasturel, Alain; Alfè, Dario

2014-04-14

316

Thermodynamic properties of LiCu$_{2}$O$_{2}$ multiferroic compound

A spin model of quasi-one dimensional LiCu$_{2}$O$_{2}$ compound with ground state of ellipsoidal helical structure in which the helical axis is along the diagonal of CuO$_{4}$ squares has been adopted. By taking into account the interchain coupling and exchange anisotropy, the exotic magnetic properties and ferroelectricity induced by spiral spin order have been studied by performing Monte Carlo simulation. The simulation results qualitatively reproduce the main characters of ferroelectric and magnetic behaviors of LiCu$_{2}$O$_{2}$ compound and confirm the low-temperature incollinear spiral ordering. Furthermore, by performing the calculations of spin structure factor, we systematically investigate the effects of different exchange coupling on the lower-temperature magnetic transition, and find that the spiral spin order depends not only on the ratio of nearest and next-nearest neighbor inchain spin coupling but also strongly on the exchange anisotropy.

Qi, Yan

2013-01-01

317

Thermodynamic properties of LiCu2O2 multiferroic compound

NASA Astrophysics Data System (ADS)

A spin model of quasi-one-dimensional LiCu2O2 compound with ground state of ellipsoidal helical structure has been adopted. The helical axis is along the diagonal of CuO4 squares. By taking into account the interchain coupling and exchange anisotropy, the exotic magnetic properties and ferroelectricity induced by spiral spin order have been studied by performing Monte Carlo simulation. The simulation results qualitatively reproduce the main characters of ferroelectric and magnetic behaviors of LiCu2O2 compound and confirm the low-temperature noncollinear spiral ordering. Furthermore, by performing the calculations of spin structure factor, we systematically investigate the effects of different exchange couplings on the lower-temperature magnetic transition, and find that the spiral spin order depends not only on the ratio of nearest and next-nearest neighbor inchain spin coupling but also strongly on the exchange anisotropy.

Qi, Yan; Du, An

2014-04-01

318

Anharmonicity, mechanical instability, and thermodynamic properties of the Cr-Re ?-phase

Using density-functional theory in combination with the direct force method and molecular dynamics we investigate the vibrational properties of a binary Cr-Re ?-phase. In the harmonic approximation, we have computed phonon dispersion curves and density of states, evidencing structural and chemical effects. We found that the ?-phase is mechanically unstable in some configurations, for example, when all crystallographic sites are occupied by Re atoms. By using a molecular-dynamics-based method, we have analysed the anharmonicity in the system and found negligible effects (?0.5 kJ/mol) on the Helmholtz energy of the binary Cr-Re ?-phase up to 2000 K (?0.8T{sub m}). Finally, we show that the vibrational contribution has significant consequences on the disordering of the ?-phase at high temperature.

Palumbo, Mauro, E-mail: mauro.palumbo@rub.de; Fries, Suzana G. [ICAMS, Ruhr University Bochum, Universität Str. 150, D-44801 Bochum (Germany)] [ICAMS, Ruhr University Bochum, Universität Str. 150, D-44801 Bochum (Germany); Pasturel, Alain [SIMAP, UMR CNRS-INPG-UJF 5266, BP 75, F-38402 Saint Martin d’Hères (France)] [SIMAP, UMR CNRS-INPG-UJF 5266, BP 75, F-38402 Saint Martin d’Hères (France); Alfè, Dario [Department of Earth Sciences, Department of Physics and Astronomy, London Centre for Nanotechnology and Thomas Young Centre-UCL, University College London, Gower Street, London WC1E 6BT (United Kingdom)] [Department of Earth Sciences, Department of Physics and Astronomy, London Centre for Nanotechnology and Thomas Young Centre-UCL, University College London, Gower Street, London WC1E 6BT (United Kingdom)

2014-04-14

319

Thermodynamic properties of short-range attractive Yukawa fluid: simulation and theory.

Coexistence properties of the hard-core attractive Yukawa potential with inverse-range parameter kappa=9, 10, 12, and 15 are calculated by applying canonical Monte Carlo simulation. As previously shown for longer ranges, we show that also for the ranges considered here the coexistence curves scaled by the critical density and temperature obey the law of corresponding states, and that a linear relationship between the critical density and the reciprocal of the critical temperature holds. The simulation results are compared to the predictions of the self-consistent Ornstein-Zernike approximation, and a good agreement is found for both the critical points and the coexistence curves, although some slight discrepancies are present. PMID:20331282

Orea, Pedro; Tapia-Medina, Carlos; Pini, Davide; Reiner, Albert

2010-03-21

320

Correlation corrections to the thermodynamic properties of spin asymmetric QGP matter

We calculate the free energy, entropy and pressure of QGP at finite temperature and density with a given fraction of spin-up and spin-down quarks using MIT bag model with corrections upto ${\\cal O} (g^4 \\ln g^2)$. The expressions for the specific heat, spin susceptibility in terms of Fermi momentum and temperature are derived. The effects of interaction between the quarks on the properties of the QGP phase are also investigated. Within our phenomenological model, we estimate the transition temperature $T_c$ by constructing the phase boundary between the hadronic phase to the QGP phase. Finally, we compute the equation of state of QGP and see the effects of temperature and density on the equation of state.

Kausik Pal

2014-05-29

321

Quantum simulations of thermodynamic properties of strongly coupled quark-gluon plasma

A strongly coupled quark-gluon plasma (QGP) of heavy constituent quasi-particles is studied by a path-integral Monte-Carlo method. This approach is a quantum generalization of the model developed by Gelman, Shuryak and Zahed. It is shown that this method is able to reproduce the QCD lattice equation of state and also yields valuable insight into the internal structure of the QGP. The results indicate that the QGP reveals liquid-like rather than gas-like properties. At temperatures just above the critical one it was found that bound quark-antiquark states still survive. These states are bound by effective string-like forces and turns out to be colorless. At the temperature as large as twice the critical one no bound states are observed. Quantum effects turned out to be of prime importance in these simulations.

V. S. Filinov; Yu. B. Ivanov; M. Bonitz; P. R. Levashov; V. E. Fortov

2011-01-11

322

NASA Astrophysics Data System (ADS)

Densities and viscosities for binary mixtures of Diethanolamine (DEA) + 2 alkanol (2 propanol up to 2 pentanol) were measured over the entire composition range and temperature interval of 293.15-323.15 K. From the density and viscosity data, values of various properties such as isobaric thermal expansibility, excess isobaric thermal expansibility, partial molar volumes, excess molar volumes and viscosity deviations were calculated. The observed variations of these parameters, with alkanols chain length and temperature, are discussed in terms of the intermolecular interactions between the unlike molecules of the binary mixtures. The ability of the perturbed chain statistical associating fluid theory (PC-SAFT) to correlate accurately the volumetric behavior of the binary mixtures is demonstrated.

Almasi, Mohammad

2014-11-01

323

The thermodynamic properties of mixtures of normal octane and branched paraffin hydrocarbons

and activity coefficients of a binary liquid-phase system under constant temperature using data reduction methods based on the x-y data is described as follows: 1 ~1 2 ln 2 (2) ln II 1 g X2 d 2 xl inII -g-x d 2 1 dxl (4) in- /2 1 2 2 ~d ~y2xl 1... ln P. ? d ln P i i V g (18) A binary system with one homogeneous liquid phase has following properties Pl = ylP (19) P = (1-y) P (2O) Vl lnP12dlnP2=Vd1 P(21) g also (yl ? xl) yl(1 Yl) (1 ? V ) g and at low pressure Vl/V is negligible, g ~1...

Liu, Edward Kou-Shan

1975-01-01

324

First principle study of elastic and thermodynamic properties of FeB{sub 4} under high pressure

The elastic properties, elastic anisotropy, and thermodynamic properties of the lately synthesized orthorhombic FeB{sub 4} at high pressures are investigated using first-principles density functional calculations. The calculated equilibrium parameters are in good agreement with the available experimental and theoretical data. The obtained normalized volume dependence of high pressure is consistent with the previous experimental data investigated using high-pressure synchrotron x-ray diffraction. The complete elastic tensors and crystal anisotropies of the FeB{sub 4} are also determined in the pressure range of 0–100?GPa. By the elastic stability criteria and vibrational frequencies, it is predicted that the orthorhombic FeB{sub 4} is stable up to 100 GPa. In addition, the calculated B/G ratio reveals that FeB{sub 4} possesses brittle nature in the range of pressure from 0 to 100?GPa. The calculated elastic anisotropic factors suggest that FeB{sub 4} is elastically anisotropic. By using quasi-harmonic Debye model, the compressibility, bulk modulus, the coefficient of thermal expansion, the heat capacity, and the Grüneisen parameter of FeB{sub 4} are successfully obtained in the present work.

Zhang, Xinyu, E-mail: xyzhang@ysu.edu.cn, E-mail: jiaqianqin@gmail.com, E-mail: riping@ysu.edu.cn; Ning, Jinliang; Sun, Xiaowei; Li, Xinting; Ma, Mingzhen; Liu, Riping, E-mail: xyzhang@ysu.edu.cn, E-mail: jiaqianqin@gmail.com, E-mail: riping@ysu.edu.cn [State Key Laboratory of Metastable Materials Science and Technology, Yanshan University, Qinhuangdao 066004 (China); Qin, Jiaqian, E-mail: xyzhang@ysu.edu.cn, E-mail: jiaqianqin@gmail.com, E-mail: riping@ysu.edu.cn [Metallurgy and Materials Science Research Institute, Chulalongkorn University, Bangkok 10330 (Thailand); State Key Laboratory of Metastable Materials Science and Technology, Yanshan University, Qinhuangdao 066004 (China)

2013-11-14

325

Normal spinel zinc ferrite (ZnFe2O4) nanoparticles (NPs) with zero net magnetization were synthesized by a facile coprecipitation method in which two kinds of organic alkali, namely, 1-amino-2-propanol (MIPA) and bis(2-hydroxypropyl)-amine (DIPA), were used. The diameters of the ZnFe2O4 NPs were determined to be about 7 and 9 nm for samples prepared with MIPA and DIPA, respectively, and the normal spinel structure was confirmed by the magnetic property measurement at room temperature and the temperature dependence of the direct current magnetization. These results are different from those reported in the literature, where ZnFe2O4 NPs show a nonzero net magnetization. The heat capacity of the ZnFe2O4 NPs synthesized using DIPA was measured using a physical property measurement system in the temperature range from 2 to 300 K, and the thermodynamic functions were calculated based on the curve fitting of the experimental heat capacity data. The heat capacity of the ZnFe2O4 NPs was compared with that of a nanosized (Zn(0.795)Fe(0.205))[Zn(0.205)Fe(1.795)]O4 material studied in the literature, indicating that the Debye temperature of the present sample is more comparable with that of the bulk ZnFe2O4 reported by Westrum et al. PMID:25192353

Zhang, Yunong; Shi, Quan; Schliesser, Jacob; Woodfield, Brian F; Nan, Zhaodong

2014-10-01

326

NASA Technical Reports Server (NTRS)

The Langley 8 foot high temperature tunnel (8 ft HTT) is used to test components of hypersonic vehicles for aerothermal loads definition and structural component verification. The test medium of the 8 ft HTT is obtained by burning a mixture of methane and air under high pressure; the combustion products are expanded through an axisymmetric conical contoured nozzle to simulate atmospheric flight at Mach 7. This facility was modified to raise the oxygen content of the test medium to match that of air and to include Mach 4 and Mach 5 capabilities. These modifications will facilitate the testing of hypersonic air breathing propulsion systems for a wide range of flight conditions. A computational method to predict the thermodynamic, transport, and flow properties of the equilibrium chemically reacting oxygen enriched methane-air combustion products was implemented in a computer code. This code calculates the fuel, air, and oxygen mass flow rates and test section flow properties for Mach 7, 5, and 4 nozzle configurations for given combustor and mixer conditions. Salient features of the 8 ft HTT are described, and some of the predicted tunnel operational characteristics are presented in the carpet plots to assist users in preparing test plans.

Venkateswaran, S.; Hunt, L. Roane; Prabhu, Ramadas K.

1992-01-01

327

Thermodynamic Properties of the Aqueous Ions (2+ and 3+) of Iron and the Key Compounds of Iron

NASA Astrophysics Data System (ADS)

Recommended thermochemical property values, ?fH°, ?fG°, and S° for the aqueous ions of iron, Fe2+ and Fe3+, are given at 298.15 K in SI units. They are consistent with the CODATA Key Values for Thermodynamics. The values are: ?fH°=-90.0±0.5 kJ?mol-1, ?fG°=-90.53±1.0 kJ?mol-1, S°=-101.6±3.7 J?mol-1?K-1 for Fe2+(ao) and ?fH°=-49.0±1.5 kJ?mol-1, ?fG°=-16.28±1.1 kJ?mol-1, S° =-278.4±7.7 J?mol-1?K-1 for Fe3+(ao). The evaluation involves the analysis of the enthalpy changes, Gibbs energy changes, and the entropy measurements for all key substances in the key network. A consistent set of thermochemical property values is given for FeOOH(cr, Goethite), FeCl2(cr), FeCl3(cr), FeBr2(cr), FeBr3(cr), FeI2(cr), and FeSO4?7H2O(cr), as well as ``reconstituted'' recommended process values with uncertainties involving these substances. All recommended values are also given for a standard state of p°=1 atm. A computer based reaction catalog of measurements accompanies the text analysis.

Parker, V. B.; Khodakovskii, I. L.

1995-09-01

328

In 1921, the American Society of Mechanical Engineers began an effort to provide reliable and consistent tables of the thermodynamic properties of steam and water. In 1936, J.H. Keenan and F.G. Keyes published a set of steam tables that served as an accepted reference. These tables were revised in 1969 using the least squares technique on a computer to interpolate

M. P. Burgess; G. L. Fuller; A. H. Kaiser

1976-01-01

329

Thermodynamic properties of excess-oxygen-doped La2CuO4.11 near a simultaneous transition superconductors are created by doping of Mott insulating materials, such as La2CuO4, which show quasi doped La2CuO4 family of super- conductors, but also because the transition to the supercon- ductivity

Hellman, Frances

330

??Density functional theory (DFT) was used to evaluate the electronic and thermodynamic properties of Ca-doped LaFeO3 (La1-xCaxFeO3-y). La1-xCaxFeO3-y exhibits ionic (O2- anions) and electronic conductivity… (more)

Daniel, Davis George

2014-01-01

331

Hypothetical Thermodynamic Properties: Vapor Pressures and Vaporization Enthalpies of the Even n-Alkanes and vapor pressures of the n-alkanes from T ) (298.15 to 540) K for heneicosane to dononacontane. The vapor" extended corresponding states principle (CSP) which uses n-alkane input parameters based on the works

Chickos, James S.

332

Hypothetical Thermodynamic Properties: Vapor Pressures and Vaporization Enthalpies of the Even n-Alkanes in combination with earlier work to evaluate the vaporization enthalpies and vapor pressures of these n-alkanes as the number of carbon atoms exceeds sixty. Introduction The n-alkanes serve as excellent standards

Chickos, James S.

333

Thermodynamic properties of Pd40Ni40P20 in the glassy, liquid, and crystalline states

NASA Astrophysics Data System (ADS)

Bulk specimens of the easy glass-forming alloy Pd40Ni40P20 have been undercooled consistently into the glassy state at cooling rates as low as 10 K/min applying the melt-fluxing technique in boron trioxide. Due to this low cooling rate, heat capacity measurements could be performed in a commercial heat-flow differential calorimeter, covering for the first time the entire undercooling regime of a liquid metal from the melting temperature down to the glass transition temperature. Based on the measured specific heat data of the undercooled liquid and the crystalline state, the differences in the thermodynamic functions enthalpy, entropy, and Gibbs free energy are determined in dependence on temperature. The entropy balance yields a value of T0=500±5 K for the ideal glass transition temperature of this metallic system. The experimental values are compared to the corresponding thermodynamic functions, derived from commonly applied Gibbs free energy approximations for the undercooled liquid.

Wilde, G.; Görler, G. P.; Willnecker, R.; Dietz, G.

1994-07-01

334

Because hydrate formation in pipelines, processing operations, and reservoirs is generally undesirable, studies of gas-hydrate thermodynamics, particularly examinations of conditions where a second hydrate phase or a hydrocarbon-rich phase exists in addition to the water, hydrate, and gas phases, are important to the natural gas industry. In this study, analysts used experimental methane-krypton and methane-argon hydrate data to generate chemical-potential,

G. D. Holder; G. Corbin; K. D. Papadopoulos

1980-01-01

335

Field emission techniques devised to measure the melting temperature and electronic structure of individual, nanometer-size clusters supported on electrically conducting substrates are reviewed. Data on the size-dependent reduction in melting temperature of Au cluster are compared to existing thermodynamic descriptions and molecular dynamic calculations. Data on the electronic structure of an individual 1nm Au cluster are compared to the predictions of simple electron shell models for cluster electronic states.

Lin, M.E.; Ramachandra, A.; Andres, R.P.; Reifenberger, R.

1991-12-31

336

An analytical investigation for thermodynamic properties of the Fe-Cr-Ni-Mg-O system

NASA Astrophysics Data System (ADS)

Present study performs excess energy values, activity coefficients and partial free energy associated with the quinary Fe-Cr-Ni-Mg-O, quaternary Au-In-Sn-Zn and ternary Pb-Au-Bi liquid alloys, based on published binary thermodynamic descriptions and Chou's model for extension into higher order systems. Using Kohler, Muggianu and Chou's model the obtained results in the present study were compared to available experimental data.

Arslan, H.; Dogan, A.

2015-02-01

337

NASA Astrophysics Data System (ADS)

Motivated by experiments showing decreasing tensile modulus of nylons with increasing plasticizer content, a model involving the disruption of nylon hydrogen bonding by addition of plasticizer is proposed. This leads to proposed further experiments and suggests a complementary phenomenological analysis that involves the bulk modulus. The surface energy as a function of plasticizer concentration is then incorporated into the phenomenology. The importance of varying the temperature in the proposed thermodynamic measurements is stressed.

Zhang, M. L.; March, N. H.; Peeters, A.; Van Alsenoy, C.; Van Doren, V. E.

2001-04-01

338

The thermodynamic properties of mixtures of normal hexane and branched paraffin hydrocarbons

Committee: Dr. Richard R. Davison The vapor-liquid equilibrium of hydracarbon binary systems of n-hexane with 2-methylpentane, 3-methylpentane, and 2, 4-dimethylpentane are studied at 10'C, 20'C, 30'C, and 40'C. Isothermal values of the total vapor... pressures of pure components and mixtures were obtained by using a modified static vapor pressure apparatus. Barker's least squares method was employed to calcu- late equilibrium vapor compositions, activity coeffi- cients, and excess thermodynamic...

Ho, Chun Leung

2012-06-07

339

The exciplex emission spectra of N-ethylcarbazole with 1,2-dicyanobenzene (NEC/1,2-DCB), N-methylcarbazole with 1,2-dicyanobenzene (NMC/1,2-DCB), 1,3-dicyanobenzene (NMC/1,3-DCB), and 1,4-dicyanobenzene (NMC/1,4-DCB) are studied in tetrahydrofuran (THF) for the temperature range starting from 253 K to 334 K. Thermochromic shifts along with the spectral properties including change in peak intensities and the ratio of exciplex peak intensity to fluorophore peak intensity are studied. Effect of temperature on the energy of zero-zero transitions h?o('), Huang-Rhys factor (S), Gauss broadening of vibronic level (?) and the dominant high-frequency vibration (h??) are also part of investigation. Enthalpy of exciplex formation (?H(EX)(?)) calculated by the model proposed by A. Weller and the Gibb's energy of electron transfer (?G(et)(?)) for all exciplex systems are also discussed in the present paper. All the exciplexes under study were observed to be dipolar in nature. The exciplex of the N-methylcarbazole/1,4-dicyanobenzene was found to be the most stable and the N-methylcarbazole/1,3-dicyanobenzene was the weakest exciplex system. PMID:24051282

Asim, Sadia; Mansha, Asim; Landgraf, Stephan; Grampp, Günter; Zahid, Muhammad; Bhatti, Haq Nawaz

2014-01-24

340

NASA Astrophysics Data System (ADS)

The exciplex emission spectra of N-ethylcarbazole with 1,2-dicyanobenzene (NEC/1,2-DCB), N-methylcarbazole with 1,2-dicyanobenzene (NMC/1,2-DCB), 1,3-dicyanobenzene (NMC/1,3-DCB), and 1,4-dicyanobenzene (NMC/1,4-DCB) are studied in tetrahydrofuran (THF) for the temperature range starting from 253 K to 334 K. Thermochromic shifts along with the spectral properties including change in peak intensities and the ratio of exciplex peak intensity to fluorophore peak intensity are studied. Effect of temperature on the energy of zero-zero transitions h?o?, Huang-Rhys factor (S), Gauss broadening of vibronic level (?) and the dominant high-frequency vibration (h??) are also part of investigation. Enthalpy of exciplex formation (?HEX?) calculated by the model proposed by A. Weller and the Gibb's energy of electron transfer (?Get?) for all exciplex systems are also discussed in the present paper. All the exciplexes under study were observed to be dipolar in nature. The exciplex of the N-methylcarbazole/1,4-dicyanobenzene was found to be the most stable and the N-methylcarbazole/1,3-dicyanobenzene was the weakest exciplex system.

Asim, Sadia; Mansha, Asim; Landgraf, Stephan; Grampp, Günter; Zahid, Muhammad; Bhatti, Haq Nawaz

2014-01-01

341

Pairing Mechanism for the High-TC Superconductivity: Symmetries and Thermodynamic Properties

The pairing mechanism for the high- superconductors based on the electron-phonon (EPH) and electron-electron-phonon (EEPH) interactions has been presented. On the fold mean-field level, it has been proven, that the obtained s-wave model supplements the predictions based on the BCS van Hove scenario. In particular: (i) For strong EEPH coupling and the energy gap () is very weak temperature dependent; up to the critical temperature extends into the anomalous normal state to the Nernst temperature. (ii) The model explains well the experimental dependence of the ratio on doping for the reported superconductors in the terms of the few fundamental parameters. In the presented paper, the properties of the d-wave superconducting state in the two-dimensional system have been also studied. The obtained results, like for s-wave, have shown the energy gap amplitude crossover from the BCS to non-BCS behavior, as the value of the EEPH potential increases. However, for the energy gap amplitude extends into the anomalous normal state to the pseudogap temperature. Finally, it has been presented that the anisotropic model explains the dependence of the ratio on doping for the considered superconductors. PMID:22529891

Szcz??niak, Rados?aw

2012-01-01

342

NASA Technical Reports Server (NTRS)

Tables of thermodynamic properties of nitrogen are presented for the liquid and vapor phases for temperatures from the freezing line to 2000K and pressures to 10,000 bar. The tables include values of density, internal energy, enthalpy, entropy, isochoric heat capacity, isobaric heat capacity velocity of sound, the isotherm derivative, and the isochor derivative. The thermodynamic property tables are based on an equation of state, P=P (p,T), which accurately represents liquid and gaseous nitrogen for the range of pressures and temperatures covered by the tables. Comparisons of property values calculated from the equation of state with measured values for P-p-T, heat capacity, enthalpy, latent heat, and velocity of sound are included to illustrate the agreement between the experimental data and the tables of properties presented here. The coefficients of the equation of state were determined by a weighted least squares fit to selected P-p-T data and, simultaneously, to isochoric heat capacity data determined by corresponding states analysis from oxygen data, and to data which define the phase equilibrium criteria for the saturated liquid and the saturated vapor. The vapor pressure equation, melting curve equation, and an equation to represent the ideal gas heat capacity are also presented. Estimates of the accuracy of the equation of state, the vapor pressure equation, and the ideal gas heat capacity equation are given. The equation of state, derivatives of the equation, and the integral functions for calculating derived thermodynamic properties are included.

Jacobsen, Richard T.; Stewart, Richard B.

1973-01-01

343

NASA Astrophysics Data System (ADS)

Calculation of the thermodynamic properties of organic solids, liquids, and gases at high temperatures and pressures is a requisite for characterizing hydrothermal metastable equilibrium states involving these species and quantifying the chemical affinities of irreversible reactions of organic molecules in natural gas, crude oil, kerogen, and coal with minerals and organic, inorganic, and biomolecular aqueous species in interstitial waters in sedimentary basins. To facilitate calculations of this kind, coefficients for the Parameters From Group Contributions (PFGC) equation of state have been compiled for a variety of groups in organic liquids and gases. In addition, molecular weights, critical temperatures and pressures, densities at 25°C and 1 bar, transition, melting, and boiling temperatures ( Tt,Pr, Tm,Pr, and Tv,Pr, respectively) and standard molal enthalpies of transition (? H° t,Pr), melting (? H° m,Pr), and vaporization (? H° v,Pr) of organic species at 1 bar ( Pr) have been tabulated, together with an internally consistent and comprehensive set of standard molal Gibbs free energies and enthalpies of formation from the elements in their stable state at 298.15 K ( Tr) and Pr (? G° f and ? H° f, respectively). The critical compilation also includes standard molal entropies ( S°) and volumes ( V°) at Tr and Pr, and standard molal heat capacity power function coefficients to compute the standard molal thermodynamic properties of organic solids, liquids, and gases as a function of temperature at 1 bar. These properties and coefficients have been tabulated for more than 500 crystalline solids, liquids, and gases, and those for many more can be computed from the equations of state group additivity algorithms. The crystalline species correspond to normal alkanes (C nH 2( n+1) ) with carbon numbers ( n, which is equal to the number of moles of carbon atoms in one mole of the species) ranging from 5 to 100, and 23 amino acids including glycine (C 2H 5NO 2), alanine (C 3H 7NO 2), valine (C 5H 11NO 2), leucine (C 6H 13NO 2), isoleucine (C 6H 13NO 2), aspartic acid (C 4H 7NO 4), glutamic acid (C 5H 9NO 4), asparagine (C 4H 8N 2O 3), glutamine (C 5H 10N 2O 3), proline (C 5H 9NO 2), phenylalanine (C 9H 11NO 2), tryptophan (C 11H 12N 2O 2), methionine (C 5H 11SNO 2), serine (C 3H 7NO 3), threonine (C 4H 9NO 3), cysteine (C 3H 7SNO 2), tyrosine (C 9H 11NO 3), lysine (C 6H 14N 2O 2), lysine:HCl (C 6H 15N 2O 2Cl), arginine (C 6H 14N 4O 2), arginine:HCl (C 6H 15N 4O 2Cl), histidine (C 6H 9N 3O 2), and histidine:HCl (C 6H 10N 3O 2Cl). The data for the latter compounds permit calculation of the standard molal thermodynamic properties of protein unfolding in biogeochemical processes (Helgeson et al 1998). The liquids and gases considered in the present study include normal alkanes (C nH 2( n+1) ) for carbon numbers ranging from 1 to 100, 2- and 3-methylalkanes (C nH 2( n+1) ) for 4 ? n ? 20 and 6 ? n ? 20, respectively, 2,3-dimethylpentane (C 7H 16), 4-methylheptane (C 8H 18), cycloalkanes (C nH 2 n) for 3 ? n ? 8, methylated benzenes (C nH 2( n-3) ) for 7 ? n ? 12, normal alkylbenzenes (C nH 2( n-3) ) for 6 ? n ? 20, normal 1-alcohols (C nH 2( n+1) O) for 1 ? n ? 20, ethylene glycol (C 2H 6O 2), glycerol (C 3H 8O 3), normal 1-alkanethiols (C nH 2( n+1) S) for 1 ? n ? 20, normal carboxylic acids (C nH 2 nO 2) for 2 ? n ? 20, and the following miscellaneous species: 2-thiabutane (C 3H 8S), thiophene (C 4H 4S), thiophenol (C 6H 6S), acetone (C 3H 6O), 2-butanone (C 4H 8O), ethyl acetate (C 4H 8O 2), pyridine (C 5H 5N), 3-methylpyridine (C 6H 7N), and quinoline (C 9H 7N). One additional liquid (2-methylthiacyclopentane (C 5H 10S)) was also considered along with crystalline and gaseous carbazole (C 12H 9N). The thermodynamic data and equations summarized below can be used together with the standard molal thermodynamic properties of high molecular weight organic compounds ( Richard and Helgeson 1995, Richard and Helgeson 1998a, Richard and Helgeson 1998b) and minerals, inorganic gases, and aqueo

Helgeson, Harold C.; Owens, Christine E.; Knox, Annette M.; Richard, Laurent

1998-03-01

344

NASA Astrophysics Data System (ADS)

The ab initio calculations suggest that the superconducting state in CaH6 under the pressure (p) at 150 GPa has the highest critical temperature among the examined hydrogen-rich compounds. For this reason, the relevant thermodynamic parameters of the superconducting state in CaH6 have been determined; a wide range of the Coulomb pseudopotential has been assumed: ???<0.1,0.3>. It has been found that: (i) The critical temperature (TC) changes in the range from 243 K to 180 K (ii) The values of the ratio of the energy gap to the critical temperature (R? ? 2?(0)/kBTC) can be found in the range from 5.42 to 5.02. (iii) The ratio of the specific heat jump (?C(TC)) to the value of the specific heat in the normal state (CN(TC)), which has been represented by the symbol RC, takes the values from 3.30 to 3.18. (iv) The ratio R?TC(T)/HC2(0), where HC(0) denotes the critical thermodynamic field, changes from 0.122 to 0.125. The above results mean that even for the strong electron depairing correlations the superconducting state in CaH6 is characterized by a very high value of TC, and the remaining thermodynamic parameters significantly deviate from the predictions of the BCS theory. The study has brought out the expressions that correctly predict the values of the thermodynamic parameters for the superconducting state in CaH6 and for the compounds: SiH4(H2)2, Si2H6, B2H6, SiH4, GeH4, and PtH. Next, in the whole family of the hydrogen-rich compounds, the possible ranges of the values have been determined for TC, R?, RC, and RH. It has been found that the maximum value of the critical temperature can be equal to 764 K, which very well correlates with TC for metallic hydrogen (p = 2 TPa). Other parameters (R?, RC, and RH) should not deviate from the predictions of the BCS theory more than the analogous parameters for CaH6.

Szcz&?acute; niak, Rados?aw; Durajski, Artur P.

2013-11-01

345

Thermodynamic properties and transport coefficients of arc lamp plasmas: argon, krypton and xenon

NASA Astrophysics Data System (ADS)

Calculated values of the density, specific heat, enthalpy, viscosity, thermal conductivity and electrical conductivity of thermal plasmas formed from three gases used in arc lamps, krypton, argon and xenon, are presented. The calculations, which assume local thermodynamic equilibrium, were performed for pressures from 1 to 100 atm and for the temperature range 300-30?000 K. The results were compared with those of previously published studies. Some discrepancies were found for krypton and xenon; these are attributed to the improved values of the collision integrals used here in calculating the transport coefficients.

Murphy, Anthony B.; Tam, Eugene

2014-07-01

346

Thermodynamic properties of diosgenin determined by oxygen-bomb calorimetry and DSC

NASA Astrophysics Data System (ADS)

The combustion enthalpy of diosgenin was determined by oxygen-bomb calorimetry. The standard mole combustion enthalpy and the standard mole formation enthalpy have been calculated to be -16098.68 and -528.52 kJ mol-1, respectively. Fusion enthalpy and melting temperature for diosgenin were also measured to be -34.43 kJ mol-1 and 212.33°C, respectively, according to differential scanning calorimetry (DSC) data. These studies can provide useful thermodynamic data for this compound.

Zhao, Ming-Rui; Wang, Hong-Jie; Wang, Shu-Yu; Yue, Xiao-Xin

2014-12-01

347

Influence of lithium doping on the thermodynamic properties of graphene based superconductors.

The superconducting phase in graphene can be induced by doping its surface with lithium atoms. In this paper, it is shown that the critical temperature (TC) for the LiC6 and Li2C6 compounds changes from 8.55 K to 21.83 K. The other thermodynamic parameters--the order parameter (?), the specific heat for the superconducting (C(S)) and the normal (C(N)) state and the thermodynamic critical field (HC)--differ from the predictions of the Bardeen-Cooper-Schrieffer theory. In particular, the ratio R? ? 2?(0)/kBTC is equal to[3.72]LiC6 and [4.21]Li2C6. Additionally, the quantities RC ? ?C(TC)/C(N)(TC) and [Formula: see text] take the values[1.47]LiC6,[1.79]Li2C6 and [0.167]LiC6, [0.144]Li2C6. Finally, it is shown that the electron effective mass at TC is high and equals:[1.61me]LiC6 and [2.12me]Li2C6. PMID:24861555

Szcz??niak, D; Durajski, A P; Szcz??niak, R

2014-06-25

348

A Thermodynamic Investigation of the Redox Properties of Ceria-Titania Mixed Oxides

Ceria-titania solutions with compositions of Ce0.9Ti0.1O2 and Ce0.8Ti0.2O2 were prepared by the citric-acid (Pechini) method and characterized using X-ray diffraction (XRD) for structure, coulometric titration for redox thermodynamics, and water-gas-shift (WGS) reaction rates. Following calcination at 973 K, XRD suggests that the mixed oxides exist as single phase, fluorite structures, although there was no significant change in the lattice parameter compared to pure ceria. The mixed oxides are shown to be significantly more reducible than bulk ceria, with enthalpies for re-oxidation being approximately -500 kJ/mol O2, compared to -760 kJ/mol O2 for bulk ceria. However, WGS rates over 1 wt% Pd supported on ceria, Ce0.8Ti0.2O2, and Ce0.8Zr0.2O2 were nearly the same. For calcination at 1323 K, the mixed oxides separated into ceria and titania phases, as indicated by both the XRD and thermodynamic results.

Zhou,G.; Hanson, J.; Gorte, R.

2008-01-01

349

Heat capacities and thermodynamic properties of one manganese-based MOFs

A metal-organic framework [Mn(4,4?-bipy)(1,3-BDC)]\\u000a n\\u000a (MnMOF, 1,3-BDC = 1,3-benzene dicarboxylate, 4,4?-bipy = 4,4?-bipyridine) has been synthesized hydrothermally and characterized\\u000a by single crystal XRD and FT-IR spectrum. The low-temperature molar heat capacities of MnMOF were measured by temperature-modulated\\u000a differential scanning calorimetry for the first time. The thermodynamic parameters such as entropy and enthalpy relative to\\u000a reference temperature 298.15 K were derived based on the above molar

Li-Fang Song; Chun-Hong Jiang; Cheng-Li Jiao; Jian Zhang; Li-Xian Sun; Fen Xu; Qing-Zhu Jiao; Yong-Heng Xing; Yong Du; Zhong Cao; Feng-Lei Huang

2010-01-01

350

Impact of Aerosols and Atmospheric Thermodynamics on Cloud Properties within the Climate System

NASA Technical Reports Server (NTRS)

A combination of cloud-top and columnar droplet sizes derived from the multi Tropical Rainfall Measurement Mission (TRMM) sensors reveals the sensitivity of the aerosols effect on cloud-precipitation process due to environmental vertical thermodynamic structure. First, the magnitude of aerosol indirect effect could be larger with the analysis of columnar droplet sizes than that derived from the cloud-top droplet sizes, since column-droplet size can account for the broader droplet spectra in the cloud layers. Second, a combination of cloud- top and columnar droplet sizes reveals that the warm rain process is prevented regardless of the aerosols concentration under a high static stability such as when a strong temperature inversion exists, while a high aerosol concentration suppresses the warm rain formulation under a low static stability.

Matsui, Toshihisa; Masunaga, Hirohiko; Pielke, Roger, Sr.; Tao, Wei-Kuo

2003-01-01

351

The liquid-phase polymerization of furfuryl alcohol catalyzed by sulfuric acid catalysts and the identities of molecular intermediates were investigated by using Raman spectroscopy and density functional theory calculation. At room temperature, with an acid catalyst, a vigorous furfuryl alcohol polymerization reaction was observed, whereas even at a high water concentration, furfuryl alcohol was very stable in the absence of an acid catalyst. Theoretical studies were carried out to investigate the thermodynamics of protonation of furfuryl alcohol, initiation of polymerization, and formation of conjugated dienes and diketonic species by using the B3LYP level of theory. A strong aliphatic C=C band observed in the calculated and measured Raman spectra provided crucial evidence to understand the polymerization reaction mechanism. It is confirmed that the formation of a conjugated diene structure rather than a diketone structure is involved in the furfuryl alcohol polymerization reaction.

Kim, T.; Assary, R. S.; Marshall, C. L.; Gosztola, D. J.; Curtiss, L. A.; Stair, P. C. (Center for Nanoscale Materials); ( CSE); ( MSD); (Northwestern Univ.)

2011-01-01

352

Cellulose is still a mysterious polymer in many ways: structure of microfibrils, thermodynamics of synthesis and degradation, and interactions with other plant cell wall components. Our aim is to uncover the details and mechanisms of cellulose digestion and synthesis. We report the details of the structure of cellulose 1-beta under several temperature conditions and report here the results of these studies and connections to experimental measurements and the measurement in-silico the free energy of decrystallization of several morphologies of cellulose. In spatially large modeling, we show the most recent work of mapping atomistic and coarse-grain models into tomographic images of cellulose and extreme coarse-grain modeling of interactions of large cellulase complexes with microfibrils. We discuss the difficulties of modeling cellulose and suggest future work both experimental and theoretical to increase our understanding of cellulose and our ability to use it as a raw material for fuels and materials.

Crowley, M. F.; Matthews, J.; Beckham, G.; Bomble, Y.; Hynninen, A. P.; Ciesielski, P. F.

2012-01-01

353

Thermodynamic properties and neutron diffraction studies of silver ferrite AgFeO2.

We present thermodynamic and neutron scattering data on silver ferrite AgFeO(2). The data imply that strong magnetic frustration ?/T(N)?10 and magnetic ordering arise via two successive phase transitions at T(2) = 7 K and T(1) = 16 K. At T

Vasiliev, A; Volkova, O; Presniakov, I; Baranov, A; Demazeau, G; Broto, J-M; Millot, M; Leps, N; Klingeler, R; Büchner, B; Stone, M B; Zheludev, A

2010-01-13

354

Thermodynamic properties and neutron diffraction studies of silver ferrite AgFeO2

We present thermodynamic and neutron scattering data on silver ferrite AgFeO2. The data imply strong magnetic frustration /TN ~ 10 and magnetic ordering takes place via two successive phase transitions at 2 = 7 K and 1 = 16 K. At T < T2, two metamagnetic phase transitions at B1 ~ 14 T and B2 ~ 30 T can be identified through the change of slope in the magnetization curve measured up to 53 T. These transitions roughly correspond to 1/8 and 1/4 of the saturation magnetizations. Unlike in the classical delafossite CuFeO2, the wave vector of the magnetic structure both at T < T2 and at T2 < T < T1 is independent of temperature.

Vasiliev, A. [Moscow State University; Volkova, A, [Moscow State University; Presniakov, I [Moscow State University; Baranov, A. [Moscow State University; Demazeau, G [Institut de Chimie de la Matiere Condensee de Bordeaux, France; Broto, J.-M. [Laboratoire National des Champs Magnetiques Intenses; Millot, M. [Laboratoire National des Champs Magnetiques Intenses; Leps, N. [Leibniz-Institute for Solid State and Materials Research; Klingeler, R [IFW Dresden; Buchner, B [IFW Dresden; Stone, Matthew B [ORNL; Zheludev, Andrey I [ORNL

2009-01-01

355

We have measured the Raman Q-branch of hydrogen in a solution with water at a temperature of about 280 K and at pressures from 20 to 200 MPa. From a least-mean-square fitting analysis of the broad Raman Q-branch, we isolated the contributions from the four lowest individual roto-vibrational lines. The vibrational lines were narrower than the pure rotational Raman lines of hydrogen dissolved in water measured previously, but significantly larger than in the gas. The separations between these lines were found to be significantly smaller than in gaseous hydrogen and their widths were slightly increasing with pressure. The lines were narrowing with increasing rotational quantum number. The Raman frequencies of all roto-vibrational lines were approaching the values of gas phase hydrogen with increasing pressure. Additionally, from the comparison of the integrated intensity signal of Q-branch of hydrogen to the integrated Raman signal of the water bending mode, we have obtained the concentration of hydrogen in a solution with water along the 280 K isotherm. Hydrogen solubility increases slowly with pressure, and no deviation from a smooth behaviour was observed, even reaching thermodynamic conditions very close to the transition to the stable hydrogen hydrate. The analysis of the relative hydrogen concentration in solution on the basis of a simple thermodynamic model has allowed us to obtain the molar volume for the hydrogen gas/water solution. Interestingly, the volume relative to one hydrogen molecule in solution does not decrease with pressure and, at high pressure, is larger than the volume pertinent to one molecule of water. This is in favour of the theory of hydrophobic solvation, for which a larger and more stable structure of the water molecules is expected around a solute molecule. PMID:24784275

Borysow, Jacek; del Rosso, Leonardo; Celli, Milva; Moraldi, Massimo; Ulivi, Lorenzo

2014-04-28

356

We have measured the Raman Q-branch of hydrogen in a solution with water at a temperature of about 280 K and at pressures from 20 to 200 MPa. From a least-mean-square fitting analysis of the broad Raman Q-branch, we isolated the contributions from the four lowest individual roto-vibrational lines. The vibrational lines were narrower than the pure rotational Raman lines of hydrogen dissolved in water measured previously, but significantly larger than in the gas. The separations between these lines were found to be significantly smaller than in gaseous hydrogen and their widths were slightly increasing with pressure. The lines were narrowing with increasing rotational quantum number. The Raman frequencies of all roto-vibrational lines were approaching the values of gas phase hydrogen with increasing pressure. Additionally, from the comparison of the integrated intensity signal of Q-branch of hydrogen to the integrated Raman signal of the water bending mode, we have obtained the concentration of hydrogen in a solution with water along the 280 K isotherm. Hydrogen solubility increases slowly with pressure, and no deviation from a smooth behaviour was observed, even reaching thermodynamic conditions very close to the transition to the stable hydrogen hydrate. The analysis of the relative hydrogen concentration in solution on the basis of a simple thermodynamic model has allowed us to obtain the molar volume for the hydrogen gas/water solution. Interestingly, the volume relative to one hydrogen molecule in solution does not decrease with pressure and, at high pressure, is larger than the volume pertinent to one molecule of water. This is in favour of the theory of hydrophobic solvation, for which a larger and more stable structure of the water molecules is expected around a solute molecule.

Borysow, Jacek, E-mail: jborysow@mtu.edu; Rosso, Leonardo del; Celli, Milva; Ulivi, Lorenzo, E-mail: lorenzo.ulivi@isc.cnr.it [Consiglio Nazionale delle Ricerche, Istituto dei Sistemi Complessi, Via Madonna del piano 10, I-50019 Sesto Fiorentino (Italy)] [Consiglio Nazionale delle Ricerche, Istituto dei Sistemi Complessi, Via Madonna del piano 10, I-50019 Sesto Fiorentino (Italy); Moraldi, Massimo [Dipartimento di Fisica e Astronomia, Università degli Studi di Firenze, Via Sansone 1, I-50019 Sesto Fiorentino (Italy)] [Dipartimento di Fisica e Astronomia, Università degli Studi di Firenze, Via Sansone 1, I-50019 Sesto Fiorentino (Italy)

2014-04-28

357

NASA Astrophysics Data System (ADS)

We have measured the Raman Q-branch of hydrogen in a solution with water at a temperature of about 280 K and at pressures from 20 to 200 MPa. From a least-mean-square fitting analysis of the broad Raman Q-branch, we isolated the contributions from the four lowest individual roto-vibrational lines. The vibrational lines were narrower than the pure rotational Raman lines of hydrogen dissolved in water measured previously, but significantly larger than in the gas. The separations between these lines were found to be significantly smaller than in gaseous hydrogen and their widths were slightly increasing with pressure. The lines were narrowing with increasing rotational quantum number. The Raman frequencies of all roto-vibrational lines were approaching the values of gas phase hydrogen with increasing pressure. Additionally, from the comparison of the integrated intensity signal of Q-branch of hydrogen to the integrated Raman signal of the water bending mode, we have obtained the concentration of hydrogen in a solution with water along the 280 K isotherm. Hydrogen solubility increases slowly with pressure, and no deviation from a smooth behaviour was observed, even reaching thermodynamic conditions very close to the transition to the stable hydrogen hydrate. The analysis of the relative hydrogen concentration in solution on the basis of a simple thermodynamic model has allowed us to obtain the molar volume for the hydrogen gas/water solution. Interestingly, the volume relative to one hydrogen molecule in solution does not decrease with pressure and, at high pressure, is larger than the volume pertinent to one molecule of water. This is in favour of the theory of hydrophobic solvation, for which a larger and more stable structure of the water molecules is expected around a solute molecule.

Borysow, Jacek; del Rosso, Leonardo; Celli, Milva; Moraldi, Massimo; Ulivi, Lorenzo

2014-04-01

358

A detailed comparative study between electrochemical lithiation and sodiation of pure antimony (Sb), relating changes in structural, thermodynamic, kinetic and electrochemical properties has been carried out. For this purpose, a wide range of measurements using electrochemical (galvanostatic cycling, GITT, PITT), x-ray diffraction (XRD) and x-ray photoelectron spectroscopy (XPS) methods as well as density functional theory (DFT) based investigations have been undertaken. Assessment of the thermodynamics reveals that the reaction proceeds identically during the first and second cycles for Li whereas it differs between the first and subsequent cycles for Na. For Li the difference between the first and subsequent cycles is rooted in an improvement of the kinetics likely due to the decrease of Sb particle size whereas the reaction with Na proceeds through a different pathway from the first to subsequent cycles and is associated with the formation of amorphous NaxSb phases. For the first time we rationalize the amorphization of NaxSb phases by the long ranged strain propagation due to Na-vacancy compared to Li-Sb. At full discharge, our XRD results show for the first time that a minor fraction of hexagonal Li3Sb forms concomitantly with cubic Li3Sb. The XRD results confirm that Sb crystallizes into hexagonal Na3Sb at full sodiation. The kinetics of the reaction is assessed by rate performance tests which highlight that both Li and Na can diffuse rapidly throughout micron thick films at room temperature. However, it is found that the (de)insertion of Li provides lower overpotentials and larger storage capacities compared to Na. The difference in rate performance is complemented by diffusion coefficient determinations near the 0 V region where both materials are crystallized into M3Sb (M=Li, Na), and the results show that the apparent diffusion coefficients for Li are equivalent or one order of magnitude higher than those for Na. Interestingly, calculations show that the energy barrier for near-neighbor vacancy motion, predominant in these close-packed phases is about twice for Na than for Li. Our analysis tries to relate the lower intrinsic diffusivity of Na compared to Li with the long-range strain propagation induced by the former, thereby leading to an intrinsic origin of differences in rates, mechanical properties and amorphization. Finally, the surface chemistry of Sb electrodes cycled in NaClO4 dissolved in pure PC with(out) the addition of 5wt% EC or FEC shows presence of ethers and NaF for the EC- and FEC-based electrolytes, respectively, and SEI films rich in Na-based carbonates.

Baggetto, Loic [ORNL] [ORNL; Ganesh, Panchapakesan [ORNL] [ORNL; Sun, Che Nan [ORNL] [ORNL; Meisner, Roberta Ann [ORNL] [ORNL; Zawodzinski, Thomas A [ORNL] [ORNL; Veith, Gabriel M [ORNL] [ORNL

2013-01-01

359

Thermal equation of state and thermodynamic properties of molybdenum at high pressures

NASA Astrophysics Data System (ADS)

A comprehensive P-V-T dataset for bcc-Mo was obtained at pressures up to 31 GPa and temperatures from 300 to 1673 K using MgO and Au pressure calibrants. The thermodynamic analysis of these data was performed using high-temperature Birch-Murnaghan (HTBM) equations of state (EOS), Mie-Grüneisen-Debye (MGD) relation combined with the room-temperature Vinet EOS, and newly proposed Kunc-Einstein (KE) approach. The analysis of room-temperature compression data with the Vinet EOS yields V0 = 31.14 ± 0.02 Å3, KT = 260 ± 1 GPa, and KT' = 4.21 ± 0.05. The derived thermoelastic parameters for the HTBM include (?KT/?T)P = -0.019 ± 0.001 GPa/K and thermal expansion ? = a0 + a1T with a0 = 1.55 ( ± 0.05) × 10-5 K-1 and a1 = 0.68 ( ± 0.07) × 10-8 K-2. Fitting to the MGD relation yields ?0 = 2.03 ± 0.02 and q = 0.24 ± 0.02 with the Debye temperature (?0) fixed at 455-470 K. Two models are proposed for the KE EOS. The model 1 (Mo-1) is the best fit to our P-V-T data, whereas the second model (Mo-2) is derived by including the shock compression and other experimental measurements. Nevertheless, both models provide similar thermoelastic parameters. Parameters used on Mo-1 include two Einstein temperatures ?E10 = 366 K and ?E20 = 208 K; Grüneisen parameter at ambient condition ?0 = 1.64 and infinite compression ?? = 0.358 with ? = 0.323; and additional fitting parameters m = 0.195, e0 = 0.9 × 10-6 K-1, and g = 5.6. Fixed parameters include k = 2 in Kunc EOS, mE1 = mE2 = 1.5 in expression for Einstein temperature, and a0 = 0 (an intrinsic anharmonicity parameter). These parameters are the best representation of the experimental data for Mo and can be used for variety of thermodynamic calculations for Mo and Mo-containing systems including phase diagrams, chemical reactions, and electronic structure.

Litasov, Konstantin D.; Dorogokupets, Peter I.; Ohtani, Eiji; Fei, Yingwei; Shatskiy, Anton; Sharygin, Igor S.; Gavryushkin, Pavel N.; Rashchenko, Sergey V.; Seryotkin, Yury V.; Higo, Yiji; Funakoshi, Kenichi; Chanyshev, Artem D.; Lobanov, Sergey S.

2013-03-01

360

Black holes with non-Abelian hair and their thermodynamical properties

NASA Astrophysics Data System (ADS)

We present some black-hole solutions of the Einstein-Yang-Mills-dilaton system and calculate their Hawking temperatures. We find that if the coupling constant of the dilaton is smaller than some critical value, the thermodynamical behavior of these black holes includes two phase transitions at points determined by the value of the mass parameter. The black holes with masses between those two critical values have a positive specific heat. This is also true for the known colored black-hole solutions. We also reanalyze Skyrme black holes and find that there exist two types of solutions (a stable type and an unstable excited type) and these two types converge to a bifurcation point at some critical horizon radius, beyond which there is no Skyrme black hole. The stable black holes have two possible fates: they can evaporate via the Hawking process, and so evolve into a particlelike (Skyrmion) solution, or they can accrete matter and evolve into the Schwarzschild solution. When a Skyrme black hole evolves into a Schwarzschild black hole, its area changes discontinuously, so that we may regard this evolution as a kind of first-order phase transition. The specific heat of stable Skyrme black holes is always negative, while there are either one or three transition points for unstable Skyrme black holes.

Torii, Takashi; Maeda, Kei-Ichi

1993-08-01

361

Mangosteen is a tropical fruit that presents beneficial effects on human health since it is rich in anthocyanins and xanthones, which are considered bioactive compounds that have been described as good free radical scavengers. One of its most active compounds is ?-mangostin. In this report, a theoretical study on the free radical scavenger capacity of ?-mangostin and its monoanion is analyzed using the density functional theory approximation. Two well-known reaction mechanisms are investigated: the hydrogen atom transfer (HAT) and the radical adduct formation (RAF). Two other mechanisms are also considered: sequential electron proton Transfer (SEPT) and proton coupled electron transfer (PCET). According to thermodynamics and kinetics, ?-mangostin and its deprotonated form are good free radical scavenger through the HAT mechanism, with the anionic (deprotonated) form being more reactive than the neutral one. Their capacity to scavenge OOH free radical is similar to that of carotenes, higher than that of allicin, much higher than that of melatonin and N-acetylcysteine amide, and about 15 times lower than that of 2-propenesulfenic acid. PMID:21936544

Martínez, Ana; Galano, Annia; Vargas, Rubicelia

2011-11-01

362

Morpholine, O(C{sub 2}H{sub 4}){sub 2}(NH), is widely used in many industrial applications as a pH buffering agent and corrosion inhibitor; in particular, it is utilized at elevated temperatures in nuclear power plants. A hydrogen-electrode concentration cell was used to monitor pH in a study of morpholine ionization in aqueous solutions to temperatures of 290 C and to ionic strengths of 1 m, maintained with either sodium trifluoromethanesulfonate or sodium chloride. The resulting hydrolysis quotients were combined with values from two previous potentiometric investigations of this reaction, as well as existing heat capacity and apparent molar volume data, to provide a global fitting equation. The computed thermodynamic parameters for the acid dissociation of the morpholinium ion at 25 C and infinite dilution are log K = ({minus}8.491 {+-} 0.003); {Delta}H = (39 {+-} 1) kJ/mol; {Delta}S = ({minus}31 {+-} 1) J/K{center_dot}mol; {Delta}C{sub p} = (40 {+-} 7) J/K{center_dot}mol; and {Delta}V = (3 {+-} 1) cm{sup 3}/mol. At low ionic strengths, including values at infinite dilution, the log Q data were found to be near linear with respect to the reciprocal temperature in Kelvin over the measured temperature range of 0 C to 300 C.

Ridley, M.K.; Xiao, C.; Palmer, D.A.; Wesolowski, D.J.

2000-06-01

363

NASA Astrophysics Data System (ADS)

Measurements of a single, levitated particle in an electrodynamic balance are an established tool for deriving thermodynamic and material data such as density, refractive index and activities of components of an aqueous solution under supersaturated conditions, where bulk measurements are not possible. The retrieval relies on combining mass-to-charge data and size data from light scattering. Here, we use a combination of low- and high-resolution Mie resonance spectroscopy to obtain radius data, enabling an accurate size determination not only when the particle is in equilibrium, but also when it is out of equilibrium due to kinetic limitation of mass transport. With the data measured under non-equilibrium conditions, it is possible to retrieve the water diffusivity. A challenge is that the radius retrieval by comparing measured light scattering with Mie theory requires the knowledge of refractive index as a function of concentration. Here, we show an iterative retrieval of refractive index and size for compounds for which data cannot be obtained in the bulk either due to lack of sufficient amounts of sample or limited solubility. We demonstrate the measurement strategy and the retrieval of water activity, density, refractive index and water diffusivity for aqueous shikimic acid. Water diffusivity in concentrated shikimic acid decreases by 6 orders of magnitude at 250 K compared to that at room temperature.

Steimer, S. S.; Krieger, U. K.; Te, Y.-F.; Lienhard, D. M.; Huisman, A. J.; Ammann, M.; Peter, T.

2015-01-01

364

Thermodynamic Properties of Fast Ramped Superconducting Accelerator Magnets for the Fair Project

NASA Astrophysics Data System (ADS)

The 100 Tm synchrotron SIS 100 is the core component of the international Facility of Antiproton and Ion Research (FAIR) to be built at GSI Darmstadt. The 108 bending magnets are 3 m long 2 T superferric dipoles providing a nominal ramp rate of 4 T/s within a usable aperture of 115 mm?60 mm. An intensive R&D period was conducted to minimise the AC losses to lower operation costs and to guarantee a safe thermal stability for long term continuous cycling with a maximum repetition frequency of 1 Hz. The latter requirement is strictly limited by the overall heat flow originated by eddy currents and hysteresis losses in iron yoke and coil as well as by its hydraulic resistance respective to the forced two phase helium cooling flow within the hollow superconducting cable. Recently three full size dipoles—and one quadrupole magnets were built and intensive tests have been started in the end of 2008 at the GSI cryogenic test facility. We present the measured thermodynamic parameters of the first tested dipole: AC losses depending on Bmax and dB/dt for various characteristic ramping modes and conclude for necessary optimisations toward the final design of the series magnets.

Fischer, E.; Mierau, A.; Schnizer, P.; Bleile, A.; Gärtner, W.; Guymenuk, O.; Khodzhibagiyan, H.; Schroeder, C.; Sikler, G.; Stafiniak, A.

2010-04-01

365

Moisture sorption isotherms and thermodynamic properties of mexican mennonite-style cheese.

Moisture adsorption isotherms of fresh and ripened Mexican Mennonite-style cheese were investigated using the static gravimetric method at 4, 8, and 12 °C in a water activity range (aw) of 0.08-0.96. These isotherms were modeled using GAB, BET, Oswin and Halsey equations through weighed non-linear regression. All isotherms were sigmoid in shape, showing a type II BET isotherm, and the data were best described by GAB model. GAB model coefficients revealed that water adsorption by cheese matrix is a multilayer process characterized by molecules that are strongly bound in the monolayer and molecules that are slightly structured in a multilayer. Using the GAB model, it was possible to estimate thermodynamic functions (net isosteric heat, differential entropy, integral enthalpy and entropy, and enthalpy-entropy compensation) as function of moisture content. For both samples, the isosteric heat and differential entropy decreased with moisture content in exponential fashion. The integral enthalpy gradually decreased with increasing moisture content after reached a maximum value, while the integral entropy decreased with increasing moisture content after reached a minimum value. A linear compensation was found between integral enthalpy and entropy suggesting enthalpy controlled adsorption. Determination of moisture content and aw relationship yields to important information of controlling the ripening, drying and storage operations as well as understanding of the water state within a cheese matrix. PMID:25328178

Martinez-Monteagudo, Sergio I; Salais-Fierro, Fabiola

2014-10-01

366

Graphene oxide (GO) nanoparticle is a high potential effective absorbent. Tetracycline (TC) is a broad-spectrum antibiotic produced, indicated for use against many bacterial infections. In the present research, a systematic study of the adsorption and release process of tetracycline on GO was performed by varying pH, sorption time and temperature. The results of our studies showed that tetracycline strongly loads on the GO surface via ?–? interaction and cation–? bonding. Investigation of TC adsorption kinetics showed that the equilibrium was reached within 15 min following the pseudo-second-order model with observed rate constants of k2?=?0.2742–0.5362 g/mg min (at different temperatures). The sorption data has interpreted by the Langmuir model with the maximum adsorption of 323 mg/g (298 K). The mean energy of adsorption was determined 1.83 kJ/mol (298 K) based on the Dubinin–Radushkevich (D–R) adsorption isotherm. Moreover, the thermodynamic parameters such as ?H°, ?S° and ?G° values for the adsorption were estimated which indicated the endothermic and spontaneous nature of the sorption process. The electrochemistry approved an ideal reaction for the adsorption under electrodic process. Simulation of GO and TC was done by LAMMPS. Force studies in z direction showed that tetracycline comes close to GO sheet by C8 direction. Then it goes far and turns and again comes close from amine group to the GO sheet. PMID:24302989

Ghadim, Ehsan Ezzatpour; Manouchehri, Firouzeh; Soleimani, Gholamreza; Hosseini, Hadi; Kimiagar, Salimeh; Nafisi, Shohreh

2013-01-01

367

NASA Astrophysics Data System (ADS)

The present work addresses the formation of water-in-diesel (W/D) nanoemulsion by blending different percentages of water along with nano-Al additive in various propositions to enhance the combustion characteristics. The roles of various surfactants such as Sorbitan monooleate (Span 80), Triton X-100, Tetradecyltrimethylammonium bromide, and newly synthesized and characterized dicationic surfactants were discussed based upon their ability to stabilize the nanoemulsions. Surface active properties of the surfactants were determined by measuring their interfacial tension and subsequently by measuring the critical micelle concentration of the surfactants. Triton X-100 was found to be the most efficient surfactant for the current water-in-diesel nanoemulsion as it stabilized the suspensions for more than 8 h. Particle size analysis proved emulsion size to be in the order of nanometer, and zeta potential values were found to have neutral behavior at water-diesel interface. Experimental studies confirmed that that blends W/D [1 % (vol.) water] and W/DA [1 % (vol.) water, 0.1 % (wt.) nano-Al] were thermodynamically stable.

Mehta, Rakhi N.; More, Utkarsh; Malek, Naved; Chakraborty, Mousumi; Parikh, Parimal A.

2015-01-01

368

As assemblies of graphene sheets, carbon nanotubes, and fullerenes become components of new nanotechnologies, it is important to be able to predict the structures and properties of these systems. A problem has been that the level of quantum mechanics practical for such systems (density functional theory at the PBE level) cannot describe the London dispersion forces responsible for interaction of the graphene planes (thus graphite falls apart into graphene sheets). To provide a basis for describing these London interactions, we derive the quantum mechanics based force field for carbon (QMFF-Cx) by fitting to results from density functional theory calculations at the M06-2X level, which demonstrates accuracies for a broad class of molecules at short and medium range intermolecular distances. We carried out calculations on the dehydrogenated coronene (C24) dimer, emphasizing two geometries: parallel-displaced X (close to the observed structure in graphite crystal) and PD-Y (the lowest energy transition state for sliding graphene sheets with respect to each other). A third, eclipsed geometry is calculated to be much higher in energy. The QMFF-Cx force field leads to accurate predictions of available experimental mechanical and thermodynamics data of graphite (lattice vibrations, elastic constants, Poisson ratios, lattice modes, phonon dispersion curves, specific heat, and thermal expansion). This validates the use of M06-2X as a practical method for development of new first principles based generations of QMFF force fields. PMID:20942530

Pascal, Tod A; Karasawa, Naoki; Goddard, William A

2010-10-01

369

Thermodynamic properties of Ca1.82Na0.18CuO2Cl2 single crystals

NASA Astrophysics Data System (ADS)

We report the experimental results on the reversible magnetization of high quality Ca1.82Na0.18CuO2Cl2 single crystals in the high-pressure condition of about 5.2 GPa. The superconducting transition temperature Tc (˜ 27 K) of this single crystal is the highest reported in this family. The magnetizations are analyzed using the Hao-Clem model and the high-field scaling law. From these analysis, we have obtained various thermodynamic parameters such as the penetration depth and the critical fields, and clarified the dimensional nature of the superconductors. Even though the doping content between Ca1.82Na0.18CuO2Cl2 and La1.82Sr0.18CuO4 is same, the physical properties of these materials are quite different. For example, ?ab(0) is estimated to be 440 nm, which is larger than that of La1.82Sr0.18CuO4. These changes are totally unexpected in this iso-structural superconductor.

Kim, Kyung-Hee; Kim, Heon-Jung; Kim, Jung-Dea; Lee, H.-G.; Lee, Sung-Ik

2006-03-01

370

Freeze-dried chia mucilage adsorption isotherms were determined at 25, 35 and 40°C and fitted with the Guggenheim-Anderson-de Boer model. The integral thermodynamic properties (enthalpy and entropy) were estimated with the Clausius-Clapeyron equation. Pore radius of the mucilage, calculated with the Kelvin equation, varied from 0.87 to 6.44nm in the temperature range studied. The point of maximum stability (minimum integral entropy) ranged between 7.56 and 7.63kg H2O per 100kg of dry solids (d.s.) (water activity of 0.34-0.53). Enthalpy-entropy compensation for the mucilage showed two isokinetic temperatures: (i) one occurring at low moisture contents (0-7.56kg H2O per 100kg d.s.), controlled by changes in water entropy; and (ii) another happening in the moisture interval of 7.56-24kg H2O per 100kg d.s. and was enthalpy driven. The glass transition temperature Tg of the mucilage fluctuated between 42.93 and 57.93°C. PMID:25659716

Velázquez-Gutiérrez, Sandra Karina; Figueira, Ana Cristina; Rodríguez-Huezo, María Eva; Román-Guerrero, Angélica; Carrillo-Navas, Hector; Pérez-Alonso, César

2015-05-01

371

Cholesterol is an important component of lipid rafts in mammalian cell membranes. Studies of phospholipid monolayers containing cholesterol provide insight into the role of cholesterol in regulating the properties of animal cells, raft stability, and organization. In this contribution, a study of the characteristics of binary Langmuir monolayers consisting of phospholipids, 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC), 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC), 2-oleoyl-1-palmitoyl-sn-glycero-3-phosphocholine (POPC), 1,2-dipalmitoyl-sn-glycero-3-phospho-rac-(1-glycerol) (DPPG), and cholesterol (Chol), was conducted on the basis of the surface pressure-area per molecule (?-A) isotherms. Analysis of the results obtained provided information on the mean molecular area, the excess Gibbs energy of mixing, and condensation in the monolayer. The mixed monolayers were also deposited onto the mica plates and investigated by the contact angle measurements of water, formamide, and diiodomethane. The contact angles allowed calculating surface free energy of the films from the van Oss et al. approach. It was found that cholesterol determines the molecular packing and ordering of the monolayers closely connected with the kind of phospholipid. This is reflected in the values of surface free energy of the model membranes. From the thermodynamic analysis of phospholipid/cholesterol/liquid interactions, one may draw conclusions about the most favorable composition (stoichiometry) of the binary film which is especially important in view of the lipid rafts formation. PMID:23470025

Jurak, Ma?gorzata

2013-04-01

372

NASA Astrophysics Data System (ADS)

As assemblies of graphene sheets, carbon nanotubes, and fullerenes become components of new nanotechnologies, it is important to be able to predict the structures and properties of these systems. A problem has been that the level of quantum mechanics practical for such systems (density functional theory at the PBE level) cannot describe the London dispersion forces responsible for interaction of the graphene planes (thus graphite falls apart into graphene sheets). To provide a basis for describing these London interactions, we derive the quantum mechanics based force field for carbon (QMFF-Cx) by fitting to results from density functional theory calculations at the M06-2X level, which demonstrates accuracies for a broad class of molecules at short and medium range intermolecular distances. We carried out calculations on the dehydrogenated coronene (C24) dimer, emphasizing two geometries: parallel-displaced X (close to the observed structure in graphite crystal) and PD-Y (the lowest energy transition state for sliding graphene sheets with respect to each other). A third, eclipsed geometry is calculated to be much higher in energy. The QMFF-Cx force field leads to accurate predictions of available experimental mechanical and thermodynamics data of graphite (lattice vibrations, elastic constants, Poisson ratios, lattice modes, phonon dispersion curves, specific heat, and thermal expansion). This validates the use of M06-2X as a practical method for development of new first principles based generations of QMFF force fields.

Pascal, Tod A.; Karasawa, Naoki; Goddard, William A.

2010-10-01

373

Ab initio thermodynamic and elastic properties of AGaH4 hydrides ( A=Li , Na, K, Rb, and Cs)

NASA Astrophysics Data System (ADS)

Systematic properties of the AGaH4 alkali gallium hydrides ( A=Li , Na, K, Rb, and Cs) are investigated within density functional theory. Seven ground-state crystal structures are identified, with two energetically indistinguishable structures found for both LiGaH4 , whose structure is as yet undetermined experimentally, and CsGaH4 . Born effective charge tensors, static and high-frequency dielectric tensors, and phonon dispersion relations incorporating longitudinal-optical/transverse-optical mode splittings are computed. Our results indicate that LiGaH4 and NaGaH4 have technologically interesting standard enthalpies of formation near -30kJ/mole H2 . We find, however, that LiGaH4 is thermodynamically unstable with respect to both LiGa and LiH, providing a possible explanation for its challenging synthesis. The Born stability criteria are evaluated with the computed elasticity tensor components, Cij . All seven structures are found to be both elastically and vibrationally stable.

Herbst, J. F.; Hector, L. G., Jr.; Wolf, W.

2010-07-01

374

The influence of locked nucleic acid (LNA) residues on the thermodynamic properties of 2?-O-methyl RNA/RNA heteroduplexes is reported. Optical melting studies indicate that LNA incorporated into an otherwise 2?-O-methyl RNA oligonucleotide usually, but not always, enhances the stabilities of complementary duplexes formed with RNA. Several trends are apparent, including: (i) a 3? terminal U LNA and 5? terminal LNAs are less stabilizing than interior and other 3? terminal LNAs; (ii) most of the stability enhancement is achieved when LNA nucleotides are separated by at least one 2?-O-methyl nucleotide; and (iii) the effects of LNA substitutions are approximately additive when the LNA nucleotides are separated by at least one 2?-O-methyl nucleotide. An equation is proposed to approximate the stabilities of complementary duplexes formed with RNA when at least one 2?-O-methyl nucleotide separates LNA nucleotides. The sequence dependence of 2?-O-methyl RNA/RNA duplexes appears to be similar to that of RNA/RNA duplexes, and preliminary nearest-neighbor free energy increments at 37°C are presented for 2?-O-methyl RNA/RNA duplexes. Internal mismatches with LNA nucleotides significantly destabilize duplexes with RNA. PMID:16155181

Kierzek, Elzbieta; Ciesielska, Anna; Pasternak, Karol; Mathews, David H.; Turner, Douglas H.; Kierzek, Ryszard

2005-01-01

375

NASA Astrophysics Data System (ADS)

The aluminosilicate garnets (E3Al2Si3O12 with E = Fe2+, Mn2+, Ca, Mg) form an important rock-forming mineral group. Much study has been directed toward determining their thermodynamic properties. The iron end-member almandine (Fe3Al2Si3O12) is a key phase in many petrologic investigations. As part of an ongoing calorimetric and thermodynamic study of the aluminosilicate garnets, the heat capacity of three synthetic well-characterized polycrystalline almandine garnets and one natural almandine-rich single crystal was measured. The various garnets were characterized by optical microscopy, electron-microprobe analysis, X-ray powder diffraction and 57Fe Mössbauer spectroscopy. Heat capacity measurements were performed in the temperature range 3 to 300 K using relaxation calorimetry and between 282 and 764 K using DSC methods. From the former, So values between 336.7 ± 0.8 and 337.8 ± 0.8 J/molK are calculated for the different samples. The smaller value is considered the best So for end-member stoichiometric almandine, because it derives from the "best" Fe3+-free synthetic sample. The Cp behavior for almandine at T > 298 K is given by the polynomial (in J/molK): Cp = 649.06(±4) - 3837.57(±122)T-0.5 - 1.44682(±0.06)107T-2 + 1.94834(±0.09)109T-3, which is calculated using DSC data together with one published heat-content datum determined by transposed-drop calorimetry along with a new determination that gives H1181K - H302K = 415.0 ± 3.2 kJ/mole. Almandine shows a ?-type heat-capacity anomaly at low temperatures resulting from a paramagnetic-antiferromagnetic phase transition at about 9 K. The lattice heat capacity was calculated using the single-parameter phonon dispersion model of Komada and Westrum (1997), which allows the non-lattice heat capacity (Cex) behavior to be modelled. An analysis shows the presence of an electronic heat-capacity contribution (Cel - Schottky anomaly) around 17 K that is superimposed on a larger magnetic heat-capacity effect (Cmag). The calculated lattice entropy at 298.15 K is Svib = 303.3 J/molK and it contributes about 90% to the total standard entropy at 298 K. The non-lattice entropy is Sex = 33.4 J/molK and consists of Smag = 32.1 J/molK and Sel = 1.3 J/molK contributions. Using the So = 336.7 J/molK value and the Cp polynomial for almandine, we derived its enthalpy of formation, ?Hof, from an analysis of experimental phase equilibrium results on the reactions almandine + 3rutile = 3ilmenite + sillimanite + 2quartz and 2ilmenite = 2iron + 2rutile + O2. ?Hof = -5269.63 kJ/mol was obtained. So for grossular, pyrope, spessartine, and almandine, as well as their Cp behavior to high temperatures, have all been measured calorimetrically. Uncertainties in older calorimetric studies appear to have been resolved. The standard thermodynamic properties Vo and So are now well determined for all four garnets. In addition, ?Hof for all, except possibly spessartine, also appear to be well known.

Dachs, E.; Geiger, C. A.; Benisek, A.

2012-12-01

376

CH4/H2O ices: infrared spectra and thermodynamic properties

NASA Astrophysics Data System (ADS)

The coexistence of solid methane and water ice has been observed in outer Solar System objects, in comets, and in interstellar ice mantles (1-3). CH4 is proposed to be the starting point of rich organic chemistry in the astrophysical media. This work presents an investigation on ice mixtures of methane and water, studied by infrared spectroscopy, following some previous results of our group (4). The spectra provide evidence of a distorted CH4 structure, characterized by an absorption band at 2900 cm-1, forbidden by symmetry in the pure solid, already observed by Hodyss et al (5). We present an estimation of the amount of distorted CH4 trapped in the water ice structure and its dependence on the ice generation procedure. The presence of methane clusters inside the sample directly affects the frequency and intensity of the dangling bonds of water. When CH4 is deposited on water ices, the adsorption process follows a Type I isotherm graphic, indicating the microporous nature of the ices. We have also determined the CH4:H2O desorption energy. References (1) Boogert, A.C.A. “Interstellar Ices”. Astrophysics of Dust, ASP Conference Series, Vol. 309, p. 547, 2004. A.N. Witt, G.C. Clayton. (2) Voss, L.F. et al., “Methane thermodynamics in nanoporous ice: A new methane reservoir on Titan.” J. Geophys. Res., 112, E05002, doi: 10.1029/2006JE002768, 2007. (3) Öberg, K.I. et al., “The c2d Spitzer Spectroscopic Survey of ices around low-mass stellar objects. III. CH4.” ApJ, 678, 1032-1041, 2008. (4) Gálvez, O. et al., “Spectroscopic effects in CH4/H2O ices”, Ap. J., in press. (5) Hodyss, R. et al, “Photochemistry of methane-water ices”, Icarus 200, 338, 2009.

Escribano, R. M.; Gálvez, O.; Maté, B.; Herrero, V. J.

2009-12-01

377

NASA Astrophysics Data System (ADS)

The Gibbs free energy of hydroxyellestadite [Ca10(SiO4)3(SO4)3(OH)2] was estimated using mineral equilibria applied to analyzed assemblages from the experimental charges of Luhr (1990). The apatite analyses of Peng et al. (1997) were used in conjunction with new analyses of the oxides and silicates in this study. An ideal mixing model was employed for apatite combined with mixing models from MELTS (Ghiorso & Sack, 1994) and Gibbs free energy data from Robie & Hemingway (1995) for the other crystalline phases. The resultant equation of the Gibbs free energy vs. T for hydroxyellestadite is as follows: DG°T(elem) = [2.817(T - 273) - 11831]/1000 kJ/mol, T in K. The calculated entropy for hydroxyellestadite is 1944 J/mol.K at 1073 K and 2151 J/mol.K at 1227 K. Independent estimates of the entropy of hydroxyellestadite obtained with the method of Robinson & Haas (1983) are within 5% of these values. The thermodynamic data on hydroxyellestadite were used to calculate the locus of the reactions: 2Ca10(SiO4)3(SO4)3(OH)2 + 7S2 + 21O2 = 20CaSO4 + 6SiO2 + 2H2O 6Ca10(SiO4)3(SO4)3(OH)2 + 102SiO2 + 20Fe3O4 = 60CaFeSi2O6 + 6H2O + 9S2 + 37O2 2Ca10(SiO4)3(SO4)3(OH)2 + 10Mg2Si2O6 + 14SiO2 = 20CaMgSi2O6 + 2H2O + 3S2 + 9O2 in fO2-fS2 space at fixed P-T. Application of these equilibria to apatite zoned in sulfate from oxidized granitoids reflects a drop in fS2 by more than 1 log unit during its growth. The zoning is interpreted to represent the removal of a magmatic vapor phase during crystallization of these plutons. Removal of sulfur from magmas by hydrothermal fluids is important to the ore-forming process and to the production of acid sulfate aerosols during eruption of oxidized magmas. Preservation of sulfatian apatite may yield data on the sulfidation states of ancient flood basalts such as the Deccan Traps of India and the Parana basalts of Brazil to address the environmental impact of these giant eruptions.

Core, D.; Essene, E. J.; Luhr, J. F.; Kesler, S. E.

2004-12-01

378

Thermodynamic properties of scapolites at temperatures ranging from 10 K to 1000 K

The heat capacities of five mineral samples from the scapolite solid-solution series, Na4Al3Si9O24Cl (marialite) to Ca4Al6Si6O24CO3 (meionite), were measured by the adiabatic method from T=8 K to T=350 K and by the differential scanning calorimetry (d.s.c.) method from T = 300 K to T = 1000 K. The meionite (Me) content in per cent {Me=100 Ca*/(Ca* + Na*)} (where the asterisk indicates that possible substituents are included) and molar heat capacity (Cp,m/R) at T=298.15 K for each sample is: Me28, 82.07; Me44, 82.09; Me55, 83.95; Me69, 85.80; Me88, 84.54. The standard molar entropies, {S,om(298.15 K)-Som(0 K)} R-1 (R=8.31451 J??K-1??mol-1), at T=298.15 K for the respective compositions are: 85.05??0.26, 83.78??0.50, 85.22??0.24, 85.76??0.21, and 84.17??0.59. The calculated standard molar entropies (as above) at T=298.15 K for the end-members marialite and meionite, and for an intermediate composition (mizzonite=Me75) are 84.85, 83.94 and 86.15, respectively. Values of the coefficients in the equation Cp,m/R = a + bT+ cT2 + dT-1/2 + eT-2 (valid from T = 300 K to T =1000 K) are: (Mex, a, b/K, c/K2, d/K-1/2, e/K-2 Me88), 315.580, -0.0795676, 1.52825.10-5, -3954.83, 1808460; Me69, 261.285, -0.0415017, 8.73053.10-7, -3028.28, 1083666; Me55, 232.236, -0.0352222, 6.49875.10-6, 2505.99, 601750; Me44, 276.696, -0.0756614, 2.39722.10-5, -3210.40, 1044363; Me28, 149.917, 0.0229399, -1.23180.10-5, 1208.87, -318470. Smoothed thermodynamic functions for the five samples are also presented. The enthalpies of solution for five natural scapolites were measured in 2PbO??B2O3 melts at T= 973 K by Calvet-type calorimetry. The values of ??solHom/R??K are: Me11, 32.14??0.7; Me28, 32.34??0.4; Me44, 33.66??0.8; Me69, 35.29??0.8; Me88, 32.87??0.3. The calculated enthalpies of formation for stoichiometric scapolites ??fHom/103??R??K at T= 298.15 K are: Me0, -1467.4??1.3; Me11, -1491.2??1.2; Me28, -1527.6??0.9; Me44, -1564.1??1.1; Me55, -1587.4??1.1; Me69, -1619.7??1.1; Me75, -1633.1??1.1; Me88, -1649.1??1.0; Me100, -1664??1.6. The heat capacity, the entropy, and the enthalpy of solution have maximal values near Me75 which may account in part for the relatively common occurrence of that composition in natural assemblages. Earlier measurements on leucite have been extended by the Komada/Westrum phonon dispersion model and corrected to end-member composition. ?? 1996 Academic Press Limited.

Komada, N.; Moecher, D.P.; Westrum, E.F., Jr.; Hemingway, B.S.; Zolotov, M. Yu; Semenov, Y.V.; Khodakovsky, I.L.

1996-01-01

379

NSDL National Science Digital Library

You will learn about the properties that will help you identify minerals. If you closed your eyes and tasted different foods, you could probably determine what the foods are by noting properties such as saltiness or sweetness. You can also determine the identity of a mineral by noting different properties. Some properties that help us determine the identy of a mineral are: COLOR, ...

Wood, Mr.

2010-11-14

380

The thermodynamic properties of CeO2 have been reevaluated by a simple but accurate scheme. All our calculations are based on the self-consistent ab initio lattice dynamical (SCAILD) method that goes beyond the quasiharmonic approximation. Through this method, the effects of phonon-phonon interactions are included. The obtained thermodynamic properties and phonon dispersion relations are in good agreement with experimental data when considering the correction of phonon-phonon interaction. We find that the correction of phonon-phonon interaction is equally important and should not be neglected. At last, by comparing with quasiharmonic approximation, the present scheme based on SCAILD method is probably more suitable for high temperature systems. PMID:25573568

Niu, Zhen-Wei; Zeng, Zhao-Yi; Hu, Cui-E; Cai, Ling-Cang; Chen, Xiang-Rong

2015-01-01

381

NASA Astrophysics Data System (ADS)

The electronic and liquid structures of water and its thermodynamic properties are studied over a wide range of temperature (0°-600 °C) and density (0.6-1.4 g/cm3) based on the ab initio molecular orbital theory combined with the integral equation method of liquid. Unlike standard treatments of water by means of the classical statistical mechanics including molecular simulations, the effective charges on oxygen and hydrogen atoms in water molecules are not "input parameters," but naturally predicted from the theory in the course of self-consistent determination of the electronic structure and the density pair correlation functions in liquids. It is found that the molecular dipole moments and electronic polarization energies decrease with increasing temperature and/or density. The theoretical results for dipole moments are in quantitative accord with the experimental data, which has been determined based on the NMR chemical shift coupled with the molecular dynamics simulation [N. Matsubayashi, C. Wakai, and M. Nakahara, J. Chem. Phys. 110, 8000 (1999)]. The state dependence of the electronic structure is discussed in terms of the thermal activation of molecules and intermolecular interactions including the hydrogen bonds. The liquid structure of water is discussed in the wide range of thermodynamic states in terms of S(r), an average response of the pair correlation functions to temperature change which is introduced in the present study in order to make structural characteristics of water more distinctive. It is concluded from the behavior of the function that the short range structure of water retains the characteristics to ice, or the tetrahedral configuration, over relatively wide range of temperature in the normal density (1.0 g/cm3). The ice-like characteristics of water disappear to large extent both at high (1.4 g/cm3) and low (0.6 g/cm3) densities for different reasons: in the high density due to the packing effect, while in the low density due to essentially entropic cause, or increased configuration space available to a molecule. The distance between the nearest-neighbor molecules in water are insensitive to the density change compared with those corresponding to the Lennard-Jones fluid. The difference in the behaviors between the two fluids is explained in terms of the intermolecular interactions and liquid structures. The number of hydrogen bonds is calculated from the oxygen-hydrogen pair correlation function using a new definition based on S(r), which enables us to distinguish the hydrogen-bonded OH pairs from those just in contact due to packing effect. The temperature and density dependence of the quantity is discussed in terms of the liquid structure of water.

Sato, Hirofumi; Hirata, Fumio

1999-11-01

382

A theoretical description of the thermodynamic properties of the battery systems: Al\\/NaCl-AlCl3 -Al2X3\\/Ni-felt (X = S, Se, Te) and the corresponding system without chalcogen has been provided for cells with basic to slightly acidic NaCl-AlCl3 melts containing small amounts of chalcogen. The model developed describes the equilibrium concentrations of constituent species in the electrolyte and equilibrium potentials of the electrodes

B. C. Knutz; H. A. Hjuler; R. W. Berg; N. J. Bjerrum

1993-01-01

383

A thermodynamic property formulation for standard dry air based upon available experimental p–&rgr;–T, heat capacity, speed of sound, and vapor–liquid equilibrium data is presented. This formulation is valid for liquid, vapor, and supercritical air at temperatures from the solidification point on the bubble-point curve (59.75 K) to 2000 K at pressures up to 2000 MPa. In the absence of reliable

Eric W. Lemmon; Richard T Jacobsen; Steven G. Penoncello; Daniel G. Friend

2000-01-01

384

Thymidine glycol residues in DNA are biologically active oxidative molecular damage sites caused by ionizing radiation and other factors. One or two thymidine glycol residues were incorporated in 19- to 31-mer DNA fragments during automatic oligonucleotide synthesis. These oligonucleotide models were used to estimate the effect of oxidized thymidines on the thermodynamic, substrate and interfacial acoustic properties of DNA. UV-monitoring melting data revealed that modified residues in place of thymidines destabilize the DNA double helix by 8-22 degrees C, depending on the number of lesions, the length of oligonucleotide duplexes and their GC-content. The diminished hybridizing capacity of modified oligonucleotides is presumably due to the loss of aromaticity and elevated hydrophilicity of thymine glycol in comparison to the thymine base. According to circular dichroism (CD) data, the modified DNA duplexes retain B-form geometry, and the thymidine glycol residue introduces only local perturbations limited to the lesion site. The rate of DNA hydrolysis by restriction endonucleases R.MvaI, R.Bst2UI, R.MspR9I and R.Bme1390I is significantly decreased as the thymidine glycol is located in the central position of the double-stranded recognition sequences 5'-CC / WGG-3' (W = A, T) or 5'-CC / NGG-3' (N = A, T, G, C) adjacent to the cleavage site. On the other hand, the catalytic properties of enzymes R.Psp6I and R.BstSCI recognizing the similar sequence are not changed dramatically, since their cleavage site is separated from the point of modification by several base-pairs. Data obtained by gel-electrophoretic analysis of radioactive DNA substrates were confirmed by direct spectrophotometric assay developed by the authors. The effect of thymidine glycol was also observed on DNA hybridization at the surface of a thickness-shear mode acoustic wave device. A 1.9-fold decrease in the rate of duplex formation was noted for oligonucleotides carrying one or two thymidine glycol residues in relation to the unmodified analog. PMID:19082173

Yang, F; Romanova, E; Kubareva, E; Dolinnaya, N; Gajdos, V; Burenina, O; Fedotova, E; Ellis, J S; Oretskaya, T; Hianik, T; Thompson, M

2009-01-01

385

The heat capacities of synthetic coesite and jadeite were measured between about 15 and 850 K by adiabatic and differential scanning calorimetry. The experimental data were smoothed and estimates were made of heat capacities to 1800 K. The following equations represent our estimate of the heat capacities of coesite and jadeite between 298.15 and 1800 K: [see original article for formula]. Tables of thermodynamic values for coesite and jadeite to 1800 K are presented. The entropies of coesite and jadeite are 40.38 ?? 0.12 and 136.5 ?? 0.32 J/(mol.K), respectively, at 298.15 K. The entropy for coesite derived here confirms the value published earlier by Holm et al. (1967). We have derived an equation to describe the quartz-coesite boundary over the temperature range of 600 to 1500 K, P(GPa) = 1.76 + 0.001T(K). Our results are in agreement with the enthalpy of transition reported by Akaogi and Navrotsky (1984) and yield -907.6 ?? 1.4 kJ/mol for the enthalpy of formation of coesite from the elements at 298.15 K and 1 bar, in agreement with the value recommended by CODATA (Khodakovsky et al. 1995). Several sources of uncertainty remain unacceptably high, including: the heat capacities of coesite at temperatures above about 1000 K; the heat capacities and volumetric properties of ?? quartz at higher pressures and at temperatures above 844 K; the pressure corrections for the piston cylinder apparatus used to determine the quartz-coesite equilibrium boundary.

Hemingway, B.S.; Bohlen, S.R.; Hankins, W.B.; Westrum, E.F., Jr.; Kuskov, O.L.

1998-01-01

386

Measurements leading to the calculation of the ideal-gas thermodynamic properties are reported for 4,5,9,10-tetrahydropyrene and 1,2,3,6,7,8-hexahydropyrene. Experimental methods included combustion calorimetry, adiabatic heat-capacity calorimetry, vibrating-tube densitometry, comparative ebulliometry, inclined-piston gauge manometry, and differential-scanning calorimetry (d.s.c.). Critical properties were estimated for both materials based on the measurement results. Entropies, enthalpies, and Gibbs energies of formation were derived for the ideal gases for selected temperatures between 380 K and 700 K. The property-measurement results reported here for 4,5,9,10-tetrahydropyrene and 1,2,3,6,7,8-hexahydropyrene are the first for these important intermediates in the pyrene/H[sub 2] hydrogenation reaction network.

Chirico, R.D.; Knipmeyer, S.E.; Nguyen, A.; Smith, N.K.; Steele, W.V.

1992-12-01

387

NASA Astrophysics Data System (ADS)

The alumino-silicate solid solution series (Al 4+2xSi2-2 xO10-x) is an important class of ceramics. Except for the end member (x=0), Al2 SiO5 the crystal structures of the other phases, called mullite, have partially occupied sites. Stoichiometric supercell models for the four mullite phases 3Al2O 3 · 2SiO2 · 2Al 2O3 · SiO2, 4 Al2O3· SiO 2, 9Al2O3 · SiO2, and iota-Al2 O3 (iota-alumina) are constructed starting from experimentally reported crystal structures. A large number of models were built for each phase and relaxed using the Vienna ab initio simulation package (VASP) program. The model with the lowest total energy for a given x was chosen as the representative structure for that phase. Electronic structure and mechanical properties of mullite phases were studied via first-principles calculations. Of the various phases of transition alumina, iota-Al 2O3 is the least well known. In addition structural details have not, until now, been available. It is the end member of the aluminosilicate solid solution series with x=1. Based on a high alumina content mullite phase, a structural model for iota- Al2O3 is constructed. The simulated x-ray diffraction (XRD) pattern of this model agrees well with a measured XRD pattern. The iota-Al2 O3 is a highly disordered ultra-low-density phase of alumina with a theoretical density of 2854kg/m3. Using this theoretically constructed model, elastic, thermodynamic, electronic, and spectroscopic properties of iota-Al2 O3 have been calculated and compared it with those of alpha- Al2O3 and gamma- Al2O3. Boron carbide (B4C) undergoes an amorphization under high velocity impacts. The mechanism of amorphization is not clear. Ab initio methods are used to carry out large-scale uniaxial compression simulations on two polytypes of stoichiometric boron carbide (B4C), B 11C-CBC, and B12- CCC where B11C or B12 is the 12-atom icosahedron and CBC or CCC is the three-atom chain. The simulations were performed on large supercells of 180 atoms. Simulated results indicate bending of the three-atom chain leads to the amorphization of the B 11C-CBC (B12-CCC ) at a uniaxial strain s=0.23 (0.22) and with a maximum stress of 168 (151) GPa. The mechanism of amorphization is analyzed with radial pair distribution function (RPDF), total density of states (TDOS), and the distribution of effective charges on atoms.

Aryal, Sita Ram

388

Hydrogen technology survey: Thermophysical properties

NASA Technical Reports Server (NTRS)

The thermodynamic functions, transport properties, and physical properties of both liquid and gaseous hydrogen are presented. The low temperature regime is emphasized. The tabulation of the properties of normal hydrogen in both Si and engineering units is given along with the tabulation of parahydrogen.

Mccarty, R. D.

1975-01-01

389

of dilution properties is developed by applying the corresponding state principle and two mixing rules. The infinite dilution partial molar volume, Henry's constant and activity coefficient at infinite dilution are predicted from critical properties... Solutions 66 at 25. 0'C 69 11. Predicted Henry's Constants, H21(atm) of Nonpolar (1) 12. -Nonpolar (2) Hydrocarbon Mixtures at 25. 0'C . . . . . . . . . . Predicted Infinite Dilution Activity Coefficients 7 2 of Nonpolar (') - Nonpolar (2) Hydrocarbon...

Kim, Eue Sook

2012-06-07

390

NASA Astrophysics Data System (ADS)

A modified Benedict-Webb-Rubin (MBWR) equation of state has been developed for R152a (1,1-difluoroethane). The correlation is based on a selection of available experimental thermodynamic property data. Single-phase pressure-volume-temperature (PVT), heat capacity, and sound speed data, as well as second virial coefficient, vapor pressure, and saturated liquid and saturated vapor density data, were used with multi-property linear least-squares fitting to determine the 32 adjustable coefficients of the MBWR equation. Ancillary equations representing the vapor pressure, saturated liquid and saturated vapor densities, and the ideal gas heat capacity were determined. Coefficients for the equation of state and the ancillary equations are given. Experimental data used in this work covered temperatures from 162 K to 453 K and pressures to 35 MPa. The MBWR equation established in this work may be used to predict thermodynamic properties of R152a from the triple-point temperature of 154.56 K to 500 K and for pressures up to 60 MPa except in the immediate vicinity of the critical point.

Outcalt, Stephanie L.; McLinden, Mark O.

1996-03-01

391

Using a phenomenological lattice model incorporating the long-range Coulomb and charge transfer caused by the deformation of the electron shells of the overlapping ions and the Hafemeister and Flygare type short-range overlap repulsion extended upto the second neighbor ions and the van der Waals (vdW) interaction, we present a comprehensive study to understand the effects of pressure on the elastic behavior as ductility (brittleness) and thermodynamical properties of Ga{sub 1-x}In{sub x}P. Estimated phase-transition pressure and the vast volume discontinuity in pressure-volume phase diagram confirm the structural phase transition from zinc blende (B3) to rock salt (B1) phase. From the elastic constants the Poisson's ratio {nu}, the ratio R{sub S/B} of S (Voigt averaged shear modulus) over B (bulk modulus), elastic wave velocity, average wave velocity and thermodynamical property Debye temperature is calculated. The Poisson's ratio {nu} and the ratio R{sub S/B} allows one to conclude that Ga{sub 1-x}In{sub x}P is brittle in zinc blende (B3) and ductile nature is inferred in sodium chloride (B1) phase. To our knowledge this is the first quantitative theoretical prediction of the doping and pressure dependent elastic properties for mixed valent Ga{sub 1-x}In{sub x}P compounds and still awaits experimental confirmations.

Varshney, Dinesh, E-mail: vdinesh33@rediffmail.com [School of Physics, Vigyan Bhawan, Devi Ahilya University, Khandwa Road Campus, Indore 452001 (India) [School of Physics, Vigyan Bhawan, Devi Ahilya University, Khandwa Road Campus, Indore 452001 (India); School of Instrumentation, USIC Bhawan, Devi Ahilya University, Khandwa Road Campus, Indore 452001 (India); Dagaonkar, Geetanjali [School of Physics, Vigyan Bhawan, Devi Ahilya University, Khandwa Road Campus, Indore 452001 (India)] [School of Physics, Vigyan Bhawan, Devi Ahilya University, Khandwa Road Campus, Indore 452001 (India); Varshney, Meenu [Department of Physics, M.B. Khalsa College, Indore 452002 (India)] [Department of Physics, M.B. Khalsa College, Indore 452002 (India)

2010-08-15

392

Using first-principles calculation, we investigate systematically the properties of ZrNi(2)Ga with fcc L 2(1) Heusler structure, including the electronic structure, phonon dispersion, electron-phonon interaction and thermodynamics. The calculated electron-phonon coupling constant ? and the logarithmically averaged frequency [Formula: see text] are 0.747 and 68.48 cm(-1), respectively, giving the superconducting transition temperature T(c) = 3.15 K according to the Allen-Dynes formula. It is in good agreement with the corresponding experimental T(c) and ZrNi(2)Ga therefore can be explained as a conventional phonon-mediated superconductor. PMID:21817328

Ming, Wenmei; Liu, Yi; Zhang, Wei; Zhao, Jianzhi; Yao, Yugui

2009-02-18

393

The citric acid cycle (CAC) is the central pathway of energy transfer for many organisms, and understanding the origin of this pathway may provide insight into the origins of metabolism. In order to assess the thermodynamics of this key pathway for microorganisms that inhabit a wide variety of environments, especially those found in high temperature environments, we have calculated the properties and parameters for the revised Helgeson-Kirkham-Flowers equation of state for the major components of the CAC. While a significant amount of data is not available for many of the constituents of this fundamental pathway, methods exist that allow estimation of these missing data. PMID:19582231

Dalla-Betta, Peter; Schulte, Mitchell

2009-01-01

394

A study on the acid–base properties and solubility of two amino acids, namely dl-Tyrosine and dl-Tryptophan, was carried out in different experimental conditions (ionic medium, ionic strength and temperature). The protonation of dl-Tyrosine and dl-Tryptophan was investigated in both (CH3)4NCl and NaCl aqueous solutions by potentiometry (ISE-[H+] glass electrode) in different ionic strength ranges (up to ?3.0molL?1 in (CH3)4NCl and

Clemente Bretti; Francesco Crea; Concetta De Stefano; Silvio Sammartano; Giuseppina Vianelli

395

Thermophysical properties of sodium

NASA Technical Reports Server (NTRS)

Assessment is given of physical and thermodynamic properties of sodium. FORTRAN subroutine computes enthalphy and entropy of sodium in given state, and composition, molecular weight, volume, and compressibility factor of corresponding vapor. Tabular results for saturated liquid and vapor are presented for a 500-2500 degree F range.

Golden, G. H.; Tokar, J. V.

1969-01-01

396

Thermophysical properties of argon

The entire report consists of tables of thermodynamic properties (including sound velocity, thermal conductivity and diffusivity, Prandtl number, density) of argon at 86 to 400/degree/K, in the form of isobars over 0.9 to 100 bars. (DLC)

Jaques, A.

1988-02-01

397

NASA Astrophysics Data System (ADS)

Using methods and approaches developed by the authors, a new low-parametric state equation for describing the thermal properties of normal substances is obtained that allows us to describe the thermal properties of gases, liquids, and fluids over a range of densities from the ideal gas state to the triple point, except for a critical region, with a high degree of accuracy close to that of an experiment. The caloric properties and speed of sound are calculated for argon, nitrogen, and carbon dioxide without using any caloric data except for the enthalpy of an ideal gas. It is established that the calculated values of enthalpy, heat capacity, the speed of speed of sound, etc., are in good agreement with the experimental (reliably tabulated) data.

Kaplun, A. B.; Meshalkin, A. B.

2013-08-01

398

NASA Astrophysics Data System (ADS)

The study of several hydrofluorocarbons (HFC) and fluorocarbons (FC) and their binary mixtures that have no ozone-depleting ability is being carried Out in the framework of Belarus National Program. The fluids include HFCs R134a. R152a, R135, and R32, and FC R218. The following properties are being investigated: ( I ) phase equilibrium parameters including the boiling and condensing curve and critical point, thermophysical properties at these parameters, and heat of evaporation: (2) isobaric and isochoric heat capacity, ethalpy, and entropy in the gas and liquid state: (3) speed of sound, thermal conductivity. viscosity, and density in the gas and liquid state: (4) dielectric properties and surface tension: (5) behavior of combined construction materials inside the refrigerant medium: and (6) solubility in compressor oils and other technological characteristics. The series of results obtained by authors during the period 1990 1993 is presented.

Grebenkov, A. J.; Zhelezny, V. P.; Klepatsky, P. M.; Beljajeva, O. V.; Chernjak, Yu. A.; Kotelevsky, Yu. G.; Timofejev, B. D.

1996-05-01

399

The study of several hydrofluorocarbons (HFC) and fluorocarbons (FC) and their binary mixtures that have no ozone-depleting ability is being carried out in the framework of Belarus National program. The fluids include HFCs R134a, R152a, R125, and R32, and FC R218. The following properties are being investigated: (1) phase equilibrium parameters including the boiling and condensing curve and critical point, thermophysical properties at these parameters, and heat of evaporation; (2) isobaric and isochoric heat capacity, ethalpy, and entropy in the gas and liquid state; (3) speed of sound, thermal conductivity, viscosity, and density in the gas and liquid state; (4) dielectric properties and surface tension; (5) behavior of combined construction materials inside the refrigerant medium; and (6) solubility in compressor oils and other technological characteristics. The series of results obtained by authors during the period 1990-1993 is presented.

Grebenkov, A.J.; Klepatsky, P.M.; Beljajeva, O.V. [Inst. of Power Engineering Problems, Minsk (Belgium)] [and others

1996-05-01

400

By combining density functional theory and lattice phonon dynamics, the thermodynamic properties of CO2 absorption/desorption reactions with dehydrated potassium carbonates through K2CO3·1.5H2O + CO2 = 2KHCO3 + 0.5H2O(g) are analyzed. The energy change and the chemical potential of this reaction have been calculated and used to evaluate its thermodynamic properties and phase transitions. The results indicate that the K2CO3·1.5H2O can only be applied for postcombustion CO2 capture technology at temperatures lower than its phase transition temperature, which depends on the CO2 pressure and the steam pressure with the best range being PH2O ? 1.0 bar. Above the phase transition temperature, the sorbent will be regenerated into anhydrous K2CO3. If the steam pressure PH2O is much greater than 1.0 bar, it is possible to use the K2CO3·1.5H2O sorbent for precombustion CO2 capture technology. Compared to anhydrous K2CO3, K2CO3·1.5H2O requires less energy for regeneration.

Duan, Yuhua; Luebkes,David R.; Pennline, Henry W; Li, Bingyun Li; Janik, Michael J.; Halley, Woods

2012-01-01

401

We report on the effect of a set of water-dispersible small-molecule surfactants (the main and the longest-hydrocarbon components of which are a citric acid ester of monostearate, a sodium salt of stearol-lactoyl lactic acid, and a polyglycerol ester of stearic acid) on molecular, thermodynamic, and functional properties of the major storage protein of broad beans (Vicia faba) legumin in different molecular states (native, heated, and acid-denatured). The interaction between legumin and the surfactants has been characterized by a combination of thermodynamic methods, namely, mixing calorimetry and multiangle laser static and dynamic light scattering. It was found that hydrogen bonds, electrostatic interactions, and hydrophobic contacts provided a basis for the interactions between the surfactants and both the native and the denatured protein in aqueous medium. Intensive association of the protein molecules in a bulk aqueous medium in the presence of the surfactants was revealed by static and dynamic laser light scattering. In consequence of this, both the surface activity and the gel-forming ability of legumin increased markedly, which has been shown by tensiometry, estimation of protein foaming capacity, and steady-state viscometry. A likely molecular mechanism underlying the effects of small-molecule surfactants on legumin structure-forming properties at the interface and in a bulk aqueous medium is discussed. PMID:15313639

Il'in, Michael M; Semenova, Maria G; Belyakova, Larisa E; Antipova, Anna S; Polikarpov, Yurii N

2004-10-01

402

Using first-principles calculations, the elastic constants, the thermodynamic properties, and the structural phase transition between the B1 (rocksalt) and the B2 (cesium chloride) phases of NaCl are investigated by means of the pseudopotential plane-waves method. The calculations are performed within the generalized gradient approximation to density functional theory with the Perdew-Burke-Ernzerhof exchange-correlation functional. On the basis of the third-order Birch-Murnaghan equation of states, the transition pressure Pt between the B1 phase and the B2 phase of NaCl is determined. The calculated values are generally speaking in good agreement with experiments and with similar theoretical calculations. From the theoretical calculations, the shear modulus, Young's modulus, rigidity modulus, and Poisson's ratio of NaCl are derived. According to the quasi-harmonic Debye model, we estimated the Debye temperature of NaCl from the average sound velocity. Moreover, the pressure derivatives of elastic constants, partial differentialC11/partial differentialP, partial differentialC12/partial differentialP, partial differentialC44/partial differentialP, partial differentialS11/partial differential P, partial differentialS12/partial differentialP, and partial differentialS44/partial differentialP, for NaCl crystal are investigated for the first time. This is a quantitative theoretical prediction of the elastic and thermodynamic properties of NaCl, and it still awaits experimental confirmation. PMID:18855434

Lu, Cheng; Kuang, Xiao-Yu; Zhu, Qin-Sheng

2008-11-01

403

NASA Technical Reports Server (NTRS)

The composition and thermodynamic properties were calculated for 100 to 110,000 K and 1.01325 x 10 to the 2nd power to 1.01325 x 10 to the 8th power N/sq m for chemical equilibrium in the Debye-Huckel and ideal-gas approximations. Quantities obtained were the concentrations of hydrogen atoms, protons, free electrons, hydrogen molecules, negative hydrogen ions, hydrogen diatomic molecular ions, and hydrogen triatomic molecular ions, and the enthalpy, entropy, average molecular weight, specific heat at constant pressure, density, and isentropic exponent. Electronically excited states of H and H2 were included. Choked, isentropic, one-dimensional nozzle flow with shifting chemical equilibrium was calculated to the Debye-Huckel and ideal-gas approximations for stagnation temperatures from 2500 to 100,000 K. The mass flow per unit throat area and the sonic flow factor were obtained. The pressure ratio, temperature, velocity, and ideal and vacuum specific impulses at the throat and for pressure ratios as low as 0.000001 downstream were found. For high temperatures at pressures approaching 1.01325 x 10 to the 8th power N/sq m, the ideal-gas approximation was found to be inadequate for calculations of composition, precise thermodynamic properties, and precise nozzle flow. The greatest discrepancy in nozzle flow occurred in the exit temperature, which was as much as 21 percent higher when the Debye-Huckel approximation was used.

Patch, R. W.

1971-01-01

404

The electrochemical behavior and thermodynamic properties of Ln(III) (Ln?=?Eu, Sm, Dy, Nd) were studied in 1-butyl-3-methylimidazolium bromide ionic liquid (BmimBr) at a glassy carbon (GC) electrode in the range of 293–338 K. The electrode reaction of Eu(III) was found to be quasi-reversible by the cyclic voltammetry, the reactions of the other three lanthanide ions were regarded as irreversible systems. An increase of the current intensity was obtained with the temperature increase. At 293 K, the cathodic peak potentials of ?0.893 V (Eu(III)), ?0.596 V (Sm(III)), ?0.637 V (Dy(III)) and ?0.641 V (Nd(III)) were found, respectively, to be assigned to the reduction of Ln(III) to Ln(II). The diffusion coefficients (Do), the transfer coefficients (?) of Ln(III) (Ln?=?Eu, Sm, Dy, Nd) and the charge transfer rate constants (ks) of Eu(III) were estimated. The apparent standard potential (E0*) and the thermodynamic properties of the reduction of Eu(III) to Eu(II) were also investigated. PMID:24752584

Yang, Xiao; He, Ling; Qin, Song; Tao, Guo-Hong; Huang, Ming; Lv, Yi

2014-01-01

405

The influences of hydroxyl functional group (-OH) on the thermodynamic and structural properties of ionic liquids (ILs) composed of 1-(2-Hydroxyethyl)-3-methyl imidazolium ([C2OHmim](+)) cation and the six different conventional anions, including [Cl](-), [NO3](-), [BF4](-), [PF6](-), [TfO](-), and [Tf2N](-) have been extensively investigated using classical molecular dynamics (MD) simulations combined with ab initio calculations over a wide range of temperature (298-550 K). The volumetric thermodynamic properties, enthalpy of vaporization, cohesive energy density, Hildebrand solubility parameter, and heat capacity at constant pressure were estimated at desired temperature. The simulated densities were in good agreement with the experimental data with a slight overestimation. The interionic interaction of selected ILs was also computed using both the MD simulations and ab initio calculations. It was found that the highest association of cation and anion is attributed to [C2OHmim][Cl] followed by [C2OHmim][NO3], and [C2OHmim][Tf2N] with the bulkiest anion has the weakest interionic interaction among chosen ILs. The similar trend of interactions energies was nearly observed from cohesive energy density results. Additional structural details were comprehensively yielded by calculating radial distribution functions (RDFs) and spatial distribution function (SDFs) at 358 K. The most stable configurations of isolated and dimer ion pairs of these ILs were in excellent consistency with RDFs and SDFs results. Significant changes in arrangement of anions around the [C2OHmim](+) cation in comparison with conventional imidazolium-based ILs can be inferred from the MD simulations and ab initio results. Also, microscopic structural properties disclosed that the most strong cation-cation interaction is ascribed to the hydroxyl-functionalized ILs composed of bulkier anions, whereas ILs incorporating [Cl](-) and [NO3](-) anions are mainly involved in cation-anion interactions. The formation of the intramolecular hydrogen bonding in the [C2OHmim](+) cation is another interesting result of the present study. PMID:25394200

Fakhraee, Mostafa; Zandkarimi, Borna; Salari, Hadi; Gholami, Mohammad Reza

2014-12-11

406

NASA Astrophysics Data System (ADS)

Structural, electronic and optical properties of Mg x Cd1- x Se (0 ? x ? 1) are calculated for the first time using density functional theory. Our results show that these properties are strongly dependent on molar fraction of particular components — x. The bond between Cd and Se is partially covalent and the covalent nature of the bond decreases as the concentration of Mg increases from 0 % to 100 %. It is found that Mg x Cd1- x Se has a direct band gap in the entire range of x and the band gap of the alloy increases from 0.43 to 2.46 eV with the increase in Mg concentration. Frequency dependent dielectric constants ?1(?), ?2(?) refractive index n(?) are also calculated and discussed in detail. The peak value of refractive indices shifts to higher energy regions with the increase in Mg. The larger value of the extraordinary refractive index confirms that the material is a positive birefringence crystal. The present comprehensive theoretical study of the optoelectronic properties of the material predicts that it can be effectively used in optoelectronic applications in the wide range of spectra: IR, visible and UV. In addition, we have also predicted the heat capacities (C V ), the entropy (S), the internal energy (U) and the Helmholtz free energy (F) of Mg x Cd1- x Se ternary alloys.

Bensaid, D.; Ameri, M.; El Hanani, M. Din; Azaz, Y.; Bendouma, D.; Al-Douri, Y.; Ameri, I.

2014-12-01

407

The authors have computed the equilibrium composition, the transport coefficients (viscosity and electrical and thermal conductivities), the thermodynamic properties (Gibbs and Helmholtz potentials, entropy, enthalpy, and specific heats), and the derived quantities (mass density and sound velocity) for sulfur hexafluoride-molecular nitrogen mixtures in conditions relevant to circuit-breaker arcs: temperature between 1000 and 30,000 K and pressure in the range 1-10 atm. The validity of the computation has been checked by a detailed comparison of the results with those available in the literature concerning pure sulfur hexafluoride and pure molecular nitrogen. In such mixtures the chemical reactions (dissociation and ionization) have a strong influence on thermal conduction and specific heat. the effect of sulfur hexafluoride on the properties of such mixtures is elucidated; in a mixture containing 40% sulfur hexafluoride, the amplitude of the thermal conduction peak appearing around 7500 K is reduced by a factor of four relative to that of pure molecular nitrogen. The influence of pressure on the properties of the plasma between 1 and 10 atm is relatively low.

Gleizes, A.; Razafinimanana, M.; Vacquie, S.

1986-03-01

408

The Fourier transform infrared (FT-IR) and Fourier transform Raman (FT-Raman) spectra of 2-amino-5-bromo-6-methyl-4-pyrimidinol (ABrMP) were recorded in the region 4000-400 and 3500-100cm(-1), respectively. The conformational stability, geometrical structure, vibrational frequencies, infrared intensities and Raman activities were carried out by DFT (B3LYP and LSDA) methods with 6-311++G(d,p) basis set. The calculated results show good agreement with observed spectra. The charge delocalization have been analyzed using NBO analysis by LSDA/6-311++G(d,p) level of theory. The NLO properties (?, ?0, ??, ?0 and ?vec) have been computed quantum mechanically. The calculated HOMO and LUMO energies show that, the charge transfer occurs within the molecule. The solvent effects have been calculated using TD-DFT and the results are in good agreement with experimental measurements. The other molecular properties like Mulliken population analysis, electrostatic potential (ESP) and thermodynamic properties of the title compound at the different temperatures have been calculated. PMID:25645233

Gladis Anitha, E; Joseph Vedhagiri, S; Parimala, K

2015-04-01

409

NASA Astrophysics Data System (ADS)

Daubreelite is a common mineral in enstatite chondrites, but its thermodynamic properties have not been studied. This greatly complicates the study of the physico - chemical parameters of enstatite chondrites formation in their parent bodies. Analysis of the quaternary system Ag-Cr-Fe-S showed that at temperatures below 423 K can be stable phase association Ag2S + Cr2S3 + FeS2 + FeCr2S4, potential silver which can be defined in a completely solid state galvanic cell: (-) Pt | Ag | RbAg4I5 | Ag2S, Cr2S3, FeS2, FeCr2S4 | Pt (+), with a RbAg4I5 as a solid electrolyte with a specific conductivity of Ag+ ion. The overall potential forming process in the cell corresponds to a chemical reaction: 2Ag + Cr2S3 + FeS2 = Ag2S + FeCr2S4 Gibbs energy of this reaction is associated with the electromotive force of galvanic cells by fundamental equation of thermodynamics ?rG =-nFE, where n = 2 - the number of electrons in the electrochemical process, F = 96485 C•mol-1 - Faraday constant, and E-electromotive force (emf) of galvanic cell in volts. Temperature dependence of the emf was determined in an electrochemical cell, a device which is described in detail in the works Osadchii and Chareev (2006), and Osadchii and Echmaeva (2007). The results were approximated by a linear dependence of E(T), which corresponds to the condition ?rCp constant and equal to zero: E(mV)=76.32+0.2296•T, 339

Osadchii, Evgeniy; Voronin, Mikhail; Osadchii, Valentin

2014-05-01

410

This thesis investigates microgrid control stability with respect to thermodynamics behaviors of generation and demand. First, a new integrated microgrid model is introduced. This model consists of a combined cycle power ...

Liu, Fang-Yu, S.M. Massachusetts Institute of Technology

2014-01-01

411

Thermophysical Properties of Hydrocarbon Mixtures

National Institute of Standards and Technology Data Gateway

SRD 4 NIST Thermophysical Properties of Hydrocarbon Mixtures (PC database for purchase) Interactive computer program for predicting thermodynamic and transport properties of pure fluids and fluid mixtures containing up to 20 components. The components are selected from a database of 196 components, mostly hydrocarbons.

412

NASA Astrophysics Data System (ADS)

The molecular interaction studies in the binary liquid mixtures of two aliphatic alcohols with 1, 4-dioxane has been carried out at 308 K using ultrasonic technique. Using measured values of ultrasonic velocity, density and viscosity, acoustical parameters such as adiabatic compressibility, free volume, free length and their excess values like VfE, ßaE, LfE are evaluated. From the properties of these excess parameters, the nature and the strength of interactions in these binary systems are discussed. It has been observed that, weak dispersive type intermolecular interactions are confirmed in the systems investigated. Dipole inducement is found to be more predominant in methanol system.

Bedare, G. R.; Bhandakkar, V. D.; Suryavanshi, B. M.

2012-12-01

413

The extraction of the Mo(VI)-calmagite complex by adsorption onto active carbon is investigated in the present paper. Thermodynamic and kinetic properties and different adsorption isotherms were determined. The adsorption studies have shown that both the empirical Freundlich and the classical Langmuir isotherms successfully fit the experimental results. The overall adsorption process was exothermic and spontaneous in the temperature range from 283 to 323 K; namely, DeltaH(0) and DeltaS(0) values were found to be -8.15 kJ mol(-1) and -3.86 J mol(-1) K, respectively. The high activation energy demanded for desorption of the Mo(VI)-calmagite complex surface indicated that the overall process was controlled by the slow desorption, while a fast and low activated adsorption of the complex onto active carbon surface was fairly favored. These features indicate that active carbon may be very useful for preconcentration of molybdenum from diluted solutions. PMID:14697689

Ferreira, Sérgio L C; Andrade, Heloysa M C; dos Santos, Hilda C

2004-02-15

414

Missense mutations in alanine 673 of the amyloid precursor protein (APP), which corresponds to the second alanine of the amyloid ? (A?) sequence, have dramatic impact on the risk for Alzheimer disease; A2V is causative, and A2T is protective. Assuming a crucial role of amyloid-A? in neurodegeneration, we hypothesized that both A2V and A2T mutations cause distinct changes in A? properties that may at least partially explain these completely different phenotypes. Using human APP-overexpressing primary neurons, we observed significantly decreased A? production in the A2T mutant along with an enhanced A? generation in the A2V mutant confirming earlier data from non-neuronal cell lines. More importantly, thioflavin T fluorescence assays revealed that the mutations, while having little effect on A?42 peptide aggregation, dramatically change the properties of the A?40 pool with A2V accelerating and A2T delaying aggregation of the A? peptides. In line with the kinetic data, A? A2T demonstrated an increase in the solubility at equilibrium, an effect that was also observed in all mixtures of the A2T mutant with the wild type A?40. We propose that in addition to the reduced ?-secretase cleavage of APP, the impaired propensity to aggregate may be part of the protective effect conferred by A2T substitution. The interpretation of the protective effect of this mutation is thus much more complicated than proposed previously. PMID:25253695

Benilova, Iryna; Gallardo, Rodrigo; Ungureanu, Andreea-Alexandra; Castillo Cano, Virginia; Snellinx, An; Ramakers, Meine; Bartic, Carmen; Rousseau, Frederic; Schymkowitz, Joost; De Strooper, Bart

2014-11-01

415

NASA Astrophysics Data System (ADS)

The Dortmund Data Bank (DDB) was started in 1973 with the intention to employ the vast store of vapor-liquid equilibrium (VLE) data from the literature for the development of models for the prediction of VLE. From the beginning, the structure of the DDB has been organized in such a way that it was possible to take advantage of the full potential of electronic computers. With the experience gained in fitting and processing VLE data, we extended the DDB system to other types of mixture properties, i.e., liquid-liquid equilibria (LLE), gas solubilities (GLE), activity coefficients at infinite dilution ??, heats of mixing ( h E), and excess heat capacities. Besides the files for mixture properties, the DDB contains pure-component data and program packages for various applications. New experimental data are checked for consistency before they are stored. For data retrieval user-specified search masks can be used. The data files are available via an online data service and through the Dechema Chemistry Data Series. For the purpose of data correlation and model testing, parameter fitting is performed with an optimization routine (Nelder-Mead). In the past years the DDB system has been successfully employed for the development of prediction methods for VLE, LLE, GLE, ??, and h E (UNIFAC, mod. UNIFAC, etc.).

Onken, U.; Rarey-Nies, J.; Gmehling, J.

1989-05-01

416

The thermodynamic properties of solid solutions with body-centered cubic (bcc), face-centered cubic (fcc) and hexagonal close-packed (hcp) structures in the Al–TM (TM=Ti, Zr and Hf) systems are calculated from first-principles using cluster expansion (CE), Monte-Carlo simulation and supercell methods. The 32-atom special quasirandom structure (SQS) supercells are employed to compute properties at 25, 50 and 75at.% TM compositions, and 64-atom

G. Ghosh; A. van de Walle; M. Asta

2008-01-01

417

Numerous fluids have been identified as promising alternative refrigerants, but much of the information needed to predict their behavior as pure fluids and as components in mixtures does not exist. In particular, reliable thermophysical properties data and models are needed to predict the performance of the new refrigerants in heating and cooling equipment and to design and optimize equipment to be reliable and energy efficient. The objective of this project is to provide highly accurate, selected thermophysical properties data for Refrigerants 32, 123, 124, and 125, and to use these data to fit simple and complex equations of state and detailed transport property models. The new data will fill gaps in the existing data sets and resolve the problems and uncertainties that exist in and between the data sets. This report describes the progress made during the fourth quarter of this fifteen-month project, which was initiated in late January, 1992.

Kayser, R.F.

1993-01-01

418

Numerous fluids have been identified as promising alternative refrigerants, but much of the information needed to predict their behavior as pure fluids and as components in mixtures does not exist. In particular, reliable thermophysical properties data and models are needed to predict the performance of the new refrigerants in heating and cooling equipment, and to design and optimize equipment to be reliable and energy efficient. Objective of this project is to provide highly accurate, selected thermophysical properties data for Refrigerants 32, 123, 124, and 125, and to use these data to fit simple and complex equations of state and detailed transport property models. The new data will fill gaps in the existing data sets and resolve the problems and uncertainties that exist in and between the data sets. This report describes the progress made during the third quarter of this fifteen-month project, which was initiated in late January, 1992.

Kayser, R.F.

1992-10-01

419

NASA Astrophysics Data System (ADS)

The temperature dependences of the heat capacities of 5-vinyltetrazole and poly-5-vinyltetrazole were measured by adiabatic vacuum calorimetry over the temperature range 6-(350-370) K with errors of ˜0.2%. The results were used to calculate the thermodynamic functions of the compounds, C {/p ?}, H ?( T) - H ?(0), S ?( T), and G ?( T) - H ?(0), over the temperature range from T ? 0 to 350-370 K. The energy of combustion of 5-vinyltetrazole and poly-5-vinyltetrazole was measured in an isothermic-shell static bomb calorimeter. The standard enthalpies of combustion ? c H ? an