Thermodynamic Properties of HCFC-124
NASA Astrophysics Data System (ADS)
Fukushima, Masato; Watanabe, Naohiro
Thermodynamic properties of HCFC-124, such as saturated densities, vapor pressures and PVT properties, were measured and the critical parameters were determined through those experimental results. The correlations for vapor pressure, saturated liquid density and PVT properties deduced from those experimental results were compared with the measured data and also with the estimates of the other correlations published in literatures. The thermodynamic functions, such as enthalpy, entropy, heat capacity, etc., can reasonably be calculated from the correlation equations in this paper.
Thermodynamic properties of cerium mononitride
NASA Astrophysics Data System (ADS)
Aristova, N. M.; Belov, G. V.
2014-09-01
Data on the thermodynamic properties of cerium mononitride CeN in the solid state are analyzed. Relations approximating the temperature dependence of the thermodynamic functions of CeN(cr.) in the temperature range of 298.15-2900 K are obtained. Using the relations of thermodynamics known for this temperature range, the thermodynamic functions of cerium mononitride (entropy, Gibbs energy, and enthalpy variation) are calculated. The resulting data is entered into the database of the IVTANTHERMO software package and is used to analyze the thermal stability of CeN(cr.), and to estimate its boiling point at atmospheric pressure.
Thermodynamic Properties of Supported Catalysts
Gorte, Raymond J.
2014-03-26
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.
The Thermodynamic Properties of Cubanite
NASA Technical Reports Server (NTRS)
Berger, E. L.; Lauretta, D. S.; Keller, L. P.
2012-01-01
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.
Thermodynamic properties of minerals
Robie, Richard A.
1962-01-01
In the ten years since the publication of the national Bureau of Standards comprehensive tables of thermochemical properties, by Rossini and other (1952), a very large body of modern calorimetric and equilibrium data has become available. Because of the complex interrelations among many thermochemical data and the necessity for internal consistency among these values, a complete revision of this standard reference is required. This is also true of the summaries of thermochemical data for the sulfides (Richardson and Jeffes 1952) and for the oxides (Coughlin 1954). The following tables present critically selected values for the heat and free energy of formation, the logarithm of the equilibrium constant of formation Log Kf, the entropy and the molar volume, at 298.15°K (25.0°C) and one atmosphere for minerals.
Thermodynamic properties of uranium dioxide
Fink, J.K.; Chasanov, M.G.; Leibowitz, L.
1981-04-01
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.
Advanced working fluids: Thermodynamic properties
NASA Astrophysics Data System (ADS)
Lee, Lloyd L.; Gering, Kevin L.
1990-10-01
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.
Thermodynamic properties of lanthanum molybdates
NASA Astrophysics Data System (ADS)
Suponitskiy, Yu. L.; Proshina, O. P.; Dyunin, A. G.; Liashenko, S. E.
2016-02-01
The enthalpy of solution of LaOHMoO4 and Cs2MoO4 in aqueous HCl at 298 K has been determined by solution calorimetry, and the standard enthalpy of formation of lanthanum hydroxomolybdate has been calculated. The enthalpies of solution of NaLa(MoO4)2 and Na5La(MoO4)4 in molybdate melt at 973 K have been determined by high-temperature melt solution microcalorimetry, and the high-temperature enthalpies of the double molybdates in the 298-1000 K range have been measured by the mixing method. The standard enthalpies of formation of the double molybdates have been calculated using data available from the literature. The low-temperature heat capacity of NaLa(MoO4)2 in the 60-300 K range has been measured on an adiabatic vacuum calorimeter. The basic thermodynamic properties of NaLa(MoO4)2, Na5La(MoO4)4, and LaOHMoO4 have been calculated.
Tables of thermodynamic properties of sodium
Fink, J.K.
1982-06-01
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.
Thermodynamic properties of liquid metals /A review/.
NASA Technical Reports Server (NTRS)
Margrave, J. L.
1970-01-01
Summary of the current state of knowledge about the thermodynamic properties of liquid metals, including heats of fusion and heat capacities. A table is presented of consistent thermodynamic data for liquid metals, including estimates for the many high-melting transition metals which have not yet been studied, based on new levitation data and on periodic table correlations.
Prediction of Thermodynamic Properties for Halogenated Hydrocarbon
NASA Astrophysics Data System (ADS)
Higashi, Yukihiro
The predictive methods of thermodynamic properties are discussed with respect to the halogenated hydrocarbons using as working fluids for refrigeration and heat pump cycles. The methods introduced into this paper can be calculated by the limited information; critical properties, normal boiling point and acentric factor. The results of prediction are compared with the experimental values of PVT property, vapor pressure and saturated liquid density. On the basis of these comparisons, Lydersen's method for predicting the critical properties, the generalized vapor pressure correlation by Ashizawa et, al., and Hankinson-Thomson's method for predicting saturated liquid density can be recommended. With respect to the equation of state, either Soave equation or Peng-Robinson equation is effective in calculating the thermodynamic properties except high density region.
Thermodynamic Properties of Ar39 Cluster
NASA Astrophysics Data System (ADS)
Eryurek, M.; Guven, M. H.
2007-04-01
The solid-liquid phase transitions of Ar39 cluster was simulated by the microcanonical Molecular Dynamics (MD) and microcanonical Parallel Tempering (PT) Monte Carlo methods using Lennard-Jones potential, and thermodynamic quantities were calculated. All thermodynamic quantities (configurational entropy, thermodynamic temperature, microcanonical heat capacity, potential energy distribution) were evaluated by using multiple histogram method. The same results were found in both simulation methods. The thermodynamic properties of microcanonical results indicate that the caloric curve has S-dent and the negative heat capacity has negative values at the solid-liquid phase transition region. At the same time by using microcanonical results melting temperature, latent heat and entropy change upon melting values were reported and compared with the values reported in the literature and the values calculated from the thermodynamic relations offered for bulk matter and, consistent values were found.
Computing Thermodynamic And Transport Properties Of Air
NASA Technical Reports Server (NTRS)
Thompson, Richard A.; Gupta, Roop N.; Lee, Kam-Pui
1994-01-01
EQAIRS computer program is set of FORTRAN 77 routines for computing thermodynamic and transport properties of equilibrium air for temperatures from 100 to 30,000 K. Computes properties from 11-species, curve-fit mathematical model. Successfully implemented on DEC VAX-series computer running VMS, Sun4-series computer running SunOS, and IBM PC-compatible computer running MS-DOS.
Thermodynamic and transport properties of gaseous tetrafluoromethane in chemical equilibrium
NASA Technical Reports Server (NTRS)
Hunt, J. L.; Boney, L. R.
1973-01-01
Equations and in computer code are presented for the thermodynamic and transport properties of gaseous, undissociated tetrafluoromethane (CF4) in chemical equilibrium. The computer code calculates the thermodynamic and transport properties of CF4 when given any two of five thermodynamic variables (entropy, temperature, volume, pressure, and enthalpy). Equilibrium thermodynamic and transport property data are tabulated and pressure-enthalpy diagrams are presented.
Thermodynamic properties of dimethylene urethane
NASA Astrophysics Data System (ADS)
Emel'yanenko, V. N.; Turovtsev, V. V.; Orlov, Yu. D.
2015-07-01
Enthalpies of the combustion and formation of crystalline dimethylene urethane (oxazolidin-2-one) are determined via combustion calorimetry. The enthalpy of sublimation is determined via the transpiration method, and the enthalpy of fusion is found by means of differential scanning calorimetry. The temperature dependence of the saturated vapor pressure is measured in the range of 323-353 K. Thermodynamic functions in the ideal gas state are calculated using the rigid rotator-anharmonic oscillator model in the range of T = 298.15-1500 K.
Thermodynamic properties of water solvating biomolecular surfaces
NASA Astrophysics Data System (ADS)
Heyden, Matthias
Changes in the potential energy and entropy of water molecules hydrating biomolecular interfaces play a significant role for biomolecular solubility and association. Free energy perturbation and thermodynamic integration methods allow calculations of free energy differences between two states from simulations. However, these methods are computationally demanding and do not provide insights into individual thermodynamic contributions, i.e. changes in the solvent energy or entropy. Here, we employ methods to spatially resolve distributions of hydration water thermodynamic properties in the vicinity of biomolecular surfaces. This allows direct insights into thermodynamic signatures of the hydration of hydrophobic and hydrophilic solvent accessible sites of proteins and small molecules and comparisons to ideal model surfaces. We correlate dynamic properties of hydration water molecules, i.e. translational and rotational mobility, to their thermodynamics. The latter can be used as a guide to extract thermodynamic information from experimental measurements of site-resolved water dynamics. Further, we study energy-entropy compensations of water at different hydration sites of biomolecular surfaces. This work is supported by the Cluster of Excellence RESOLV (EXC 1069) funded by the Deutsche Forschungsgemeinschaft.
Thermodynamic Properties of Aqueous Sodium Chloride Solutions
NASA Astrophysics Data System (ADS)
Pitzer, Kenneth S.; Peiper, J. Christopher; Busey, R. H.
1984-01-01
Experimental measurements of the osmotic and activity coefficients, the enthalpy, and the heat capacity were used to derive a semiempirical equation for the thermodynamic properties of NaCl(aq) at constant pressure. This equation may be combined with results contained in the previous paper on the volumetric properties to yield a complete equation of state valid in the region 273 K≤T≤573 K, saturation pressure ≤P≤1 kbar, 0≤m≤6.0 mol kg-1. It is shown that this equation may be extrapolated to higher solute molalities at lower pressures. An estimation of uncertainties in various quantities is given. Tables of values for various thermodynamic properties are presented in the appendix.
Thermodynamics and statistical mechanics. [thermodynamic properties of gases
NASA Technical Reports Server (NTRS)
1976-01-01
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.
Thermodynamic properties of ferrocene dicarboxylic acid
NASA Astrophysics Data System (ADS)
Kozlova, M. S.; Markin, A. V.; Larina, V. N.; Letyanina, I. A.
2014-02-01
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.
The thermodynamic properties of benzothiazole and benzoxazole
Steele, W.V.; Chirico, R.D.; Knipmeyer, S.E.; Nguyen, A.
1991-08-01
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.
The thermodynamic properties of thianthrene and phenoxathiin
Steele, W.V.; Chirico, R.D.; Knipmeyer, S.E.; Nguyen, A.
1993-04-01
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.
Thermodynamic Properties of Actinides and Actinide Compounds
NASA Astrophysics Data System (ADS)
Konings, Rudy J. M.; Morss, Lester R.; Fuger, Jean
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.
Thermodynamic properties of Heisenberg magnetic systems
NASA Astrophysics Data System (ADS)
Qin, Wei; Wang, Huai-Yu; Long, Gui-Lu
2014-03-01
In this paper, we present a comprehensive investigation of the effects of the transverse correlation function (TCF) on the thermodynamic properties of Heisenberg antiferromagnetic (AFM) and ferromagnetic (FM) systems with cubic lattices. The TCF of an FM system is positive and increases with temperature, while that of an AFM system is negative and decreases with temperature. The TCF lowers internal energy, entropy and specific heat. It always raises the free energy of an FM system but raises that of an AFM system only above a specific temperature when the spin quantum number is S >= 1. Comparisons between the effects of the TCFs on the FM and AFM systems are made where possible.
GRI thermodynamics and physical properties research
Fish, F.
1981-03-01
The paper focuses on planning and implementing a comprehensive gas-related research and development program that is being conducted by the Gas Research Institute (GRI). Chicago, Ill. Emphasis is on the gas thermodynamical and thermophysical properties of fluids but GRI also has small programs in gas hydrates and in gas separation science. All of the GRI's projects are contracted to research institutes, technical consulting firms, universities, energy companies, and equipment manufacturers engaged in gas-related research and development. Most of basic research's effort in support of GRI's strategic objective is in long-term gas supply options.
Statistical Thermodynamic Properties of Linear Protein Solutions
NASA Astrophysics Data System (ADS)
Li, Li-fen; Liang, Xi-xia; Li, Qian-zhong
2010-04-01
The thermodynamic properties of linear protein solutions are discussed by a statistical mechanics theory with a lattice model. The numerical results show that the Gibbs function of the solution decreases, and the protein chemical potential is enhanced with increase of the protein concentration for dilute solutions. The influences of chain length and temperature on the Gibbs function of the solution as well as the protein chemical potential are analyzed. As an application of the theory, the chemical potentials of some mutants of type I antifreeze proteins are computed and discussed.
Prediction of thermodynamic properties of coal derivatives
Donohue, M.D.
1990-09-01
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.
Thermodynamic properties for R-404A
Fujiwara, K.; Nakamura, S.; Noguchi, M.
1999-01-01
An 18-coefficient modified Benedict-Webb-Rubin equation of state has been developed for R-404A, a ternary mixture of 44% by mass of pentafluoroethane (R-125), 52% by mass of 1,1,1-trifluoroethane (R-143a), and 4% by mass of 1,1,1,2-tetrafluoroethane (R-134a). Correlations of bubble point pressures, dew point pressures, saturated liquid densities, and saturated vapor densities are also presented. This equation of state has been developed based on the reported experimental data of PVT properties, saturation properties, and isochoric heat capacities by using least-squares fitting. These correlations are valid in the temperature range from 250 K to the critical temperature. This equation of state is valid at pressures up to 19 MPa, densities to 1,300 kg {center_dot} m{sup {minus}3}, and temperatures from 250 to 400 K. The thermodynamic properties except for the saturation pressures are calculated from this equation of state.
Thermodynamic Properties in Triangular-Lattice Superconductors
NASA Astrophysics Data System (ADS)
Ma, Xixiao; Qin, Ling; Zhao, Huaisong; Lan, Yu; Feng, Shiping
2016-06-01
The study of superconductivity arising from doping a Mott insulator has become a central issue in the area of superconductivity. Within the framework of the kinetic-energy-driven superconducting (SC) mechanism, we discuss the thermodynamic properties in the triangular-lattice cobaltate superconductors. It is shown that a sharp peak in the specific heat appears at the SC transition temperature T_c, and then the specific heat varies exponentially as a function of temperature for temperatures T
Thermodynamic Properties in Triangular-Lattice Superconductors
NASA Astrophysics Data System (ADS)
Ma, Xixiao; Qin, Ling; Zhao, Huaisong; Lan, Yu; Feng, Shiping
2016-02-01
The study of superconductivity arising from doping a Mott insulator has become a central issue in the area of superconductivity. Within the framework of the kinetic-energy-driven superconducting (SC) mechanism, we discuss the thermodynamic properties in the triangular-lattice cobaltate superconductors. It is shown that a sharp peak in the specific heat appears at the SC transition temperature T_c , and then the specific heat varies exponentially as a function of temperature for temperatures T
Thermodynamic properties and amorphization of Zr-Si melts
NASA Astrophysics Data System (ADS)
Arutyunyan, N. A.; Zaitsev, A. I.; Dunaev, S. F.; Shaposhnikov, N. G.
2016-02-01
The relationship between the thermodynamic properties of Zr-Si liquid alloys and their propensity to amorphization is studied. The temperature-concentration dependences of the thermodynamic properties of melts are presented using the concept of associated solutions. It is shown that the range of amorphization coincides with the range of the predominant concentration of Zr3Si associative groups with low formation entropy.
Universal relation for size dependent thermodynamic properties of metallic nanoparticles.
Xiong, Shiyun; Qi, Weihong; Cheng, Yajuan; Huang, Baiyun; Wang, Mingpu; Li, Yejun
2011-06-14
The previous model on surface free energy has been extended to calculate size dependent thermodynamic properties (i.e., melting temperature, melting enthalpy, melting entropy, evaporation temperature, Curie temperature, Debye temperature and specific heat capacity) of nanoparticles. According to the quantitative calculation of size effects on the calculated thermodynamic properties, it is found that most thermodynamic properties of nanoparticles vary linearly with 1/D as a first approximation. In other words, the size dependent thermodynamic properties P(n) have the form of P(n) = P(b)(1 -K/D), in which P(b) is the corresponding bulk value and K is the material constant. This may be regarded as a scaling law for most of the size dependent thermodynamic properties for different materials. The present predictions are consistent literature values. PMID:21523307
Thermopower Puck for Measurement of Thermodynamic Properties
NASA Astrophysics Data System (ADS)
Vargas, Andres; Fukuda, Ryan; Soliz, Nicholas; Ho, Pei-Chun
2014-03-01
A thermopower puck was created in order to measure the thermoelectric power and thermal conductance of strongly correlated electron materials from 10K to 300K. The puck consists of a 2k Ω resistivity heater and 2 thermometers. The heater is connected to the top of the sample and applies heat until thermal equilibrium is reached. This creates a temperature gradient across the sample and is read by the 2 thermometers, one reading the hotter temperature and the other reading the colder temperature. The wire that is used as the thermal anchor for the high temperature thermometer, which is electrically isolated from thermometer, is also used as one of the leads to measure the thermal voltage produced across the sample. To calibrate the measurement probe, the thermoelectric power and thermal conductance of a nickel sample, which was purchased from Quantum Design, was measured. The data obtained qualitatively agrees with the literature data provided to us by Quantum Design. For future work, we will be using the measurement probe to investigate the thermodynamic properties of intermetallic compounds. Research at CSU-Fresno is supported by NSF DMR-1104544. Felipe Vargas is also supported by Undergraduate Research Grant at CSU Fresno.
Calculation of the standard molal thermodynamic properties of crystalline peptides
NASA Astrophysics Data System (ADS)
LaRowe, Douglas E.; Dick, Jeffrey M.
2012-03-01
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.
The Thermodynamic Properties of Semiconductor Nanocrystals
NASA Astrophysics Data System (ADS)
Goldstein, Avery Nathan
Semiconductor nanocrystals or "quantum dots" exhibit changes in electronic band structure when their size becomes comparable to the bulk electronic delocalization lengths (tens to hundreds of Angstroms). The band structure modifications are manifest as a blue shift in the nanocrystal optical absorption spectrum. It is essential to characterize the size dependence of the absorption shift and the thermal stability before one may harness nanocrystal properties for device applications. Semiconductor nanocrystals are prepared by arrested precipitation techniques and as such the nanocrystal surface is passivated with an organic layer. Due to the colloidal growth process polydisperse particles result. The size distribution of CdSe nanocrystal samples ranging in radius from 8 A to 45 A are determined using small angle X-ray scattering (SAXS) and transmission electron microscopy (TEM). The results are compared with the tight binding and pseudo-potential calculations. Based on the size dependence measured and the single particle absorption spectrum, the sample size distribution is directly obtainable from the absorption spectrum of the sample. TEM and thermoanalytical melting studies of the II-VI and III-V semiconductors CdS and GaAs show that in the small size regime the melting temperature is size dependent and follows an inverse radius relationship and can be modelled with simple thermodynamic equations. CdS nanocrystals can be melted and recrystallized whereas GaAs decomposes upon phase transformation. The surface tensions of nanocrystals are greater than those of the bulk, in agreement with results for metallic clusters. The melting process involves particle annealing, organic desorption and melting. The melting mechanism appears to involve nucleation on the particle surface and a lobular progression of the melt into the solid.
Thermodynamic properties of doped lanthanum manganites
Hildrum, R.; Brustad, M. . Dept. of Electrochemistry); Wang Changzhen . Div. of Physicochemistry of Metallurgy); Johannesen, O. )
1994-08-01
The thermodynamic properties of the perovskite compounds La[sub 0.8]Sr[sub 0.2]MnO[sub 3] (LSM), La[sub 0.9]Na[sub 0.1]MnO[sub 3] (LNM), and LaMnO[sub 3] (LM) were studied by use of the solid electrolyte galvanic cell method at 1,000 C, 1,050 C, and 1,100 C. Two samples of each compound were investigated as well as decomposed samples of LSM and LNM. The cell assembly was constructed by means of eight small stabilized zirconia tubes and a common Ni/NiO reference electrode. The equilibrium partial pressures of the samples were calculated form the measured EMF values. The results reveal that the equilibrium pO[sub 2] of LM appears to be one or two orders of magnitude lower than that of LSM and LNM, respectively, which means that LM is more stable than the doped perovskites. The variation in the standard free energy with temperature for the perovskite decomposition reaction was calculated from the pO[sub 2] equilibrium values, i.e. [Delta]G[degree]d (LSM) = 140.86 [minus] 0.05199T kJ/mole and [Delta]G[degree]d (LNM) = 106.06 [minus] 0.02572T kJ/mole. On the basis of the above equations, the reaction enthalpy and entropy changes were calculated. Perovskite oxides have received considerable attention in recent years for their use as cathodes in solid oxide fuel cells.
Measurement of Thermodynamic Properties of Titanium Aluminum Alloys
NASA Technical Reports Server (NTRS)
Mehrotra, Gopal
1995-01-01
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.
Microcomputer Simulation of Real Gases--Part 2: Thermodynamical Properties.
ERIC Educational Resources Information Center
Sperandeo-Mineo, R. M.; Tripi, G.
1988-01-01
Studies the pressure and energy of particles interacting through a Lennard-Jones potential and correlates thermodynamical properties with system structural characteristics. Analyzes the relationships between computer simulated data and the van der Waals equation. (YP)
Composition and Thermodynamic Properties of Air in Chemical Equilibrium
NASA Technical Reports Server (NTRS)
Moeckel, W E; Weston, Kenneth C
1958-01-01
Charts have been prepared relating the thermodynamic properties of air in chemical equilibrium for temperatures to 15,000 degrees k and for pressures 10(-5) to 10 (plus 4) atmospheres. Also included are charts showing the composition of air, the isentropic exponent, and the speed of sound. These charts are based on thermodynamic data calculated by the National Bureau of Standards. (author)
Thermodynamic property determination in low gravity
NASA Technical Reports Server (NTRS)
Margrave, J. L.
1977-01-01
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.
A Pseudopotential Approach to Compute Thermodynamic Properties of Liquid Semiconductors
NASA Astrophysics Data System (ADS)
Prajapati, Anand; Thakor, Pankaj; Sonvane, Yogesh
2015-03-01
This paper deals with the theoretical approach for calculating the thermodynamical properties viz. Enthalpy(E),Entropy(S) and Helmholtz free energy(F) of some liquid semiconductors (Si, Ga, Ge, In, Sn, Tl, Bi, As, Se, Te and Sb). The Gibbs-Bogoliubov(GB) variational method is applied to compute the thermodynamical properties. Our well established model potential is used to define the electron-ion interaction. Charged Hard Sphere (CHS) reference system is used to describe the structural contribution to the Helmholtz free energy in the liquid phase. Local field correction function proposed by Farid et al is adopted to see the screening effect. Lastly, our newly constructed model potential is an effective one to produce the data of thermodynamical properties of some liquid semiconductor.
Thermodynamical properties of graphene in noncommutative phase–space
Santos, Victor; Maluf, R.V.; Almeida, C.A.S.
2014-10-15
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.
Thermodynamical properties of liquid lanthanides-A variational approach
Patel, H. P.; Thakor, P. B.; Sonvane, Y. A.
2015-06-24
Thermodynamical properties like Entropy (S), Internal energy (E) and Helmholtz free energy (F) of liquid lanthanides using a variation principle based on the Gibbs-Bogoliubuv (GB) inequality with Percus Yevick hard sphere reference system have been reported in the present investigation. To describe electron-ion interaction we have used our newly constructed parameter free model potential along with Sarkar et al. local field correction function. Lastly, we conclude that our newly constructed model potential is capable to explain the thermodynamical properties of liquid lanthanides.
Thermodynamic properties of the sodium-tellurium system
Morachesvkii, A.G.; Maiorova, E.A.; Romanchenko, N.M.; Kozlova, M.V.
1982-08-01
This paper presents the results of a study of the thermodynamic properties of liquid alloys and solid phases in this system and also its phase diagrams. The results of calculations of thermodynamic properties of the compounds are given in the report. The value obtained for the enthalpy of fusion of the compound NaTe/sub 3/ is in good agreement with the results of direct calorimetric measurements, according to which ..delta..H/sup m/ = 29.2+/-0.8 kJ/mole.
Thermodynamic properties and phase transitions in CO2 molecular clusters
NASA Technical Reports Server (NTRS)
Etters, R. D.; Flurchick, K.; Pan, R. P.; Chandrasekharan, V.
1981-01-01
The thermodynamic properties of (CO2)N molecular aggregates of size N between 2 and 13 have been investigated. These crystallites exhibit well defined orientational order-disorder rotational transitions accompanied by a structural transition into a plastic crystallite phase. In addition, they exhibit melting and disassociation transitions. It is shown that the interpretation of experimental data, based upon dimer properties, depends crucially on these results. Equilibrium structures and orientations are also given.
Reference Fluid Thermodynamic and Transport Properties Database (REFPROP)
National Institute of Standards and Technology Data Gateway
SRD 23 NIST Reference Fluid Thermodynamic and Transport Properties Database (REFPROP) (PC database for purchase) NIST 23 contains revised data in a Windows version of the database, including 105 pure fluids and allowing mixtures of up to 20 components. The fluids include the environmentally acceptable HFCs, traditional HFCs and CFCs and 'natural' refrigerants like ammonia
Composition and thermodynamic properties of thermal plasma with condensed phases
NASA Astrophysics Data System (ADS)
Coufal, O.; Živný, O.
2011-01-01
The initial relations of a method for calculating the composition and thermodynamic properties of a closed heterogeneous system in thermodynamic equilibrium at constant pressure and temperature are given. The gaseous phase is always present in the system, and substances in the condensed state can also be present, which are divided into several condensed phases. The essence of the method consists in the minimizing the Gibbs energy of a system in ideal state. The application possibilities of the method described are discussed in detail. The main aim of the article is to provide solutions to problems arising in the calculations of composition and thermodynamic properties. These problems are not only of physico-chemical nature but they also relate to the numerical calculations and stability. The nature of the problems is general and independent of computation method.
NASA Glenn Coefficients for Calculating Thermodynamic Properties of Individual Species
NASA Technical Reports Server (NTRS)
McBride, Bonnie J.; Zehe, Michael J.; Gordon, Sanford
2002-01-01
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.
Thermodynamic properties of germanium/carbon microclusters
NASA Astrophysics Data System (ADS)
Wielgus, Pawel; Roszak, Szczepan; Majumdar, Devashis; Leszczynski, Jerzy
2005-12-01
Theoretical studies on the GenCm (n =1,2; m =1-3) microclusters have been performed using the state of the art calculations. Several alternative structures of these clusters were studied to locate the lowest-energy isomers. It is observed that the structures of the complexes result from the competition between ionic Ge-C, conjugated covalent C-C, and metallic Ge-Ge bonds. The ionization of the molecules enhances the ionic character of the Ge-C bond and has significant structural consequences. Using theoretically determined partition functions, thermodynamic data are computed and experimental enthalpies are enhanced. The ab initio atomization energies of germanium carbides compare well with corrected experimental functions. The experimental appearance potentials are well reproduced by the theoretical ionization potentials.
Thermodynamic properties of fluids from Fluctuation Solution Theory
O'Connell, J.P.
1990-01-01
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.
Thermodynamic properties of fluids from Fluctuation Solution Theory
O`Connell, J.P.
1990-12-31
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.
Predicting Thermodynamic Properties of PBXTHs with New Quantum Topological Indexes.
Xiao, Fangzhu; Peng, Guowen; Nie, Changming; Yu, Limei
2016-01-01
Novel group quantitative structure-property relationship (QSPR) models on the thermodynamic properties of PBXTHs were presented, by the multiple linear regression (MLR) analysis method. Four thermodynamic properties were studied: the entropy (Sθ), the standard enthalpy of formation (ΔfHθ), the standard Gibbs energy of formation (ΔfGθ), and the relative standard Gibbs energy of formation (ΔRGθ). The results by the formula indicate that the calculated and predicted data in this study are in good agreement with those in literature and the deviation is within the experimental errors. To validate the estimation reliability for internal samples and the predictive ability for other samples, leave-one-out (LOO) cross validation (CV) and external validation were performed, and the results show that the models are satisfactory. PMID:26900689
Predicting Thermodynamic Properties of PBXTHs with New Quantum Topological Indexes
Peng, Guowen; Yu, Limei
2016-01-01
Novel group quantitative structure-property relationship (QSPR) models on the thermodynamic properties of PBXTHs were presented, by the multiple linear regression (MLR) analysis method. Four thermodynamic properties were studied: the entropy (Sθ), the standard enthalpy of formation (ΔfHθ), the standard Gibbs energy of formation (ΔfGθ), and the relative standard Gibbs energy of formation (ΔRGθ). The results by the formula indicate that the calculated and predicted data in this study are in good agreement with those in literature and the deviation is within the experimental errors. To validate the estimation reliability for internal samples and the predictive ability for other samples, leave-one-out (LOO) cross validation (CV) and external validation were performed, and the results show that the models are satisfactory. PMID:26900689
Thermodynamic properties of bulk and confined water
Mallamace, Francesco; Corsaro, Carmelo; Mallamace, Domenico; Vasi, Sebastiano; Vasi, Cirino; Stanley, H. Eugene
2014-11-14
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{sub L} ≃ 225 K). The second, T{sup *} ∼ 315 ± 5 K, is a special locus of the isothermal compressibility K{sub T}(T, P) and the thermal expansion coefficient α{sub 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{sub L}) and the onset of the unfolding process (T{sup *})
Thermodynamic and melting properties of RDX at elevated pressures
NASA Technical Reports Server (NTRS)
Carlson, D. W.; Nauflett, G. W.; Brasch, J. W., Sr.; Austin, T. D.
1980-01-01
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.
Thermodynamical properties of Strunz’s quantum dissipative models
Zen, Freddy P.; Sulaiman, A.
2015-09-30
The existence of the negative of specific heat from quantum dissipative theory is investigated. Strunz’s quantum dissipative model will be used in this studies. The thermodynamical properties will be studied starts out from the thermo-dynamic partition function of the dissipative system. The path integral technique is used to calculate the partition function under consideration. The results shows that the specific heat can be negative if the damping parameter more than a half the oscillator frequency and also occur at low temperatures. For damping factor greater than the frequency of harmonic oscillator then specific heat will oscillate at low temperatures and approaching normal conditions at a high temperature.
Simple estimation of thermodynamic properties of Yukawa systems.
Khrapak, S A; Khrapak, A G; Ivlev, A V; Morfill, G E
2014-02-01
A simple analytical approach to estimate thermodynamic properties of model Yukawa systems is presented. The approach extends the traditional Debye-Hückel theory into the regime of moderate coupling and is able to qualitatively reproduce thermodynamics of Yukawa systems up to the fluid-solid phase transition. The simplistic equation of state (pressure equation) is derived and applied to the hydrodynamic description of the longitudinal waves in Yukawa fluids. The relevance of this study to the topic of complex (dusty) plasmas is discussed. PMID:25353581
Intermolecular interactions and the thermodynamic properties of supercritical fluids.
Yigzawe, Tesfaye M; Sadus, Richard J
2013-05-21
The role of different contributions to intermolecular interactions on the thermodynamic properties of supercritical fluids is investigated. Molecular dynamics simulation results are reported for the energy, pressure, thermal pressure coefficient, thermal expansion coefficient, isothermal and adiabatic compressibilities, isobaric and isochoric heat capacities, Joule-Thomson coefficient, and speed of sound of fluids interacting via both the Lennard-Jones and Weeks-Chandler-Andersen potentials. These properties were obtained for a wide range of temperatures, pressures, and densities. For each thermodynamic property, an excess value is determined to distinguish between attraction and repulsion. It is found that the contributions of intermolecular interactions have varying effects depending on the thermodynamic property. The maxima exhibited by the isochoric and isobaric heat capacities, isothermal compressibilities, and thermal expansion coefficient are attributed to interactions in the Lennard-Jones well. Repulsion is required to obtain physically realistic speeds of sound and both repulsion and attraction are necessary to observe a Joule-Thomson inversion curve. Significantly, both maxima and minima are observed for the isobaric and isochoric heat capacities of the supercritical Lennard-Jones fluid. It is postulated that the loci of these maxima and minima converge to a common point via the same power law relationship as the phase coexistence curve with an exponent of β = 0.32. This provides an explanation for the terminal isobaric heat capacity maximum in supercritical fluids. PMID:23697423
Thermodynamic properties and diffusion of water + methane binary mixtures
Shvab, I.; Sadus, Richard J.
2014-03-14
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.
Interactive calculations of thermodynamics properties of minerals in VLab
NASA Astrophysics Data System (ADS)
Kelly, N.; da Silveira, P. R.; Wentzcovitch, R. M.
2009-12-01
We have developed a page within the VLab web site from which calculations of thermodynamics properties of minerals can be performed interactively. Previously published first principles calculations based on qhasiharmonic theory by our group have produced pressure dependent vibrational density of states (VDOSs). These calculations were costly and the essential information they produced, the VDOSs, are now stored on a database. They can be used to regenerate published results or calculate thermodynamics properties using specific user entered information (pressure and temperature range and grids, equation of state type, etc). Results are presented in numerical or graphics format (Gnuplot 4.2.2) that are interactively customized and downloadable. All codes behind the Web container are written in Java.
Thermodynamic properties of liquid water from a polarizable intermolecular potential
NASA Astrophysics Data System (ADS)
Yigzawe, Tesfaye M.; Sadus, Richard J.
2013-01-01
Molecular dynamics simulation results are reported for the pressure, isothermal pressure coefficient, thermal expansion coefficient, isothermal and adiabatic compressibilities, isobaric and isochoric heat capacities, Joule-Thomson coefficient and speed of sound of liquid water using a polarizable potential [Li et al., J. Chem. Phys. 127, 154509 (2007)]. These properties were obtained for a wide range of temperatures and pressures at a common liquid density using the treatment of Lustig [J. Chem. Phys. 100, 3048 (1994)] and Meier and Kabelac [J. Chem. Phys. 124, 064104 (2006)], whereby thermodynamic state variables are expressible in terms of phase-space functions determined directly from molecular dynamics simulations. Comparison with experimental data indicates that the polarizable potential can be used to predict most thermodynamic properties with a very good degree of accuracy.
Thermodynamic properties of highly undercooled liquid TiAl alloy
NASA Astrophysics Data System (ADS)
Wang, N.; Wei, B.
2002-05-01
The specific heat of an undercooled liquid TiAl alloy was measured by an electromagnetic levitation drop calorimeter and the related thermodynamic properties, difference in Gibbs free energy and change in entropy are calculated based on the experimental results and some well known models. Under the containerless processing condition, the liquid alloy was undercooled by up to 219 K (0.122TL). The change in enthalpy shows a linear relationship with the temperature and a nearly constant specific heat was determined even though this alloy was undercooled far below its liquidus temperature. The calculated results of the thermodynamic properties reveal that even though semiquantitative models fit with the experimental curve of the difference in Gibbs free energy well, they lead to different degrees of deviation in the entropy difference calculation.
A thermodynamic approach to obtain materials properties for engineering applications
NASA Technical Reports Server (NTRS)
Chang, Y. Austin
1993-01-01
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.
Coefficients for calculating thermodynamic and transport properties of individual species
NASA Technical Reports Server (NTRS)
Mcbride, Bonnie J.; Gordon, Sanford; Reno, Martin A.
1993-01-01
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.
Detection of DNA Hybridization Properties Using Thermodynamic Method
NASA Astrophysics Data System (ADS)
Kim, Do-Kyun; Kwon, Young-Soo; Takamura, Yuzuru; Tamiya, Eiichi
2006-01-01
The determination of DNA hybridization reaction can apply the molecular biology research, clinic diagnostics, bioengineering, environment monitoring, food science and application area. So, the improvement of DNA hybridization detection method is very important for the determination of hybridization reaction. Several molecular biological techniques require accurate predictions of match versus mismatch hybridization thermodynamics, such as polymerase chain reaction (PCR), sequencing by hybridization, gene diagnostics and antisense DNA probes. In addition, recent developments of DNA chip array as means for biochemical assays and DNA sequencing requires accurate knowledge of hybridization thermodynamics and population ratios at match and mismatch target sites. In this study, we report the properties of the probe oligonucleotide and match, mismatch target oligonucleotide hybridization reaction using thermodynamic method. Thermodynamics of 5'-oligonucleotides with central and terminal mismatch sequences are obtained by measuring UV-absorbance as a function of temperature. The data show that the nearest-neighbor base-pair model is adequate for predicting thermodynamics of oligonucleotides with average deviations for enthalpy (? H0), entropy (? S0), free energy change at 37C (?{G37}0) and melting temperature (Tm), respectively.
Thermodynamic properties of average-atom interatomic potentials for alloys
NASA Astrophysics Data System (ADS)
Nöhring, Wolfram Georg; Curtin, William Arthur
2016-05-01
The atomistic mechanisms of deformation in multicomponent random alloys are challenging to model because of their extensive structural and compositional disorder. For embedded-atom-method interatomic potentials, a formal averaging procedure can generate an average-atom EAM potential and this average-atom potential has recently been shown to accurately predict many zero-temperature properties of the true random alloy. Here, the finite-temperature thermodynamic properties of the average-atom potential are investigated to determine if the average-atom potential can represent the true random alloy Helmholtz free energy as well as important finite-temperature properties. Using a thermodynamic integration approach, the average-atom system is found to have an entropy difference of at most 0.05 k B/atom relative to the true random alloy over a wide temperature range, as demonstrated on FeNiCr and Ni85Al15 model alloys. Lattice constants, and thus thermal expansion, and elastic constants are also well-predicted (within a few percent) by the average-atom potential over a wide temperature range. The largest differences between the average atom and true random alloy are found in the zero temperature properties, which reflect the role of local structural disorder in the true random alloy. Thus, the average-atom potential is a valuable strategy for modeling alloys at finite temperatures.
Structural and thermodynamics properties of organo-modified montmorillonite clay
NASA Astrophysics Data System (ADS)
Anoukou, K.; Zaoui, A.; Zaïri, F.; Naït-Abdelaziz, M.; Gloaguen, J. M.
2015-01-01
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.
Optical and thermodynamic property measurements of liquid metals and alloys
NASA Technical Reports Server (NTRS)
Weber, J. K. R.; Krishnan, Shankar; Schiffman, Robert A.; Nordine, Paul C.
1991-01-01
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.
Anomalous thermodynamic properties of ice XVI and metastable hydrates
NASA Astrophysics Data System (ADS)
Yagasaki, Takuma; Matsumoto, Masakazu; Tanaka, Hideki
2016-02-01
A new ice polymorph, called ice XVI, has recently been discovered experimentally by extracting the guest molecules from Ne hydrate. The ice and its filled form (clathrate hydrate) have a unique network topology which results in several interesting properties. Here we provide a theoretical method to calculate thermodynamic properties of a semiopen system in equilibrium with guest gas and thus occupancy of the guest can be varied with temperature and pressure. Experimental observations such as the disappearance of negative thermal expansivity and contraction of the host lattice upon encaging guest molecules are well reproduced, and those behaviors are elucidated in terms of the free energy of cage occupation and its temperature and pressure dependence. We propose an application of the method for preparing ice XVI to create metastable clathrate hydrates having intriguing properties with much lower occupancy of guest molecules than that at equilibrium, which otherwise cannot form.
Thermodynamic properties of magnetic strings on a square lattice
NASA Astrophysics Data System (ADS)
Mol, Lucas; Oliveira, Denis Da Mata; Bachmann, Michael
2015-03-01
In the last years, spin ice systems have increasingly attracted attention by the scientific community, mainly due to the appearance of collective excitations that behave as magnetic monopole like particles. In these systems, geometrical frustration induces the appearance of degenerated ground states characterized by a local energy minimization rule, the ice rule. Violations of this rule were shown to behave like magnetic monopoles connected by a string of dipoles that carries the magnetic flux from one monopole to the other. In order to obtain a deeper knowledge about the behavior of these excitations we study the thermodynamics of a kind of magnetic polymer formed by a chain of magnetic dipoles in a square lattice. This system is expected to capture the main properties of monopole-string excitations in the artificial square spin ice. It has been found recently that in this geometry the monopoles are confined, but the effective string tension is reduced by entropic effects. To obtain the thermodynamic properties of the strings we have exactly enumerated all possible string configurations of a given length and used standard statistical mechanics analysis to calculate thermodynamic quantities. We show that the low-temperature behavior is governed by strings that satisfy ice rules. Financial support from FAPEMIG and CNPq (Brazilian agencies) are gratefully acknowledged.
Thermodynamic and structural properties of Bi-based liquid alloys
NASA Astrophysics Data System (ADS)
Yadav, S. K.; Jha, L. N.; Adhikari, D.
2015-10-01
Thermodynamic and microscopic structural properties of two Bi-based liquid alloys, such as In-Bi at 900 K and Tl-Bi at 750 K have been studied employing the regular associated solution model. We have estimated the mole fractions of the complexes and the free monomers assuming the existence of complexes In2 Bi in In-Bi melt and TlBi in Tl-Bi melt. The thermodynamic properties have been studied by computing the Gibbs free energy of mixing, enthalpy of mixing, entropy of mixing and activities of the monomers. The compositional contributions of the heat associated with the formation of complexes and the heat of mixing of the monomers to the net enthalpy change has also been studied. The structural properties of the liquid alloys have been studied by computing concentration fluctuation in the long-wavelength limit, chemical short-range order parameter and the ratio of mutual to intrinsic diffusion coefficients. For both of the alloy systems, the theoretical as well as the experimental values of SCC (0) are found to be lower than the corresponding ideal values over the whole composition range, indicating the hetero-coordinating nature of Bi-In and Bi-Tl alloy melts. All the interaction energy parameters are found to be negative and temperature dependent, and both the alloy systems are found to be weakly interacting.
Simplified curve fits for the thermodynamic properties of equilibrium air
NASA Technical Reports Server (NTRS)
Srinivasan, S.; Tannehill, J. C.; Weilmuenster, K. J.
1987-01-01
New, improved curve fits for the thermodynamic properties of equilibrium air have been developed. The curve fits are for pressure, speed of sound, temperature, entropy, enthalpy, density, and internal energy. These curve fits can be readily incorporated into new or existing computational fluid dynamics codes if real gas effects are desired. The curve fits are constructed from Grabau-type transition functions to model the thermodynamic surfaces in a piecewise manner. The accuracies and continuity of these curve fits are substantially improved over those of previous curve fits. These improvements are due to the incorporation of a small number of additional terms in the approximating polynomials and careful choices of the transition functions. The ranges of validity of the new curve fits are temperatures up to 25 000 K and densities from 10 to the -7 to 10 to the 3d power amagats.
Thermodynamic properties of liquid gallium from picosecond acoustic velocity measurements
NASA Astrophysics Data System (ADS)
Ayrinhac, S.; Gauthier, M.; Le Marchand, G.; Morand, M.; Bergame, F.; Decremps, F.
2015-07-01
Due to discrepancies in the literature data the thermodynamic properties of liquid gallium are still in debate. Accurate measurements of adiabatic sound velocities as a function of pressure and temperature have been obtained by the combination of laser picosecond acoustics and surface imaging on sample loaded in diamond anvil cell. From these results the thermodynamic parameters of gallium have been extracted by a numerical procedure up to 10 GPa and 570 K. It is demonstrated that a Murnaghan equation of state accounts well for the whole data set since the isothermal bulk modulus BT has been shown to vary linearly with pressure in the whole temperature range. No evidence for a previously reported liquid-liquid transition has been found in the whole pressure and temperature range explored.
Thermodynamic Properties of Organometallic Dihydrogen Complexes for Hydrogen Storage Applications
NASA Astrophysics Data System (ADS)
Abrecht, David Gregory
The mechanism and thermodynamic properties of hydrogen binding to the solid-state complexes [M(CO)dppe2][BArF24] (M = Mn, Re, Tc) and [M'Hdppe2][NTf2] (M' = Fe, Ru, Os) were investigated experimentally and computationally over the temperature range 298K-373K and pressure range 0-2800 torr, based on the Sieverts method. The bulk absorption behavior was found to be accurately described by Langmuir isotherms. Enthalpy and entropy values of ΔH° = -52.2 kJ/mol and ΔS° = -99.6 J/mol-K were obtained experimentally for hydrogen absorption onto [Mn(CO)dppe2][BArF24] from the Langmuir equilibrium constant, and values obtained from electronic structure calculations using the LANL2DZ-ECP basis set were found to successfully reproduce both the pressure-temperature-composition behavior and the thermodynamic values to within 5% of those obtained through experiment. Results from simulations for all complexes yielded large enthalpy values similar to metal hydride formation enthalpies for all complexes studied, and the substitution of the metal center reproduced qualitative binding strength trends of 5d>3d>4d consistent with those previously reported for the group 6 metals. X-ray diffraction patterns and Mössbauer spectra were taken to determine the thermal decomposition pathway for [FeH(η2-H 2)dppe2][NTf2]. Simulations at the B3LYP/TZVP level of theory and experimental Mössbauer spectra confirmed the direct thermal decomposition from singlet-state [FeH(η2-H 2)dppe2][NTf2] to triplet-state [FeHdppe 2][NTf2] under vacuum conditions at 398K. Evaluation of the partial quadrupole splitting values of Q(H2) = -0.245 mm/s from Mössbauer spectroscopy significantly differ from typical values obtained for hydrides, indicating an underutilized mechanism for identification of dihydrogen ligands. Singlet-state thermodynamic values from simulation were consistent with experimental observations for Ru and Os, and ruthenium complexes were found to have thermodynamic properties within appropriate ranges for hydrogen storage applications. Simulated thermodynamic values for Fe complexes were found to significantly underestimate experimental behavior, demonstrating the importance of the magnetic spin state of the molecule to hydrogen binding properties.
Spectroscopic and thermodynamic properties of L-ornithine monohydrochloride
Raja, M. Dinesh; Kumar, C. Maria Ashok; Arulmozhi, S.; Madhavan, J.
2015-06-24
L-Ornithine Monohydrochloride (LOMHCL) has been investigated with the help of B3LYP density functional theory with 6-31 G (d, p) basis set. Fourier transform infrared and Fourier transform Raman spectra is to identify the various functional groups. The theoretical frequencies showed very good agreement with experimental values. On the basis of the thermodynamic properties of the title compound at different temperatures have been calculated, revealing the correlations between standard heat capacities (C) standard entropies (S), and standard enthalpy changes (H) and temperatures. Second harmonic generation (SHG) efficiency of the grown crystal has been studied.
Spectroscopic and thermodynamic properties of L-ornithine monohydrochloride
NASA Astrophysics Data System (ADS)
Raja, M. Dinesh; Kumar, C. Maria Ashok; Arulmozhi, S.; Madhavan, J.
2015-06-01
L-Ornithine Monohydrochloride (LOMHCL) has been investigated with the help of B3LYP density functional theory with 6-31 G (d, p) basis set. Fourier transform infrared and Fourier transform Raman spectra is to identify the various functional groups. The theoretical frequencies showed very good agreement with experimental values. On the basis of the thermodynamic properties of the title compound at different temperatures have been calculated, revealing the correlations between standard heat capacities (C) standard entropies (S), and standard enthalpy changes (H) and temperatures. Second harmonic generation (SHG) efficiency of the grown crystal has been studied.
Thermodynamic properties of real gases and BWR equation of state
NASA Astrophysics Data System (ADS)
Vestfálová, Magda
2015-05-01
The fundamental base for the calculation of the thermodynamic properties of materials is thermal equation of state and dependence of some of the basic specific heat capacities on temperature. The dependence of the specific thermal capacity on the second independent variable (for example on the volume) it is already possible to deduce from the thermal equation of state. The aim of this paper is to assess the compliance values of specific heat capacity which was calculated using the BWR thermal equation of the state and experimentally obtained known values of specific heat capacity for the substance, whose characteristics are available in a wide range of state space.
A generalized model for the thermodynamic properties of mixtures
Lemmon, E.W.; Jacobsen, R.T.
1999-05-01
A mixture model explicit in Helmholtz energy has been developed which is capable of predicting thermodynamic properties of mixtures containing nitrogen, argon, oxygen, carbon dioxide, methane, ethane, propane, n-butane, i-butane, R-32, R-125, R-134a, and R-152a within the estimated accuracy of available experimental data. The Helmholtz energy of the mixture is the sum of the ideal gas contribution, the compressibility for real gas contribution, and the contribution from mixing. The contribution from mixing is given by a single generalized equation which is applied to all mixtures studied in this work. The independent variables are the density, temperature, and composition. The model may be used to calculate the thermodynamic properties of mixtures at various compositions including dew and bubble point properties and critical points. It incorporates accurate published equations of state for each pure fluid. The estimated accuracy of calculated properties is {+-}0.2% in density, {+-}0.1% in the speed of sound at pressures below 10 MPa, {+-}0.5% in the speed of sound for pressures above 10 MPa, and {+-}1% in heat capacities. In the region from 250 to 350 K at pressures up to 30 MPa, calculated densities are within {+-}0.1% for most gaseous phase mixtures. For binary mixtures where the critical point temperatures of the pure fluid constituents are within 100 K of each other, calculated bubble point pressures are generally accurate to within {+-}1 to 2%. For mixtures with critical points further apart, calculated bubble point pressures are generally accurate to within {+-}5 to 10%.
FLUID- THERMODYNAMIC AND TRANSPORT PROPERTIES OF FLUIDS (IBM VERSION)
NASA Technical Reports Server (NTRS)
Fessler, T. E.
1994-01-01
The accurate computation of the thermodynamic and transport properties of fluids is a necessity for many engineering calculations. The FLUID program was developed to calculate the thermodynamic and transport properties of pure fluids in both the liquid and gas phases. Fluid properties are calculated using a simple gas model, empirical corrections, and an efficient numerical interpolation scheme. FLUID produces results that are in very good agreement with measured values, while being much faster than older more complex programs developed for the same purpose. A Van der Waals equation of state model is used to obtain approximate state values. These values are corrected for real-gas effects by model correction factors obtained from tables based on experimental data. These tables also accurately compensate for the special circumstances which arise whenever phase conditions occur. Viscosity and thermal conductivity values are computed directly from tables. Interpolation within tables is based on Lagrange's three point formula. A set of tables must be generated for each fluid implemented. FLUID currently contains tables for nine fluids including dry air and steam. The user can add tables for any fluid for which adequate thermal property data is available. The FLUID routine is structured so that it may easily be incorporated into engineering programs. The IBM 360 version of FLUID was developed in 1977. It is written in FORTRAN IV and has been implemented on an IBM 360 with a central memory requirement of approximately 222K of 8 bit bytes. The IBM PC version of FLUID is written in Microsoft FORTRAN 77 and has been implemented on an IBM PC with a memory requirement of 128K of 8 bit bytes. The IBM PC version of FLUID was developed in 1986.
FLUID- THERMODYNAMIC AND TRANSPORT PROPERTIES OF FLUIDS (IBM PC VERSION)
NASA Technical Reports Server (NTRS)
Fessler, T. E.
1994-01-01
The accurate computation of the thermodynamic and transport properties of fluids is a necessity for many engineering calculations. The FLUID program was developed to calculate the thermodynamic and transport properties of pure fluids in both the liquid and gas phases. Fluid properties are calculated using a simple gas model, empirical corrections, and an efficient numerical interpolation scheme. FLUID produces results that are in very good agreement with measured values, while being much faster than older more complex programs developed for the same purpose. A Van der Waals equation of state model is used to obtain approximate state values. These values are corrected for real-gas effects by model correction factors obtained from tables based on experimental data. These tables also accurately compensate for the special circumstances which arise whenever phase conditions occur. Viscosity and thermal conductivity values are computed directly from tables. Interpolation within tables is based on Lagrange's three point formula. A set of tables must be generated for each fluid implemented. FLUID currently contains tables for nine fluids including dry air and steam. The user can add tables for any fluid for which adequate thermal property data is available. The FLUID routine is structured so that it may easily be incorporated into engineering programs. The IBM 360 version of FLUID was developed in 1977. It is written in FORTRAN IV and has been implemented on an IBM 360 with a central memory requirement of approximately 222K of 8 bit bytes. The IBM PC version of FLUID is written in Microsoft FORTRAN 77 and has been implemented on an IBM PC with a memory requirement of 128K of 8 bit bytes. The IBM PC version of FLUID was developed in 1986.
Vibrational and thermodynamic properties of transition-metal nanoclusters
NASA Astrophysics Data System (ADS)
Grigoryan, Valeri G.; Springborg, Michael
2013-03-01
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. This work was supported by the DFG through Project No. Sp439/23-1
Chemical and Thermodynamic Properties at High Temperatures: A Symposium
NASA Technical Reports Server (NTRS)
Walker, Raymond F.
1961-01-01
This book contains the program and all available abstracts of the 90' invited and contributed papers to be presented at the TUPAC Symposium on Chemical and Thermodynamic Properties at High Temperatures. The Symposium will be held in conjunction with the XVIIIth IUPAC Congress, Montreal, August 6 - 12, 1961. It has been organized, by the Subcommissions on Condensed States and on Gaseous States of the Commission on High Temperatures and Refractories and by the Subcommission on Experimental Thermodynamics of the Commission on Chemical Thermodynamics, acting in conjunction with the Organizing Committee of the IUPAC Congress. All inquiries concerning participation In the Symposium should be directed to: Secretary, XVIIIth International Congress of Pure and Applied Chemistry, National Research Council, Ottawa, 'Canada. Owing to the limited time and facilities available for the preparation and printing of the book, it has not been possible to refer the proofs of the abstracts to the authors for checking. Furthermore, it has not been possible to subject the manuscripts to a very thorough editorial examination. Some obvious errors in the manuscripts have been corrected; other errors undoubtedly have been introduced. Figures have been redrawn only when such a step was essential for reproduction purposes. Sincere apologies are offered to authors and readers for any errors which remain; however, in the circumstances neither the IUPAC Commissions who organized the Symposium, nor the U. S. Government Agencies who assisted in the preparation of this book can accept responsibility for the errors.
ERIC Educational Resources Information Center
Piele, Philip K.
Several court cases involving acquisition, use, and disposal of property by institutions of higher education are briefly summarized in this chapter. Cases discussed touch on such topics as municipal annexation of university property; repurchase of properties temporarily allocated to faculty members; implications of zoning laws and zoning board…
ERIC Educational Resources Information Center
Goldblatt, Steven M.
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…
ERIC Educational Resources Information Center
Piele, Philip K.
Several court cases involving acquisition, use, and disposal of property by institutions of higher education are briefly summarized in this chapter. Cases discussed touch on such topics as municipal annexation of university property; repurchase of properties temporarily allocated to faculty members; implications of zoning laws and zoning board
Thermodynamic properties of pulverized coal during rapid heating devolatilization processes
Proscia, W.M.; Freihaut, J.D.
1993-03-01
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.
2014-01-01
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
Thermodynamic and kinetic properties of some diatomic gases
NASA Astrophysics Data System (ADS)
Holbrook, Robert Thomas, III
1997-11-01
In this work, the thermodynamic and kinetic properties of some diatomic gases are calculated and analyzed. In chapter 1, the partition functions of the species composing a dissociating and ionizing iodine vapor, specifically those for homonuclear diatomic 127I127I molecules, 127I atoms, 127I+ ions, and free electrons, are calculated. These partition functions are subsequently used in statistical mass action equations to determine the local thermal equilibrium dissociation degree a and the ionization degree φ of the iodine vapor over the temperature range 700 <= T/ /le 12000 K for total atomic number densities nA = 1014, 1016, 1018, and 1020 cm-3. With the equilibrium composition of the iodine vapor so specified and the partition functions, the thermodynamic properties of the iodine vapor are calculated for 700 <= T/ /le 12000 K from statistical thermodynamic equations for the four values of the total number density. In chapter 2, the statistical-mechanical treatment is extended to the more complicated cases of gas systems based on the rare earth halide molecules, DyF, HoF, and TmF. Such systems are composed of seven different species: LnF and F2 molecules (Ln≡Dy, Ho, and Tm), LnF+ molecular ions, Ln and F atoms, LnF+ atomic ions, and free electrons. Once again, the partition functions are calculated for the various species and used in statistical expressions to determine the local thermal equilibrium compositions and thermodynamic properties of the LnF-based gas mixtures for the temperature range 3000 <= T/ /le 9000 K and initial molecular number densities 1014, 1016, and 1018 cm-3. Finally, in chapter 3, the Monte Carlo trajectory method is used to study the probabilities P(Vr, b, v1, J1, v2, J2) for dissociation via collisions between two ground electronic state X1Σ(0g+) I2 molecules. The two molecules interact with an impact parameter b and a relative speed Vr. The incident molecule is in the vibrational-rotational state specified by the vibrational quantum number v1 and the rotational quantum number J1 while the target molecule is in the state specified by the quantum numbers v2 and J2.
Thermodynamic properties of pulverized coal during rapid heating devolatilization processes
Proscia, W.M.; Freihaut, J.D.; Rastogi, S.; Klinzing, G.E.
1994-07-01
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.
Solvation of polymers as mutual association. II. Basic thermodynamic properties
NASA Astrophysics Data System (ADS)
Dudowicz, Jacek; Freed, Karl F.; Douglas, Jack F.
2013-04-01
The theory of equilibrium solvation of polymers B by a relatively low molar mass solvent A, developed in the simplest form in Paper I, is used to explore some essential trends in basic thermodynamic properties of solvated polymer solutions, such as the equilibrium concentrations of solvated polymers AiB and free solvent molecules A, the mass distribution φ _{{AiB}}(i) of solvated clusters, the extent of solvation of the polymer Φsolv, the solvation transition lines T_{solv}(φ _{{B}}o), the specific heat CV, the osmotic second virial coefficient B2, phase stability boundaries, and the critical temperatures associated with closed loop phase diagrams. We discuss the differences between the basic thermodynamic properties of solvated polymers and those derived previously for hierarchical mutual association processes involving the association of two different species A and B into AB complexes and the subsequent polymerization of these AB complexes into linear polymeric structures. The properties of solvated polymer solutions are also compared to those for solutions of polymers in a self-associating solvent. Closed loop phase diagrams for solvated polymer solutions arise in the theory from the competition between the associative and van der Waals interactions, a behavior also typical for dispersed molecular and nanoparticle species that strongly associate with the host fluid. Our analysis of the temperature dependence of the second osmotic virial coefficient reveals that the theory must be generalized to describe the association of multiple solvent molecules with each chain monomer, and this complex extension of the present model will be developed in subsequent papers aimed at a quantitative rather than qualitative treatment of solvated polymer solutions.
Thermodynamic properties of the Group 1A elements
Alcock, C.B.; Itkin, V.P.; Chase, M.W.
1994-05-01
This review describes thermodynamic properties of condensed phases of the alkali metals, excluding francium for which the amount of information is too limited. The properties considered are: heat capacities from 0 to 1600 K, temperatures and enthalpies of fusion and martensitic transformation in Li and Na; discussion of the Debye temperature and electronic heat capacity coefficient at absolute zero temperature is also included. The paper is the second part of a series. Similar to previous assessment of the IIA group [93ALC/CHA], this paper considers original studies, especially with respect to factors which influence the accuracy and reliability of results. Recommendations derived from such analyses are compared with most advanced previous reviews made at the Institute for High Temperatures (Moscow) [70SHP/YAK], [82GUR] and the National Institute of Standards and Technology (Washington) [85JAN]. The properties of individual elements of the group are compared and suggestions are made for experimental studies which should improve poorly measured quantities. The review is supplemented by an IBM PC database which contains references, assessed data, brief description of studies and has facilities for fitting and plotting of data and for adding new information.
ms2: A molecular simulation tool for thermodynamic properties
NASA Astrophysics Data System (ADS)
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
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.
Thermodynamic properties for polycyclic systems by non-calorimetric methods
NASA Astrophysics Data System (ADS)
Steele, W. V.; Chirico, R. D.; Klots, T. D.
1993-03-01
A detailed vibrational spectroscopic study of furan, pyrrole, and thiophene has been completed. These compounds form part of the base of five-membered ring systems on which the rest of the research program will be built. Several methyl-substituted derivatives were also studied. The results will be used to confirm the model for alkyl-substitution in the ring systems. Gas-phase spectra and fundamental frequency assignments were completed for 2,3- and 2,5-dihydrofuran. Those compounds initiate work on ring-puckering within the research program. A paper describing the need for third virial estimation, when using the virial equation of state to derive thermodynamic properties at pressures greater than 1 bar was completed.
Thermodynamic properties derived from the free volume model of liquids
NASA Technical Reports Server (NTRS)
Miller, R. I.
1974-01-01
An equation of state and expressions for the isothermal compressibility, thermal expansion coefficient, heat capacity, and entropy of liquids have been derived from the free volume model partition function suggested by Turnbull. The simple definition of the free volume is used, and it is assumed that the specific volume is directly related to the cube of the intermolecular separation by a proportionality factor which is found to be a function of temperature and pressure as well as specific volume. When values of the proportionality factor are calculated from experimental data for real liquids, it is found to be approximately constant over ranges of temperature and pressure which correspond to the dense liquid phase. This result provides a single-parameter method for calculating dense liquid thermodynamic properties and is consistent with the fact that the free volume model is designed to describe liquids near the solidification point.
Note on electrical and thermodynamic properties of isolated horizons
NASA Astrophysics Data System (ADS)
Chen, Gerui; Wu, Xiaoning; Gao, Sijie
2015-03-01
The electrical laws and Carnot cycle of isolated horizons (IH) are investigated in this paper. We establish Ohm's law and Joule's law of isolated horizons and find that the conceptual picture of black holes (membrane paradigm) can also apply to this kind of quasilocal black holes. We also investigate the geometrical properties near nonrotating IHs and find that under the first-order approximation of r , there exist a Killing vector ∂∂u/ and a Hamiltonian conjugate to it, so this vector can be thought to be a physical observer. We calculate the energy as measured at infinity of a particle at rest outside a nonrotating IH, and we use this result to construct a reversible Carnot cycle with the isolated horizon as a cold reservoir, which confirms the thermodynamic nature of isolated horizons.
Thermodynamic properties of hydrate phases immersed in ice phase
NASA Astrophysics Data System (ADS)
Belosludov, V. R.; Subbotin, O. S.; Krupskii, D. S.; Ikeshoji, T.; Belosludov, R. V.; Kawazoe, Y.; Kudoh, J.
2006-01-01
Thermodynamic properties and the pressure of hydrate phases immersed in the ice phase with the aim to understand the nature of self-preservation effect of methane hydrate in the framework of macroscopic and microscopic molecular models was studied. It was show that increasing of pressure is happen inside methane hydrate phases immersed in the ice phase under increasing temperature and if the ice structure does not destroy, the methane hydrate will have larger pressure than ice phase. This is because of the thermal expansion of methane hydrate in a few times larger than ice one. The thermal expansion of the hydrate is constrained by the thermal expansion of ice because it can remain in a region of stability within the methane hydrate phase diagram. The utter lack of preservation behavior in CS-II methane- ethane hydrate can be explain that the thermal expansion of ethane-methane hydrate coincide with than ice one it do not pent up by thermal expansion of ice. The pressure and density during the crossing of interface between ice and hydrate was found and dynamical and thermodynamic stability of this system are studied in accordance with relation between ice phase and hydrate phase.
Simplified curve fits for the thermodynamic properties of equilibrium air
NASA Technical Reports Server (NTRS)
Srinivasan, S.; Tannehill, J. C.; Weilmuenster, K. J.
1986-01-01
New improved curve fits for the thermodynamic properties of equilibrium air were developed. The curve fits are for p = p(e,rho), a = a(e,rho), T = T(e,rho), s = s(e,rho), T = T(p,rho), h = h(p,rho), rho = rho(p,s), e = e(p,s) and a = a(p,s). These curve fits can be readily incorporated into new or existing Computational Fluid Dynamics (CFD) codes if real-gas effects are desired. The curve fits were constructed using Grabau-type transition functions to model the thermodynamic surfaces in a piecewise manner. The accuracies and continuity of these curve fits are substantially improved over those of previous curve fits appearing in NASA CR-2470. These improvements were due to the incorporation of a small number of additional terms in the approximating polynomials and careful choices of the transition functions. The ranges of validity of the new curve fits are temperatures up to 25,000 K and densities from 10 to the minus 7th to 100 amagats (rho/rho sub 0).
The thermodynamic properties of hydrated -Al2O3 nanoparticles
Spencer, Elinor; Huang, Baiyu; Parker, Stewart F.; Kolesnikov, Alexander I; Ross, Dr. Nancy; Woodfield, Brian
2013-01-01
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.
Thermodynamic Properties of Ultracold Bose Gas: Transition Exponents and Universality
NASA Astrophysics Data System (ADS)
Goswami, Sanchari; Das, Tapan Kumar; Biswas, Anindya
2013-08-01
We report exact numerical calculations of the chemical potential, condensate fraction and specific heat of N non-interacting bosons confined in an isotropic harmonic oscillator trap in one, two and three dimensions, as also for interacting bosons in a 3D trap. Quasi phase transitions (QPT) are observed in all these cases, including in one-dimension, as shown by a rapid change of several thermodynamic quantities at the transition point. The change becomes more rapid as N increases in 2D and 3D cases. However with increase in N, the sudden change in the nature of specific heat, gets gradually wiped out in 1D, while it becomes more drastic in 2D and 3D. But the sudden changes in the condensate fraction and chemical potential become more drastic as N increases, even in 1D. This shows that a QPT is possible in 1D also. We define the transition exponent, which characterizes the nature of a thermodynamic quantity at the transition point of a quasi phase transition, and evaluate them by careful numerical calculations, very near the transition temperature. These exponents are found to be independent of the size of the system. They are also the same for interacting and non-interacting bosons. These demonstrate the universality property of the transition exponents.
ERIC Educational Resources Information Center
Piele, Philip K.; Johnson, Margaret M.
This chapter deals with 1981 cases involving disputes over property. Cases involving the detachment and attachment of land continue to dominate the property chapter with 11 cases reported, the same number summarized in last year's chapter. One case involving school board referenda raised the interesting question of whether or not a state could…
ERIC Educational Resources Information Center
Bickel, Robert D.; Zeller, Trisha A.
A number of cases related to property issues involving institutions of higher education are examined in this chapter. Cases discussed touch on such topics as funding for property and equipment acquisition; opposition to building construction or demolition; zoning issues; building construction and equipment contracts; and lease agreements. Current…
ERIC Educational Resources Information Center
Goldblatt, Steven M.; Piele, Philip K.
This chapter reviews 1982 cases related to school property. Cases involving citizen efforts to overturn school board decisions to close schools dominate the property chapter, and courts continue to uphold school board authority to close schools, transfer students, and sell or lease the buildings. Ten cases involving detachment and attachment of…
NASA Technical Reports Server (NTRS)
Gordon, S.
1982-01-01
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.
NASA Technical Reports Server (NTRS)
Nguyen, Huy H.; Martin, Michael A.
2004-01-01
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.
Ideal gas thermodynamic properties for the phenyl, phenoxy, and o-biphenyl radicals
NASA Technical Reports Server (NTRS)
Burcat, A.; Zeleznik, F. J.; Mcbride, B. J.
1985-01-01
Ideal gas thermodynamic properties of the phenyl and o-biphenyl radicals, their deuterated analogs and the phenoxy radical were calculated to 5000 K using estimated vibrational frequencies and structures. The ideal gas thermodynamic properties of benzene, biphenyl, their deuterated analogs and phenyl were also calculated.
Investigation of thermodynamic properties of metal-oxide catalysts
NASA Astrophysics Data System (ADS)
Shah, Parag Rasiklal
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.
Thermodynamic properties and phase equilibria of selected Heusler compounds
NASA Astrophysics Data System (ADS)
Yin, Ming
Heusler compounds are ternary intermetallics with many promising properties such as spin polarization and magnetic shape memory effect. A better understanding of their thermodynamic properties facilitates future design and development. Therefore, standard enthalpies of formation and heat capacities from room temperature to 1500 K of selected Heusler compounds X2YZ (X = Co, Fe, Ni, Pd, Rh, Ru; Y = Co, Cu, Fe, Hf, Mn, Ni, Ti, V, Zr; Z = Al, Ga, In, Si, Ge, Sn) and half-Heusler compounds XYSn (X = Au, Co, Fe, Ir, Ni, Pd, Pt, Rh; Y = Hf, Mn, Ti, Zr) were measured using high temperature direct reaction calorimetry. The measured standard enthalpies of formation were compared with those predicted from ab initio calculations and the extended semi-empirical Miedema's model. Trends in standard enthalpy of formation with respect to the periodic classification of elements were discussed. The effect of a fourth element (Co, Cu, Fe, Pd; Ti, V; Al, Ga, In, Si, Ge) on the standard enthalpy of formation of Ni2MnSn was also investigated. Lattice parameters of the compounds with an L21 structure were determined using X-ray powder diffraction analysis. Differential scanning calorimetry was used to determine melting points and phase transformation temperatures. Phase relationships were investigated using scanning electron microscopy with an energy dispersive spectrometer. The isothermal section of the Fe-Sn-Ti ternary system at 873 K was established using equilibrated alloys. Three ternary compounds including the Heusler compound Fe2SnTi were observed. A new ternary compound Fe5Sn9Ti 6 was reported and the crystal structure of FeSnTi2 was determined for the first time.
NASA Technical Reports Server (NTRS)
Thompson, R. A.
1994-01-01
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.
Thermodynamic and transport properties of air/water mixtures
NASA Technical Reports Server (NTRS)
Fessler, T. E.
1981-01-01
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.
Thermodynamic properties of aluminum, magnesium, and calcium in molten silicon
Miki, Takahiro; Morita, Kazuki; Sano, Nobuo |
1998-10-01
The thermodynamic properties of aluminum, magnesium, and calcium in molten silicon were investigated using a chemical equilibration technique at 1723 to 1848 K, 1698 to 1798 K, and 1723 to 1823 K, respectively. The activity coefficient of aluminum in molten silicon was determined by equilibrating molten silicon-aluminum alloys with solid Al{sub 2}O{sub 3} and Al{sub 6}Si{sub 2}O{sub 13}, that of magnesium was determined by equilibrating molten silicon-magnesium alloys and MgO-SiO{sub 2}-Al{sub 2}O{sub 3} melts doubly saturated with MdSiO{sub 3} and SiO{sub 2}, and that of calcium was determined by equilibrating molten silicon-calcium alloys with SiO{sub 2}-saturated CaO-SiO{sub 2} melts. The activity coefficients at infinite dilution relative to the pure liquid state were determined as follows: log {gamma}{sub Al({ell})in Si}{sup o} = {minus} 1570/T + 0.236, (1723 to 1848 K); log {gamma}{sub Mg({ell}) in Si}{sup o} = {minus} 4900/T + 1.96, (1698 to 1798 K); and log {gamma}{sub Ca({ell})in Si}{sup o} = {minus} 7670/T + 1.53, (1723 to 1823 K).
Thermodynamic properties and thermometry of 1D Bose gases.
NASA Astrophysics Data System (ADS)
Kheruntsyan, Karen; Hu, Hui; Drummond, Peter
2006-05-01
We investigate the thermodynamic properties of an array of independent 1D Bose gases formed by a two-dimensional optical lattice. In particular, we calculate the total entropy of the system and compare it with the respective result for the 3D Bose-Einstein condensate as a function of the temperature and the interaction strength. This allows us to analyze how the temperature of the system is altered upon an adiabatic transfer of the 3D gas into an array of 1D tubes. The calculation is based on the exact finite temperature solution for a uniform 1D Bose gas, combined with the local density approximation [1]. The results can be applied to the recent experimental measurements of the local pair correlations in 1D Bose gases [2], which potentially can include finite temperature effects and no fitting parameters. In addition, we point out that the pair correlation function can be used as a thermometer for 1D Bose gases, under conditions when the density profiles become insensitive to temperature changes. [1] K. V. Kheruntsyan, D. M. Gangardt, P. D. Drummond, G. V. Shlyapnikov, Phys. Rev. A 71, 053615 (2005). [2] T. Kinoshita, T. Wenger, D. S. Weiss, Phys. Rev. Lett. 95, 190406 (2005).
Thermodynamic properties of liquid Au–Bi–Sn alloys
Guo, Zhongnan; Yuan, Wenxia; Hindler, Michael; Mikula, Adolf
2012-01-01
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. PMID:25550675
Thermodynamic properties of model CdTe/CdSe mixtures
van Swol, Frank; Zhou, Xiaowang W.; Challa, Sivakumar R.; Martin, James E.
2015-02-20
We report on the thermodynamic properties of binary compound mixtures of model groups II–VI semiconductors. We use the recently introduced Stillinger–Weber Hamiltonian to model binary mixtures of CdTe and CdSe. We use molecular dynamics simulations to calculate the volume and enthalpy of mixing as a function of mole fraction. The lattice parameter of the mixture closely follows Vegard's law: a linear relation. This implies that the excess volume is a cubic function of mole fraction. A connection is made with hard sphere models of mixed fcc and zincblende structures. We found that the potential energy exhibits a positive deviation frommore » ideal soluton behaviour; the excess enthalpy is nearly independent of temperatures studied (300 and 533 K) and is well described by a simple cubic function of the mole fraction. Using a regular solution approach (combining non-ideal behaviour for the enthalpy with ideal solution behaviour for the entropy of mixing), we arrive at the Gibbs free energy of the mixture. The Gibbs free energy results indicate that the CdTe and CdSe mixtures exhibit phase separation. The upper consolute temperature is found to be 335 K. Finally, we provide the surface energy as a function of composition. Moreover, it roughly follows ideal solution theory, but with a negative deviation (negative excess surface energy). This indicates that alloying increases the stability, even for nano-particles.« less
Structural, electronic and thermodynamic properties of magnesium chalcogenide ternary alloys
NASA Astrophysics Data System (ADS)
El Haj Hassan, F.; Amrani, B.
2007-09-01
The full potential-linearized augmented plane wave (FP-LAPW) method within the density functional theory (DFT) was applied to study the structural, electronic and thermodynamic properties of MgSxSe1-x, MgSxTe1-x and MgSexTe1-x ternary alloys. The calculated lattice parameters at different compositions of MgSxSe1-x and MgSexTe1-x alloys were found to vary almost linearly, while a significant deviation of the lattice parameter from Vegard's law for MgSxTe1-x alloy was observed. This is mainly due to the large mismatch of the lattice parameters of the binary compounds MgS and MgTe. A large deviation of the bulk modulus from linear concentration dependence (LCD) was observed for all three alloys. The calculated optical bowing was found to be mainly caused by the structural relaxation. Moreover, a significant charge exchange contribution was observed in the case of MgSxTe1-x alloy. The calculated phase diagram shows a broad miscibility gap for these alloys with a high critical temperature.
Thermodynamic properties of model CdTe/CdSe mixtures
van Swol, Frank; Zhou, Xiaowang W.; Challa, Sivakumar R.; Martin, James E.
2015-02-20
We report on the thermodynamic properties of binary compound mixtures of model groups II–VI semiconductors. We use the recently introduced Stillinger–Weber Hamiltonian to model binary mixtures of CdTe and CdSe. We use molecular dynamics simulations to calculate the volume and enthalpy of mixing as a function of mole fraction. The lattice parameter of the mixture closely follows Vegard's law: a linear relation. This implies that the excess volume is a cubic function of mole fraction. A connection is made with hard sphere models of mixed fcc and zincblende structures. We found that the potential energy exhibits a positive deviation from ideal soluton behaviour; the excess enthalpy is nearly independent of temperatures studied (300 and 533 K) and is well described by a simple cubic function of the mole fraction. Using a regular solution approach (combining non-ideal behaviour for the enthalpy with ideal solution behaviour for the entropy of mixing), we arrive at the Gibbs free energy of the mixture. The Gibbs free energy results indicate that the CdTe and CdSe mixtures exhibit phase separation. The upper consolute temperature is found to be 335 K. Finally, we provide the surface energy as a function of composition. Moreover, it roughly follows ideal solution theory, but with a negative deviation (negative excess surface energy). This indicates that alloying increases the stability, even for nano-particles.
Thermodynamics of water-permeated unwelded pyroclasts, 1: equilibrium properties
NASA Astrophysics Data System (ADS)
Ascolese, E.; Aurisicchio, A.; Briggs-Smith, M.; Mita, D. G.; Perna, G.; Rossi, S.; Gaeta, F. S.
1993-10-01
We report here the results of an investigation of thermodynamic equilibrium properties of systems constituted by Phlegraean unwelded pyroclasts, dry or saturated with water. We have experimentally measured the porosity of samples of Phlegraean rocks and determined the values of the heat capacity and of thermal expansion of dry and water-perfused tuffs having different texture structures. Also the energetics of the process of adsorption of water on the large internal surface of these porous materials has been investigated. The amount of heat exchanged during the reversible formation of an adsorbed layer has been determined, in dependence of its thickness and as a function of temperature. The coherent picture emerging from the ensemble of all these measurements is that of a direct connection between the processes of adsorption/desorption and the stress of the porous rock. In very unsaturated soils these processes may constitute a much more efficient mechanism of transformation of thermal energy into soil deformation, compared with that of thermal expansion of the solid matrix.
Molecular Dynamics Simulation of Thermodynamic Properties in Uranium Dioxide
Wang, Xiangyu; Wu, Bin; Gao, Fei; Li, Xin; Sun, Xin; Khaleel, Mohammad A.; Akinlalu, Ademola V.; Liu, L.
2014-03-01
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
ERIC Educational Resources Information Center
Piele, Philip K.; Johnson, Margaret M.
While the number of cases dealing with school property issues was significantly lower than in previous years, a significant number of cases involving the detachment and attachment of land to school districts arose. Eight of the eleven cases dealing with land detachment come from Illinois. The cases concerned requests from parents that their
ERIC Educational Resources Information Center
Piele, Philip K.
Reflecting widespread unhappiness with the growing tax burdens in this country, the most active area of litigation reported in the property chapter this year involves various attempts by taxpayers to prevent the construction or remodeling of public school facilities. While some taxpayers fought to keep schools from being built, others in New York…
NASA Technical Reports Server (NTRS)
Hansen, C Frederick; Heims, Steve P
1958-01-01
Thermodynamic and transport properties of high temperature air, and the reaction rates for the important chemical processes which occur in air, are reviewed. Semiempirical, analytic expressions are presented for thermodynamic and transport properties of air. Examples are given illustrating the use of these properties to evaluate (1) equilibrium conditions following shock waves, (2) stagnation region heat flux to a blunt high-speed body, and (3) some chemical relaxation lengths in stagnation region flow.
NASA Technical Reports Server (NTRS)
Svehla, R. A.; Mcbride, B. J.
1973-01-01
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.
Thermodynamic properties of UF sub 6 measured with a ballistic piston compressor
NASA Technical Reports Server (NTRS)
Sterritt, D. E.; Lalos, G. T.; Schneider, R. T.
1973-01-01
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.
THERMODYNAMIC PROPERTIES OF MC (M = V, Nb, Ta): FIRST-PRINCIPLES CALCULATIONS
NASA Astrophysics Data System (ADS)
Cao, Yong; Zhu, Jingchuan; Liu, Yong; Long, Zhishen
2013-07-01
Through the quasi-harmonic Debye model, the pressure and temperature dependences of linear expansion coefficient, bulk modulus, Debye temperature and heat capacity have been investigated. The calculated thermodynamic properties were compared with experimental data and satisfactory agreement is reached.
NASA Astrophysics Data System (ADS)
Wilson, H. F.
2013-12-01
First-principles atomistic simulation is a vital tool for understanding the properties of materials at the high-pressure high-temperature conditions prevalent in giant planet interiors, but properties such as solubility and phase boundaries are dependent on entropy, a quantity not directly accessible in simulation. Determining entropic properties from atomistic simulations is a difficult problem typically requiring a time-consuming integration over molecular dynamics trajectories. Here I will describe recent advances in first-principles thermodynamic calculations which substantially increase the simplicity and efficiency of thermodynamic integration and make entropic properties more readily accessible. I will also describe the use of first-principles thermodynamic calculations for understanding problems including core solubility in gas giants and superionic phase changes in ice giants, as well as future prospects for combining first-principles thermodynamics with planetary-scale models to help us understand the origin and consequences of compositional inhomogeneity in giant planet interiors.
Tables of thermodynamic and transport properties of UO/sub 2/
Fink, J.K.
1982-06-01
The thermodynamic and transport properties of solid and liquid UO/sub 2/ are tabulated as a function of temperature. Properties are given for the temperature range 298.15 K to 3120 K for solid UO/sub 2/ and from 3120 to 6000 K for liquid UO/sub 2/. Thermodynamic properties tabulated include enthalpy, heat capacity, pressure, density, instantaneous thermal expansion coefficient, compressibility, thermal pressure coefficient, and speed of sound. Tabulated transport properties include thermal conductivity, thermal diffusivity, emissivity, electrical conductivity, and viscosity. Tables are given in SI units and cgs units.
Thermodynamic equilibria in xylene isomerization. 1: The thermodynamic properties of p-xylene
Chirico, R.D.; Knipmeyer, S.E.; Nguyen, A.; Steele, W.V.
1997-03-01
Measurements and calculations leading to the determination of thermodynamic properties for the gaseous and condensed phases of p-xylene (Chemical Abstracts registry number (supplied by the authors) [106-42-3]) are reported. All measurement results reported were obtained with a differential-scanning calorimeter (DSC). The critical temperature was measured by DSC. Saturation heat capacities for the liquid phase between 370 K and 550 K, the critical density and the critical pressure were derived with fitting procedures involving the new DSC results and literature vapor pressures and ensities. Results were combined with heat capacities reported in the literature obtained with adiabatic calorimetry and the enthalpy of combustion to derive standard molar entropies, enthalpies, and Gibbs free energies of formation at selected temperatures between 250 K and 550 K. The standard state is defined as the ideal gas at the pressure p = p{degree} = 101.325 kPa. Standard entropies are compared with those calculated statistically on the basis of assigned vibrational spectra. Results are compared with literature values. Literature vapor pressures, enthalpies of vaporization, virial coefficients, densities, and heat capacities for the condensed and gaseous phases are checked for consistency with the values used in this research.
Thermodynamic equilibria in xylene isomerization. 2: The thermodynamic properties of m-xylene
Chirico, R.D.; Knipmeyer, S.E.; Nguyen, A.; Reynolds, J.W.; Steele, W.V.
1997-05-01
Measurements leading to the calculation of the ideal-gas thermodynamic properties for m-xylene are reported. Experimental methods included adiabatic heat-capacity calorimetry (5 K to 430 K), vibrating-tube densitometry (323 K to 523 K), comparative ebulliometry (309 K to 453 K), and differential-scanning calorimetry (DSC). The critical temperature was measured by DSC. Saturation heat capacities for the liquid phase between 430 K and 550 K and the critical pressure were derived with the vapor-pressure and DSC results. Results were combined with an enthalpy of combustion reported in the literature to derive standard molar entropies, enthalpies, and Gibbs free energies of formation at selected temperatures between 250 K and 550 K. The standard state is defined as the ideal gas at the pressure p = p{degree} = 101.325 kPa. Standard entropies are compared with those calculated statistically on the basis of assigned vibrational spectra for the vapor phase. All results are compared with literature values.
Thermodynamic equilibria in xylene isomerization. 3: The thermodynamic properties of o-xylene
Chirico, R.D.; Knipmeyer, S.E.; Nguyen, A.; Cowell, A.B.; Reynolds, J.W.; Steele, W.V.
1997-07-01
Measurements leading to the calculation of the ideal-gas thermodynamic properties for o-xylene (Chemical Abstracts registry number [95-47-6]) are reported. Experimental methods included adiabatic heat-capacity calorimetry (5 K to 420 K), comparative ebulliometry (313 K to 459 K), differential-scanning calorimetry (DSC), and vibrating-tube densitometry (323 K to 523 K). The critical temperature was measured by DSC. Saturation heat capacities for the liquid phase between 420 K and 550 K, the critical density, and the critical pressure were derived with the vapor-pressure, density, and DSC results. Results were combined with an enthalpy of combustion reported in the literature to derive standard molar entropies, enthalpies, and Gibbs free energies of formation at selected temperatures between 250 K and 550 K. The standard state is defined as the ideal gas at the pressure p = p{degree} = 101.325 kPa. Standard entropies are compared with those calculated statistically on the basis of assigned vibrational spectra from the literature for the vapor phase. A preliminary value for the barrier to methyl-group rotation is derived. All results are compared with literature values.
NASA Technical Reports Server (NTRS)
Nguyen, Huy H.; Martin, Michael A.
2003-01-01
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.
WETAIR: A computer code for calculating thermodynamic and transport properties of air-water mixtures
NASA Technical Reports Server (NTRS)
Fessler, T. E.
1979-01-01
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.
EquilTheTA: Thermodynamic and transport properties of complex equilibrium plasmas
Colonna, G.; D'Angola, A.
2012-11-27
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.
Thermodynamics and optical properties of ionized gases at temperatures to 100 eV
Protasov, Y.S.
1991-01-01
The book presents analytical data on the composition and principal thermodynamic and optical properties of plasma of Venusian and Martian atmospheres, fluorine, carbon dioxide, nitrogen and oxygen at temperatures T from 1 to 100 eV and densities p between 10{sup {minus}4} and 1 kg/m{sup 3}. The above plasma temperature and density ranges cover a significant proportion of plasma states occurring in different plasma systems and processes, and makes it possible to validate the composition, thermodynamic and optical properties within the framework of a well-tested unified model of a slightly nonideal plasma in local thermodynamic equilibrium, which is convenient for solving applied problems.
NASA Astrophysics Data System (ADS)
Singh, Gurpreet; Sharma, Rohit; Singh, Kuldip
2015-09-01
Thermodynamic properties (compressibility coefficient Z ? , specific heat at constant volume c v , adiabatic coefficient ? a , isentropic coefficient ? i s e n , and sound speed c s ) of non-local thermodynamic equilibrium hydrogen thermal plasma have been investigated for different values of pressure and non-equilibrium parameter ? (=Te/Th) in the electron temperature range from 6000 K to 60 000 K. In order to estimate the influence of pressure derivative of partition function on thermodynamic properties, two cases have been considered: (a) in which pressure derivative of partition function is taken into account in the expressions and (b) without pressure derivative of partition function in their expressions. Here, the case (b) represents expressions already available in literature. It has been observed that the temperature from which pressure derivative of partition function starts influencing a given thermodynamic property increases with increase of pressure and non-equilibrium parameter ?. Thermodynamic property in the case (a) is always greater than its value in the case (b) for compressibility coefficient and specific heat at constant volume, whereas for adiabatic coefficient, isentropic coefficient, and sound speed, its value in the case (a) is always less than its value in the case (b). For a given value of ?, the relationship of compressibility coefficient with degree of ionization depends upon pressure in the case (a), whereas it is independent of pressure in the case (b). Relative deviation between the two cases shows that the influence of pressure derivative of partition function is significantly large and increases with the augmentation of pressure and ? for compressibility coefficient, specific heat at constant volume, and adiabatic coefficient, whereas for isentropic coefficient and sound speed, it is marginal even at high values of pressure and non-equilibrium parameter ?.
Generalizing thermodynamic properties of bulk single-walled carbon nanotubes
Rodriguez, Kenneth R. Nanney, Warren A.; Maddux, Cassandra J.A.; Martínez, Hernán L.; Malone, Marvin A.; Coe, James V.
2014-12-15
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
Generalizing thermodynamic properties of bulk single-walled carbon nanotubes
Rodriguez, Kenneth R.; Nanney, Warren A.; A. Maddux, Cassandra J.; Martnez, Hernn L.
2014-01-01
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
Electrolytes: transport properties and non-equilibrium thermodynamics
Miller, D.G.
1980-12-01
This paper presents a review on the application of non-equilibrium thermodynamics to transport in electrolyte solutions, and some recent experimental work and results for mutual diffusion in electrolyte solutions.
NASA Technical Reports Server (NTRS)
Allison, D. O.
1972-01-01
Computer programs for flow fields around planetary entry vehicles require real-gas equilibrium thermodynamic properties in a simple form which can be evaluated quickly. To fill this need, polynomial approximations were found for thermodynamic properties of air and model planetary atmospheres. A coefficient-averaging technique was used for curve fitting in lieu of the usual least-squares method. The polynomials consist of terms up to the ninth degree in each of two variables (essentially pressure and density) including all cross terms. Four of these polynomials can be joined to cover, for example, a range of about 1000 to 11000 K and 0.00001 to 1 atmosphere (1 atm = 1.0133 x 100,000 N/m sq) for a given thermodynamic property. Relative errors of less than 1 percent are found over most of the applicable range.
Solvent effect on the thermodynamic and spectrophotometric properties of chargetransfer complexesII
NASA Astrophysics Data System (ADS)
Chattopadhyay, Sankar P.; Bhowmik, Benoy B.
The thermodynamic and spectrophotometric properties of the hexamethylbenzeneiodine chargetransfer complex in different donor solvents such as benzene, toluene, xylene ( o-, m-, p-) and mesitylene are found to depend on the solvent. The results show that the oscillator strengths of the chargetransfer bands of the hexamethylbenzeneiodine complex in these donor solvents increase with the heats of formation but these values of oscillator strengths are found comparatively high in comparison with the results observed earlier in inert solvents. The chargetransfer interaction of donor solvents with iodine is responsible for changing both thermodynamic as well as spectrophotometric properties of the hexamethylbenzeneiodine complex. An attempt is made to calculate the thermodynamic and spectrophotometric properties of these complexes free from other interaction.
Thermodynamic properties of sophocarpine and oxysophocarpine alkaloids in aqueous glucose solutions
NASA Astrophysics Data System (ADS)
Li, Zongxiao; Zhao, Weiwei; Pu, Xiaohua
2012-04-01
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, Δsol 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.
Atomistic simulation on the structure and thermodynamic properties of the UCu5Al7 derivatives
NASA Astrophysics Data System (ADS)
Qian, Ping; Tian, Hui-Jun; Shen, Jiang; Chen, Nan-Xian
2008-06-01
In order to study the effect of transition element M substitution on the structural properties of UCu3M2Al7 and UCu4MAl7 (M = Cr, Mn and Fe) compounds, the structural properties are investigated using the pair potentials based on the lattice inversion technique. The calculated lattice constants are found to be in good agreement with the experimental values. The properties related to lattice vibration, such as the phonon density of states, specific heat and vibrational entropy, are also evaluated. This is an attempt to predict the structural and thermodynamic properties for actinide materials with a complex structure.
An Equation of State for the Thermodynamic Properties of Cyclohexane
Zhou, Yong Liu, Jun; Penoncello, Steven G.; Lemmon, Eric W.
2014-12-15
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 pρT, 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{sup −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.
An Equation of State for the Thermodynamic Properties of Cyclohexane
NASA Astrophysics Data System (ADS)
Zhou, Yong; Liu, Jun; Penoncello, Steven G.; Lemmon, Eric W.
2014-12-01
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 pρT, 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.
NASA Technical Reports Server (NTRS)
Thompson, Richard A.; Lee, Kam-Pui; Gupta, Roop N.
1990-01-01
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.
Experimental verification of the thermodynamic properties for a jet-A fuel
NASA Technical Reports Server (NTRS)
Graciasalcedo, Carmen M.; Brabbs, Theodore A.; Mcbride, Bonnie J.
1988-01-01
Thermodynamic properties for a Jet-A fuel were determined by Shell Development Company in 1970 under a contract for NASA Lewis Research Center. The polynomial fit necessary to include Jet-A fuel (liquid and gaseous phases) in the library of thermodynamic properties of the NASA Lewis Chemical Equilibrium Program is calculated. To verify the thermodynamic data, the temperatures of mixtures of liquid Jet-A injected into a hot nitrogen stream were experimentally measured and compared to those calculated by the program. Iso-octane, a fuel for which the thermodynamic properties are well known, was used as a standard to calibrate the apparatus. The measured temperatures for the iso-octane/nitrogen mixtures reproduced the calculated temperatures except for a small loss due to the non-adiabatic behavior of the apparatus. The measurements for Jet-A were corrected for this heat loss and showed excellent agreement with the calculated temperatures. These experiments show that this process can be adequately described by the thermodynamic properties fitted for the Chemical Equilibrium Program.
Thermodynamic properties of aqueous polyatomic ions at extreme temperatures and pressures.
Djamali, Essmaiil; Cobble, James W
2010-03-25
Recently a theoretical treatment (J. Phys. Chem. B 2009, 113, 2398-2404) was developed for predicting the standard state thermodynamic properties of electrolytes up to and beyond the critical temperature of water (1273 K and at pressures up to 1000 MPa). In general, the model requires sufficient data at 298.15 K including the Gibbs free energy of hydration and at two higher temperatures to fix two constants for each electrolyte. This communication describes an extension of this "two constant" theory to thermodynamic properties of polyatomic ions for which no accurate data for the Gibbs free energy of hydration exits at 298.15 K. PMID:20192172
NASA Astrophysics Data System (ADS)
Cari, C.; Suparmi, A.; Yunianto, M.; Husein, A. S.
2016-02-01
The analytical solution of Ddimensional Dirac equation for Coulombic potential is investigated using Nikiforov-Uvarov method. The D dimensional relativistic energy spectra are obtained from relativistic energy eigenvalue equation by using Mat Lab software.The corresponding D dimensional radial wave functions are formulated in the form of generalized Jacobi and Laguerre Polynomials. In the non-relativistic limit, the relativistic energy equation reduces to the non-relativistic energy which will be applied to determine some thermodynamical properties of the system. The thermodynamical properties of the system are expressed in terms of error function and imaginary error function.
Symmetry, Optical Properties and Thermodynamics of Neptunium(V) Complexes
Rao, Linfeng; Tian, Guoxin
2009-12-21
Recent results on the optical absorption and symmetry of the Np(V) complexes with dicarboxylate and diamide ligands are reviewed. The importance of recognizing the 'silent' feature of centrosymmetric Np(V) species in analyzing the absorption spectra and calculating the thermodynamic constants of Np(V) complexes is emphasized.
Two-temperature thermodynamic and transport properties of SF6-Cu plasmas
NASA Astrophysics Data System (ADS)
Wu, Yi; Chen, Zhexin; yang, Fei; Cressault, Yann; Murphy, Anthony B.; Guo, Anxiang; Liu, Zirui; Rong, Mingzhe; Sun, Hao
2015-10-01
SF6 and Cu are widely adopted in electrical equipment as a dielectric medium and for conductive components, respectively. SF6-Cu plasmas are frequently formed, particularly in high-voltage circuit breaker arcs and fault current arcs, due to erosion of the Cu components. In this paper, calculated values of the thermodynamic and transport properties of plasmas in SF6-Cu mixtures are presented for both thermal equilibrium and non-equilibrium conditions. The composition is determined by the two-temperature Saha equation and Guldberg-Waage equation in the form derived by van de Sanden. The composition and the thermodynamic properties are evaluated through a classical statistical mechanics approach. For the transport coefficients, the simplified Chapman-Enskog method developed by Devoto, which decouples the electrons and heavy species, has been applied using the most recent collision integrals. The thermodynamic and transport properties are calculated for different electron temperatures (300-40 000 K), ratios of electron to heavy-species temperature (1-10), pressures (0.1-10 atm) and copper molar proportions (0-50%). It is found that deviations from thermal equilibrium strongly affect the thermodynamic and transport properties of the SF6-Cu plasmas. Further, the presence of copper has different effects on some of the properties for plasmas in and out of thermal equilibrium. The main reason for these changes is that dissociation reactions are delayed for non-thermal equilibrium plasmas, which in turn influences the ionization reactions that occur.
Ritter, E R
1991-08-01
A computer package has been developed called THERM, an acronym for THermodynamic property Estimation for Radicals and Molecules. THERM is a versatile computer code designed to automate the estimation of ideal gas phase thermodynamic properties for radicals and molecules important to combustion and reaction-modeling studies. Thermodynamic properties calculated include heat of formation and entropies at 298 K and heat capacities from 300 to 1500 K. Heat capacity estimates are then extrapolated to above 5000 K, and NASA format polynomial thermodynamic property representations valid from 298 to 5000 K are generated. This code is written in Microsoft Fortran version 5.0 for use on machines running under MSDOS. THERM uses group additivity principles of Benson and current best values for bond strengths, changes in entropy, and loss of vibrational degrees of freedom to estimate properties for radical species from parent molecules. This ensemble of computer programs can be used to input literature data, estimate data when not available, and review, update, and revise entries to reflect improvements and modifications to the group contribution and bond dissociation databases. All input and output files are ASCII so that they can be easily edited, updated, or expanded. In addition, heats of reaction, entropy changes, Gibbs free-energy changes, and equilibrium constants can be calculated as functions of temperature from a NASA format polynomial database. PMID:1939398
Thermodynamic properties and bulk viscosity near phase transition in the Z(2) and O(4) models
Li Baochun; Huang Mei
2009-08-01
We investigate the thermodynamic properties including equation of state, the trace anomaly, the sound velocity, and the specific heat, as well as transport properties like bulk viscosity in the Z(2) and O(4) models in the Hartree approximation of Cornwall-Jackiw-Tomboulis formalism. We study these properties in different cases, e.g. first-order phase transition, second-order phase transition, crossover and the case without phase transition, and discuss the correlation between the bulk viscosity and the thermodynamic properties of the system. We find that the bulk viscosity over entropy density ratio exhibits an upward cusp at the second-order phase transition, and a sharp peak at the first-order phase transition. However, this peak becomes smooth or disappears in the case of crossover. This result supports the idea that the bulk viscosity over entropy density ratio is a better quantity than the shear viscosity over entropy density ratio to locate the critical end point.
Thermodynamic properties of uranium in gallium-aluminium based alloys
NASA Astrophysics Data System (ADS)
Volkovich, V. A.; Maltsev, D. S.; Yamshchikov, L. F.; Chukin, A. V.; Smolenski, V. V.; Novoselova, A. V.; Osipenko, A. G.
2015-10-01
Activity, activity coefficients and solubility of uranium was determined in gallium-aluminium alloys containing 1.6 (eutectic), 5 and 20 wt.% aluminium. Additionally, activity of uranium was determined in aluminium and Ga-Al alloys containing 0.014-20 wt.% Al. Experiments were performed up to 1073 K. Intermetallic compounds formed in the alloys were characterized by X-ray diffraction. Partial and excess thermodynamic functions of U in the studied alloys were calculated.
Coherent States for Landau Levels: Algebraic and Thermodynamical Properties
NASA Astrophysics Data System (ADS)
Aremua, Isiaka; Hounkonnou, Mahouton Norbert; Baloïtcha, Ezinvi
2015-10-01
This work describes coherent states for a physical system governed by a Hamiltonian operator, in two-dimensional space, of spinless charged particles subject to a perpendicular magnetic field B, coupled with a harmonic potential. The underlying su(1 , 1) Lie algebra and Barut-Girardello coherent states are constructed and discussed. Then, the Berezin-Klauder-Toeplitz quantization, also known as coherent state (or anti-Wick) quantization, is discussed. The thermodynamics of such a quantum gas system is elaborated and analyzed.
Duan, Yuhua
2012-11-02
Since current technologies for capturing CO{sub 2} to fight global climate change are still too energy intensive, 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. Only those selected CO{sub 2} sorbent candidates were further considered for experimental validations. The ab initio thermodynamic technique has the advantage of identifying thermodynamic properties of CO{sub 2} capture reactions without any experimental input beyond crystallographic structural information of the solid phases involved. Such methodology not only can be used to search for good candidates from existing database of solid materials, but also can provide some guidelines for synthesis new materials. In this presentation, we first introduce our screening methodology and the results on a testing set of solids with known thermodynamic properties to validate our methodology. Then, by applying our computational method to several different kinds of solid systems, we demonstrate that our methodology can predict the useful information to help developing CO{sub 2} capture Technologies.
dos Ramos, Mara Carolina; Blas, Felipe J
2005-06-23
A modification of the statistical associating fluid theory, the so-called Soft-SAFT equation of state, is proposed to predict the excess thermodynamic properties of binary mixtures of n-alkanes. n-Alkane molecules are modeled as fully flexible Lennard-Jones chains. This molecular model accounts for the most important microscopic features of real chainlike molecules: attractive and repulsive interactions between different chemical groups and the connectivity of the segments that form the molecules. In this work we consider an additional microscopic effect that can profoundly affect certain thermodynamic properties, namely, the conformational changes when two different n-alkane molecules are mixed. We propose, following the work of Vega and co-workers [J. Chem. Phys. 1999, 111, 3192], a simple model to account for the conformational changes in molecules. The resulting free energy is combined with the SAFT free energy to describe the excess thermodynamic properties of binary mixtures of n-alkanes. Predictions from the theory are compared with experimental data taken from the literature. The agreement between the experiments and the theoretical predictions is excellent in all cases. This work shows that although minor microscopic effects, such as the conformational changes in the molecules that form the mixtures, have only a very small effect on the usual thermodynamic properties, such as pressure, chemical potential, phase equilibria, and excess volumes, they can contribute significantly to other thermodynamic properties. In fact, one of the main conclusions of this work is that it is essential that conformational effects be taken into account in molecular-based theories if an accurate description of certain excess properties (excess enthalpy for instance) is desired. PMID:16852498
Thermodynamic Properties for A Drop-in Refrigerant R-SP34E
NASA Astrophysics Data System (ADS)
Kayukawa, Yohei; Hondo, Takashi; Watanabe, Koichi
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.
Červinka, Ctirad; Pádua, Agilio A H; Fulem, Michal
2016-03-10
This work presents a molecular dynamics simulation study concerning the thermodynamic data of ionic liquids (ILs) including phase change enthalpies, liquid phase densities, radial and spatial distribution functions, and diffusive properties. Three homologous series of ILs were selected for this study, namely, 1-alkyl-3-methylimidazolium tetrafluoroborates, hexafluorophosphates, and 1,1,2,2-tetrafluoroethanesulfonates, so that properties of 36 ILs are calculated in total. The trends of calculated properties are compared to available experimental data and thoroughly discussed in context of the homologous series. The calculated trends of the vaporization enthalpies within the series are supported by analyzing the structural properties of the ILs. An excellent agreement of calculated structural properties (liquid phase density) with the experimental counterparts is reached. The calculated enthalpic properties are overestimated considerably; thus, further development of the force fields for ILs is required. PMID:26848831
Static properties of hydrophobic polyelectrolytes in the thermodynamic limit
NASA Astrophysics Data System (ADS)
Carbajal-Tinoco, M. D.; Williams, C. E.
2000-11-01
A series of hydrophobic sodium poly(styrene-co-styrene sulfonate) of different charge fractions has been studied by static light scattering in the thermodynamic limit. In the examined concentration range ( <= 0.1 M/l, in monomers), the solutions show an ideal gas behaviour. A quantitative comparison with previous osmotic pressure measurements reveals the existence of a strong variation of the polarizability, which is related to a change of local chain conformation. This result can be interpreted in terms of the globular instability model for hydrophobic polyelectrolytes (pearl necklace model).
The standard thermodynamic properties of 4 f metal dichlorides
NASA Astrophysics Data System (ADS)
Chervonnyi, A. D.; Chervonnaya, N. A.
2008-02-01
The experimental data on heterogeneous and homogeneous equilibria with the participation of 4f metal dichlorides LnCl2 (where Ln = La, …, Lu) were analyzed using the thermodynamic functions of these substances in the gaseous and condensed states described earlier. These data and appearance potential AP(Ln+/LnCl2) measurements were used to calculate the enthalpies of sublimation Δsub H {298/o}. The enthalpies of atomization of these compounds under standard conditions were also calculated. Correlations between the enthalpies of sublimation and crystal lattice structure of 4 f metal trifluorides, trichlorides, and dichlorides are described.
NASA Astrophysics Data System (ADS)
Satoh, Katsuhiko
2013-08-01
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^{γ _τ }, where T and V are the temperature and volume, respectively. The scaling parameter γτ was in excellent agreement with the thermodynamic parameter Γ, 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 Γ and γτ 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.
Thermodynamic and structural properties of the rare-earth Co3 hydrides
NASA Astrophysics Data System (ADS)
Kierstead, H. A.
The thermodynamic and structural properties of the hydrides of the intermetallic compounds LnCo3 (Ln = Nd, Gd, Tb, Dy, Ho, Er, Tm, and Y) are presented. Systematic changes in the absorption isotherms; the heat, entropy, and free energy of absorption; and the X-ray lattice parameters are discussed and interpreted.
Levitation calorimetry. IV - The thermodynamic properties of liquid cobalt and palladium.
NASA Technical Reports Server (NTRS)
Treverton, J. A.; Margrave, J. L.
1971-01-01
Some of the thermodynamic properties of liquid cobalt and palladium investigated by means of levitation calorimetry are reported and discussed. The presented data include the specific heats and heats of fusion of the liquid metals, and the emissivities of the liquid metal surfaces.
Thermodynamically-robust Pitzer equations for volumetric properties of electrolyte solutions.
Rowland, Darren
2015-11-01
Pitzer equations are widely employed to correlate and predict the volumetric properties of aqueous electrolyte solutions over broad ranges of pressure and temperature. However, the currently-used pressure and temperature terms are empirical and tend to violate known thermodynamic behaviour. Three functional constraints have been identified that overcome this problem. PMID:26452795
The Problem of Counting the Number of Molecules and Calculating Thermodynamic Properties.
ERIC Educational Resources Information Center
Torres, Luis Alfonso; And Others
1995-01-01
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)
Thermodynamic properties of a quantum Hall anti-dot interferometer
NASA Astrophysics Data System (ADS)
Levy Schreier, Sarah; Stern, Ady; Rosenow, Bernd; Halperin, Bertrand I.
2016-02-01
We study quantum Hall interferometers in which the interference loop encircles a quantum anti-dot. We base our study on thermodynamic considerations, which we believe reflect the essential aspects of interference transport phenomena. We find that similar to the more conventional Fabry-Perot quantum Hall interferometers, in which the interference loop forms a quantum dot, the anti-dot interferometer is affected by the electro-static Coulomb interaction between the edge modes defining the loop. We show that in the Aharonov-Bohm regime, in which effects of fractional statistics should be visible, is easier to access in interferometers based on anti-dots than in those based on dots. We discuss the relevance of our results to recent measurements on anti-dots interferometers.
Thermodynamic properties of some metal oxide-zirconia systems
NASA Technical Reports Server (NTRS)
Jacobson, Nathan S.
1989-01-01
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.
Thermodynamic properties of mesoscale convective systems observed during BAMEX
Correia, James; Arritt, R.
2008-11-01
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.
Metastable Solution Thermodynamic Properties and Crystal Growth Kinetics
NASA Technical Reports Server (NTRS)
Kim, Soojin; Myerson, Allan S.
1996-01-01
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.
Theoretical Investigations on the Elastic and Thermodynamic Properties of Rhenium Phosphide
NASA Astrophysics Data System (ADS)
Wei, Qun; Yan, Haiyan; Zhu, Xuanmin; Lin, Zhengzhe; Yao, Ronghui
2016-01-01
Structural, mechanical, and electronic properties of orthorhombic rhenium phosphide (Re2P) are systematically investigated by using first principles calculations. The elastic constants and anisotropy of elastic properties are obtained. The metallic character of Re2P is demonstrated by density of state calculations. The quasi-harmonic Debye model is applied to the study of the thermodynamic properties. The thermal expansion, heat capacities, and Grüneisen parameter on the temperature and pressure have been determined as a function of temperature and pressure in the pressure range from 0 to 100 GPa and the temperature range from 0 to 1600 K.
The thermodynamic properties of 2-methylaniline and trans-(R,S)- decahydroquinoline
Steele, W.V.; Chirico, R.D.; Nguyen, A.; Knipmeyer, S.E.
1990-02-01
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.
Thermodynamic and fluid properties of cells, tissues and membranes
NASA Astrophysics Data System (ADS)
Upadhyaya, Arpita
2000-10-01
This dissertation studies cellular rearrangements in tissues and attempts to establish the role of physical properties of cells, tissues and membranes in several biological phenomena. Using experiments and statistical mechanical modeling, we study cell sorting, tissue engulfment, single cell motion and membrane fluctuations. When cells of two different types are mixed together, they sort out, with the less cohesive tissue surrounding the more cohesive one. This sorting out resembles the phase separation of a mixture of immiscible liquids. We have measured the rate of sorting in tissues and compared it with a cellular automaton based model of cell aggregates. We have also established that cell sorting agrees well with the theory for phase separating fluids. Engulfment is the spreading of one type of tissue over the surface of another tissue placed adjacent to it. Differences in adhesion cause an imbalance of surface tension forces which drives tissue spreading. We have quantitatively studied engulfment between different tissue types and compared the experimental rate with results from computer simulations and a liquid model. Our results suggest that simple physical principles can model tissue motion. Studying the motion of single cells in aggregates is important to understanding the overall pattern formation in tissues. We characterized cell motion in different types of adhesive aggregates to elucidate the role of adhesion in cell motion. We also observed that the cells exhibited a novel type of statistics including correlations and collective motion. Membrane deformations of cells played a negligible role in large scale cell motion. Our results indicate the importance of correlated motion for cells to move long distances in tissues. At the single cell level, tension of the cell membrane and intracellular membrane can play an important role in cell shape changes, regulation of cell motility and membrane dynamics. We used optical tweezers to measure the membrane tension of tubulo-vesicular networks obtained from Golgi and Endoplasmic Reticulum (ER) membranes within cells. As expected on the basis of some previous experiments, the ER has a higher membrane tension than the Golgi.
Concentration dependence of thermodynamic, transport and surface properties in Ag-Cu liquid alloys
NASA Astrophysics Data System (ADS)
Jha, I. S.; Koirala, I.; Singh, B. P.; Adhikari, D.
2014-09-01
Thermodynamic, transport and surface properties of Ag-Cu liquid alloys have been investigated on the basis of a simple statistical model. The free energy of mixing, heat of mixing and entropy of mixing have been computed to understand the thermodynamic properties of Ag-Cu alloys in liquid state at 1,423 K. The concentration-concentration fluctuations in the long wavelength limit and the chemical short range order parameter have been determined to comprehend the microscopic and structural information of the alloy. The viscosity and surface tension of the alloy have been evaluated to analyze the transport and surface properties. The theoretical analysis reveals that the energy parameter is temperature dependent, and that Ag-Cu liquid alloy is a weakly interacting-phase separating system.
Thermodynamic properties of Cu-Zr melts: The role of chemical interaction
NASA Astrophysics Data System (ADS)
Kulikova, T. V.; Majorova, A. V.; Shunyaev, K. Yu.; Ryltsev, R. E.
2015-06-01
General statistical model is applied to analyze the role of chemical interaction in associated systems. We show that, at certain conditions, chemical interaction between associates may be not essential above a distectic point and so the model of ideal associated solutions is a good approximation for describing high temperature properties of associated system with chemical interaction. Within the frames of such conception, we calculate thermodynamic properties of Cu-Zr system in liquid state. The enthalpies of formation of Cu-Zr intermetallic compounds were redefined by using matching procedure taking into account the additive manifestation of chemical interaction. We conclude that simple model which is free of adjusting parameters allows us to calculate thermodynamic properties of Cu-Zr melts with quite good accuracy.
Prediction of the thermodynamic properties of electrolytes at high pressures and temperatures
NASA Astrophysics Data System (ADS)
Helgeson, Harold C.
The thermodynamic behavior of aqueous electrolytes at high pressures and temperatures can be predicted with the aid of theoretical equations incorporating explicit provision for ion association, solvation, and long- and short-range interaction, the intrinsic properties of aqueous species, and electrostriction collapse of the local solvent structure. Parameters derived from fits of the equations to experimental data at low pressures and temperatures can be used to predict both the standard and relative partial molal properties of aqueous electrolytes at high pressures and temperatures. Calculations of this kind afford estimates of the relative enthalpies, heat capacities, and densities of NaCl solutions at pressures and temperatures to 5 kbar and 600°C. These estimates and the theoretical equations used to calculate them are summarized below, together with predicted activity and osmotic coefficients, apparent standard partial molal Gibbs free energies of formation, and other thermodynamic properties of aqueous electrolytes at high pressures and temperatures.
Thermodynamic and mechanical properties of TiC from ab initio calculation
Dang, D. Y.; Fan, J. L.; Gong, H. R.
2014-07-21
The temperature-dependent thermodynamic and mechanical properties of TiC are systematically investigated by means of a combination of density-functional theory, quasi-harmonic approximation, and thermal electronic excitation. It is found that the quasi-harmonic Debye model should be pertinent to reflect thermodynamic properties of TiC, and the elastic properties of TiC decease almost linearly with the increase of temperature. Calculations also reveal that TiC possesses a pronounced directional pseudogap across the Fermi level, mainly due to the strong hybridization of Ti 3d and C 2p states. Moreover, the strong covalent bonding of TiC would be enhanced (reduced) with the decrease (increase) of temperature, while the change of volume (temperature) should have negligible effect on density of states at the Fermi level. The calculated results agree well with experimental observations in the literature.
Low-Temperature Thermodynamic Properties of a One-Dimensional Generalized Wigner Crystal
NASA Astrophysics Data System (ADS)
Slavin, V.
The low-temperature thermodynamic properties of a one-dimensional generalized Wigner crystal at arbitrary values of electron density and arbitrary number of interacting electrons are studied. The modified transfer-matrixes method is applied. It is shown that increasing the number of interacting electrons leads to the appearance of more and more fine "stairs" in low-temperature dependence of chemical potential against electron density. An influence of the disorder in host-lattice site positions on thermodynamic characteristics of the system is considered. It is established that the disorder destroys the "stairs".
Thermodynamic properties by non-calorimetric methods. Progress report, August 1, 1988--July 31, 1989
Steele, W.V.; Chirico, R.D.; Collier, W.B.; Strube, M.M. |
1989-12-31
This three year research program provides a valuable complement to the experimental programs currently in progress at NIPER for the Advanced Research and Technology Development (AR and TD) and Advanced Exploration and Process Technology (AEPT) divisions of the Department of Energy. These experimental programs are focused on the calorimetric determination of thermodynamic properties of key polynuclear heteroatom-containing aromatic molecules. This project for the Office of Energy Research focuses on the non-calorimetric determination of thermodynamic properties through the extension of existing correlation methodologies and through molecular spectroscopy with statistical mechanics. The paper discusses progress in three areas: (1) Improvement of thermochemical and thermophysical property predictions via enhancement of group-contribution methods using two approaches, namely, development and improvement of group-contribution parameters via correlations involving the expanded modern thermodynamics data base and development of group-contribution parameters via molecular spectroscopy and statistical mechanics of key monocyclic organic compounds; (2) Molecular spectroscopy and statistical mechanics: equipment development and developments in interpretation and assignment of spectra; and (3) Thermophysical property correlations.
NASA Technical Reports Server (NTRS)
Mccarty, R. D.
1980-01-01
The thermodynamic and transport properties of selected cryogens had programmed into a series of computer routines. Input variables are any two of P, rho or T in the single phase regions and either P or T for the saturated liquid or vapor state. The output is pressure, density, temperature, entropy, enthalpy for all of the fluids and in most cases specific heat capacity and speed of sound. Viscosity and thermal conductivity are also given for most of the fluids. The programs are designed for access by remote terminal; however, they have been written in a modular form to allow the user to select either specific fluids or specific properties for particular needs. The program includes properties for hydrogen, helium, neon, nitrogen, oxygen, argon, and methane. The programs include properties for gaseous and liquid states usually from the triple point to some upper limit of pressure and temperature which varies from fluid to fluid.
A web based program to visualize the transport and thermodynamic properties of thermal plasma
NASA Astrophysics Data System (ADS)
Sreekumar, Ambili; Thiyagarajan, T. K.; Ravi, Vijayalakshmi; Padmanabhan, P. V. A.
2010-02-01
The data of transport properties like viscosity, thermal conductivity and electrical conductivity of high temperature gases or gas mixtures used in thermal plasma devices, as a function of temperature is very much essential for the process modeling and theoretical simulation. Similarly the temperature variation of thermodynamic properties like density, specific heat and enthalpy also should be known. Calculated values of these properties of the gases or gas mixtures specific to thermal plasma devices are available as a function of temperature in tabular form. To share the knowledge about these values of properties, web based package of codes and database documents are developed. The modules present in the package works in client-server environment, where the inter communication is through HTTP protocol. The developed package is tested with Apache tomcat web container. The details of the code development and working procedure are described in this paper.
Perruchot, Christian; Chehimi, Mohamed M.; Vaulay, Marie-Josephe; Benzarti, Karim . E-mail: benzarti@lcpc.fr
2006-02-15
The surface thermodynamic properties of three main inorganic compounds formed during hydration of Portland cement: calcium hydroxide (Ca(OH){sub 2}), ettringite (3CaO.Al{sub 2}O{sub 3}.3CaSO{sub 4}.32H{sub 2}O) and calcium-silicate-hydrates (C-S-H), respectively, and one mineral filler: calcium carbonate (CaCO{sub 3}), have been characterised by inverse gas chromatography at infinite dilution (IGC-ID) at 35 deg. C. The thermodynamic properties have been investigated using a wide range of non-polar (n-alkane series), Lewis acidic (CH{sub 2}Cl{sub 2} and CHCl{sub 3}), Lewis basic (diethyl ether) and aromatic (benzene) and n-alkene series molecular probes, respectively. The tested samples are fairly high surface energy materials as judged by the high dispersive contribution to the total surface energy (the dispersive components {gamma} {sub s} {sup d} range from 45.6 up to 236.2 mJ m{sup -2} at 35 deg. C) and exhibit amphoteric properties, with a predominant acidic character. In the case of hydrated components (i.e. ettringite and C-S-H), the surface thermodynamic properties have been determined at various temperatures (from 35 up to 120 deg. C) in order to examine the influence of the water content. The changes of both dispersive and specific components clearly demonstrate that the material surface properties are activated with temperature. The changes in the acid-base properties are correlated with the extent of the overall water loss induced by the thermal treatment as demonstrated by thermogravimetric analysis (TGA). The elemental surface composition of these compounds has been determined by X-ray photoelectron spectroscopy (XPS)
Thermodynamic properties and atomic structure of Ca-based liquid alloys
NASA Astrophysics Data System (ADS)
Poizeau, Sophie
To identify the most promising positive electrodes for Ca-based liquid metal batteries, the thermodynamic properties of diverse Ca-based liquid alloys were investigated. The thermodynamic properties of Ca-Sb alloys were determined by emf measurements. It was found that Sb as positive electrode would provide the highest voltage for Ca-based liquid metal batteries (1 V). The price of such a battery would be competitive for the grid-scale energy storage market. The impact of Pb, a natural impurity of Sb, was predicted successfully and confirmed via electrochemical measurements. It was shown that the impact on the open circuit voltage would be minor. Indeed, the interaction between Ca and Sb was demonstrated to be much stronger than between Ca and Pb using thermodynamic modeling, which explains why the partial thermodynamic properties of Ca would not vary much with the addition of Pb to Sb. However, the usage of the positive electrode would be reduced, which would limit the interest of a Pb-Sb positive electrode. Throughout this work, the molecular interaction volume model (MIVM) was used for the first time for alloys with thermodynamic properties showing strong negative deviation from ideality. This model showed that systems such as Ca-Sb have strong short-range order: Ca is most stable when its first nearest neighbors are Sb. This is consistent with what the more traditional thermodynamic model, the regular association model, would predict. The advantages of the MIVM are the absence of assumption regarding the composition of an associate, and the reduced number of fitting parameters (2 instead of 5). Based on the parameters derived from the thermodynamic modeling using the MIVM, a new potential of mixing for liquid alloys was defined to compare the strength of interaction in different Ca-based alloys. Comparing this trend with the strength of interaction in the solid state of these systems (assessed by the energy of formation of the intermetallics), the systems with the most stable intermetallics were found to have the strongest interaction in the liquid state. Eventually, a new criteria was formulated to select electrode materials for liquid metal batteries. Systems with the most stable intermetallics, which can be evaluated by the enthalpy of formation of these systems, will yield the highest voltage when assembled as positive and negative electrodes in a liquid metal battery. (Copies available exclusively from MIT Libraries, libraries.mit.edu/docs - docs@mit.edu)
NASA Astrophysics Data System (ADS)
Noh, Seunghyo; Kwak, Dohyun; Lee, Juseung; Kang, Joonhee; Han, Byungchan
2014-03-01
We utilized first-principles density-functional-theory (DFT) calculations to evaluate the thermodynamic feasibility of a pyroprocessing methodology for reducing the volume of high-level radioactive materials and recycling spent nuclear fuels. The thermodynamic properties of transuranium elements (Pu, Np and Cm) were obtained in electrochemical equilibrium with a LiCl-KCl molten salt as ionic phases and as adsorbates on a W(110) surface. To accomplish the goal, we rigorously calculated the double layer interface structures on an atomic resolution, on the thermodynamically most stable configurations on W(110) surfaces and the chemical activities of the transuranium elements for various coverages of those elements. Our results indicated that the electrodeposition process was very sensitive to the atomic level structures of Cl ions at the double-layer interface. Our studies are easily expandable to general electrochemical applications involving strong redox reactions of transition metals in non-aqueous solutions.
Accuracy Based Generation of Thermodynamic Properties for Light Water in RELAP5-3D
Cliff B. Davis
2010-09-01
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.
NASA Astrophysics Data System (ADS)
Xing, Mengjiang; Li, Binhua; Yu, Zhengtao; Chen, Qi
2016-04-01
The structural, mechanical, electronic and thermodynamic properties of the tetragonal structure germanium carbonitride (t-GeCN) were first investigated using the density function theory with the ultrasoft psedopotential scheme in the frame of the generalized gradient approximation and the local density approximation. The elastic constants have confirmed that the t-GeCN is mechanically stable and phonon spectra have confirmed that the t-GeCN is dynamically stable. The anisotropy studies show that t-GeCN exhibits a larger anisotropy in its Poisson's ratio, Young's modulus, shear modulus, sound velocities and universal elastic anisotropy index. Electronic structure study shows that t-GeCN is an indirect semiconductor with band gap of 0.628 eV. The thermodynamic properties of t-GeCN, including Debye temperature, heat capacity, Grüneisen parameter and thermal expansion coefficient are investigated utilizing the quasi-harmonic Debye model.
Elastic and thermodynamic properties of Fe3Ga from first-principles calculations
NASA Astrophysics Data System (ADS)
Lin, Ya-Ning; Li, Lin-Ling; Yan, Xiang-Hong; Zhang, Ya-Ping; Zhang, Dong-yun; Zhang, Peng
2016-03-01
First-principles calculations within the framework of density functional theory (DFT) are performed to investigate the elastic and thermodynamic properties of DO3-type Fe3Ga alloy. The obtained lattice constants and the bulk modulus are in good agreement with available experimental data. In terms of the calculated formation energy and Poisson's ratio, the Fe3Ga alloy is mechanically stable and exhibit a negative Poisson's ratio of -0.81 along the <110> direction. The thermodynamic properties such as the Gibbs free energy, thermal expansion, and the specific heat are obtained by the first-principles phonon calculations with the quasiharmonic approximation method. The predicted coefficient of linear thermal expansion and specific heat may provide a helpful reference for experimental work.
Ab Initio Calculation of Structure and Thermodynamic Properties of Zintl Aluminide SrAl2
NASA Astrophysics Data System (ADS)
Fu, Zhi-Jian; Jia, Li-Jun; Xia, Ji-Hong; Tang, Ke; Li, Zhao-Hong; Sun, Xiao-Wei; Chen, Qi-Feng
2015-12-01
The structural and thermodynamic properties of the orthorhombic and cubic structure SrAl2 at pressure and temperature are investigated by using the ab initio plane-wave pseudopotential density functional theory methodwithin the generalised gradient approximation (GGA). The calculated lattice parameters are in agreement with the available experimental data and other theoretical results. The phase transition predicted takes place at 0.5 GPa from the orthorhombic to the cubic structure at zero temperature. The thermodynamic properties of the zinc-blende structure SrAl2 are calculated by the quasi-harmonic Debye model. The pressure-volume relationship and the variations inthe thermal expansion α are obtained systematically in the pressure and temperature ranges of 0-5 GPa and 0-500 K, respectively.
Theoretical study of the thermodynamic properties of lithium, sodium, and potassium nitrates
NASA Astrophysics Data System (ADS)
Korabel'nikov, D. V.; Zhuravlev, Yu. N.
2013-08-01
The thermal properties of lithium, sodium, and potassium nitrates have been studied in a gradient approximation of the density functional theory using the method of linear combination of atomic orbitals of the CRYSTAL09 program package. The long-wave frequencies and corresponding mode Grüneisen parameters are calculated. The quasi-harmonic Debye-Einstein model is used to calculate the parameters of the equation of states and also the dependences of the thermodynamic potentials, the entropy, the heat capacity, the thermal expansion coefficient, and the Grüneisen parameter on pressure and temperature. The role of external and intramolecular vibrations in the interpretation of thermodynamic properties is determined. The obtained results agree well with the available experimental data.
Numerical prediction of the thermodynamic properties of ternary Al-Ni-Hf alloys
Romanowska, Jolanta; Kotowski, Sławomir; Zagula-Yavorska, Maryana
2014-10-06
Thermodynamic properties of ternary Al-Hf-Ni system, such as {sup ex}G, μ{sub Al}, μ{sub Ni} and μ{sub Zr} at 1373K were predicted on the basis of thermodynamic properties of binary systems included in the investigated ternary system. The idea of predicting {sup ex}G values was regarded as the calculation of excess Gibbs energy values inside a certain area (a Gibbs triangle) unless all boundary conditions, that is values of {sup ex}G on all legs of the triangle are known. {sup ex}G and L{sub ijk} ternary interaction parameters in the Muggianu extension of the Redlich-Kister formalism are calculated numerically using Wolfram Mathematica 9 software.
Thermodynamic properties of liquid Au–Cu–Sn alloys determined from electromotive force measurements
Guo, Zhongnan; Hindler, Michael; Yuan, Wenxia; Mikula, Adolf
2011-01-01
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
Pressure effect on structural, elastic, and thermodynamic properties of tetragonal B4C4
NASA Astrophysics Data System (ADS)
Zheng, Baobing; Zhang, Meiguang; Luo, Hong-Gang
2015-03-01
The compressibility, elastic anisotropy, and thermodynamic properties of the recently proposed tetragonal B4C4 (t-B4C4) are investigated under high temperature and high pressure by using of first-principles calculations method. The elastic constants, bulk modulus, shear modulus, Young's modulus, Vickers hardness, Pugh's modulus ratio, and Poisson's ratio for t-B4C4 under various pressures are systematically explored, the obtained results indicate that t-B4C4 is a stiffer material. The elastic anisotropies of t-B4C4 are discussed in detail under pressure from 0 GPa to 100 GPa. The thermodynamic properties of t-B4C4, such as Debye temperature, heat capacity, and thermal expansion coefficient are investigated by the quasi-harmonic Debye model.
Thermodynamic properties of liquid Au-Cu-Sn alloys determined from electromotive force measurements.
Guo, Zhongnan; Hindler, Michael; Yuan, Wenxia; Mikula, Adolf
2011-10-20
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
Experimental study and modeling of the thermodynamic properties of Cu-Fe-Ni melts
NASA Astrophysics Data System (ADS)
Dreval', L. A.; Abdulov, A. R.; Agraval, P. G.; Turchanin, M. A.
2010-01-01
The partial mixing enthalpy of nickel in ternary liquid Cu-Fe-Ni alloys is studied at 1873 K along sections characterized by ratios x Cu: x Fe = 3, 1, and 1/3 at x Ni = 0-0.55. The investigations are undertaken using a high-temperature isoperibolic calorimeter. The temperature and composition dependence of the excess mixing Gibbs energy of liquid Cu-Fe-Ni alloys are described in terms of the Muggianu-Redlich-Kister model using the data obtained, the literature data on the activities of liquid alloy components, and the thermodynamic properties of melts of the boundary binary systems. This model is used to calculate isotherms of the thermodynamic properties of the liquid alloys over the entire composition range. The contribution of a ternary interaction to the integral mixing enthalpy of liquid Cu-Fe-Ni alloys is found to be mainly positive.
Numerical prediction of the thermodynamic properties of ternary Al-Ni-Hf alloys
NASA Astrophysics Data System (ADS)
Romanowska, Jolanta; Kotowski, Sławomir; Zagula-Yavorska, Maryana
2014-10-01
Thermodynamic properties of ternary Al-Hf-Ni system, such as exG, μAl, μNi and μZr at 1373K were predicted on the basis of thermodynamic properties of binary systems included in the investigated ternary system. The idea of predicting exG values was regarded as the calculation of excess Gibbs energy values inside a certain area (a Gibbs triangle) unless all boundary conditions, that is values of exG on all legs of the triangle are known. exG and Lijk ternary interaction parameters in the Muggianu extension of the Redlich-Kister formalism are calculated numerically using Wolfram Mathematica 9 software.
NASA Astrophysics Data System (ADS)
Zemzemi, M.; Elghoul, N.; Khirouni, K.; Alaya, S.
2014-02-01
Cuprous oxide is selected as a promising material for photovoltaic applications. Density functional theory is used to study the structural, electronic, and thermodynamic properties of cuprous oxide by using the local density approximation and generalized-gradient approximation. The effect of pressure on the structural and electronic properties of Cu2O is investigated. This study confirms and characterizes the existence of new phases. Hexagonal and tetragonal phases are not completely indentified. We focus on the phase transition of the cuprous oxide under hydrostatic pressure to tetragonal and hexagonal (CdI2) structures. Variation of enthalpy with pressure is used to calculate the pressure of the phase transition.
Thermodynamic Properties of Molecular Crystals Calculated within the Quasi-Harmonic Approximation.
Červinka, Ctirad; Fulem, Michal; Stoffel, Ralf Peter; Dronskowski, Richard
2016-03-31
A computational study of the possibilities of contemporary theoretical chemistry as regards calculated thermodynamic properties for molecular crystals from first-principles is presented. The study is performed for a testing set of 22 low-temperature crystalline phases whose properties such as densities of phonon states, isobaric heat capacities, and densities are computed as functions of temperature within the quasi-harmonic approximation. Electronic structure and lattice dynamics are treated by plane-wave based calculations with optPBE-vdW functional. Comparison of calculated results with reliable critically assessed experimental data is especially emphasized. PMID:26959684
Two-fluid theory and thermodynamic properties of liquid mixtures: General theory
Brandani, V.; Prausnitz, J. M.
1982-01-01
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 attention is given to the problem of nonrandomness in mixtures. A quantitative description of nonrandomness is achieved by combining the two-fluid concept with a hypothesis for ensemble averaging of a distribution of nearest-neighbor pairs. PMID:16593213
Thermodynamic and magnetic properties of the finite spin complexes of the Ising type
NASA Astrophysics Data System (ADS)
Khamzin, A. A.; Nigmatullin, R. R.
2014-05-01
In the frame of the static fluctuation approximation (SFA) the analysis of the thermodynamic and magnetic properties of the finite spin clusters in the 1D Ising model is performed It has been shown that under the influence of the magnetic impurity that forms the fixed value of the magnetization on the ends of spin complex the total magnetic ordering of the whole chain becomes possible. The results obtained in the frame of this model can open a way to understanding of magnetic properties of a wide class of the finite cluster systems.
NASA Astrophysics Data System (ADS)
Ezhov, Yu. S.
2008-03-01
Using the program package from the IVTANTERMO databank, the thermodynamic properties of CH3SiH3, CCl3SiH3, SiCl3CH3, SiCl3SiH3, SiCl3CCl3, and SiCl3SiCl3 were calculated and the thermolysis process was studied for CCl3SiH3, SiCl3CCl3, and SiCl3SiCl3.
Ebulliometers for measuring the thermodynamic properties of fluids and fluid mixtures
Weber, L.A.; Silva, A.M.
1994-09-01
The design and operation of two ebulliometers is described. One is constructed of glass and is used for measuring vapor pressures of fluids at low reduced temperatures and pressures. The other is constructed of metal. It can be used for vapor pressure measurements, and also for the study of fluid mixture thermodynamics through the determination of the activity coefficients at infinite dilution. The advantages and potential problems associated with ebulliometers are described, and typical results are given for the properties of alternative refrigerants.
Quartz: heat capacities from 340 to 1000 K and revised values for the thermodynamic properties.
Hemingway, B.S.
1987-01-01
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.
Vibrational and thermodynamic properties of GeSe in the quasiharmonic approximation
NASA Astrophysics Data System (ADS)
Deringer, Volker L.; Stoffel, Ralf P.; Dronskowski, Richard
2014-03-01
Finite-temperature properties such as thermodynamic state functions can be obtained for a range of crystalline materials by combining density functional theory (DFT) with lattice-dynamics approaches. Despite the usefulness of such first-principles predictions, their results must be carefully checked for accuracy, especially in cases where the DFT description of the material itself is nontrivial. Here, we investigate a prototypical layered semiconductor, namely, germanium selenide (GeSe) by dispersion-corrected DFT, lattice-dynamics computations, and a thermodynamic framework that relies on the quasiharmonic approximation (QHA). We study phonon band structures, their evolution under pressure, and finite-temperature thermodynamic state functions. Besides the layered orthorhombic structure, this analysis includes the high-temperature cubic (rocksalt-type) polymorph of GeSe, which is shown to exhibit imaginary vibrational modes but emerging dynamic stability under increasing external pressure. The effect of these imaginary vibrational modes on the QHA and hence on computed thermochemical properties is critically evaluated. First-principles thermodynamics correctly predict a high-temperature transition from the orthorhombic to the cubic structure, albeit the transition temperature is severely underestimated. This simple compound allows us to address important methodological questions regarding the QHA treatment of crystalline solids.
Singh, Kuldip; Singh, Gurpreet; Sharma, Rohit
2010-07-15
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.
Structural and Thermodynamic Properties of Amyloid-β Peptides: Impact of Fragment Size
NASA Astrophysics Data System (ADS)
Kitahara, T.; Wise-Scira, O.; Coskuner, O.
2010-10-01
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-β 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 Aβ1-16, Aβ1-28, and Aβ1-42 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.
Computer programs for thermodynamic and transport properties of hydrogen (tabcode-II)
NASA Technical Reports Server (NTRS)
Roder, H. M.; Mccarty, R. D.; Hall, W. J.
1972-01-01
The thermodynamic and transport properties of para and equilibrium hydrogen have been programmed into a series of computer routines. Input variables are the pair's pressure-temperature and pressure-enthalpy. The programs cover the range from 1 to 5000 psia with temperatures from the triple point to 6000 R or enthalpies from minus 130 BTU/lb to 25,000 BTU/lb. Output variables are enthalpy or temperature, density, entropy, thermal conductivity, viscosity, at constant volume, the heat capacity ratio, and a heat transfer parameter. Property values on the liquid and vapor boundaries are conveniently obtained through two small routines. The programs achieve high speed by using linear interpolation in a grid of precomputed points which define the surface of the property returned.
Improved relationships for the thermodynamic properties of carbon phases at detonation conditions
NASA Astrophysics Data System (ADS)
Stiel, L. I.; Baker, E. L.; Murphy, D. J.
2014-05-01
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.
First-principles study of the structural and thermodynamic properties of AsNMg 3 antiperovskite
NASA Astrophysics Data System (ADS)
Belaroussi, Tayeb; Benmessabih, Tounsi; Hamdache, Fatima; Amrani, Bouhalouane
2008-08-01
The structural and elastic properties of the antiperovskite semiconductor AsNMg 3 are investigated using the full-potential linearized augmented plane wave plus local orbital (FP-LAPW+lo) method within the generalized gradient in the frame of the density functional theory. The ground state properties such as lattice constant, bulk modulus, pressure derivative of the bulk modulus and elastic constants are in good agreement with numerous experimental and theoretical data. Through the quasi-harmonic Debye model, in which the phononic effects are considered, we have obtained successfully the thermodynamic properties such as the thermal expansion coefficient, Debye temperature and specific heats in the whole pressure range from 0 to 30 GPa and temperature range from 0 to 1200 K.
Temperature Dependence of Thermodynamic Properties of Thallium Chloride and Thallium Bromide
NASA Astrophysics Data System (ADS)
Kavanoz, H. B.
2015-02-01
Thermodynamic properties as lattice parameters, thermal expansion, heat capacities Cp and Cv, bulk modulus, and Gruneisen parameter of ionic halides TlCl and TlBr in solid and liquid phases were studied using classical molecular dynamics simulation (MD) with interionic Vashistha-Rahman (VR) model potential. In addition to the static and transport properties which have been previously reported by the author [13], this study further confirms that temperature dependence of the calculated thermophysical properties of TlCl and TlBr are in agreement with the available experimental data at both solid and liquid phases in terms of providing an alternative rigid ion potential. The results give a fairly good description of TlCl and TlBr in the temperature range 10-1000 K.
NASA Technical Reports Server (NTRS)
Thompson, Richard A.; Lee, Kam-Pui; Gupta, Roop N.
1991-01-01
The computer codes developed here provide self-consistent thermodynamic and transport properties for equilibrium air for temperatures from 500 to 30000 K over a temperature range of 10 (exp -4) to 10 (exp -2) atm. These properties are computed through the use of temperature dependent curve fits for discrete values of pressure. Interpolation is employed for intermediate values of pressure. The curve fits are based on mixture values calculated from an 11-species air model. Individual species properties used in the mixture relations are obtained from a recent study by the present authors. A review and discussion of the sources and accuracy of the curve fitted data used herein are given in NASA RP 1260.
Free energy of formation of Mo2C and the thermodynamic properties of carbon in solid molybdenum
NASA Technical Reports Server (NTRS)
Seigle, L. L.; Chang, C. L.; Sharma, T. P.
1979-01-01
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.
Thermodynamic properties of reaction mixture of air and copper up to 4000 K for 0.05 to 2 MPa
NASA Astrophysics Data System (ADS)
Coufal, O.
2014-06-01
This paper deals with the thermodynamic properties of a system of products of the reaction of air with copper. Unlike the results that have been published up to now, this system is assumed to contain species in the condensed state. The system is supposed to be in thermodynamic equilibrium for temperatures ranging from ambient temperature to 4000 K. The thermodynamic properties are obtained directly from the equilibrium composition and the thermochemical properties of the species. The occurrence of condensed species and their phase transformations considerably affect the composition and thermodynamic properties of the system. The calculated data are in agreement with the published data, which are the results of measurement and observation, but the calculated data cover an incomparably wider region of pressures, temperatures and amounts of copper in the system.
NASA Technical Reports Server (NTRS)
Gordon, S.
1982-01-01
The equilibrium compositions corresponding to the thermodynamic and transport combustion properties for a wide range of conditions for the reaction of hydrocarbons with air are presented. The compositions presented correspond to Rankine temperature schedules.
NASA Astrophysics Data System (ADS)
Jacobs, M. H.; van den Berg, A. P.; de Jong, B. H.
2007-12-01
We are currently constructing a thermodynamic database providing phase diagrams, thermophysical and thermochemical properties for materials with a geophysical relevance, applicable in the pressure and temperature regime of the Earth's mantle. The computational technique is based on Kieffer's (1979) approach to model the vibrational density of states of a substance, a key property to derive the Helmholtz energy. The developed thermodynamic framework, which allows the calculation of Vp and Vs sound wave velocities, uses model-input properties related to Raman and infrared spectroscopic data. It puts tighter constraints on thermodynamic properties compared to methods based on polynomial parameterizations of thermal expansivity, heat capacity and isothermal bulk modulus. Jacobs & de Jong (2005, 2007) showed that this framework discriminates, based on internal consistency, between the quality of disparate sets of experimental thermochemical, thermophysical and phase diagram data. The present work focuses on the application of vibrational modeling to the magnesium-olivine-pyroxene system, a system relevant to Earth's mantle. We show how our approach is used to point to inconsistencies in experimental datasets. Pressure calibration problems affecting the derivation of phase diagrams are discussed. The results, presented here, were used in a numerical model of convection in the Earth's mantle to reveal, effects of phase transitions on the degree of layering, mineral distribution and sound wave velocities in the transition zone, around 660 km depth in the Earth. References Kieffer S.W. (1979), Rev. Geophys. Space Physics, 17, 35-59. Jacobs M.H.G. and B.H.W.S. de Jong (2005), Phys. Chem. Minerals, 32, 614-626. Jacobs M.H.G., and de Jong B.H.W.S. (2007), Geochim. Cosmochim. Acta, 71, 3630-3655.
Structural, mechanical and thermodynamic properties of N-dope BBi compound under pressure
NASA Astrophysics Data System (ADS)
Yalcin, Battal G.
2016-04-01
The structural, mechanical and thermodynamic properties of N-dope BBi compound have been reported in the current study. The structural and mechanical results of the studied binary compounds (BN and BBi) and their ternary alloys BBi1- x N x structures are presented by means of density functional theory. The exchange and correlation effects are taken into account by using the generalized gradient approximation functional of Wu and Cohen which is an improved form of the most popular Perdew-Burke-Ernzerhof. The quasi-harmonic Debye model is used for the thermodynamic properties of studied materials. The basic physical properties of considered structures such as the equilibrium lattice parameter (a 0), bulk modulus (B 0), its pressure derivative (B'), elastic constants (C 11, C 12 and C 44), Kleinman's internal-strain parameter (ƺ), shear modulus anisotropy (A), the average shear modulus (G), Young's modulus (Y) and Poisson's ratio (v), B 0/ G ratio, microhardness parameter (H), Cauchy pressure (C″), and 1st and 2nd Lame constants (λ, μ), debye temperature (θ D), wave velocities (ν l, ν t and ν m), melting temperature (T m) and minimum thermal conductivity (κ min) have been calculated at zero pressure. In order to obtain more information, thermodynamic properties, such as internal energy (U), Helmoltz free energy (F), entropy (S), Debye temperature (θ D), thermal expansion (α), constant volume and pressure heat capacities (C V and C P ), are analyzed under the whole range from 0 to 20 GPa and temperature range from 0 to 1500 K. The obtained results of the studied binary compounds are in coincidence with experimental works.
Thermodynamic properties of LnBa2Cu3O6 + z (Ln = Gd, Dy, Ho, Yb, and Y) compounds
NASA Astrophysics Data System (ADS)
Kovba, M. L.; Voskov, A. L.
2015-05-01
Thermodynamic properties of superconductors of LnBa2Cu3O6 + z (Ln = Gd, Dy, Ho, Yb, and Y) are determined by means of EMF using fluoro-ion electrolyte in the temperature range of 900-1250 K. Comparative analyses of the experimental data and thermodynamic models is performed for YBa2Cu3O6 + z compound.
First-principles study of structural, elastic, and thermodynamic properties of ZrHf alloy
NASA Astrophysics Data System (ADS)
Wei, Zhao; Zhai, Dong; Shao, Xiao-Hong; Lu, Yong; Zhang, Ping
2015-04-01
Structural parameters, elastic constants, and thermodynamic properties of ordered and disordered solid solutions of ZrHf alloys are investigated through first-principles calculations based on density-functional theory (DFT). The special quasi-random structure (SQS) method is used to model the disordered phase as a single unit cell, and two lamella structures are generated to model the ordered alloys. Small strains are applied to the unit cells to measure the elastic behavior and mechanical stability of ZrHf alloys and to obtain the independent elastic constants by the stress-strain relationship. Phonon dispersions and phonon density of states are presented to verify the thermodynamic stability of the considered phases. Our results show that both the ordered and disordered phases of ZrHf alloys are structurally stable. Based on the obtained phonon frequencies, thermodynamic properties, including Gibbs free energy, entropy, and heat capacity, are predicted within the quasi-harmonic approximation. It is verified that there are no obvious differences in energy between ordered and disordered phases over a wide temperature range. Project supported by the National Natural Science Foundation of China (Grant No. 51102009) and the Long-Term Subsidy Mechanism from the Ministry of Finance and the Ministry of Education of China.
Determination and modeling of the thermodynamic properties of liquid calcium-antimony alloys
Poizeau, S; Kim, H; Newhouse, JM; Spatocco, BL; Sadoway, DR
2012-08-01
The thermodynamic properties of Ca-Sb alloys were determined by emf measurements in a cell configured as Ca(s)vertical bar CaF2 vertical bar Ca-Sb over the temperature range 550-830 degrees C. Activity coefficients of Ca and Sb, enthalpy, Gibbs free energy, and entropy of mixing of Ca-Sb alloys were calculated for xc(a) < 0.55. To explain the connection between short-range order of liquid Ca-Sb alloys and the strong deviation from ideality in the thermodynamic properties, two thermodynamic models were invoked and reconciled: the regular associated solution model, assuming the presence of a CaSb2 associate, and the molecular interaction volume model (MIVM). For the first time, the MIVM was used successfully to model the activity coefficients of a system with high-melting intermetallics, reducing the number of fitting parameters necessary from 5 (regular associated model) to 2 (MIVM). From the interaction parameters optimized by fitting at 800 degrees C, the with an average error of less than value. (C) 2012 Elsevier Ltd. All rights reserved,
Numerical Prediction of the Thermodynamic Properties of Ternary Al-Ni-Pd Alloys
NASA Astrophysics Data System (ADS)
Zagula-Yavorska, Maryana; Romanowska, Jolanta; Kotowski, Sławomir; Sieniawski, Jan
2016-01-01
Thermodynamic properties of ternary Al-Ni-Pd system, such as exGAlNPd, µAl(AlNiPd), µNi(AlNiPd) and µPd(AlNiPd) at 1,373 K, were predicted on the basis of thermodynamic properties of binary systems included in the investigated ternary system. The idea of predicting exGAlNiPd values was regarded as calculation of values of the exG function inside a certain area (a Gibbs triangle) unless all boundary conditions, that is values of exG on all legs of the triangle are known (exGAlNi, exGAlPd, exGNiPd). This approach is contrary to finding a function value outside a certain area, if the function value inside this area is known. exG and LAl,Ni,Pd ternary interaction parameters in the Muggianu extension of the Redlich-Kister formalism were calculated numerically using the Excel program and Solver. The accepted values of the third component xx differed from 0.01 to 0.1 mole fraction. Values of LAlNiPd parameters in the Redlich-Kister formula are different for different xx values, but values of thermodynamic functions: exGAlNiPd, µAl(AlNiPd), µNi(AlNiPd) and µPd(AlNiPd) do not differ significantly for different xx values. The choice of xx value does not influence the accuracy of calculations.
Thermodynamic and structural properties of the acid molten globule state of horse cytochrome C.
Nakamura, Shigeyoshi; Seki, Yasutaka; Katoh, Etsuko; Kidokoro, Shun-ichi
2011-04-19
To understand the stabilization, folding, and functional mechanisms of proteins, it is very important to understand the structural and thermodynamic properties of the molten globule state. In this study, the global structure of the acid molten globule state, which we call MG1, of horse cytochrome c at low pH and high salt concentrations was evaluated by solution X-ray scattering (SXS), dynamic light scattering, and circular dichroism measurements. MG1 was globular and slightly (3%) larger than the native state, N. Calorimetric methods, such as differential scanning calorimetry and isothermal acid-titration calorimetry, were used to evaluate the thermodynamic parameters in the transitions of N to MG1 and MG1 to denatured state D of horse cytochrome c. The heat capacity change, ΔC(p), in the N-to-MG1 transition was determined to be 2.56 kJ K(-1) mol(-1), indicating the increase in the level of hydration in the MG1 state. Moreover, the intermediate state on the thermal N-to-D transition of horse cytochrome c at pH 4 under low-salt conditions showed the same structural and thermodynamic properties of the MG1 state in both SXS and calorimetric measurements. The Gibbs free energy changes (ΔG) for the N-to-MG1 and N-to-D transitions at 15 °C were 10.9 and 42.2 kJ mol(-1), respectively. PMID:21388230
Thermodynamic properties of asymptotically Reissner–Nordström black holes
Hendi, S.H.
2014-07-15
Motivated by possible relation between Born–Infeld type nonlinear electrodynamics and an effective low-energy action of open string theory, asymptotically Reissner–Nordström black holes whose electric field is described by a nonlinear electrodynamics (NLED) are studied. We take into account a four dimensional topological static black hole ansatz and solve the field equations, exactly, in terms of the NLED as a matter field. The main goal of this paper is investigation of thermodynamic properties of the obtained black holes. Moreover, we calculate the heat capacity and find that the nonlinearity affects the minimum size of stable black holes. We also use Legendre-invariant metric proposed by Quevedo to obtain scalar curvature divergences. We find that the singularities of the Ricci scalar in Geometrothermodynamics (GTD) method take place at the Davies points. -- Highlights: •We examine the thermodynamical properties of black holes in Einstein gravity with nonlinear electrodynamics. •We investigate thermodynamic stability and discuss about the size of stable black holes. •We obtain analytical solutions of higher dimensional theory.
Optimization of the thermodynamic properties and phase diagrams of P2O5-containing systems
NASA Astrophysics Data System (ADS)
Hudon, Pierre; Jung, In-Ho
2014-05-01
P2O5 is an important oxide component in the late stage products of numerous igneous rocks such as granites and pegmatites. Typically, P2O5 combines with CaO and crystallizes in the form of apatite, while in volatile-free conditions, Ca-whitlockite is formed. In spite of their interest, the thermodynamic properties and phase diagrams of P2O5-containg systems are not well known yet. In the case of the pure P2O5 for example, no experimental thermodynamic data are available for the liquid and the O and O' solid phases. As a result, we re-evaluated all the thermodynamic and phase diagram data of the P2O5 unary system [1]. Optimization of the thermodynamic properties and phase diagrams of the binary P2O5 systems was then performed including the Li2O-, Na2O-, MgO-, CaO-, BaO-, MnO-, FeO-, Fe2O3-, ZnO-, Al2O3-, and SiO2-P2O5 [2] systems. All available thermodynamic and phase equilibrium data were simultaneously reproduced in order to obtain a set of model equations for the Gibbs energies of all phases as functions of temperature and composition. In particular, the Gibbs energy of the liquid solution was described using the Modified Quasichemical Model [3-5] implemented in the FactSage software [6]. Thermodynamic modeling of the Li2O-Na2O-K2O-MgO-CaO-FeO-Fe2O3-Al2O3-SiO2 system, which include many granite-forming minerals such as nepheline, leucite, pyroxene, melilite, feldspar and spinel is currently in progress. [1] Jung, I.-H., Hudon, P. (2012) Thermodynamic assessment of P2O5. J. Am. Ceram. Soc., 95 (11), 3665-3672. [2] Rahman, M., Hudon, P. and Jung, I.-H. (2013) A coupled experimental study and thermodynamic modeling of the SiO2-P2O5 system. Metall. Mater. Trans. B, 44 (4), 837-852. [3] Pelton, A.D. and Blander, M. (1984) Computer-assisted analysis of the thermodynamic properties and phase diagrams of slags. Proc. AIME Symp. Metall. Slags Fluxes, TMS-AIME, 281-294. [4] Pelton, A.D. and Blander, M. (1986) Thermodynamic analysis of ordered liquid solutions by a modified quasichemical approach application to silicate slags. Metall. Trans. B, 17, 805-815. [5] A.D. Pelton, S.A. Decterov, G. Eriksson, C. Robelin and Y. Dessureault (2000) The modified quasichemical model - I Binary solutions. Metall. Mater. Trans. B, 31, 651-660. [6] C.W. Bale, P. Chartrand, S.A. Decterov, G. Eriksson, K. Hack, R. Ben Mahfoud, J. Melançon, A.D. Pelton and S. Petersen. (2002) FactSage Thermochemical Software and Databases. Calphad, 26, 189-228.
Santos, Ana Filipa L O M; Oliveira, Juliana A S A; Ribeiro da Silva, Maria D M C; Monte, Manuel J S
2016-03-01
This work reports the experimental determination of relevant thermodynamic properties and the characterization of luminescence properties of the following polycyclic aromatic hydrocarbons (PAHs): 2,6-diethylnaphthalene, 2,6-diisopropylnaphthalene and 2,6-di-tert-butylnaphthalene. The standard (p(o) = 0.1 MPa) molar enthalpies of combustion, ΔcHm(o), of the three compounds were determined using static bomb combustion calorimetry. The vapor pressures of the crystalline phase of 2,6-diisopropylnaphthalene and 2,6-di-tert-butylnaphthalene were measured at different temperatures using the Knudsen effusion method and the vapor pressures of both liquid and crystalline phases of 2,6-diethylnaphthalene were measured by means of a static method. The temperatures and the molar enthalpies of fusion of the three compounds were determined using differential scanning calorimetry. The gas-phase molar heat capacities and absolute entropies of the three 2,6-dialkylnaphthalenes studied were determined computationally. The thermodynamic stability of the compounds in both the crystalline and gaseous phases was evaluated by the determination of the Gibbs energies of formation and compared with the ones reported in the literature for 2,6-dimethylnaphthalene. From fluorescence spectroscopy measurements, the optical properties of the compounds studied and of naphthalene were evaluated in solution and in the solid state. PMID:26716880
NASA Astrophysics Data System (ADS)
Zhou, Xue; Cui, Xinglei; Chen, Mo; Zhai, Guofu
2016-05-01
Species composites of Ag-N2, Ag-H2 and Ag-He plasmas in the temperature range of 3,000-20,000 K and at 1 atmospheric pressure were calculated by using the minimization of Gibbs free energy. Thermodynamic properties and transport coefficients of nitrogen, hydrogen and helium plasmas mixed with a variety of silver vapor were then calculated based on the equilibrium composites and collision integral data. The calculation procedure was verified by comparing the results obtained in this paper with the published transport coefficients on the case of pure nitrogen plasma. The influences of the silver vapor concentration on composites, thermodynamic properties and transport coefficients were finally analyzed and summarized for all the three types of plasmas. Those physical properties were important for theoretical study and numerical calculation on arc plasma generated by silver-based electrodes in those gases in sealed electromagnetic relays and contacts. supported by National Natural Science Foundation of China (Nos. 51277038 and 51307030)
NASA Astrophysics Data System (ADS)
Khlystov, A.; Lin, M.; Saleh, R.
2008-12-01
Ambient aerosol, a significant portion of which is composed of a complex mixture of semi-volatile organic compounds, has substantial impact on human welfare via adverse health effects and global climate change. Prediction of ambient semi-volatile organic aerosol remains highly problematic and air quality models often do not agree with observations. One of the pieces of knowledge needed for better predictions of ambient semi- volatile organic aerosol is understanding of the partitioning of semi-volatile compounds between the gas and the aerosol phases. In this study the equilibrium thermodynamic properties of a number of multi-component aerosols were investigated under controlled laboratory conditions, as well as in the field. In the laboratory experiments, model mixtures of organic compounds as well as modified ambient aerosols were tested. The ambient aerosols were modified in a controlled way by adding known amounts of different organic substances of known thermodynamic properties. The equilibrium gas / aerosol partitioning in a temperature range relevant to ambient conditions was investigated using the Integrated Volume Method (IVM). The field measurements of ambient aerosol equilibrium properties were carried out during June 2007 - January 2008 at the FACTS research facility in Duke Forest (Chapel Hill, NC). The results can be used to derive equilibrium vapor pressures and activity coefficients of test compounds and to verify and improve the parameterizations used in group contribution models, such as UNFAC.
Intermolecular potentials and the accurate prediction of the thermodynamic properties of water
NASA Astrophysics Data System (ADS)
Shvab, I.; Sadus, Richard J.
2013-11-01
The ability of intermolecular potentials to correctly predict the thermodynamic properties of liquid water at a density of 0.998 g/cm3 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.
Study of thermodynamic properties of liquid binary alloys by a pseudopotential method
NASA Astrophysics Data System (ADS)
Vora, Aditya M.
2010-11-01
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.
NASA Astrophysics Data System (ADS)
Farsaci, F.; Ficarra, S.; Russo, A.; Galtieri, A.; Tellone, E.
2015-07-01
In this paper, we will show the possibility of studying physical properties and irreversible phenomena that occur in blood by applying the dielectric Kluitenberg's nonequilibrium thermodynamic theory. Namely, we shall use some recent extensions of this theory that allow to infer its main characteristic parameters from experimental measures. Applying these results to the study of normal and diabetic blood we show, by comparing them, that it is possible to determine the difference, in some details, of the amount of particular phenomena occurring inside them and give a biological meaning to these phenomena. Moreover, observing a correspondence between a particular value of the frequency for which state coefficients are equal and glucose levels we introduce an alternative diagnostic method to measure the values of the glucose in the blood by determining only this frequency value. The thermodynamic description will be completed by determining the trend of the entropy production.
First-Principles Study for Thermodynamic Properties of Solid {KNO}2 System
NASA Astrophysics Data System (ADS)
Peng, Qiang; Ding, Jing; Wei, Xiaolan; Jiang, Gan; Yang, Xiaoxi
2015-11-01
To enable us better understand the performance of molten salt energy storage in a solar thermal power system, thermodynamic properties of the solid {KNO}2 system at ambient pressure and temperatures between 0 K and 711 K are determined by first-principles simulation based on density functional perturbation theory calculations with plane waves and pseudopotentials. Thermodynamic parameters of the Debye temperature, specific heat capacity at constant volume, phonon transfer speed, phonon mean free path, and phonon thermal conductivity as a function of temperature are estimated. The results show that the calculated phonon thermal conductivity is in good agreement with experimental values, but the calculated specific heat capacity at constant volume is lower than measured values. The isometric specific heat capacity of {KNO}2 is 75.03 {J}{\\cdot }{mol}^{-1}{\\cdot }{K}^{-1}, and the phonon thermal conductivity is 2.37 {W}{\\cdot }{m}^{-1}{\\cdot }{K}^{-1} at ambient temperature.
Thermodynamic properties of a geothermal working fluid; 90% isobutane-10% isopentane: Final report
Gallagher, J.S.; Linsky, D.; Morrison, G.; Levelt Sengers, J.M.H.
1987-04-01
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.
Steele, W.V.; Chirico, R.D.; Knipmeyer, S.E.; Nguyen, A.
1990-12-01
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.
Naden, Levi N; Shirts, Michael R
2016-04-12
We show how thermodynamic properties of molecular models can be computed over a large, multidimensional parameter space by combining multistate reweighting analysis with a linear basis function approach. This approach reduces the computational cost to estimate thermodynamic properties from molecular simulations for over 130,000 tested parameter combinations from over 1000 CPU years to tens of CPU days. This speed increase is achieved primarily by computing the potential energy as a linear combination of basis functions, computed from either modified simulation code or as the difference of energy between two reference states, which can be done without any simulation code modification. The thermodynamic properties are then estimated with the Multistate Bennett Acceptance Ratio (MBAR) as a function of multiple model parameters without the need to define a priori how the states are connected by a pathway. Instead, we adaptively sample a set of points in parameter space to create mutual configuration space overlap. The existence of regions of poor configuration space overlap are detected by analyzing the eigenvalues of the sampled states' overlap matrix. The configuration space overlap to sampled states is monitored alongside the mean and maximum uncertainty to determine convergence, as neither the uncertainty or the configuration space overlap alone is a sufficient metric of convergence. This adaptive sampling scheme is demonstrated by estimating with high precision the solvation free energies of charged particles of Lennard-Jones plus Coulomb functional form with charges between -2 and +2 and generally physical values of σij and ϵij in TIP3P water. We also compute entropy, enthalpy, and radial distribution functions of arbitrary unsampled parameter combinations using only the data from these sampled states and use the estimates of free energies over the entire space to examine the deviation of atomistic simulations from the Born approximation to the solvation free energy. PMID:26849009
Emergence of equilibrium thermodynamic properties in quantum pure states. I. Theory
Fresch, Barbara; Moro, Giorgio J.
2010-07-21
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.
Emergence of equilibrium thermodynamic properties in quantum pure states. I. Theory
NASA Astrophysics Data System (ADS)
Fresch, Barbara; Moro, Giorgio J.
2010-07-01
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 Schrödinger 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.
Thermodynamical and structural properties of some liquid transition metals near melting point
NASA Astrophysics Data System (ADS)
Uçar, Sevilay; Kartal, Sehban; Armaǧan, Turgay
2016-03-01
Structure factor S(q) and thermodynamic properties like entropy (S), isothermal compressibility (χT), specific heat (CV) have been calculated for liquid 3d (Ti, V, Cr and Mn), 4d (Pd, Zr) and 5d (Pt) transition metals. In this work, we have used newly constructed Bretonnet-Silbert potential to describe electron-ion and ion-ion interaction using different reference systems. It is observed that our results are found to be in good agreement with experimental data as well as with other theoretical results.
Smith, W.H.; Costa, D.A.
1998-12-31
This is the final report of a six-month, Laboratory Directed Research and Development (LDRD) project at Los Alamos National Laboratory (LANL). The goal of this work was to establish a capability for the measurement of fundamental thermodynamic properties of actinide elements in room temperature molten salts. This capability will be used to study in detail the actinide chloro- and oxo-coordination chemistries that dominate in the chloride-based molten salt media. Uranium will be the first actinide element under investigation.
NASA Technical Reports Server (NTRS)
Rees, T. H.; Suttles, J. T.
1972-01-01
A computer study was conducted to compare the numerical behavior of two approaches to describing the thermodynamic properties of oxygen near the critical point. Data on the relative differences between values of specific heats at constant pressure (sub p) density, and isotherm and isochor derivatives of the equation of state are presented for selected supercritical pressures at temperatures in the range 100 to 300 K. The results of a more detailed study of the sub p representations afforded by the two methods are also presented.
Thermodynamic properties of a solid exhibiting the energy spectrum given by the logistic map
Curado; Rego-Monteiro
2000-06-01
We show that the infinite-dimensional representation of the recently introduced logistic algebra can be interpreted as a nontrivial generalization of the Heisenberg or oscillator algebra. This allows us to construct a quantum Hamiltonian having the energy spectrum given by the logistic map. We analyze the Hamiltonian of a solid whose collective modes of vibration are described by this generalized oscillator and compute the thermodynamic properties of the model in the two-cycle and r=3.6785 chaotic region of the logistic map. PMID:11088298
Thermodynamic properties of semiconductor compounds studied based on Debye-Waller factors
NASA Astrophysics Data System (ADS)
Van Hung, Nguyen; Toan, Nguyen Cong; Ba Duc, Nguyen; Vuong, Dinh Quoc
2015-08-01
Thermodynamic properties of semiconductor compounds have been studied based on Debye-Waller factors (DWFs) described by the mean square displacement (MSD) which has close relation with the mean square relative displacement (MSRD). Their analytical expressions have been derived based on the statistical moment method (SMM) and the empirical many-body Stillinger-Weber potentials. Numerical results for the MSDs of GaAs, GaP, InP, InSb, which have zinc-blende structure, are found to be in reasonable agreement with experiment and other theories. This paper shows that an elements value for MSD is dependent on the binary semiconductor compound within which it resides.
Thermodynamic properties of noninteracting quantum gases with spin-orbit coupling
He Li; Yu Zengqiang
2011-08-15
In this brief report we study thermodynamic properties of noninteracting quantum gases with isotropic spin-orbit coupling. At high temperature, coefficients of virial expansion depend on both temperature T and spin-orbit coupling strength {kappa}. For strong coupling, virial expansion is applicable to the temperature region below the conventional degenerate temperature T{sub F}. At low temperature, specific heat is proportional to {radical}(T) in Bose gases and T in Fermi gases. Temperature dependence of the chemical potential of fermions shows a different behavior when the Fermi surface is above and below the Dirac point.
Calculating the thermodynamic properties of aqueous solutions of alkali metal carboxylates
NASA Astrophysics Data System (ADS)
Rudakov, A. M.; Sergievskii, V. V.; Zhukova, T. V.
2014-06-01
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.
Messerly, J.F.; Todd, S.S.; Finke, H.L.; Gammon, B.E.
1987-01-01
Condensed-phase heat capacities and enthalpies were determined at temperatures from near 10 to 400 K for N-methylpyrrole, 2,5-dimethylpyrrole, piperidine, 2-methylpiperidine, 4-methylpyridine, and N-methylcarbazole and were used to provide the Gibbs energy, enthalpy, entropy and heat capacity along the vapor saturation line at temperatures from 0 to 400 K. The corresponding ideal gas thermodynamic properties were derived with available vapor pressure and enthalpy of vaporization data. The Gibbs energy, enthalpy, and entropy of formation were derived for the ideal gas at selected temperatures with available enthalpy of combustion data. 37 refs., 9 tabs.
Theoretical study of elastic and thermodynamic properties of chalcopyrite CdGeAs2
NASA Astrophysics Data System (ADS)
Yu, Y.; Zhao, B. J.; Zhu, S. F.; Gao, T.; Hou, H. J.; He, Z. Y.
2013-05-01
The structural, elastic and thermodynamic properties of chalcopyrite CdGeAs2 were investigated using the pseudopotential plane wave within the local density approximation. The calculated lattice parameters agree well with experimental and previous theoretical works. Based on the elastic constants and their related parameters, the crystal mechanical stability has been discussed. Moreover the pressure and temperature dependences of the lattice parameters, bulk modulus, Debye temperature, Grüneisen parameter, entropy, volume thermal expansion coefficient and specific heat capacities were predicted using the quasi-harmonic Debye model.
NASA Astrophysics Data System (ADS)
Moustafa, Sabry Gad Al-Hak Mohammad
Molecular simulation (MS) methods (e.g. Monte Carlo (MC) and molecular dynamics (MD)) provide a reliable tool (especially at extreme conditions) to measure solid properties. However, measuring them accurately and efficiently (smallest uncertainty for a given time) using MS can be a big challenge especially with ab initio-type models. In addition, comparing with experimental results through extrapolating properties from finite size to the thermodynamic limit can be a critical obstacle. We first estimate the free energy (FE) of crystalline system of simple discontinuous potential, hard-spheres (HS), at its melting condition. Several approaches are explored to determine the most efficient route. The comparison study shows a considerable improvement in efficiency over the standard MS methods that are known for solid phases. In addition, we were able to accurately extrapolate to the thermodynamic limit using relatively small system sizes. Although the method is applied to HS model, it is readily extended to more complex hard-body potentials, such as hard tetrahedra. The harmonic approximation of the potential energy surface is usually an accurate model (especially at low temperature and large density) to describe many realistic solid phases. In addition, since the analysis is done numerically the method is relatively cheap. Here, we apply lattice dynamics (LD) techniques to get the FE of clathrate hydrates structures. Rigid-bonds model is assumed to describe water molecules; this, however, requires additional orientation degree-of-freedom in order to specify each molecule. However, we were able to efficiently avoid using those degrees of freedom through a mathematical transformation that only uses the atomic coordinates of water molecules. In addition, the proton-disorder nature of hydrate water networks adds extra complexity to the problem, especially when extrapolating to the thermodynamic limit is needed. The finite-size effects of the proton disorder contribution is shown to vary slowly with system-size. This allow us to get the FE in the thermodynamic limit by extrapolating the one isomer results to infinity and correct for that by the effect from considering proton-disorder measured at a small system. These techniques are applied to empty hydrates (of types: SI, SII, and SH) to estimate their thermodynamic stability. For conditions where the harmonic model fails, performing MS is needed to estimate rigorously the full (harmonic plus anharmonic) quantity. Although several MS methods are available for that purpose, they do not benefit from the harmonic nature of crystals---which represents the main contribution and is cheap to compute. In other words, those "conventional" methods always "start from scratch" even at states where anharmonic part is negligible. In this work, we develop very efficient MS methods that leverage information, on-the-fly, from the harmonic behavior of configurations such that the anharmonic contributions are directly measured. The approach is named harmonically-mapped averaging (HMA) for the rest of this thesis. Since the major contribution of thermodynamic properties comes from the harmonic nature of crystal, the fluctuations in the anharmonic quantities is to be small; hence, uncertainty associated with the HMA method is small. The HMA method is given in a general formulation such that it can handle properties related to both first- and second-derivatives of free energy. The HMA approach is first applied to Lennard-Jones (LJ) model. First- and second-derivatives of FE with respect to temperature and volume yield the following properties: energy, pressure, isochoric heat capacity, bulk modulus, and thermal pressure coefficient. A considerable improvement in the efficiency of measuring those properties is observed even at melting conditions where anharmonicity is non-negligible. First-derivative properties are computed with 100 to 10,000 times less computational effort, while speedup for the second-derivative properties exceeds a millionfold for the highest density examined. In addition, the finite-size and long-range cutoff effects of the anharmonic contribution is much smaller than those due to harmonic part. Therefore, we were able to get the thermodynamic limit of thermodynamic properties by extrapolating the harmonic contribution to infinity and fix that with the anharmonic contribution from MS of small systems. Moreover, the anharmonic trajectory shows better features than the conventional one; it equilibrates almost instantaneously and data is less correlated (i.e. good statistics can be obtained with shorter trajectory). As a byproduct of the HMA, the free energy along an isochore is computed using thermodynamic integration (TI) technique of energy. Again, the HMA shows substantial improvement (50--1000 speedup) over the well-known Frenkel-Ladd integration (with Einstein crystal reference) method. Finally, to test the method against a more sophisticated model, we applied it to an embedded-atom-model (EAM) model of iron system. The results show a qualitatively similar behavior as that of LJ model. Finally, the method is applied to tackle one of the long-standing problems of Earth science; namely, the crystal structure of the Earth's inner core (IC). (Abstract shortened by UMI.).
Thermodynamic and Transport Properties of H2O + NaCl from Polarizable Force Fields.
Jiang, Hao; Mester, Zoltan; Moultos, Othonas A; Economou, Ioannis G; Panagiotopoulos, Athanassios Z
2015-08-11
Molecular dynamics and Monte Carlo simulations were performed to obtain thermodynamic and transport properties of the binary H2O + NaCl system using the polarizable force fields of Kiss and Baranyai ( J. Chem. Phys. 2013 , 138 , 204507 and 2014 , 141 , 114501 ). In particular, liquid densities, electrolyte and crystal chemical potentials of NaCl, salt solubilities, mean ionic activity coefficients, vapor pressures, vapor-liquid interfacial tensions, and viscosities were obtained as functions of temperature, pressure, and salt concentration. We compared the performance of the polarizable force fields against fixed-point-charge (nonpolarizable) models. Most of the properties of interest are better represented by the polarizable models, which also remain physically realistic at elevated temperatures. PMID:26574461
Atomic structure, mechanical quality, and thermodynamic property of TiHx phases
NASA Astrophysics Data System (ADS)
Liang, C. P.; Gong, H. R.
2013-07-01
Titanium hydrides TiHx (x = 1, 1.25, 1.5, 1.75, and 2) with the cubic fluorite-type (face-centered cubic, δ phase) and face-centered-tetragonal (ɛ phase, c/a < 1; γ phase, c/a > 1) structures were systematically investigated and compared through first-principles calculation. The H location of TiHx was carefully determined by comparing the calculated properties with experimental results. Moreover, the mechanical properties of ɛ and γ phases were calculated and found to play an important role in the brittle/ductile behavior of TiHx phases. In addition, the thermodynamic quantities were also derived for providing a deeper understanding of TiHx phases. The calculated results were widely compared with the available experimental results in the literature, and could clarify the three controversies regarding atomic configuration, stability, and hydrogen embrittlement of TiHx phases in the literature.
Improved Relationships for the Thermodynamic Properties of Carbon Phases at Detonation Conditions
NASA Astrophysics Data System (ADS)
Stiel, Leonard; Baker, Ernest; Murphy, Daniel
2013-06-01
In order to improve the procedures utilized in the Jaguar thermochemical program for carbon, volumetric and heat capacity relationships have been developed for graphite, diamond, and liquid carbon forms. Available experimental thermodynamic property and Hugoniot data have been analyzed to establish optimum equations of state for the carbon phases. The appropriate carbon form or multiple forms at equilibrium results from the minimization of the Gibbs free energy of the system. The resulting relationships are utilized to examine the phase behavior of carbon at elevated temperatures and pressures. The behavior of metastable carbon states is optimized by analyses of Hugoniot data for hydrocarbons, and C-J and cylinder velocities for a database of CHNO explosives. The accuracy of the resulting relationships is demonstrated by comparisons for several properties, including the Hugoniot behavior of oxygen-deficient explosives at overdriven conditions.
Physical and thermodynamic properties of Al(n)C(m) clusters: quantum-chemical study.
Loukhovitski, Boris I; Sharipov, Alexander S; Starik, Alexander M
2015-02-26
Geometrical structures and physical properties, such as rotational constants and characteristic vibrational temperatures, collision diameter, enthalpy of formation, dipole moment, static isotropic polarizability, and magnetic moment of different forms of Al(n)C(m) clusters with n = 0-5, m = 0-5, have been studied with the usage of density functional theory. Different forms of clusters with the electronic energy up to 5 eV have been identified by using the original multistep heuristic algorithm based on semiempirical calculations and density functional theory. Temperature dependencies of thermodynamic properties such as enthalpy, entropy, and specific heat capacity were calculated for both the individual isomers and the Boltzmann ensembles of each class of clusters. PMID:25629238
NASA Astrophysics Data System (ADS)
Mishra, Rashmi; Srivastava, Anubha; Sharma, Anamika; Tandon, Poonam; Baraldi, Cecilia; Gamberini, Maria Christina
2013-01-01
The global problem of advancing bacterial resistance to newer drugs has led to renewed interest in the use of Chloramphenicol Palmitate (C27H42Cl2N2O6) [Palmitic acid alpha ester with D-threo-(-),2-dichloro-N-(beta-hydroxy-alpha-(hydroxymethyl)-p-nitrophenethyl)acetamide also known as Detereopal]. The characterization of the three polymorphic forms of Chloramphenicol Palmitate (CPP) was done spectroscopically by employing FT-IR and FT-Raman techniques. The equilibrium geometry, various bonding features, and harmonic wavenumbers have been investigated for most stable form A with the help of DFT calculations and a good correlation was found between experimental data and theoretical values. Electronic properties have been analyzed employing TD-DFT for both gaseous and solvent phase. The theoretical calculation of thermodynamical properties along with NBO analysis has also been performed to have a deep insight into the molecule for further applications.
Structural, elastic and thermodynamic properties of Mo3Si and Mo3Ge
NASA Astrophysics Data System (ADS)
Zhong, Sheng-Yi; Chen, Zhe; Wang, Mingliang; Chen, Dong
2016-01-01
The structural, elastic and thermodynamic properties of the cubic Mo3Si and Mo3Ge intermetallics were investigated using density functional theory within the local density approximation (LDA) and generalized gradient approximation (GGA) methods. The results showed that the structural and elastic properties (i.e., elastic constants, bulk modulus, shear modulus and Young's modulus) derived by the GGA method were in good agreement with the available experimental and theoretical values. Using the quasi-harmonic Debye model, the variations of the Debye temperature, heat capacity and coefficient of thermal expansion under pressure ranging from 0 to 25 GPa and at temperature ranging from 0 to 1800 K were obtained and analyzed for both compounds.
First-principles calculations on thermodynamic properties of BaTiO3 rhombohedral phase.
Bandura, Andrei V; Evarestov, Robert A
2012-07-01
The calculations based on the linear combination of atomic orbitals have been performed for the low-temperature phase of BaTiO(3) crystal. Structural and electronic properties, as well as phonon frequencies were obtained using hybrid PBE0 exchange-correlation functional. The calculated frequencies and total energies at different volumes have been used to determine the equation of state and thermal contribution to the Helmholtz free energy within the quasiharmonic approximation. For the first time, the bulk modulus, volume thermal expansion coefficient, heat capacity, and Grüneisen parameters in BaTiO(3) rhombohedral phase have been estimated at zero pressure and temperatures form 0 to 200 K, based on the results of first-principles calculations. Empirical equation has been proposed to reproduce the temperature dependence of the calculated quantities. The agreement between the theoretical and experimental thermodynamic properties was found to be satisfactory. PMID:22514059
Murphy, R.W. )
1992-02-10
Magneto-thermodynamic property characterizations were selected, adapted, and compared to material property data for gadolinium gallium garnet in the temperature range 4--40 K and magnetic field range 0--6 T. The most appropriate formulations were incorporated into a model in which methods similar to those previously developed for other materials and temperature ranges were used to make limitation and relative performance assessments of Carnot, ideal regenerative, and pseudo-constant field regenerative cycles. Analysis showed that although Carnot cycle limitations on available temperature lift for gadolinium gallium garnet are not as severe as those for materials previously examined, substantial improvements in cooling capacity/temperature lift combinations can be achieved using regenerative cycles within specified fields limits if significant loss mechanisms are mitigated.
Murphy, R.W.
1992-09-01
Magneto-thermodynamic property characterizations were selected, adapted, and compared to material property data for gadolinium gallium garnet in the temperature range 4--40 K and magnetic field range 0--6 T. The most appropriate formulations were incorporated into a model in which methods similar to those previously developed for other materials and temperature ranges were used to make limitation and relative performance assessments of Carnot, ideal regenerative, and pseudo-constant field regenerative cycles. Analysis showed that although Carnot cycle limitations on available temperature lift for gadolinium gallium garnet are not as severe as those for materials previously examined, substantial improvements in cooling capacity/temperature lift combinations can be achieved using regenerative cycles within specified field limits if significant loss mechanisms are mitigated.
NASA Astrophysics Data System (ADS)
Pokrovski, Gleb; Gout, Robert; Schott, Jacques; Zotov, Alexandre; Harrichoury, Jean-Claude
1996-03-01
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 As 2O 3-H 2O solutions (0.02 ≤ As ≤ 6 m; 0 ≤ pH ≤ 9) at temperatures from 20 to 275 °C. Results indicate that H 3AsO 30(aq) is the dominant As-bearing species at concentrations up to ~1 m over a wide range of pH (0-8) and temperature (20-300 °C). At higher As concentrations (≥1-2 m), a polymerization-dehydration of H 3AsO 30(aq) occurs via the formation of As-O-As bonds, leading to the formation of poly-As aqueous complexes. These experimental results were combined with corresponding properties for arsenolite, claudetite, and orpiment obtained in this study to generate H 3AsO 30(aq) thermodynamic properties within the framework of the revised HKF equation of state ( Helgeson et al., 1981; Tanger and Helgeson, 1988). Calculations carried out using these properties indicate that orpiment, realgar, and native As can control As concentration in epithermal fluids at T ≤ 150-200 °C. At higher temperatures (≥250 °C), it is shown that arsenopyrite in association with pyrite and pyrrhotite or cassiterite can control As deposition in hydrothermal environments.
NASA Technical Reports Server (NTRS)
Talcott, N. A., Jr.
1977-01-01
Equations and computer code are given for the thermodynamic properties of gaseous fluorocarbons in chemical equilibrium. In addition, isentropic equilibrium expansions of two binary mixtures of fluorocarbons and argon are included. The computer code calculates the equilibrium thermodynamic properties and, in some cases, the transport properties for the following fluorocarbons: CCl2F, CCl2F2, CBrF3, CF4, CHCl2F, CHF3, CCL2F-CCl2F, CCLF2-CClF2, CF3-CF3, and C4F8. Equilibrium thermodynamic properties are tabulated for six of the fluorocarbons(CCl3F, CCL2F2, CBrF3, CF4, CF3-CF3, and C4F8) and pressure-enthalpy diagrams are presented for CBrF3.
Calculations and curve fits of thermodynamic and transport properties for equilibrium air to 30000 K
NASA Technical Reports Server (NTRS)
Gupta, Roop N.; Lee, Kam-Pui; Thompson, Richard A.; Yos, Jerrold M.
1991-01-01
A self-consistent set of equilibrium air values were computed for enthalpy, total specific heat at constant pressure, compressibility factor, viscosity, total thermal conductivity, and total Prandtl number from 500 to 30,000 K over a range of 10(exp -4) atm to 10(exp 2) atm. The mixture values are calculated from the transport and thermodynamic properties of the individual species provided in a recent study by the authors. The concentrations of the individual species, required in the mixture relations, are obtained from a free energy minimization calculation procedure. Present calculations are based on an 11-species air model. For pressures less than 10(exp -2) atm and temperatures of about 15,000 K and greater, the concentrations of N(++) and O(++) become important, and consequently, they are included in the calculations determining the various properties. The computed properties are curve fitted as a function of temperature at a constant value of pressure. These curve fits reproduce the computed values within 5 percent for the entire temperature range considered here at specific pressures and provide an efficient means for computing the flowfield properties of equilibrium air, provided the elemental composition remains constant at 0.24 for oxygen and 0.76 for nitrogen by mass.
Sologubov, Semen S; Markin, Alexey V; Smirnova, Natalia N; Novozhilova, Natalia A; Tatarinova, Elena A; Muzafarov, Aziz M
2015-11-12
The temperature dependences of heat capacities of carbosilane dendrimers of the sixth generation with ethyleneoxide terminal groups, denoted as G6[(OCH2CH2)1OCH3]256 and G6[(OCH2CH2)3OCH3]256, were measured in the temperature range from T = (6 to 520) K by precision adiabatic calorimetry and differential scanning calorimetry (DSC). In the above temperature range the physical transformations, such as glass transition and high-temperature relaxation transition, were detected. The standard thermodynamic characteristics of the revealed transformations were determined and analyzed. The standard thermodynamic functions, namely, heat capacity Cp°(T), enthalpy H°(T) - H°(0), entropy S°(T) - S°(0), and Gibbs energy G°(T) - H°(0) for the range from T → 0 to 520 K, and the standard entropies of formation ΔfS° of the investigated dendrimers in the devitrified state at T = 298.15 K, were calculated per corresponding moles of the notional structural units. The standard thermodynamic properties of dendrimers under study were discussed and compared with literature data for carbosilane dendrimers with different functional terminal groups. PMID:26494191
NASA Astrophysics Data System (ADS)
Smirnova, N. N.; Markin, A. V.; Letyanina, I. A.; Sologubov, S. S.; Novozhilova, N. A.; Tatarinova, E. A.; Muzafarov, A. M.
2014-05-01
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.
Magneto-elastic effects and thermodynamic properties of ferromagnetic hcp Co
NASA Astrophysics Data System (ADS)
Kuang, Fang-Guang; Kuang, Xiao-Yu; Kang, Shu-Ying; Mao, Ai-Jie
2014-05-01
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 Grneisen ratio, Anderon-Grneisen parameter and the volume dependence of Grneisen ratio display manifestly temperature and pressure dependences.
NASA Astrophysics Data System (ADS)
Kawai, Soshi
2014-11-01
In this talk, we first propose a numerical strategy that is robust and high-order accurate for enabling to simulate transcritical flows at supercritical pressures under abrupt variations in thermodynamic properties due to the real fluid effects. The method is based on introducing artificial density diffusion in a physically-consistent manner in order to capture the steep variation of thermodynamic properties in transcritical conditions robustly, while solving a pressure evolution equation to achieve pressure equilibrium at the transcritical interfaces. We then discuss the direct numerical simulation (DNS) of transcritical heated turbulent boundary layers on a zero-pressure-gradient flat plate at supercritical pressures. To the best of my knowledge, the present DNS is the first DNS of zero-pressure-gradient flat-plate transcritical turbulent boundary layer. The turbulent kinetic budget indicates that the compressibility effects (especially, pressure-dilatation correlation) are not negligible at the transcritical conditions even if the flow is subsonic. The unique and interesting interactions between the real fluid effects and wall turbulence, and their turbulence statistics, which have never been seen in the ideal-fluid turbulent boundary layers, are also discussed. This work was supported in part by Japan Society for the Promotion of Science (JSPS) Grant-in-Aid for Young Scientists (A) KAKENHI 26709066 and the JAXA International Top Young Fellowship Program.
Evaluation of the thermodynamic properties of hydrated metal oxide nanoparticles by INS techniques
Spencer, Elinor; Ross, Dr. Nancy; Parker, Stewart F.; Kolesnikov, Alexander I
2013-01-01
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].
Vermeulen, Paul; Ledovskikh, Alexander; Danilov, Dmitry; Notten, Peter H L
2006-10-19
Recently, a lattice gas model was presented and successfully applied to simulate the absorption/desorption isotherms of various hydride-forming materials. The simulation results are expressed by parameters corresponding to several energy contributions, e.g., interaction energies. However, the use of a model system is indispensable in order to show the strength of the simulations. The palladium-hydrogen system is one of the most thoroughly described metal hydrides found in the literature and is therefore ideal for this purpose. The effects of decreasing the thickness of Pd thin films on the isotherms have been monitored experimentally and subsequently simulated. An excellent fit of the lattice gas model to the experimental data is found, and the corresponding parameters are used to describe several thermodynamic properties. It is analyzed that the contribution of H-H interaction energies to the total energy and the influence of the host lattice energy are significantly and systematically changing as a function of Pd thickness. Conclusively, it has been verified that the lattice gas model is a useful tool to analyze thermodynamic properties of hydrogen storage materials. PMID:17034217
Liu, Ze; Han, Jiuqiang; Lv, Hongqiang; Liu, Jun; Liu, Ruiling
2016-04-01
Circular RNAs (circRNAs) were found more than 30 years ago, but have been treated as molecular flukes in a long time. Combining deep sequencing studies with bioinformatics technique, thousands of endogenous circRNAs have been found in mammalian cells, and some researchers have proved that several circRNAs act as competing endogenous RNAs (ceRNAs) to regulate gene expression. However, the mechanism by which the precursor mRNA to be transformed into a circular RNA or a linear mRNA is largely unknown. In this paper, we attempted to bioinformatically identify shared genomic features that might further elucidate the mechanism of formation and proposed a SVM-based model to distinguish circRNAs from non-circularized, expressed exons. Firstly, conformational and thermodynamic dinucleotide properties in the flanking introns were extracted as potential features. Secondly, two feature selection methods were applied to gain the optimal feature subset. Our 10-fold cross-validation results showed that the model can be used to distinguish circRNAs from non-circularized, expressed exons with an Sn of 0.884, Sp of 0.900, ACC of 0.892, MCC of 0.784, respectively. The identification results suggest that conformational and thermodynamic properties in the flanking introns are closely related to the formation of circRNAs. Datasets and the tool involved in this paper are all available at https://sourceforge.net/projects/predicircrnatool/files/. PMID:26917277
NASA Astrophysics Data System (ADS)
Varshney, Dinesh; Shriya, S.; Varshney, M.; Singh, N.; Khenata, R.
2015-08-01
Pressure-dependent first-order phase transition, mechanical, elastic, and thermodynamical properties of cubic zinc blende to rock-salt structures in 3 C silicon carbide (SiC) are presented. An effective interatomic interaction potential for SiC is formulated. The potential for SiC incorporates long-range Coulomb, charge transfer interactions, covalency effect, Hafemeister and Flygare type short-range overlap repulsion extended up to the second-neighbour ions, van der Waals interactions and zero point energy effects. The developed potential including many body non-central forces validates the Cauchy discrepancy successfully to explain the high-pressure structural transition, and associated volume collapse. The 3 C SiC ceramics lattice infers mechanical stiffening, thermal softening, and ductile (brittle) nature from the pressure (temperature) dependent elastic constants behaviour. To our knowledge, these are the first quantitative theoretical predictions of the pressure and temperature dependence of mechanical and thermodynamical properties explicitly the mechanical stiffening, thermally softening, and brittle/ductile nature of 3 C SiC and still awaits experimental confirmations.
First principal studya of structural, electronic and thermodynamic properties of KTaO3-perovskite.
NASA Astrophysics Data System (ADS)
Bouafia, H.; Akriche, A.; Ascri, R.; Ghalouci, L.; Sahli, B.; Hiadsi, S.; Abidri, B.; Amrani, B.
2013-03-01
The results of first-principles theoretical study of structural, elastic, electronic and thermodynamic properties of KTaO3 compound, have been performed using the full-potential linear augmented plane-wave method plus local orbitals (FP-APW+lo) as implemented in the Wien2k code. The exchange-correlation energy, is treated in generalized gradient approximation (GGA) using the Perdew-Burke-Ernzerhof (PBE96) and PBEsol, Perdew 2008 parameterization. Also we have used the Engel-Vosko GGA optimizes the corresponding potential for band structure calculations. The calculated equilibrium parameter is in good agreement with other works. The elastic constants were calculated by using the Mehl method. The electronic band structure of this compound has been calculated using the Angel-Vosko (EV) generalized gradient approximation (GGA) for the exchange correlation potential. We deduced that KTaO3-perovskite exhibit an indirect from R to Γ point. To complete the fundamental characterization of KTaO3 material we have analyzed the thermodynamic properties using the quasi-harmonic Debye model.
Study of structural, elastic, electronic and thermodynamic properties of NaAlO3-perovskite
NASA Astrophysics Data System (ADS)
Bouafia, H.; Sahli, B.; Hiadsi, S.; Abidri, B.; Rached, D.; Amrani, B.
2012-06-01
The structural, elastic, electronic, and thermodynamic properties of the cubic NaAlO3-perovskite are calculated using the full potential linearized augmented plane wave with local orbital (FP-LAPW)+lo. The exchange-correlation energy, is treated in generalized gradient approximation (GGA) using the Perdew-Burke-Ernzerhof (PBE) parameterization. The calculated equilibrium parameter is in good agreement with other works. The bulk modulus, elastic constants and their related parameters, such as Young modulus, shear modulus, and Poisson ratio were predicted. The electronic band structure of this compound has been calculated using the Angel-Vosko (EV) generalized gradient approximation (GGA) for the exchange correlation potential. We deduced that NaAlO3-perovskite exhibit a wide-gap which it is an indirect from R to Γ point. The analysis of the density of states (DOS) curves shows ionic and covalent character bond for Al-O and Na-O respectively. To complete the fundamental characterization of NaAlO3 material we have analyzed the thermodynamic properties using the quasi-harmonic Debye model.
Thermodynamic properties of calcium-magnesium alloys determined by emf measurements
Newhouse, JM; Poizeau, S; Kim, H; Spatocco, BL; Sadoway, DR
2013-02-28
The thermodynamic properties of calcium-magnesium alloys were determined by electromotive force (emf) measurements using a Ca(in Bi)vertical bar CaF2 vertical bar Ca(in Mg) cell over the temperature range 713-1048 K. The activity and partial molar Gibbs free energy of calcium in magnesium were calculated for nine Ca-Mg alloys, calcium mole fractions varying from x(ca) = 0.01 to 0.80. Thermodynamic properties of magnesium in calcium and the molar Gibbs free energy of mixing were estimated using the Gibbs-Duhem relationship. In the all-liquid region at 1010 K, the activity of calcium in magnesium was found to range between 8.8 x 10(-4) and 0.94 versus pure calcium. The molecular interaction volume model (MIVM) was used to model the activity coefficient of Ca and Mg in Ca-Mg liquid alloys. Based on this work, Ca-Mg alloys show promise as the negative electrode of a liquid metal battery in which calcium is the itinerant species: alloying with Mg results in both a decrease in operating temperature and suppression of Ca metal solubility in the molten salt electrolyte. (C) 2012 Elsevier Ltd. All rights reserved.
The thermodynamic properties to 700 K of naphthalene and 2,7-dimethylnaphthalene
Chirico, R.D.; Knipmeyer, S.E.; Nguyen, A.; Steele, W.V.
1993-08-01
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.
Thermodynamics of water-permeated unwelded pyroclasts, 2: non-equilibrium properties
NASA Astrophysics Data System (ADS)
Ascolese, E.; Aurisicchio, A.; Briggs-Smith, M.; Mita, D. G.; Perna, G.; Rossi, S.; Gaeta, F. S.
1993-10-01
Reported here are the results of an investigation of thermodynamic non-equilibrium properties of some Phlegraean unwelded pyroclasts. We experimentally determined: (a) hydraulic isothermal permeability of water-saturated samples; (b) thermal conductivity of the dry and liquid-permeated rock; (c) the effects produced by the superimposition of pressure and temperature gradients to water-saturated samples. Throughout the explored ranges of driving pressure and temperature, the hydraulic flow in porous rock samples has been found to be laminar. The thermal conductivity of water-permeated porous rocks is strongly enhanced by local convection occurring within the liquid-filled cavities. The superimposition of pressure and temperature gradients in saturated samples induces characteristic non-linear temperature distributions dependent on the intensity and orientation of the gradients as well as on the constitutive properties of the solid and liquid phases and on boundary and initial conditions. Interestingly, the temperature distribution with depth, found by drilling in the Phlegraean Fields area, nicely reproduces the distribution produced by a liquid flux ascending from a buried heat source. The phenomenological coefficients needed to apply the field equations to liquid-saturated soils in a temperature field are now in our hands. Measurement of other coefficients relative to interactions among gradients of pressure, temperature and electrochemical potential may be obtained in a similar way. Accordingly, it should be now possible to develop a rigorous thermodynamic approach to the causes of Phlegraean bradyseism.
Correlation of thermodynamic and genetic properties in the Tn10 encoded TET gene control region.
Hillen, W; Unger, B
1982-01-01
The thermal stability of the Tn10 encoded tetracycline resistance (TET) gene control region is investigated by melting studies using purified DNA restriction fragments containing various amounts of flanking sequences. In order to study the thermodynamic properties of this control region under conditions, where enough flanking DNA is present to mimic the situation in the chromosome, the five step melting process of a 1450-bp DNA fragment is analyzed. Because most of the sequence of this DNA is not known, the assignment of the melting transitions to segments of the DNA is done by an experimental method. This employs the preparation of subfragments from the 1450-bp DNA and comparison of their denaturation profiles with the one of the intact sequence. This approach results in the complete assignment of the five denaturation steps. Rather than from the ends, the unwinding starts from the TET gene control region in the middle of the 1450-bp sequence. A clear correlation between the thermodynamic and genetic properties of this DNA is observed. The regulatory sequence forms a small cooperative unit with the lowest stability in the entire fragment. The thermal denaturation of the TET repressor. TET operator complex reveals, that the TET repressor specifically recognizes the double stranded TET operator DNA and stabilizes this structure by 2.4 degrees C. This results is also discussed as an example of the possible action of denaturing or stabilizing proteins on this genetic control region. PMID:6281740
NASA Astrophysics Data System (ADS)
Deckman, Jason
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, Λ, 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 Λ 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.
Kang, H.S.; Ree, F.H.
1997-12-01
Recently, we developed the perturbative hypernetted-chain (PHNC) integral equation which can predict reliable thermodynamic and structural data for a system of particles interacting with either short range or long range (Coulomb) potential. The present work extends this earlier work to mixtures. This is done by employing a reference potential which is designed to satisfy a thermodynamic consistency on the isothermal compressibility as described in the next section. We test the present theory in Sec. III by applying it to plasma mixtures interacing with either an unscreened or a screened Coulomb potential. We made comparisons of results from the present theory with those from the best available theory, i.e., Rosenfeld`s density functional theory (DFT). The DFT was shown to give internal energy with three to five fignre accuracy compared to a wide range of Monte Carlo data. Meanwhile, small deviations of excess internal energy from the so-called ``liner mixing rule`` (LMR) are better predicted by a less sophiscated theory like the hypernetted- chain (HNC) equation. This rule relates thermodynamics of an unscreened mixture to those for individual components in a strongly coupled regime where the potential energy of a constituent particle is much larger than its kinetic energy. We also apply the present theory to a H{sub 2} + H mixture interacting with Morse potentials. For this sytem, comparison of thermodynamic properties and radial distribution functions from the present theory will be made with those from another successful theory of dense fluid, i.e., the HMSA equation of Zerah and Hansen.
Magnetic and thermodynamic properties of the 3-D periodic anderson lattice hamiltonian
Huscrot, C.; McMahan, A. K.; Pollock, E. I; Scalettar, R. T.
1998-09-10
Tight-binding models capture many of the qualitative features of interaction-induced effects in solids. For example, the simplest such model, the single-band Hubbard Hamiltonian, describes the Mott insulating phase which occurs in correlated systems, despite the fact that the one electron band is nominally only half-filled, as well as the tendency towards magnetic order. Both phenomena occur in the transition metal oxides. The Periodic Anderson Model (PAM) is a step towards incorporating more complex orbital structure. It contains a pair of orbitals on each site--a delocalized conduction band and a set of highly correlated, localized states. The PAM successfully describes conditions for transitions between antiferromagnetic order of the local moments and phases in which these moments are quenched into singlets paired with conduction electrons. These phenomena are central to heavy fermion systems. The pressure-induced volume collapse in Ce has also been attributed to Kondo-like quenching of the local f moments in this metal, as has been discussed in the context of the impurity Anderson Model. The authors describe Quantum Monte Carlo (QMC) calculations of the magnetic and thermodynamic properties of the PAM in three dimensions. Previous QMC studies have been reported in one and two dimensions. A focus of our attention will be on the density of states and the specific heat. The organization of this paper is as follows. They first introduce the PAM and outline some of its properties. Next, a brief presentation of the Quantum Monte Carlo, Maximum Entropy, and Hartree-Fock methods is given. They then show the equilibrium magnetic properties of the PAM, including the spin correlations between conduction and localized orbitals, and antiferromagnetic correlations in the localized band, before turning to the thermodynamics and the density of states. A concluding section describes connections of this work to the problem of the rare earth volume collapse transitions.
Han, Bumsoo; Bischof, John C
2004-04-01
Understanding the phase change behavior of biomaterials during freezing/thawing including their thermal properties at low temperatures is essential to design and improve cryobiology applications such as cryopreservation and cryosurgery. However, knowledge of phase change behavior and thermal properties of various biomaterials is still incomplete, especially at cryogenic temperatures (< or = -40 degrees C). Moreover, in these applications, chemicals are often added to improve their outcome, which can result in significant variation in the phase change behavior and thermal properties from those of the original biomaterials. These chemical additives include cryoprotective agents (CPAs), antifreeze protein (AFP), or cryosurgical adjuvants like sodium chloride (NaCl). In the present study, phase change behavior and thermal properties of saline solutions--either water-NaCl or phosphate buffered saline (PBS)--with various chemical additives were investigated. The chemical additives studied are glycerol and raffinose as CPAs, an AFP (Type III, molecular weight = 6500), and NaCl as a cryosurgical adjuvant. The phase change behavior was investigated using a differential scanning calorimeter (DSC) and a cryomicroscope. The specific and latent heat of these solutions were also measured with the DSC. The saline solutions have two distinct phase changes--water/ice and eutectic phase changes. During freezing, eutectic solidification of both water-NaCl and PBS are significantly supercooled below their thermodynamic equilibrium eutectic temperatures. However, their melting temperatures are close to thermodynamic equilibrium during thawing. These eutectic phase changes disappear when even a small amount (0.1 M glycerol) of CPA was added, but they are still observed after the addition of an AFP. The specific heats of these solutions are close to that of ice at very low temperatures (< or = -100 degrees C) regardless of the additives, but they increase between -100 degrees C and -30 degrees C with the addition of CPAs. The amount of latent heat, which is evaluated with sample weight, generally decreases with the addition of the additives, but can be normalized to approximately 300 J/g based on the weight of water which participates in the phase change. This illustrates that thermal properties, especially latent heat, of a biomaterial should be evaluated based on the understanding of its phase change behavior. The results of the present study are discussed in the context of the implications for cryobiology applications. PMID:15179849
NASA Astrophysics Data System (ADS)
Neuenschwander, Wilmer
1989-06-01
Simple relationships are presented that accurately approximate the thermodynamic properties of equilibrium air mixtures from 360 to 25,000 R over the pressure range from 0.00005 to 10 atmospheres. Relationships of this approximation are based on a newly introduced concept of kinetic specific heat that relates air temperature to the kinetic energy component of enthalpy. Unique features of this methodology include: (1) explicitness of relationships, (2) enhanced computational efficiency by orders of magnitude, and (3) comparable or improved accuracy when compared with accepted approximations. Additionally, the kinetic specific heat parameter can be directly applied for accurate, computationally efficient calculation of the thermodynamic properties of nonequilibrium, dissociated air mixtures. Summary descriptions of the kinetic specific heat concept and development of the thermodynamic relationships are presented. The relationship accuracies are identified and demonstrated by extensive comparisons with the exact solution data of Hilsenrath and Beckett. A similar thermodynamic concept and analysis capability is not known to be available in the published literature.
Phonon densities of states and related thermodynamic properties of high temperature ceramics.
Loong, C.-K.
1998-08-28
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}.
Donohue, M.D.
1990-09-01
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.
Thermodynamic and electromagnetic properties of hard-core charged bosons on a lattice
Micnas, R.; Robaszkiewicz, S.; Kostyrko, T.
1995-09-01
We study thermodynamic and electromagnetic properties of the local electron pair system being equivalent to that of hard-core charged bosons on a lattice. The theory of the response kernel is given and static electromagnetic properties of the model are analyzed in the superfluid phase in the random-phase approximation. The effects of quantum fluctuations on the superfluid density are analyzed in detail for cubic lattices. A generic feature of the London penetration depths ratio [{lambda}(0)/{lambda}({ital T})]{sup 2} in the considered system is the {ital T}{sup 4} behavior in the {ital T}{r_arrow}0 limit and the 3D {ital XY} critical point behavior near {ital T}{sub {ital c}} (for the screened long-range intersite interaction). In the low-density limit, a consistent description of superfluid characteristics is obtained with the use of the exact scattering length. The effects of long-range Coulomb interaction on the excitation spectrum and finite temperature properties of the superconducting phase are also discussed. Finally, we briefly comment on the relevance of our results to the recent experimental data concerning the London penetration depth and the universal critical behavior in high-{ital T}{sub {ital c}} superconductors.
Quantum and Thermodynamic Properties of Spontaneous and Low-Energy Induced Fission of Nuclei
Kadmensky, S.G.
2005-12-01
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.
Mesoscopic modeling of structural and thermodynamic properties of fluids confined by rough surfaces.
Terrón-Mejía, Ketzasmin A; López-Rendón, Roberto; Gama Goicochea, Armando
2015-10-21
The interfacial and structural properties of fluids confined by surfaces of different geometries are studied at the mesoscopic scale using dissipative particle dynamics simulations in the grand canonical ensemble. The structure of the surfaces is modeled by a simple function, which allows us to simulate readily different types of surfaces through the choice of three parameters only. The fluids we have modeled are confined either by two smooth surfaces or by symmetrically and asymmetrically structured walls. We calculate structural and thermodynamic properties such as the density, temperature and pressure profiles, as well as the interfacial tension profiles for each case and find that a structural order-disorder phase transition occurs as the degree of surface roughness increases. However, the magnitude of the interfacial tension is insensitive to the structuring of the surfaces and depends solely on the magnitude of the solid-fluid interaction. These results are important for modern nanotechnology applications, such as in the enhanced recovery of oil, and in the design of porous materials with specifically tailored properties. PMID:26387742
Advanced working fluids: Thermodynamic properties. Final report, 1 December 1987-30 November 1989
Lee, L.L.; Gering, K.L.
1990-09-01
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.
A Thermodynamic Property Model for R-125/143a Mixtures Based on a New Cubic Equation of State
NASA Astrophysics Data System (ADS)
Zhang, Heng-Liang; Tada, Satoru; Waranabe, Koichi
The binary mixture of two hydrofluorocarbons, R-125 and R-143a, behaves almost like an azeotrope and has been considered as a promising refrigerant to substitute R-502. In this paper, we present a thermodynamic property model for the R-125/143a system, which was developed on the basis of a new cubic equation of state proposed in our previous publications. The essential thermodynamic properties such as PVTx properties, vapor-liquid equilibrium, enthalpy, entropy, isobaric specific heat, and speed of sound are well represented simultaneously by the new model in the entire fluid-phase of theR-125/143a system including the pure components.The model is valid for any composition with thermodynamic consistency to cover a range broad enough for refrigeration engineering applications. A pressure-enthalpy diagram for the R-125/143a mixture with 50 mass% R-125 is also presented.
NASA Technical Reports Server (NTRS)
Weber, L. A.
1975-01-01
Compressibility measurements and thermodynamic properties data for parahydrogen were extended to higher temperatures and pressures. Results of an experimental program are presented in the form of new pressure, volume and temperature data in the temperature range 23 to 300 K at pressures up to 800 bar. Also given are tables of thermodynamic properties on isobars to 1000 bar including density, internal energy, enthalpy, entropy, specific heats at constant volume and constant pressure, velocity of sound, and surface derivatives. The accuracy of the data is discussed and comparisons are made with previous data.
Electronic, vibrational and thermodynamic properties of Ca10(AsO4)6(OH)2: first principles study
NASA Astrophysics Data System (ADS)
Zheng, Yuanlei; Gao, Tao; Gong, Yanrong; Ma, Shenggui; Yang, Mingli; Chen, Piheng
2015-12-01
The electronic, vibrational and thermodynamic properties of johnbaumite (AHAP Ca10(AsO4)6(OH)2) have been performed by First principles approach. AHAP is an indirect band-gap material of 3.98 eV. The calculated phonon dispersion indicates that AHAP is stable. For AHAP, the optical vibrational modes at the Γ-point are assigned: 21E1 + 19A + 22E2 + 24B, and the frequencies agree well with available experimental data. The largest LO-TO phonon frequency splitting occurs at A mode (770.2 cm-1 to 807.6 cm-1). Finally, the thermodynamic properties of AHAP are predicted.
Mao, Pingli Yu, Bo; Liu, Zheng; Wang, Feng; Ju, Yang
2015-03-21
The structural, mechanical, electronic, and thermodynamic properties of Mg{sub 2}Sr with C14-type structure under pressures ranging from 0 to 40 GPa have been systematically studied within the framework of density functional theory in this work. The results at zero pressure were in good agreement with the available theoretical and experimental values. The pressure dependence of structure and elastic constants, elastic anisotropy, Cauchy pressure, melting points, and hardness was successfully calculated and discussed. In addition, the electronic density of states (DOSs) under various pressures were investigated. Debye temperature and the dependences of thermodynamic properties on temperature and pressure were also discussed in the present paper.
Thermodynamic properties of non-conformal soft-sphere fluids with effective hard-sphere diameters.
Rodríguez-López, Tonalli; del Río, Fernando
2012-01-28
In this work we study a set of soft-sphere systems characterised by a well-defined variation of their softness. These systems represent an extension of the repulsive Lennard-Jones potential widely used in statistical mechanics of fluids. This type of soft spheres is of interest because they represent quite accurately the effective intermolecular repulsion in fluid substances and also because they exhibit interesting properties. The thermodynamics of the soft-sphere fluids is obtained via an effective hard-sphere diameter approach that leads to a compact and accurate equation of state. The virial coefficients of soft spheres are shown to follow quite simple relationships that are incorporated into the equation of state. The approach followed exhibits the rescaling of the density that produces a unique equation for all systems and temperatures. The scaling is carried through to the level of the structure of the fluids. PMID:22158949
Some physical and thermodynamic properties of rocket exhaust clouds measured with infrared scanners
NASA Technical Reports Server (NTRS)
Gomberg, R. I.; Kantsios, A. G.; Rosensteel, F. J.
1977-01-01
Measurements using infrared scanners were made of the radiation from exhaust clouds from liquid- and solid-propellant rocket boosters. Field measurements from four launches were discussed. These measurements were intended to explore the physical and thermodynamic properties of these exhaust clouds during their formation and subsequent dispersion. Information was obtained concerning the initial cloud's buoyancy, the stabilized cloud's shape and trajectory, the cloud volume as a function of time, and it's initial and stabilized temperatures. Differences in radiation intensities at various wavelengths from ambient and stabilized exhaust clouds were investigated as a method of distinguishing between the two types of clouds. The infrared remote sensing method used can be used at night when visible range cameras are inadequate. Infrared scanning techniques developed in this project can be applied directly to natural clouds, clouds containing certain radionuclides, or clouds of industrial pollution.
First-principles study of structural, elastic and thermodynamic properties of AuIn2
NASA Astrophysics Data System (ADS)
Wu, Hai Ying; Chen, Ya Hong; Deng, Chen Rong; Yin, Peng Fei; Cao, Hong
2015-12-01
The structural, elastic and thermodynamic properties of AuIn2 in the CaF2 structure under pressure have been investigated using abinitio plane wave pseudopotential method within the generalized gradient approximation. The calculated structural parameters and equation of state are in excellent agreement with the available experimental and theoretical results. The elastic constants of AuIn2 at ambient condition are calculated, and the bulk modulus obtained from these calculated elastic constants agrees well with the experimental data. The pressure dependence of the elastic constants, bulk modulus, shear modulus and Youngs modulus has also been investigated. The Debye temperature presents a slight increase with pressure. AuIn2 exhibits ductibility and low hardness characteristics, the ductibility increases while the hardness decreases with the increasing of pressure. The pressure effect on the heat capacity and thermal expansion coefficient for AuIn2 is much larger.
The thermodynamic properties of a spin-1/2 Heisenberg ferromagnetic system using Oguchi's method
NASA Astrophysics Data System (ADS)
Mert, Gülistan
2015-11-01
The thermodynamic properties of spin-1/2 Heisenberg ferromagnetic system on the simple cubic lattice are investigated by using of Oguchi's approximation. The effects of the second-nearest-neighbor exchange interactions on the magnetization, internal energy, heat capacity, entropy and free energy of the Heisenberg ferromagnet are considered. One obtains typical ferromagnetic magnetization curves and obtains that the critical temperature increases when the second-nearest-neighbor exchange parameter increases. In the heat capacity curve, Schottky-like peaks are observed for a certain values of the second-nearest-neighbor interactions. The behaviors of magnetic entropy and free energy are presented. When the only nearest neighbor interaction is included, magnetic entropy does not reach maximum value, but the system with the second-nearest-neighbor exchange interaction reaches it. Free energy has a discontinuity point at the critical temperature.
Thermodynamic properties of melts of Mn-Sc(Y, Ln) systems
NASA Astrophysics Data System (ADS)
Shevchenko, M. A.; Ivanov, M. I.; Berezutski, V. V.; Kudin, V. G.; Sudavtsova, V. S.
2012-12-01
Partial and integral mixing enthalpies of melts of binary systems Mn-Sc and Mn-Y at 1873 and 1830 K, respectively, are determined by calorimetry. It is found that the minima of the mixing enthalpies are -7.1 ± 0.4 and -3.2 ± 0.2 kJ/mol at x Mn = 0.60 and 0.61, respectively. The initial partial mixing enthalpies of Sc and Y are -33.2 ± 2.1 and -16.6 ± 0.8 kJ/mol, respectively. The thermodynamic properties of melts of binary Mn-Sc(Y) systems are calculated using the ideal associated solution (IAS) model. It is found that the activities of the components exhibit slight negative deviations from the ideal solutions, and the excess Gibbs energies reach -3.0 and -1.6 kJ/mol, respectively.
Thermodynamic and Ultrasonic Properties of Ascorbic Acid in Aqueous Protic Ionic Liquid Solutions
Singh, Vickramjeet; Sharma, Gyanendra; Gardas, Ramesh L.
2015-01-01
In this work, we report the thermodynamic and ultrasonic properties of ascorbic acid (vitamin C) in water and in presence of newly synthesized ammonium based protic ionic liquid (diethylethanolammonium propionate) as a function of concentration and temperature. Apparent molar volume and apparent molar isentropic compression, which characterize the solvation state of ascorbic acid (AA) in presence of protic ionic liquid (PIL) has been determined from precise density and speed of sound measurements at temperatures (293.15 to 328.15) K with 5 K interval. The strength of molecular interactions prevailing in ternary solutions has been discussed on the basis of infinite dilution partial molar volume and partial molar isentropic compression, corresponding volume of transfer and interaction coefficients. Result has been discussed in terms of solute-solute and solute-solvent interactions occurring between ascorbic acid and PIL in ternary solutions (AA + water + PIL). PMID:26009887
NASA Technical Reports Server (NTRS)
Klich, G. F.
1976-01-01
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.
Kozlov, Sergey S; Blennow, Andreas; Krivandin, Alexei V; Yuryev, Vladimir P
2007-04-10
A combined DSC-SAXS approach was employed to study the effects of amylose and phosphate esters on the assembly structures of amylopectin in B-type polymorphic potato tuber starches. Amylose and phosphate levels in the starches were specifically engineered by antisense suppression of the granule bound starch synthase (GBSS) and the glucan water dikinase (GWD), respectively. Joint analysis of the SAXS and DSC data for the engineered starches revealed that the sizes of amylopectin clusters, thickness of crystalline lamellae and the polymorphous structure type remained unchanged. However, differences were found in the structural organization of amylopectin clusters reflected in localization of amylose within these supramolecular structures. Additionally, data for annealed starches shows that investigated potato starches possess different types of amylopectin defects. The relationship between structure of investigated potato starches and their thermodynamic properties was recognized. PMID:17188347
Ab initio calculation of the thermodynamic properties of InSb under intense laser irradiation
Feng, ShiQuan; Cheng, XinLu; Key Laboratory of High Energy Density Physics and Technology of Ministry of Education, Sichuan University, Chengdu, 610064 ; Zhao, JianLing; Zhang, Hong
2013-07-28
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.
Nearest-neighbor effects in hot and dense plasmas: Thermodynamic properties
NASA Astrophysics Data System (ADS)
Stein, J.; Goldberg, I. B.; Shalitin, D.; Salzmann, D.
1989-02-01
A model for describing the influence of the nearest-neighbor interaction on the thermodynamic properties of plasmas is presented. This model is a generalization of the Thomas-Fermi model to cylindrical symmetry. The model was applied to the calculation of the electric potential of a pair of identical ions. An iron plasma at an ion density of 1023 cm-3 at a range of temperatures of practical interest was used to illustrate the predictions of the model. The ionization-potential reduction, the ion-pair free energy, and the average distance to the nearest neighbor were calculated. Our results indicate that the inclusion of the nearest-neighbor interaction predicts a plasma which is slightly more compressible than predicted by the spherically symmetric Thomas-Fermi model.
Lattice dynamics and thermodynamic properties of the β-Sn phase in Si
NASA Astrophysics Data System (ADS)
Ekman, Mathias; Persson, Kristin; Grimvall, Göran
2000-12-01
The lattice dynamics of silicon in the metastable β-Sn structure is studied using the density-functional linear-response theory. The Grüneisen parameters and thermal expansion are calculated in the quasiharmonic approximation for the cubic diamond (cd) and β-Sn phase and the thermodynamic properties are compared with the liquid phase at zero pressure. We relate the anomalously high entropy of fusion in Si to the difference in entropy between the β-Sn and the cd phase. The melting temperature and phase boundary slopes for the β-Sn phase at zero pressure are qualitatively different from those deduced from the experimental pressure-temperature phase diagram. This suggests that the reported experimental liquid-metallic solid phase boundary does not refer to the β-Sn phase.
Thermodynamic properties of aqueous solutions of sodium ibuprofen at 293.15-318.15 K
NASA Astrophysics Data System (ADS)
Manin, N. G.; Perlovich, G. L.
2015-04-01
The enthalpies of solution and dilution of aqueous solutions of sodium ibuprofen (NaIBP) with concentrations of m < 1.4 mol/kg water are measured at 293.15, 298.15, 308.15, and 318.5 K using an isoperibolic calorimeter. The heat capacity of NaIBP in the temperature range of 273.15-528.15 K is measured using a DSC 204 F1 Phoenix differential scanning calorimeter (NETZSCH, Germany). The virial coefficients of the enthalpies of aqueous solutions of NaIBP are derived in terms of the Pitzer model, and the thermodynamic properties of both the solutions and the solution components are calculated over the range of compound solubility. The variation in these characteristics as a function of concentration and temperature is analyzed.
Impact of oceanic heat transport on global thermodynamical properties in the climate system
NASA Astrophysics Data System (ADS)
Schroeder, Alexander; Lunkeit, Frank; Lucarini, Valerio
2014-05-01
We investigate how properties of macroscale thermodynamics of the climate system respond to changes in the intensity of the oceanic heat transport by utilising PlaSim, an Earth-like general circulation model of intermediate complexity, in an aqua-planet configuration. By increasing the magnitude of the meridional heat transport in the ocean, characterised by an export out of the tropics and a poleward convergence, we observe a surface warming of about 10K and a decrease in the equator-to-pole temperature difference, while the total poleward heat transport remains unchanged. The Carnot efficiency, the intensity of the Lorenz energy cycle and the material entropy production of the system decline with increasing oceanic heat transport. These results suggest that the climate system becomes less efficient and turns into a state of reduced entropy production, as the oceanic transport of heat out of the tropics is reinforced.
NASA Astrophysics Data System (ADS)
Suntsov, Yu. K.; Vlasov, M. V.; Chuikov, A. M.
2015-06-01
The boiling points of solutions of five binary systems are measured using the ebulliometric method in the pressure range of 4.4-101.3 kPa. Compositions of the equilibrium vapor phases of systems are calculated, based on the constructed pressure isotherms of saturated vapor. The values of excess Gibbs energy and the enthalpy and entropy of solutions are calculated from the data on the liquid-vapor equilibrium. The patterns of change in the phase equilibria and thermodynamic properties of the solutions are established, based on the composition and temperature of the systems. The liquid-vapor equilibrium of systems is described using the equations of Wilson and the NRTL (Non-Random Two-Liquid model).
Kabadi, V.N.
1992-10-01
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.
Fournier, René; Mohareb, Amir
2016-01-14
We devised a global optimization (GO) strategy for optimizing molecular properties with respect to both geometry and chemical composition. A relative index of thermodynamic stability (RITS) is introduced to allow meaningful energy comparisons between different chemical species. We use the RITS by itself, or in combination with another calculated property, to create an objective function F to be minimized. Including the RITS in the definition of F ensures that the solutions have some degree of thermodynamic stability. We illustrate how the GO strategy works with three test applications, with F calculated in the framework of Kohn-Sham Density Functional Theory (KS-DFT) with the Perdew-Burke-Ernzerhof exchange-correlation. First, we searched the composition and configuration space of CmHnNpOq (m = 0-4, n = 0-10, p = 0-2, q = 0-2, and 2 ≤ m + n + p + q ≤ 12) for stable molecules. The GO discovered familiar molecules like N2, CO2, acetic acid, acetonitrile, ethane, and many others, after a small number (5000) of KS-DFT energy evaluations. Second, we carried out a GO of the geometry of CumSnn (+) (m = 1, 2 and n = 9-12). A single GO run produced the same low-energy structures found in an earlier study where each CumSnn (+) species had been optimized separately. Finally, we searched bimetallic clusters AmBn (3 ≤ m + n ≤ 6, A,B= Li, Na, Al, Cu, Ag, In, Sn, Pb) for species and configurations having a low RITS and large highest occupied Molecular Orbital (MO) to lowest unoccupied MO energy gap (Eg). We found seven bimetallic clusters with Eg > 1.5 eV. PMID:26772561
NASA Astrophysics Data System (ADS)
Fournier, René; Mohareb, Amir
2016-01-01
We devised a global optimization (GO) strategy for optimizing molecular properties with respect to both geometry and chemical composition. A relative index of thermodynamic stability (RITS) is introduced to allow meaningful energy comparisons between different chemical species. We use the RITS by itself, or in combination with another calculated property, to create an objective function F to be minimized. Including the RITS in the definition of F ensures that the solutions have some degree of thermodynamic stability. We illustrate how the GO strategy works with three test applications, with F calculated in the framework of Kohn-Sham Density Functional Theory (KS-DFT) with the Perdew-Burke-Ernzerhof exchange-correlation. First, we searched the composition and configuration space of CmHnNpOq (m = 0-4, n = 0-10, p = 0-2, q = 0-2, and 2 ≤ m + n + p + q ≤ 12) for stable molecules. The GO discovered familiar molecules like N2, CO2, acetic acid, acetonitrile, ethane, and many others, after a small number (5000) of KS-DFT energy evaluations. Second, we carried out a GO of the geometry of Cu m Snn + (m = 1, 2 and n = 9-12). A single GO run produced the same low-energy structures found in an earlier study where each Cu m S nn + species had been optimized separately. Finally, we searched bimetallic clusters AmBn (3 ≤ m + n ≤ 6, A,B= Li, Na, Al, Cu, Ag, In, Sn, Pb) for species and configurations having a low RITS and large highest occupied Molecular Orbital (MO) to lowest unoccupied MO energy gap (Eg). We found seven bimetallic clusters with Eg > 1.5 eV.
Kabadi, V.N.
1995-06-30
The work on this project was initiated on September 1, 1991. The project consisted of two different tasks: (1) Development of a model to compute viscosities of coal derived liquids, and (2) Investigate new models for estimation of thermodynamic properties of solid and liquid compounds of the type that exist in coal, or are encountered during coal processing. As for task 1, a model for viscosity computation of coal model compound liquids and coal derived liquids has been developed. The detailed model is presented in this report. Two papers, the first describing the pure liquid model and the second one discussing the application to coal derived liquids, are expected to be published in Energy & Fuels shortly. Marginal progress is reported on task 2. Literature review for this work included compilation of a number of data sets, critical investigation of data measurement techniques available in the literature, investigation of models for liquid and solid phase thermodynamic computations. During the preliminary stages it was discovered that for development of a liquid or solid state equation of state, accurate predictive models for a number of saturation properties, such as, liquid and solid vapor pressures, saturated liquid and solid volumes, heat capacities of liquids and solids at saturation, etc. Most the remaining time on this task was spent in developing predictive correlations for vapor pressures and saturated liquid volumes of organic liquids in general and coal model liquids in particular. All these developments are discussed in this report. Some recommendations for future direction of research in this area are also listed.
Thermodynamic properties of an alternating-spin (1/2,1) two-leg ladder
NASA Astrophysics Data System (ADS)
Chen, X. Y.; Jiang, Q.; Shen, W. Z.
2004-01-01
With the aid of the Schwinger-boson mean-field method, we study the low-lying excitations and thermodynamic properties of a ferrimagnetic Heisenberg two-leg ladder (i.e., a ferrimagnetic double-chain with an antiferromagnetic interaction). The interaction between the two chains plays an important role in producing a low-lying excitation energy gap, affecting the low-lying excited spectrum, and increasing the disorder of the ferrimagnetic double-chain. The excitation spectrum, energy gap, and spin reduction in the ground state are calculated. Thermodynamic quantities such as the short-range spin correlation and short-range order are also obtained at low temperatures. In this gapful system, we observed the exponential behaviors in both the specific heat (C_V) and the product of magnetic susceptibility and temperature (χ T) at low temperatures. The exponential behavior of the χ T versus temperature agrees qualitatively with the experimental results in NiCu(pba)(D_2O)_3\\cdot D_2O at low temperatures.
On the thermodynamic properties of the Rb3C60 superconductor
NASA Astrophysics Data System (ADS)
Szcze&şacute; niak, R.; Durajski, A. P.; Pach, P. W.
2014-05-01
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 (μC★=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 (RΔ≡2Δ(0)/kBTC), the ratio of the specific heat jump to the normal state specific heat (RC≡ΔCTC/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: RΔ=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.
The structural, elastic and thermodynamic properties of intermetallic compound CeGa2
NASA Astrophysics Data System (ADS)
Çiftci, Yasemin; Çolakoǧlu, Kemal; Çoban, Cansu; Deligöz, Engin
2012-02-01
The structural, elastic and thermodynamic characteristics of CeGa2 compound in the AlB2 (space group: P6/mmm) and the omega trigonal (space group: P-3m1) type structures are investigated using the methods of density functional theory within the generalized gradient approximation (GGA). The thermodynamic properties of the considered structures are obtained through the quasi-harmonic Debye model. The results on the basic physical parameters, such as the lattice constant, the bulk modulus, the pressure derivative of bulk modulus, the phase-transition pressure (P t) from P6/mmm to P-3m1 structure, the second-order elastic constants, Zener anisotropy factor, Poisson's ratio, Young's modulus, and the isotropic shear modulus are presented. In order to gain further information, the pressure and temperature-dependent behavior of the volume, the bulk modulus, the thermal expansion coefficient, the heat capacity, the entropy, Debye temperature and Grüneisen parameter are also evaluated over a pressure range of 0-6 GPa and a wide temperature range of 0-1800 K. The obtained results are in agreement with the available experimental and the other theoretical values.
The structural, elastic and thermodynamic properties of intermetallic compound CeGa2
NASA Astrophysics Data System (ADS)
Çiftci, Yasemin Ö.; Çolakoǧlu, Kemal; Çoban, Cansu; Deligöz, Engin
2012-02-01
The structural, elastic and thermodynamic characteristics of CeGa2 compound in the AlB2 (space group: P6/mmm) and the omega trigonal (space group: P-3m1) type structures are investigated using the methods of density functional theory within the generalized gradient approximation (GGA). The thermodynamic properties of the considered structures are obtained through the quasi-harmonic Debye model. The results on the basic physical parameters, such as the lattice constant, the bulk modulus, the pressure derivative of bulk modulus, the phase-transition pressure ( P t ) from P6/mmm to P-3m1 structure, the second-order elastic constants, Zener anisotropy factor, Poisson's ratio, Young's modulus, and the isotropic shear modulus are presented. In order to gain further information, the pressure and temperature-dependent behavior of the volume, the bulk modulus, the thermal expansion coefficient, the heat capacity, the entropy, Debye temperature and Grüneisen parameter are also evaluated over a pressure range of 0-6 GPa and a wide temperature range of 0-1800 K. The obtained results are in agreement with the available experimental and the other theoretical values.
Paganini, Iván E; Pastorino, Claudio; Urrutia, Ignacio
2015-06-28
We study a system of few colloids confined in a small spherical cavity with event driven molecular dynamics simulations in the canonical ensemble. The colloidal particles interact through a short range square-well potential that takes into account the basic elements of attraction and excluded-volume repulsion of the interaction among colloids. We analyze the structural and thermodynamic properties of this few-body confined system in the framework of inhomogeneous fluids theory. Pair correlation function and density profile are used to determine the structure and the spatial characteristics of the system. Pressure on the walls, internal energy, and surface quantities such as surface tension and adsorption are also analyzed for a wide range of densities and temperatures. We have characterized systems from 2 to 6 confined particles, identifying distinctive qualitative behavior over the thermodynamic plane T - ρ, in a few-particle equivalent to phase diagrams of macroscopic systems. Applying the extended law of corresponding states, the square well interaction is mapped to the Asakura-Oosawa model for colloid-polymer mixtures. We link explicitly the temperature of the confined square-well fluid to the equivalent packing fraction of polymers in the Asakura-Oosawa model. Using this approach, we study the confined system of few colloids in a colloid-polymer mixture. PMID:26133449
Thermodynamic and Transport Properties of Superconducting Mg{sup 10}B{sub 2}
Finnemore, D. K.; Ostenson, J. E.; Bud'ko, S. L.; Lapertot, G.; Canfield, P. C.
2001-03-12
Transport and thermodynamic properties of a sintered pellet of the newly discovered MgB{sub 2} superconductor have been measured to determine the characteristic critical magnetic fields and critical current densities. Both resistive transition and magnetization data give similar values of the upper critical field, H{sub c2} , with magnetization data giving dH{sub c2}/dT=0.44 T/ K at the transition temperature of T{sub c}=40.2 K . Close to the transition temperature, magnetization curves are thermodynamically reversible, but at low temperatures the trapped flux can be on the order of 1T. The value of dH{sub c}/dT at T{sub c} is estimated to be about 12 mT/K , a value similar to classical superconductors like Sn. Hence, the Ginzburg-Landau parameter {kappa}{approx}26 . Estimates of the critical supercurrent density, J{sub c} , using hysteresis loops and the Bean model, give critical current densities on the order of 10{sup 5} A/cm {sup 2} . Hence the supercurrent coupling through the grain boundaries is comparable to intermetallics like Nb{sub 3}Sn .
NASA Astrophysics Data System (ADS)
Bhatt, N. K.; Jani, A. R.; Vyas, P. R.; Gohel, V. B.
2005-03-01
In the present paper, we report theoretical calculations for the thermodynamic properties of lead (Pb) at high temperatures and pressures. We use the mean-field potential (MFP) model proposed recently by Wang and Li (Phys. Rev. B 62 (2000) 196) for evaluating the vibrational contribution of the lattice ion to the total free energy. The MFP seen by the lattice ion is constructed, for the first time, in terms of the total energy-volume relation using the local pseudopotential due to Fiolhais et al. (Phys. Rev. B 51 (1995) 14 001). We have calculated static compression, shock-wave compression, thermal expansion ( β), isothermal and adiabatic bulk moduli ( BT and BS), internal energy, specific heats ( CV and CP), thermodynamic Grüneisen parameter ( γ), anharmonic contribution to the specific heat and temperature along shock Hugoniot. The results are satisfactorily comparable with those generated through first-principles methods, other theoretical methods and with experiments. We demonstrate that in comparison with other theoretical models, the present model has the advantages of computational simplicity and physical transparency.
NASA Astrophysics Data System (ADS)
Ran, Shi-Ju; Xi, Bin; Liu, Tao; Su, Gang
2013-08-01
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.
The thermodynamic properties of hydrated γ-Al{sub 2}O{sub 3} nanoparticles
Spencer, Elinor C.; Ross, Nancy L.; Huang, Baiyu; Woodfield, Brian F.; Parker, Stewart F.; Kolesnikov, Alexander I.
2013-12-28
In this paper we report a combined calorimetric and inelastic neutron scattering (INS) study of hydrated γ-Al{sub 2}O{sub 3} (γ-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 γ-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 γ-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 γ-alumina nanoparticles.
Bichara, C.; Bergman, C.; Mathieu, J.-C.
1985-01-01
Monte Carlo calculations are carried out to give exact values of some thermodynamic properties of alloys. The calculations are performed within the framework of the surrounded atom model the main assumptions of which are: quasilattice structure of the alloy, nearest neighbour interactions, description of the configuration in terms of ''surrounded atoms''. The results are then compared wit those obtained using current approximations: the Bragg-Williams treatment and the quasichemical treatment. This work enables the authors to generalize the previous conclusions drawn in the study of the regular solution model. In every case, whatever the sign of the interactions (ordering or clustering tendency) Monte Carlo calculations yield a local order that both approximations fail to reproduce. In order to compare the calculations with experimental data, Cowley's short range order parameter is calculated by Monte Carlo and by the approximate methods (the parameters of the surrounded atom model are derived from thermodynamic data). The Monte Carlo values compare better than the quasichemical ones with the data obtained by X-ray or neutron diffraction in three actual systems.
Mittal, Shruti; Singh, Laishram Rajendrakumar
2013-01-01
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 α-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
NASA Astrophysics Data System (ADS)
Song, Mei-Ying; Hou, Yi-Fang; Wen, Long-Mei; Wang, Shu-Ping; Yang, Shu-Tao; Zhang, Jian-Jun; Geng, Li-Na; Shi, Shi-Kao
2016-03-01
Four new nitronyl nitroxide radical-Ln(III) complexes, Ln(hfac)3(NITPhSCF3)2 (Ln(III) = Sm(1), Gd(2), Tb(3), Dy(4); NITPhSCF3 = 2-(4-trifluoromethylthiophenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl- 3-oxide; hfac = hexafluoroacetylacetonate), have been synthesized and characterized. They are isostructural, which show mononuclear tri-spin structures. The central Ln(III) ion is eight-coordinated by three hfac anions and two NITPhSCF3 molecules. Direct-current magnetic study shows that there exist ferromagnetic interactions between Gd(III) ion and radicals (NITPhSCF3) with JGd-Rad = 1.61 cm-1, and antiferromagnetic interactions between radicals with JRad-Rad = -2.83 cm-1 in complex 2. The magnetic analysis with the rough approximate model show that a ferromagnetic coupling exists between Tb(III) and radical in 3, while a antiferromagnetic coupling between Dy(III) and radical in 4. The thermodynamics properties of four complexes were studied with differential scanning calorimetry (DSC), such as heat capacity, thermodynamic functions (HT-H298.15K), (ST-S298.15K), and (GT-G298.15K).
Structure, thermodynamic properties, and phase diagrams of few colloids confined in a spherical pore
NASA Astrophysics Data System (ADS)
Paganini, Iván E.; Pastorino, Claudio; Urrutia, Ignacio
2015-06-01
We study a system of few colloids confined in a small spherical cavity with event driven molecular dynamics simulations in the canonical ensemble. The colloidal particles interact through a short range square-well potential that takes into account the basic elements of attraction and excluded-volume repulsion of the interaction among colloids. We analyze the structural and thermodynamic properties of this few-body confined system in the framework of inhomogeneous fluids theory. Pair correlation function and density profile are used to determine the structure and the spatial characteristics of the system. Pressure on the walls, internal energy, and surface quantities such as surface tension and adsorption are also analyzed for a wide range of densities and temperatures. We have characterized systems from 2 to 6 confined particles, identifying distinctive qualitative behavior over the thermodynamic plane T - ρ, in a few-particle equivalent to phase diagrams of macroscopic systems. Applying the extended law of corresponding states, the square well interaction is mapped to the Asakura-Oosawa model for colloid-polymer mixtures. We link explicitly the temperature of the confined square-well fluid to the equivalent packing fraction of polymers in the Asakura-Oosawa model. Using this approach, we study the confined system of few colloids in a colloid-polymer mixture.
Ergodic properties of a generic nonintegrable quantum many-body system in the thermodynamic limit.
Prosen, T
1999-10-01
We study a generic but simple nonintegrable quantum many-body system of locally interacting particles, namely, a kicked-parameter (t,V) model of spinless fermions on a one-dimensional lattice (equivalent to a kicked Heisenberg XX-Z chain of 1/2 spins). The statistical properties of the dynamics (quantum ergodicity and quantum mixing) and the nature of quantum transport in the thermodynamic limit are considered as the kick parameters (which control the degree of nonintegrability) are varied. We find and demonstrate ballistic transport and nonergodic, nonmixing dynamics (implying infinite conductivity at all temperatures) in the integrable regime of zero or very small kick parameters, and more generally and importantly, also in the nonintegrable regime of intermediate values of kicked parameters, whereas only for sufficiently large kick parameters do we recover quantum ergodicity and mixing implying normal (diffusive) transport. We propose an order parameter (charge stiffness D) which controls the phase transition from nonmixing and nonergodic dynamics (ordered phase, D>0) to mixing and ergodic dynamics (disordered phase, D=0) in the thermodynamic limit. Furthermore, we find exponential decay of time correlation functions in the regime of mixing dynamics. The results are obtained consistently within three different numerical and analytical approaches: (i) time evolution of a finite system and direct computation of time correlation functions, (ii) full diagonalization of finite systems and statistical analysis of stationary data, and (iii) algebraic construction of quantum invariants of motion of an infinite system, in particular the time-averaged observables. PMID:11970231
Thermodynamic properties of 9-methylcarbazole and 1,2,3,4-tetrahydro-9-methylcarbazole
Steele, W.V.; Knipmeyer, S.E.; Nguyen, A.; Chirico, R.D.
1991-04-01
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.
NASA Technical Reports Server (NTRS)
Simmonds, A. L.; Miller, C. G., III; Nealy, J. E.
1976-01-01
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.
Steele, W.V.; Chirico, R.D.
1989-06-01
Ideal-gas thermodynamic properties for indoline and 2-methylindole based on accurate calorimetric measurements (between 300 to 500 K and 300 to 700 K, respectively) were determined; well into the range of typical chemical process temperatures. The calorimetrically derived values provide a firm basis for the prediction of thermodynamic properties for a large family of structures including many substituted indoles and indolines. Critical-temperature/density measurements obtained using a differential scanning calorimeter (DSC) are reported for 2-methylindole. A critical pressure and acentric factor are derived for 2-methylindole. Group-additivity estimation methods are employed to estimate the Gibbs energies of formation for the reactants, intermediates, and products in a reaction scheme for the hydrodenitrogenation (HDN) of indole. Thermodynamic equilibria calculations on the indole/indoline/hydrogen system are compared with experimental batch-reaction measurements reported in the literature. The interplay between thermodynamics and kinetics in the HDN of indole is discussed. 41 refs., 11 figs., 23 tabs.
NASA Technical Reports Server (NTRS)
Miller, C. G., III; Wilder, S. E.
1976-01-01
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.
NASA Astrophysics Data System (ADS)
Antoshechkina, P. M.; Wolf, A. S.; Hamecher, E. A.; Asimow, P. D.; Ghiorso, M. S.
2013-12-01
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 χ2-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.
NASA Astrophysics Data System (ADS)
Yanilkin, Alexey; Migdal, Kirill; Pokatashkin, Pavel; Sergeev, Oleg
2015-06-01
The application of molecular dynamics allows us to take into account the influence of thermal properties on thermodynamic properties and phase transitions. In this work different uranium phases are investigated at finite temperatures by means quantum and classical molecular dynamics. In order to verify simulations the lattice constants, elastic modulus, isotherms, Gruniesen coefficient and heat expansion are calculated for α, γ and liquid phases. The results are in good agreement with experimental data. The stability of high temperature γ phase is discussed. The diffusion coefficient is calculated for liquid phase at different densities and pressure. The boundaries of phase stability are estimated based on QMD results. Furthermore hugoniot calculated is in a good agreement with other calculations and experimental data up to 2TPa. In order to investigate phase transitions EAM interatomic potentials are derived by force-matching method. Different parameterizations are used for different part of phase diagram to improve the reproduction of QMD data. The coexistence and transition rates of two phases are investigated based on Z- and two phase methods.
Influence of volume magnetostriction on the thermodynamic properties of Ni-Mn-Ga shape memory alloys
NASA Astrophysics Data System (ADS)
Kosogor, Anna; L'vov, Victor A.; Cesari, Eduard
2015-10-01
In the present article, the thermodynamic properties of Ni-Mn-Ga ferromagnetic shape memory alloys exhibiting the martensitic transformations (MTs) above and below Curie temperature are compared. It is shown that when MT goes below Curie temperature, the elastic and thermal properties of alloy noticeably depend on magnetization value due to spontaneous volume magnetostriction. However, the separation of magnetic parts from the basic characteristics of MT is a difficult task, because the volume magnetostriction does not qualitatively change the transformational behaviour of alloy. This problem is solved for several Ni-Mn-Ga alloys by means of the quantitative theoretical analysis of experimental data obtained in the course of stress-strain tests. For each alloy, the entropy change and the transformation heat evolved in the course of MT are evaluated, first, from the results of stress-strain tests and, second, from differential scanning calorimetry data. For all alloys, a quantitative agreement between the values obtained in two different ways is observed. It is shown that the magnetic part of transformation heat exceeds the non-magnetic one for the Ni-Mn-Ga alloys undergoing MTs in ferromagnetic state, while the elevated values of transformation heat measured for the alloys undergoing MTs in paramagnetic state are caused by large MT strains.
First principle study of elastic and thermodynamic properties of FeB4 under high pressure
NASA Astrophysics Data System (ADS)
Zhang, Xinyu; Qin, Jiaqian; Ning, Jinliang; Sun, Xiaowei; Li, Xinting; Ma, Mingzhen; Liu, Riping
2013-11-01
The elastic properties, elastic anisotropy, and thermodynamic properties of the lately synthesized orthorhombic FeB4 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 FeB4 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 FeB4 is stable up to 100 GPa. In addition, the calculated B/G ratio reveals that FeB4 possesses brittle nature in the range of pressure from 0 to 100 GPa. The calculated elastic anisotropic factors suggest that FeB4 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 FeB4 are successfully obtained in the present work.
Donohue, M.D.
1988-11-01
The progress of our efforts toward understanding molecular behavior and its effect on thermodynamic properties is presented. This included work in the following areas: The repulsive and attractive terms in various equations for chain molecules have been compared with computer simulation results. We found that PHCT fit the data more closely than the other equations. For non-polar, polar and hydrogen bonding pure substances, APACT molecular parameters were correlated with molecular size. The density dependence in the SPHCT has been modified in order to improve the accuracy of pure-component property calculations. Our knowledge of the partitioning of intermolecular interactions has been used to study how the solubility parameter in Regular Solution Theory can be related to fundamental molecular constants. We have made substantial progress toward understanding how our theories can be applied to polymer solutions. Computer simulations of chain molecules have been carried out in order to test our equations and to determine radial distribution functions of various groups used in a group-group interaction approach. Finally, our theoretical efforts have been supplemented by appropriate experimental measurements. 10 refs.
NASA Astrophysics Data System (ADS)
Mysen, B.; Lee, S.; Cody, G. D.; Fei, Y.
2006-12-01
Recent developments and advances in solid state NMR and synchrotron x-ray techniques, together with theoretical analyses using quantum-chemical calculations and statistical mechanical modeling, make it possible to quantify the detailed distribution of cations and anions in model oxide glasses and melts with varying pressure, temperature, and composition (e.g. Lee SK. Geochim. Cosmochim. Acta 2005, 69, p3695; J. Phys. Chem. B. 2006, 110, p16408 Lee SK et al. Nature Materials 2005, 4, p851). These results allow us to estimate quantitatively the configurational thermodynamic properties of oxide glasses and their precursor liquids. We present several examples that establish a link among microscopic spectroscopic and scattering measurements, quantification of disorder, and the configurational thermodynamic properties. These examples include enthalpy of mixing, activity coefficient of silica in archetypal and complex silicate, germanate glasses and melts at ambient and high pressure. Most glasses and melts show a tendency toward chemical ordering among framework cations (Si and Al) at ambient pressure. This information provides a basis for quantitative understanding of the degree of Al-avoidance and phase separation in more complex multi-component melts and glasses. This chemical ordering, a manifestation of energetics in the melts and glasses, also contributes to the total negative deviation of activity of oxides from ideal solution in silicate melts (reduced activity). While no definite evidence of clustering among non-framework cations was found, these cations tend to form dissimilar pairs upon mixing with other types of network modifying cations. The chemical order appears maintained at high pressure where there exists higher- coordinated framework units (^{[5,6]}Si and ^{[5,6]}Al). It appears that the distribution of these units is not random, but shows significant chemical order, favoring mixing between different types of framework units (e.g. ^{[4]}Si -O-^{[5,6]}Si). Topologically, the peak width of each oxygen site, as seen in NMR spectra, increases with increasing pressure. This implies that bond angle and length, as well as the distortion of framework polyhedra, increase with increasing pressure, thus increasing topological entropy. We then calculate key macroscopic properties, including the activity coefficient of silica and configurational enthalpy from the quantitative estimates of the extent of disorder from solid-state NMR. These results are remarkably similar to existing experimental solution calorimetric data for aluminosilicates and borosilicate glasses (Navrotsky et al. Geochim. Cosmochim. Acta 1982, 46, p2036; Hervig et al. 1985 J. Am. Ceram. Soc.68, p314).
Molecular simulation of thermodynamic and transport properties for the H2O+NaCl system.
Orozco, Gustavo A; Moultos, Othonas A; Jiang, Hao; Economou, Ioannis G; Panagiotopoulos, Athanassios Z
2014-12-21
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
Phase relations and thermodynamic properties of condensed phases in the system Ca-Cu-O
Mathews, T.; Hajra, J.P.; Jacob, K.T. )
1993-11-01
Because of the discovery of superconducting compounds in the systems Ca-Sr-Bi-Cu-O and Ca-Ba-Tl-Cu-O, there is considerable interest in phase relations in these systems. The isothermal sections of the phase diagram for the system Ca-Cu-O at 1073 and 1223 K have been determined. Several compositions in the ternary system were quenched after equilibration, and the phases present were identified by optical microscopy, X-ray diffraction, and electron probe microanalysis. Two ternary compounds Ca[sub 2]CuO[sub 3] and Ca[sub 0.828]CuO[sub 1.93] were identified at 1073 K. However, only Ca[sub 2]CuO[sub 3] was found to be stable at 1223 K. The thermodynamic properties of the two ternary compounds were determined using solid-state cells incorporating either an oxide or a fluoride solid electrolyte. The results for both types of cells were internally consistent. The compound Ca[sub 0.828]CuO[sub 1.93], which can also be represented as Ca[sub 15]Cu[sub 18]O[sub 35], has been identified in an earlier investigation as Ca[sub 0.828]CuO[sub 2]. Using a novel variation of the galvanic cell technique, in which the emf of a cell incorporating a fluoride electrolyte is measured as a function of the oxygen potential of the gas phase in equilibrium with the condensed phase electrodes, it has been confirmed that the compound Ca[sub 0.828]CuO[sub 1.93] (Ca[sub 15]Cu[sub 18]O[sub 35]) does not have significant oxygen nonstoichiometry. Phase relations have been deduced from the thermodynamic data as a function of the partial pressure of oxygen for the system Ca-Cu-O at 873, 1073, and 1223 K. 18 refs., 11 figs., 3 tabs.
NASA Astrophysics Data System (ADS)
Hallett, Paul; Ogden, Mike; Karim, Kamal; Schmidt, Sonja; Yoshida, Shuichiro
2014-05-01
Soil aggregates are a figment of your energy input and initial boundary conditions, so the basic thermodynamics that drive soil structure formation are needed to understand soil structure dynamics. Using approaches from engineering and materials science, it is possible quantify basic thermodynamic properties, but at present tests are generally limited to highly simplified, often remoulded, soil structures. Although this presents limitations, the understanding of underlying processes driving soil structure dynamics is poor, which could be argued is due to the enormity of the challenge of such an incredibly complex system. Other areas of soil science, particularly soil water physics, relied on simplified structures to develop theories that can now be applied to more complex pore structures. We argue that a similar approach needs to gain prominence in the study of soil aggregates. An overview will be provided of approaches adapted from other disciplines to quantify particle bonding, fracture resistance, rheology and capillary cohesion of soil that drive its aggregation and structure dynamics. All of the tests are limited as they require simplified soil structures, ranging from repacked soils to flat surfaces coated with mineral particles. A brief summary of the different approaches will demonstrate the benefits of collecting basic physical data relevant to soil structure dynamics, including examples where they are vital components of models. The soil treatments we have tested with these engineering and materials science approaches include field soils from a range of management practices with differing clay and organic matters contents, amendment and incubation of soils with a range of microorganisms and substrates in the laboratory, model clay-sand mixes and planar mineral surfaces with different topologies. In addition to advocating the wider adoption of these approaches, we will discuss limitations and hope to stimulate discussion on how approaches could be improved and made more useful for studying soil structure dynamics in the future.
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
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.
NASA Astrophysics Data System (ADS)
Honecker, A.; Wessel, S.; Kerkdyk, R.; Pruschke, T.; Mila, F.; Normand, B.
2016-02-01
Quantum antiferromagnets have proven to be some of the cleanest realizations available for theoretical, numerical, and experimental studies of quantum fluctuation effects. At finite temperatures, however, the additional effects of thermal fluctuations in the restricted phase space of a low-dimensional system have received much less attention, particularly the situation in frustrated quantum magnets, where the excitations may be complex collective (bound or even fractionalized) modes. We investigate this problem by studying the thermodynamic properties of the frustrated two-leg S =1/2 spin ladder, with particular emphasis on the fully frustrated case. We present numerical results for the magnetic specific heat and susceptibility, obtained from exact diagonalization and quantum Monte Carlo studies, which we show can be rendered free of the sign problem even in a strongly frustrated system and which allow us to reach unprecedented sizes of L =200 ladder rungs. We find that frustration effects cause an unconventional evolution of the thermodynamic response across the full parameter regime of the model. However, close to the first-order transition they cause a highly anomalous reduction in temperature scales with no concomitant changes in the gap; the specific heat shows a very narrow peak at very low energies and the susceptibility rises abruptly at extremely low temperatures. Unusually, the two quantities have different gaps over an extended region of the parameter space. We demonstrate that these results reflect the presence of large numbers of multiparticle bound-state excitations, whose energies fall below the one-triplon gap in the transition region.
Experimental Study of the Thermodynamic Properties of Diethyl Ether (DEE) at Saturation
NASA Astrophysics Data System (ADS)
Polikhronidi, N. G.; Abdulagatov, I. M.; Batyrova, R. G.; Stepanov, G. V.; Ustuzhanin, E. E.; Wu, J. T.
2011-03-01
The isochoric heat capacities {({C_{V1}^' ,{C_{V1}^'',{C_{V2}^',{C_{V2}^'')}, saturation densities ({ρ _S^' and ({ρ_S^'')}), vapor pressures ( P S), thermal-pressure coefficients {γ_V=left({partial P/partial T}right)_V}, and first temperature derivatives of the vapor pressure γ 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, γ 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 - τ plot) and baro-gram (readings of the tensotransducer, P - τ plot) techniques were used to accurately measure the phase-transition parameters ( P S , ρ S , T S) and γ V . The total experimental uncertainty of density ( ρ S), pressure ( P S), temperature ( T S), isochoric heat capacities {({C_{V1}^' ,{C_{V1}^'',{C_{V2}^',{C_{V2}^'')}, and thermal-pressure coefficient, γ 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, ρ S, T S) properties were used to calculate other derived thermodynamic properties C P , C S, W, K T , P int, Δ 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 μ/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 μ on the coexistence-curve diameter behavior near the critical point was studied. Extended scaling-type equations for the measured properties P S ( T), ρ S ( T), and {({C_{V1}^' ,{C_{V1}^'',{C_{V2}^',{C_{V2}^'')} as a function of temperature were developed.
Elstnerová, Pavlína; Friák, Martin; Fabritius, Helge Otto; Lymperakis, Liverios; Hickel, Tilmann; Petrov, Michal; Nikolov, Svetoslav; Raabe, Dierk; Ziegler, Andreas; Hild, Sabine; Neugebauer, Jörg
2010-12-01
Arthropoda, which represent nearly 80% of all known animal species, are protected by an exoskeleton formed by their cuticle. The cuticle represents a hierarchically structured multifunctional biocomposite based on chitin and proteins. Some groups, such as Crustacea, reinforce the load-bearing parts of their cuticle with calcite. As the calcite sometimes contains Mg it was speculated that Mg may have a stiffening impact on the mechanical properties of the cuticle (Becker et al., Dalton Trans. (2005) 1814). Motivated by these facts, we present a theoretical parameter-free quantum-mechanical study of the phase stability and structural and elastic properties of Mg-substituted calcite crystals. The Mg-substitutions were chosen as examples of states that occur in complex chemical environments typical for biological systems in which calcite crystals contain impurities, the role of which is still the topic of debate. Density functional theory calculations of bulk (Ca,Mg)CO₃ were performed employing 30-atom supercells within the generalized gradient approximation as implemented in the Vienna Ab-initio Simulation Package. Based on the calculated thermodynamic results, low concentrations of Mg atoms are predicted to be stable in calcite crystals in agreement with experimental findings. Examining the structural characteristics, Mg additions nearly linearly reduce the volume of substituted crystals. The predicted elastic bulk modulus results reveal that the Mg substitution nearly linearly stiffens the calcite crystals. Due to the quite large size-mismatch of Mg and Ca atoms, Mg substitution results in local distortions such as off-planar tilting of the CO₃²⁻ group. PMID:20650336
Comper, W D
1994-06-21
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
Effects of abasic sites on structural, thermodynamic and kinetic properties of quadruplex structures
Esposito, Veronica; Martino, Luigi; Citarella, Giuseppe; Virgilio, Antonella; Mayol, Luciano; Giancola, Concetta; Galeone, Aldo
2010-01-01
Abasic sites represent the most frequent lesion in DNA. Since several events generating abasic sites concern guanines, this damage is particularly important in quadruplex forming G-rich sequences, many of which are believed to be involved in several biological roles. However, the effects of abasic sites in sequences forming quadruplexes have been poorly studied. Here, we investigated the effects of abasic site mimics on structural, thermodynamic and kinetic properties of parallel quadruplexes. Investigation concerned five oligodeoxynucleotides based on the sequence d(TGGGGGT), in which all guanines have been replaced, one at a time, by an abasic site mimic (dS). All sequences preserve their ability to form quadruplexes; however, both spectroscopic and kinetic experiments point to sequence-dependent different effects on the structural flexibility and stability. Sequences d(TSGGGGT) and d(TGGGGST) form quite stable quadruplexes; however, for the other sequences, the introduction of the dS in proximity of the 3′-end decreases the stability more considerably than the 5′-end. Noteworthy, sequence d(TGSGGGT) forms a quadruplex where dS does not hamper the stacking between the G-tetrads adjacent to it. These results strongly argue for the central role of apurinic/apyrimidinic site damages and they encourage the production of further studies to better delineate the consequences of their presence in the biological relevant regions of the genome. PMID:20026588
Nichols, T.T.; Taylor, D.D.
2002-07-18
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.
NASA Astrophysics Data System (ADS)
Yang, Xiao-Yong; Lu, Yong; Zheng, Fa-Wei; Zhang, Ping
2015-11-01
Mechanical, electronic, and thermodynamic properties of zirconium carbide have been systematically studied using the ab initio calculations. The calculated equilibrium lattice parameter, bulk modulus, and elastic constants are all well consistent with the experimental data. The electronic band structure indicates that the mixture of C 2p and Zr 4d and 4p orbitals around the Fermi level makes a large covalent contribution to the chemical bonds between the C and Zr atoms. The Bader charge analysis suggests that there are about 1.71 electrons transferred from each Zr atom to its nearest C atom. Therefore, the Zr-C bond displays a mixed ionic/covalent character. The calculated phonon dispersions of ZrC are stable, coinciding with the experimental measurement. A drastic expansion in the volume of ZrC is seen with increasing temperature, while the bulk modulus decreases linearly. Based on the calculated phonon dispersion curves and within the quasi-harmonic approximation, the temperature dependence of the heat capacities is obtained, which gives a good description compared with the available experimental data. Project supported by the National Natural Science Foundation of China (Grant No. 51071032).
NASA Astrophysics Data System (ADS)
Varshney, Dinesh; Jain, S.; Shriya, S.; Khenata, R.
2016-04-01
Pressure- and temperature-dependent mechanical, elastic, and thermodynamical properties of rock salt to CsCl structures in semiconducting SrX (X = O, S, Se, and Te) chalcogenides are presented based on model interatomic interaction potential with emphasis on charge transfer interactions, covalency effect, and zero point energy effects apart from long-range Coulomb, short-range overlap repulsion extended and van der Waals interactions. The developed potential with non-central forces validates the Cauchy discrepancy among elastic constants. The volume collapse (V P/V 0) in terms of compressions in SrX at higher pressure indicates the mechanical stiffening of lattice. The expansion of SrX lattice is inferred from steep increase in V T/V 0 and is attributed to thermal softening of SrX lattice. We also present the results for the temperature-dependent behaviors of hardness, heat capacity, and thermal expansion coefficient. From the Pugh's ratio (ϕ = B T /G H), the Poisson's ratio (ν) and the Cauchy's pressure (C 12-C 44), we classify SrO as ductile but SrS, SrSe, and SrTe are brittle material. To our knowledge these are the first quantitative theoretical prediction of the pressure and temperature dependence of mechanical stiffening, thermally softening, and brittle nature of SrX (X = O, S, Se, and Te) and still await experimental confirmations.
Influence of Alloying Elements on the Thermodynamic Properties of Titanium in Molten Steel
NASA Astrophysics Data System (ADS)
Yoshikawa, Takeshi; Morita, Kazuki
2007-08-01
The influences of alloying elements of chromium, nickel, manganese, molybdenum, copper, and oxygen on the thermodynamic property of titanium in molten iron were investigated at 1873 K to improve control of the formation of titanium compounds in the steelmaking processes. At a certain titanium potential controlled by the coexistence of Ti3O5 and Ti2O3 with steel, the interaction parameters between alloying elements and titanium in molten iron were determined as follows. \\varepsilon ^{{{text{Mn}}}}_{{{text{Ti}}}} = - 27.4( ± 0.66),quad \\varepsilon ^{{{text{Cr}}}}_{{{text{Ti}}}} = 5.33( ± 0.84),quad \\varepsilon ^{{{text{Ni}}}}_{{{text{Ti}}}} = - 3.93( ± 0.51),quad \\varepsilon ^{{{text{Mo}}}}_{{{text{Ti}}}} = 5.76( ± 0.69),quad \\varepsilon ^{{{text{Cu}}}}_{{{text{Ti}}}} = 3.44( ± 0.69) Through the investigation of titanium deoxidation equilibria in molten iron, the activity coefficient of titanium and the first-order interaction parameter between oxygen and titanium were determined as follows: γ _{{{text{Ti}}}}^{ circ} = 0.0215(±0.00062),quad \\varepsilon ^{{{text{Ti}}}}_{{text{O}}} = - 160(±10) Also, titanium deoxidation of molten 304 stainless steel was measured and compared with the calculated results using the determined interaction parameters.
Méndez-Morales, T; Carrete, J; Cabeza, O; Gallego, L J; Varela, L M
2011-09-29
In this work, extensive molecular dynamics simulations of mixtures of alcohols of several chain lengths (methanol and ethanol) with the ionic liquids (ILs) composed of the cation 1-hexyl-3-methylimidazolium and several anions of different hydrophobicity degrees (Cl(-), BF(4)(-), PF(6)(-)) are reported. We analyze the influence of the nature of the anion, the length of the molecular chain of the alcohol, and the alcohol concentration on the thermodynamic and structural properties of the mixtures. Densities, excess molar volumes, total and partial radial distribution functions, coordination numbers, and hydrogen bond degrees are reported and analyzed for mixtures of the ILs with methanol and ethanol. The aggregation process is shown to be highly dependent on the nature of the anion and the size of the alcohol, since alcohol molecules tend to interact predominantly with the anionic part of the IL, especially in mixtures of the halogenated IL with methanol. Particularly, our results suggest that the formation of an apolar network similar to that previously reported in mixtures of ILs with water does not take place in mixtures with alcohol when the chloride anion is present, the alcohol molecules being instead homogeneously distributed in the polar network of IL. Moreover, the alcohol clusters formed in mixtures of [HMIM][PF(6)] with alcohol were found to have a smaller size than in mixtures with water. Additionally, we provide a semiquantitative analysis of the dependence of the hydrogen bonding degree of the mixtures on the alcohol concentration. PMID:21899260
Structural, Elastic, Electronic Optical and Thermodynamic Properties of {ZnAl}2{S}4
NASA Astrophysics Data System (ADS)
Haddou, A.; Murtaza, G.; Khachai, H.; Khenata, R.; Bin Omran, S.; Ullah, Naeem; Varshney, Dinesh; Bouhemadou, A.
2015-11-01
The structural, elastic, electronic, optical, and thermodynamic properties of the {ZnAl}2{S}_{4 } compound are calculated in the frame work of the density functional theory where the calculated structural parameters are found to be in good agreement with the experimental data and other theoretical calculations. The calculations show that the material is elastically stable and isotropic. Furthermore, the calculated band gap is observed to be wide and direct and is comparable with earlier experimental data as well as with other theoretical calculations; hence, it is an optically active material for optoelectronic applications. In addition, the compound is found to have mixed ionic and covalent bonding nature. The optical nature of the compound is described in terms of the complex dielectric function, complex refractive index, reflectivity, and energy loss function. On the other hand, variation of the unit cell volume, bulk modulus, heat capacity, and Debye temperature are described as a function of temperature at different pressures for the {ZnAl}2{S}4 compound.
Energetic stability, structural transition, and thermodynamic properties of ZnSnO3
NASA Astrophysics Data System (ADS)
Gou, Huiyang; Zhang, Jingwu; Li, Zhiping; Wang, Gongkai; Gao, Faming; Ewing, Rodney C.; Lian, Jie
2011-02-01
First principles calculations were performed on ZnSnO3 polymorphs to understand their energetic stability and structural transition under high pressure environments. The experimentally-identified ilmenite (IL)-type and LiNbO3 (LN)-type ZnSnO3 may coexist at zero pressure considering the effect of zero point energy. IL-type ZnSnO3 becomes unstable under high pressure due to the appearance of imaginary frequency in phonon spectra. Enthalpy differences suggest that the phase stability follows the sequence: ZnO+SnO2 below 5.9 GPa, Zn2SnO4+SnO2 up to 7.1 GPa, and LN-type phase above 7.1 GPa. Pressurization at 34.5 GPa causes a phase transformation from the LN-type to the orthorhombic CdSnO3-type. Thermodynamic properties including Helmholtz free energy, specific heat at constant volume and Debye temperature were also calculated.
Thermodynamics of A?16-21 dissociation from a fibril: Enthalpy, entropy, and volumetric properties.
Rao Jampani, Srinivasa; Mahmoudinobar, Farbod; Su, Zhaoqian; Dias, Cristiano L
2015-11-01
Here, we provide insights into the thermodynamic properties of A ?16-21 dissociation from an amyloid fibril using all-atom molecular dynamics simulations in explicit water. An umbrella sampling protocol is used to compute potentials of mean force (PMF) as a function of the distance ? between centers-of-mass of the A ?16-21 peptide and the preformed fibril at nine temperatures. Changes in the enthalpy and the entropic energy are determined from the temperature dependence of these PMF(s) and the average volume of the simulation box is computed as a function of ?. We find that the PMF at 310 K is dominated by enthalpy while the entropic energy does not change significantly during dissociation. The volume of the system decreases during dissociation. Moreover, the magnitude of this volume change also decreases with increasing temperature. By defining dock and lock states using the solvent accessible surface area (SASA), we find that the behavior of the electrostatic energy is different in these two states. It increases (unfavorable) and decreases (favorable) during dissociation in lock and dock states, respectively, while the energy due to Lennard-Jones interactions increases continuously in these states. Our simulations also highlight the importance of hydrophobic interactions in accounting for the stability of A ?16-21. PMID:26264694
Manifestations of Kitaev physics in thermodynamic properties of hexagonal iridates and α-RuCl3
NASA Astrophysics Data System (ADS)
Tsirlin, Alexander
Kitaev model is hard to achieve in real materials. Best candidates available so far are hexagonal iridates M2IrO3 (M = Li and Na) and the recently discovered α-RuCl3 featuring hexagonal layers coupled by weak van der Waals bonding. I will review recent progress in crystal growth of these materials and compare their thermodynamic properties. Both hexagonal iridates and α-RuCl3 feature highly anisotropic Curie-Weiss temperatures that not only differ in magnitude but also change sign depending on the direction of the applied magnetic field. Néel temperatures are largely suppressed compared to the energy scale of the Curie-Weiss temperatures. These experimental observations will be linked to features of the electronic structure and to structural peculiarities associated with deviations from the ideal hexagonal symmetry. I will also discuss how the different nature of ligand atoms affects electronic structure and magnetic superexchange. This work has been done in collaboration with M. Majumder, M. Schmidt, M. Baenitz, F. Freund, and P. Gegenwart.
Temperature dependence of thermodynamic and electrical properties of CuIrRhS4
NASA Astrophysics Data System (ADS)
Ito, Masakazu; Ebisu, Shuji; Nagata, Shoichi
2016-05-01
We have investigated the thermodynamic and electrical properties of spinel CuIrRhS4. The temperature (T) dependence of the electrical resistivity (ρ) shows metallic behaviour defined as ∂ ρ / ∂ T > 0, in the range of 5 ≤ T ≤ 300 K. The T dependence of thermal conductivity, κ(T), has a broad peak resulting from the Umklapp process at 35 K and increases gradually above 80 K with increasing T. κ(T) can be reproduced by the combination of the usual Debye model and the localized-vibrations hopping model. Thermoelectric power, S(T), changes from negative to positive at 32 K and gradually increases with increasing T. The positive value of S(T) is due to carrier diffusion, which shows a hole-like band dispersion at the Fermi level. On the other hand, the negative value originates from phonon drag and variable-range hopping. We also estimated the T dependence of the dimensionless figure of merit, ZT, from ρ(T) , κ(T), and S(T).
Molecular dynamics study of the thermodynamic properties of calcium apatites. 2. Monoclinic phases.
Cruz, Fernando J A L; Canongia Lopes, José N; Calado, Jorge C G
2006-03-01
Structural and thermodynamic properties of crystalline monoclinic calcium apatites, Ca10(PO4)6(X)2 (X=OH, Cl), were investigated for the first time using a molecular dynamics (MD) technique under a wide range of temperature and pressure conditions. The accuracy of the model at room temperature and atmospheric pressure was checked against crystal structural data, yielding maximum deviations of ca. 2%. The standard molar lattice enthalpy (DeltalatHo298) of the apatites was also calculated and compared with previously published experimental and MD results for the hexagonal polymorphs. High-temperature simulation runs were used to estimate the isobaric thermal expansivity coefficient and study the behavior of the crystal structure under heating. The heat capacity at constant pressure, Cp, in the range 298-1298 K, was estimated from the plot of the molar enthalpy of the crystal as a function of temperature, Hm=(Hm,298-298Cp,m)+Cp,mT, yielding Cp,m=635+/-7 J.mol-1.K-1 and Cp,m=608+/-14 J.mol-1.K-1 for hydroxy- and chlorapatite, respectively. High-pressure MD experiments, in the 0.5-75 kbar range, were performed to estimate the isothermal compressibility. The Parsafar-Mason equation of state was successfully used to fit the high-pressure p-Vm data, with an accuracy better than 0.03%. PMID:16509739
Strictly two-dimensional self-avoiding walks: thermodynamic properties revisited.
Schulmann, N; Xu, H; Meyer, H; Polińska, P; Baschnagel, J; Wittmer, J P
2012-09-01
The density crossover scaling of various thermodynamic properties of solutions and melts of self-avoiding and highly flexible polymer chains without chain intersections confined to strictly two dimensions is investigated by means of molecular dynamics and Monte Carlo simulations of a standard coarse-grained bead-spring model. In the semidilute regime we confirm over an order of magnitude of the monomer density ρ the expected power law scaling for the interaction energy between different chains e(int) ~ ρ(21/8), the total pressure P ~ ρ(3) and the dimensionless compressibility g(T) = lim(q→0)S(q) ~ 1/ρ(2). Various elastic contributions associated to the affine and non-affine response to an infinitesimal strain are analyzed as functions of density and sampling time. We show how the size ξ(ρ) of the semidilute blob may be determined experimentally from the total monomer structure factor S(q) characterizing the compressibility of the solution at a given wave vector q. We comment briefly on finite persistence length effects. PMID:23015277
Xu, Wen-Sheng; Freed, Karl F.
2015-07-14
The lattice cluster theory (LCT) for semiflexible linear telechelic melts, developed in Paper I, is applied to examine the influence of chain stiffness on the average degree of self-assembly and the basic thermodynamic properties of linear telechelic polymer melts. Our calculations imply that chain stiffness promotes self-assembly of linear telechelic polymer melts that assemble on cooling when either polymer volume fraction ϕ or temperature T is high, but opposes self-assembly when both ϕ and T are sufficiently low. This allows us to identify a boundary line in the ϕ-T plane that separates two regions of qualitatively different influence of chain stiffness on self-assembly. The enthalpy and entropy of self-assembly are usually treated as adjustable parameters in classical Flory-Huggins type theories for the equilibrium self-assembly of polymers, but they are demonstrated here to strongly depend on chain stiffness. Moreover, illustrative calculations for the dependence of the entropy density of linear telechelic polymer melts on chain stiffness demonstrate the importance of including semiflexibility within the LCT when exploring the nature of glass formation in models of linear telechelic polymer melts.
Zaghloul, Mofreh R.
2015-11-15
We present computational results and tables of the equation-of-state, thermodynamic properties, and shock Hugoniot for hot dense fluid deuterium. The present results are generated using a recently developed chemical model that takes into account different high density effects such as Coulomb interactions among charged particles, partial degeneracy, and intensive short range hard core repulsion. Internal partition functions are evaluated in a statistical-mechanically consistent way implementing recent developments in the literature. The shock Hugoniot curve derived from the present tables is overall in reasonable agreement with the Hugoniot derived from the Nova-laser shock wave experiments on liquid deuterium, showing that deuterium has a significantly higher compressibility than predicted by the SESAME tables or by Path Integral Monte Carlo calculations. Computational results are presented as surface plots for the dissociated fraction, degree of ionization, pressure, and specific internal energy for densities ranging from 0.0001 to 40 g/cm{sup 3} and temperatures from 2000 to ∼10{sup 6 }K. Tables for values of the above mentioned quantities in addition to the specific heat at constant pressure, c{sub p}, ratio of specific heats, c{sub p}/c{sub v}, sound speed and Hugoniot curve (for a specific initial state) are presented for practical use.
NASA Astrophysics Data System (ADS)
Dogan, Ali; Arslan, Hüseyin
2015-08-01
In the present study, the enthalpies of mixing associated with the liquid phase in Ni-Cr-Co-Al-Ti-Cu, Au-In-Sn-Zn, and In-Pd-Sn systems at a temperature of 2000 K (1727 °C) through the six components, ternary, and quaternary geometric models are calculated. The values calculated from different geometric models are compared with those obtained in the experiments. In this respect, the results of some thermodynamic prediction methods were applied to the six-component Ni-Cr-Co-Al-Ti-Cu system, the quaternary alloy Au-In0.45-Sn0.45-Zn0.1, and the subsystem ternary alloy In-Pd-Sn in the present study in order to analytically determine the integral properties associated with the six-component alloy systems in the liquid phase. The Chou's general solution model and the traditional models of Toop, Colinet, Muggianu, and Kohler were included in the calculation for comparison and discussion. A comparison among the results of the models and experiments carried out for ternary and quaternary systems displays good mutual agreement.
NASA Astrophysics Data System (ADS)
Zaghloul, Mofreh R.
2015-11-01
We present computational results and tables of the equation-of-state, thermodynamic properties, and shock Hugoniot for hot dense fluid deuterium. The present results are generated using a recently developed chemical model that takes into account different high density effects such as Coulomb interactions among charged particles, partial degeneracy, and intensive short range hard core repulsion. Internal partition functions are evaluated in a statistical-mechanically consistent way implementing recent developments in the literature. The shock Hugoniot curve derived from the present tables is overall in reasonable agreement with the Hugoniot derived from the Nova-laser shock wave experiments on liquid deuterium, showing that deuterium has a significantly higher compressibility than predicted by the SESAME tables or by Path Integral Monte Carlo calculations. Computational results are presented as surface plots for the dissociated fraction, degree of ionization, pressure, and specific internal energy for densities ranging from 0.0001 to 40 g/cm3 and temperatures from 2000 to 106 K. Tables for values of the above mentioned quantities in addition to the specific heat at constant pressure, cp, ratio of specific heats, cp/cv, sound speed and Hugoniot curve (for a specific initial state) are presented for practical use.
Thermodynamic properties of H{sub 2}O and D{sub 2}O in the critical region
Wyczalkowska, A. Kostrowicka; Abdulkadirova, Kh. S.; Anisimov, M. A.; Sengers, J. V.
2000-09-22
An analysis is presented of the thermodynamic properties of H{sub 2}O and D{sub 2}O in the critical region in terms of a six-term Landau expansion for the Helmholtz-energy density transformed so as to incorporate crossover from Ising-type to mean-field critical behavior. It is shown that the effects of the critical fluctuations on the thermodynamic properties of H{sub 2}O and D{sub 2}O satisfy the principle of corresponding states, so that the amplitudes of the asymptotic scaling laws, as well as the parameters that govern the crossover from Ising-type to mean-field critical behavior, are identical for H{sub 2}O and D{sub 2}O. For H{sub 2}O, our results provide information supplementing a formulation for calculating thermodynamic properties of H{sub 2}O for general and scientific use adopted by the International Association for the Properties of Water and Steam. (c) 2000 American Institute of Physics.
NASA Astrophysics Data System (ADS)
Fisenko, Anatoliy I.; Lemberg, Vladimir
2015-07-01
The thermodynamics of blackbody radiation has been constructed for the entire range of the spectrum. However, in practical applications, thermodynamic functions must be calculated within a finite range of frequencies. The analytical expressions for the radiative and thermodynamic properties of blackbody radiation over an arbitrary spectral range of the electromagnetic spectrum are obtained. The Wien displacement law, Stefan-Boltzmann law, total energy density, number density of photons, Helmholtz free energy density, internal energy density, enthalpy density, entropy density, heat capacity at constant volume, and pressure are expressed in terms of the polylogarithm functions. These expressions are important when we build a theoretical model of radiative heat transfer, for example. The thermodynamic functions of blackbody radiation are calculated for various ranges of the spectrum at different temperatures. As an example of practical applications, thermodynamics of the cosmic microwave background radiation measured by the COBE FIRAS instrument is constructed. The expressions obtained for the radiative and thermodynamic functions of blackbody radiation can easily be presented in wavelength and wavenumber domains.
Thermodynamic properties of bromomethanes and bromomethyl radicals: An ab initio study
Paddison, S.J.; Tschuikow-Roux, E.
1998-05-01
Thermochemical data on volatile organic compounds containing bromine are needed for atmospheric modeling, in view of their ozone depletion potential upon photodissociation and the release of atomic bromine. Yet even for the bromomethane series, with the exception of CH{sub 3}Br, thermodynamic properties are not well established. Similarly, structural and thermochemical information on brominated methyl radicals is incomplete or not available. In this paper the authors have adopted a computational approach to obtain this needed information. Equilibrium geometries for the molecules CH{sub 4{minus}n}Br{sub n} (n = 0--4) and radicals CH{sub 3{minus}m}Br{sub m} (m = 0--3) were optimized at both HF/6-31G{sup *} and MP2/6-31G{sup *} levels of theory. Moments of inertia, harmonic vibrational frequencies, and thermodynamic functions were determined at the HF/6-31G{sup *} level. Electron correlation contributions were performed by single-point calculations at both second- and fourth-order Moeller-Plesset perturbation theory for derived MP2/6-31G{sup *} geometries. Enthalpies of formation were obtained from a consideration of applicable isodesmic reactions using the derived MP4/6-31G{sup **}//MP2/6-31G{sup *} total energies in conjunction with experimentally established enthalpies of formation for CH{sub 3}Br, CH{sub 4}, and CH{sub 3}. These data were then used in the determination of {Delta}H{degree}{sub f,T}, {Delta}G{degree}{sub f,T}, and K{sub f,T} for all species over the temperature range 0 to 1500 K. A comparison was made to the existing standard enthalpies of formation at 298 K, both experimentally measured and theoretically estimated, for CH{sub 2}Br{sub 2}, CHBr{sub 3}, CBr{sub 4}, CH{sub 2}Br{sm_bullet}, CHBr{sub 2}{sm_bullet}, and CBr{sub 3}{sm_bullet}.
NASA Astrophysics Data System (ADS)
Chai, Weisin
The scarcity and sustainability of energy sources have always been a concern while seeking for alternative fuels. Biofuels have drawn the attention of various researchers due to their abundancy and renewability. Understanding the physical and chemical properties of these molecules is essential to determining their potential as alternative fuels or fuel additives. In this work, the properties of these molecules are predicted through methods developed from quantum mechanics and statistical mechanics theories. The heats of formations are calculated with the Gaussian program and combined with the Benson group contribution method to predict the Benson parameters of unknown functional groups in a molecule. The methods developed are used to expand the Benson database and improve the practicability of the group contribution method. The heats of formations are also used to predict and correlate heat capacities across a range of temperatures and energy densities in this study.
NASA Astrophysics Data System (ADS)
Jacobs, M.; Schmid-Fetzer, R.
2012-04-01
A prerequisite for the determination of pressure in static high pressure measurements, such as in diamond anvil cells is the availability of accurate equations of state for reference materials. These materials serve as luminescence gauges or as X-ray gauges and equations of state for these materials serve as secondary pressure scales. Recently, successful progress has been made in the development of consistency between static, dynamic shock-wave and ultrasonic measurements of equations of state (e.g. Dewaele et al. Phys. Rev. B70, 094112, 2004, Dorogokupets and Oganov, Doklady Earth Sciences, 410, 1091-1095, 2006, Holzapfel, High Pressure Research 30, 372-394, 2010) allowing testing models to arrive at consistent thermodynamic descriptions for X-ray gauges. Apart from applications of metallic elements in high-pressure work, thermodynamic properties of metallic elements are also of mandatory interest in the field of metallurgy for studying phase equilibria of alloys, kinetics of phase transformation and diffusion related problems, requiring accurate thermodynamic properties in the low pressure regime. Our aim is to develop a thermodynamic data base for metallic alloy systems containing Ag, Al, Au, Cu, Fe, Ni, Pt, from which volume properties in P-T space can be predicted when it is coupled to vibrational models. This mandates the description of metallic elements as a first step aiming not only at consistency in the pressure scales for the elements, but also at accurate representations of thermodynamic properties in the low pressure regime commonly addressed in metallurgical applications. In previous works (e.g. Jacobs and de Jong, Geochim. Cosmochim. Acta, 71, 3630-3655, 2007, Jacobs and van den Berg, Phys. Earth Planet. Inter., 186, 36-48, 2011) it was demonstrated that a lattice vibrational framework based on Kieffer's model for the vibrational density of states, is suitable to construct a thermodynamic database for Earth mantle materials. Such a database aims at, when coupled to a thermodynamic computation program, the calculation and prediction of phase equilibria and thermo-physical properties of phase equilibrium assemblages in pressure-temperature-composition space. In Jacobs and van den Berg (2011) the vibrational method, together with a thermodynamic data base, was successfully applied to mantle convection of materials in the Earth. These works demonstrate that the vibrational method has the advantages of (1) computational speed, (2) coupling or making comparisons with ab initio methods and (3) making reliable extrapolations to extreme conditions. We present results of thermodynamic analyses, using lattice vibrational methods, of Ag, Al, Au, Cu and MgO covering the pressure and temperature regime of the Earth's interior. We show results on consistency of the pressure scales for these materials using different equations of state, under the constraint that thermodynamic properties in the low-pressure regime are accurately represented.
NASA Astrophysics Data System (ADS)
Jafari, R.
2012-05-01
The presence of a quantum critical point can significantly affect the thermodynamic properties of a material at finite temperatures. This is reflected, e.g., in the entropy landscape S(T, c) in the vicinity of a quantum critical point, yielding particularly strong variations for varying the tuning parameter c such as magnetic field. In this work we have studied the thermodynamic properties of the quantum compass model in the presence of a transverse field. The specific heat, entropy and cooling rate under an adiabatic demagnetization process have been calculated. During an adiabatic (de)magnetization process temperature drops in the vicinity of a field-induced zero-temperature quantum phase transitions. However close to field-induced quantum phase transitions we observe a large magnetocaloric effect.
NASA Technical Reports Server (NTRS)
Colon, G.
1981-01-01
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.
NASA Astrophysics Data System (ADS)
Zhang, Shen; Zhao, Shijun; Kang, Wei; Zhang, Ping; He, Xian-Tu
2016-03-01
A precise calculation that translates shifts of x-ray K absorption edges to variations of thermodynamic properties allows quantitative characterization of interior thermodynamic properties of warm dense plasmas by x-ray absorption techniques, which provides essential information for inertial confinement fusion and other astrophysical applications. We show that this interpretation can be achieved through an improved first-principles method. Our calculation shows that the shift of K edges exhibits selective sensitivity to thermal parameters and thus would be a suitable temperature index to warm dense plasmas. We also show with a simple model that the shift of K edges can be used to detect inhomogeneity inside warm dense plasmas when combined with other experimental tools.
Thermodynamic properties of CexTh1-xO2 solid solution from first-principles calculations
Xiao, Haiyan Y.; Zhang, Yanwen; Weber, William J.
2012-11-02
A systematic study based on first-principles calculations along with a quasi-harmonic approximation has been conducted to calculate the thermodynamic properties of the CexTh1xO2 solid solution. The predicted density, thermal expansion coefficients, heat capacity and thermal conductivity for the CexTh1xO2 solid solution all agree well with the available experimental data. The thermal expansion coefficient for ThO2 increases with CeO2 substitution, and complete substitution shows the highest expansion coefficient. On the other hand, the mixed CexTh1xO2 (0 < x < 1) solid solution generally exhibits lower heat capacity and thermal conductivity than the ThO2 and CeO2 end members. Our calculations indicate a strong effect of Ce concentration on the thermodynamic properties of the CexTh1xO2 solid solution.
Pressure effect on structural, elastic, and thermodynamic properties of tetragonal B{sub 4}C{sub 4}
Zheng, Baobing; Zhang, Meiguang; Luo, Hong-Gang
2015-03-15
The compressibility, elastic anisotropy, and thermodynamic properties of the recently proposed tetragonal B{sub 4}C{sub 4} (t-B{sub 4}C{sub 4}) are investigated under high temperature and high pressure by using of first-principles calculations method. The elastic constants, bulk modulus, shear modulus, Young’s modulus, Vickers hardness, Pugh’s modulus ratio, and Poisson’s ratio for t-B{sub 4}C{sub 4} under various pressures are systematically explored, the obtained results indicate that t-B{sub 4}C{sub 4} is a stiffer material. The elastic anisotropies of t-B{sub 4}C{sub 4} are discussed in detail under pressure from 0 GPa to 100 GPa. The thermodynamic properties of t-B{sub 4}C{sub 4}, such as Debye temperature, heat capacity, and thermal expansion coefficient are investigated by the quasi-harmonic Debye model.
NASA Astrophysics Data System (ADS)
Wentzcovitch, R. M.; Da Silveira, P. R.; Wu, Z.; Yu, Y.
2013-12-01
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.
EFFECT OF HEATING RATE ON THE THERMODYNAMIC PROPERTIES OF PULVERIZED COAL
Ramanathan Sampath
2000-01-01
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.
NASA Technical Reports Server (NTRS)
Gordon, S.
1982-01-01
The equilibrium compositions that correspond to the thermodynamic and transport combustion properties for a wide range of conditions for the reaction of hydrocarbons with air are presented. Initially 55 gaseous species and 3 coin condensed species were considered in the calculations. Only 17 of these 55 gaseous species had equilibrium mole fractions greater than 0.000005 for any of the conditions studied and therefore these were the only ones retained in the final tables.
Heat capacity and thermodynamic properties of HoMnO3 in the range of 364-1046 K
NASA Astrophysics Data System (ADS)
Denisova, L. T.; Chumilina, L. G.; Shaikhutdinov, K. A.; Patrin, G. S.; Denisov, V. M.
2016-03-01
The temperature dependence of the molar heat capacity of HoMnO3 has been measured by differential scanning calorimetry. The experimental data have been used to calculate the thermodynamic properties of the oxide compound (changes in the enthalpy H°( T)- H°(364 K), entropy S°( T)- S°(364 K), and reduced Gibbs energy Φ°( T)). The data on the heat capacity of HoMnO3 have been generalized in the range of 40-1000 K.
Zhang, JunMin E-mail: guanyg@tsinghua.edu.cn; Lu, ChunRong; Guan, YongGang E-mail: guanyg@tsinghua.edu.cn; Liu, WeiDong
2015-10-15
Because the fault arc in aircraft electrical system often causes a fire, it is particularly important to analyze its energy and transfer for aircraft safety. The calculation of arc energy requires the basic parameters of the arc. This paper is mainly devoted to the calculations of equilibrium composition, thermodynamic properties (density, molar weight, enthalpy, and specific heat at constant pressure) and transport coefficients (thermal conductivity, electrical conductivity, and viscosity) of plasmas produced by a mixture of air, Cu, and polytetrafluoroethylene under the condition of local thermodynamic equilibrium. The equilibrium composition is determined by solving a system of equations around the number densities of each species. The thermodynamic properties are obtained according to the standard thermodynamic relationships. The transport coefficients are calculated using the Chapman-Enskog approximations. Results are presented in the temperature range from 3000 to 30 000 K for pressures of 0.08 and 0.1 MPa, respectively. The results are more accurate and are reliable reference data for theoretical analysis and computational simulation of the behavior of fault arc.
NASA Astrophysics Data System (ADS)
Zhang, JunMin; Lu, ChunRong; Guan, YongGang; Liu, WeiDong
2015-10-01
Because the fault arc in aircraft electrical system often causes a fire, it is particularly important to analyze its energy and transfer for aircraft safety. The calculation of arc energy requires the basic parameters of the arc. This paper is mainly devoted to the calculations of equilibrium composition, thermodynamic properties (density, molar weight, enthalpy, and specific heat at constant pressure) and transport coefficients (thermal conductivity, electrical conductivity, and viscosity) of plasmas produced by a mixture of air, Cu, and polytetrafluoroethylene under the condition of local thermodynamic equilibrium. The equilibrium composition is determined by solving a system of equations around the number densities of each species. The thermodynamic properties are obtained according to the standard thermodynamic relationships. The transport coefficients are calculated using the Chapman-Enskog approximations. Results are presented in the temperature range from 3000 to 30 000 K for pressures of 0.08 and 0.1 MPa, respectively. The results are more accurate and are reliable reference data for theoretical analysis and computational simulation of the behavior of fault arc.
[Characterization and thermodynamic properties of Cu(II) imprinted chitosan crosslinked membrane].
Zhang, Yu-Hong; Zhang, Ai-Li; Zhou, Ji-Ti; Sun, Xiao-Yu
2012-07-01
A new type of Cu(II)-imprinted chitosan crosslinked membrane (IM Cu(II)-E-CTS) was prepared via molecular imprinting technology, chemical pre-crosslinking and crosslinking methods for treatment of wastewater containing low concentration of copper ion. IM Cu(II)-E-CTS was characterized by porosity, swelling ratio, amino group content, surface morphology, functional group and crystallinity. The thermodynamic properties of Cu (II) adsorption on the as-synthesized membrane at the low concentration (20-70 mg x L(-1)) were studied. It is found that porosity, swelling ratio and amino group contents of IM Cu(II)-E-CTS are 76.9%, 109% and 4.26 mmol x g(-1), respectively. Compared to the pristine chitosan membrane (CTS), 44.0% lower swelling ratio, 528% higher of porosity, 16.5% lower of amino group content are found with IM(Cu) (II)-E-CTS. Compared to crosslinked chitosan membranes (E-CTS), 24.6% higher amino group content is found with IM(Cu) (II)-E-CTS. Compared to CTS and E-CTS, the membrane morphology of IM Cu(II) E-CTS has undergone significant changes, and the internal structure became loose. Compared with CTS, molecular chain of IM Cu(II)-E-CTS is irregular and its crystallinity ability is lowered. IM Cu(II)-E-CTS adsorbs more Cu(II) than that of the other two metal cations [Ni(II) and Zn(II)]. The adsorption of copper ion on IM Cu(II)-E-CTS for 20-70 mg x L(-1) of initial Cu(II) concentration follows the Freundlich adsorption isotherm (R2 > 0.99). The adsorption is a spontaneous, exothermic, and entropy-decreased process. PMID:23002619
Thermodynamic properties of alloys of the Al-Co and Al-Co-Sc systems
NASA Astrophysics Data System (ADS)
Shevchenko, M. A.; Berezutskii, V. V.; Ivanov, M. I.; Kudin, V. G.; Sudavtsova, V. S.
2014-05-01
Enthalpies of mixing for melts of the binary Al-Co system at 1870 K in the range 0 < x Co < 0.25, and at 1620 K, 0 < x Co < 0.12, are investigated by means of isoperibolic calorimetry. Enthalpies of mixing for melts of the ternary Al-Co-Sc system are investigated at 1870 K for sections Al0.75(1 - x)Co0.25(1 - x)Sc x , 0 < x < 0.024, and Al0.88(1 - x)Co0.12(1 - x)Sc x , 0 < x < 0.044. Using the literature data on the enthalpies of mixing for liquid and solid alloys, the activities of melt components, and the phase diagram of the Al-Co system, the thermodynamic properties of liquid and solid alloys of the Al-Co system over a wide range of temperatures and compositions are calculated using a software package of our own design, based on the model of ideal associated solutions (IAS). The enthalpies of mixing and the liquidus surface of the phase diagram of the ternary Al-Co-Sc system over the interval of concentrations are estimated by modeling with data on binary boundary subsystems. All of the components of both the binary Al-Co and ternary Al-Co-Sc systems tend to interact with one another quite strongly: Δ H min(Al-Co) = -32.5 kJ/mol at x Co = 0.44; Δ H min(Al-Co-Sc) = -46 kJ/mol for Al0.4Co0.3Sc0.3 (estimated).
Structural and Thermodynamic Properties of Septin 3 Investigated by Small-Angle X-Ray Scattering.
Ortore, Maria Grazia; Macedo, Joci N A; Araujo, Ana Paula U; Ferrero, Claudio; Mariani, Paolo; Spinozzi, Francesco; Itri, Rosangela
2015-06-16
Septins comprise a family of proteins involved in a variety of cellular processes and related to several human pathologies. They are constituted by three structural domains: the N- and C-terminal domains, highly variable in length and composition, and the central domain, involved in the guanine nucleotide (GTP) binding. Thirteen different human septins are known to form heterogeneous complexes or homofilaments, which are stabilized by specific interactions between the different interfaces present in the domains. In this work, we have investigated by in-solution small-angle x-ray scattering the structural and thermodynamic properties of a human septin 3 construct, SEPT3-GC, which contains both of both interfaces (G and NC) responsible for septin-septin interactions. In order to shed light on the role of these interactions, small-angle x-ray scattering measurements were performed in a wide range of temperatures, from 2 up to 56°C, both with and without a nonhydrolysable form of GTP (GTPγS). The acquired data show a temperature-dependent coexistence of monomers, dimers, and higher-order aggregates that were analyzed using a global fitting approach, taking into account the crystallographic structure of the recently reported SEPT3 dimer, PDB:3SOP. As a result, the enthalpy, entropy, and heat capacity variations that control the dimer-monomer dissociation equilibrium in solution were derived and GTPγS was detected to increase the enthalpic stability of the dimeric species. Moreover, a temperature increase was observed to induce dissociation of SEPT3-GC dimers into monomers just preceding their reassembling into amyloid aggregates, as revealed by the Thioflavin-T fluorescence assays. PMID:26083929
Thermodynamic and mechanical properties of copper precipitates in α-iron from atomistic simulations
NASA Astrophysics Data System (ADS)
Erhart, Paul; Marian, Jaime; Sadigh, Babak
2013-07-01
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.
Thermodynamic properties of calcium-bismuth alloys determined by emf measurements
Kim, H; Boysen, DA; Bradwell, DJ; Chung, BC; Jiang, K; Tomaszowska, AA; Wang, KL; Wei, WF; Sadoway, DR
2012-01-15
The thermodynamic properties of Ca-Bi alloys were determined by electromotive force (emf) measurements to assess the suitability of Ca-Bi electrodes for electrochemical energy storage applications. Emf was measured at ambient pressure as a function of temperature between 723 K and 1173 K using a Ca(s)vertical bar CaF2(s)vertical bar Ca(in Bi) cell for twenty different Ca-Bi alloys spanning the entire range of composition from chi(Ca) = 0 to 1. Reported are the temperature-independent partial molar entropy and enthalpy of calcium for each Ca-Bi alloy. Also given are the measured activities of calcium, the excess partial molar Gibbs energy of bismuth estimated from the Gibbs-Duhem equation, and the integral change in Gibbs energy for each Ca-Bi alloy at 873 K, 973 K, and 1073 K. Calcium activities at 973 K were found to be nearly constant at a value a(Ca) = 1 x 10(-8) over the composition range chi(Ca) = 0.32-0.56, yielding an emf of similar to 0.77 V. Above chi(Ca) = 0.62 and coincident with Ca5Bi3 formation, the calcium activity approached unity. The Ca-Bi system was also characterized by differential scanning calorimetry over the entire range of composition. Based upon these data along with the emf measurements, a revised Ca-Bi binary phase diagram is proposed. (C) 2011 Elsevier Ltd. All rights reserved.
Ab initio calculation of thermodynamic, transport, and optical properties of CH{sub 2} plastics
Knyazev, D. V.; Levashov, P. R.
2015-05-15
This work covers an ab initio calculation of thermodynamic, transport, and optical properties of plastics of the effective composition CH{sub 2} at density 0.954 g/cm{sup 3} in the temperature range from 5 kK up to 100 kK. The calculation is based on the quantum molecular dynamics, density functional theory, and the Kubo-Greenwood formula. The temperature dependence of the static electrical conductivity σ{sub 1{sub D{sub C}}}(T) has a step-like shape: σ{sub 1{sub D{sub C}}}(T) grows rapidly for 5 kK ≤ T ≤ 10 kK and is almost constant for 20 kK ≤ T ≤ 60 kK. The additional analysis based on the investigation of the electron density of states (DOS) is performed. The rapid growth of σ{sub 1{sub D{sub C}}}(T) at 5 kK ≤ T ≤ 10 kK is connected with the increase of DOS at the electron energy equal to the chemical potential ϵ = μ. The frequency dependence of the dynamic electrical conductivity σ{sub 1}(ω) at 5 kK has the distinct non-Drude shape with the peak at ω ≈ 10 eV. This behavior of σ{sub 1}(ω) was explained by the dip at the electron DOS.
2014-01-01
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, ΔH, E a , and ΔS, 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
NASA Astrophysics Data System (ADS)
Tanaka, Hideki; Gubbins, Keith E.
1992-08-01
Thermodynamic properties and structures of water-methanol mixtures at various temperatures have been investigated by means of Monte Carlo simulations and subsequent analyses. The OPLS model by Jorgensen was used for the methanol-methanol interaction and both the Caravetta-Clementi (CC) potential and TIP4P potential by Jorgensen et al. were used for the water-water interaction. We show that the role of water-water interaction is very important in discussing aqueous solutions of alcohols, and examine the origin of the exothermic mixing processes. We have investigated the sensitivity of the temperature dependence of the enthalpy of mixing to the water-water interaction. The CC potential is able to reproduce the temperature dependence observed in experiments, although the absolute values of the mixing enthalpy were larger than the experimental ones. While the TIP4P potential results in better agreement for the excess enthalpy and volume near room temperature, the temperature dependence of the excess enthalpy did not agree with experiment. The difference in the magnitude of the exothermic hydration for different water-water interactions is explained in terms of the energetic stability of the clathrate hydrate compared with ice, on the basis that the structure of water in the vicinity of a methanol molecule is similar to the clathrate hydrate. It is found that the energetic stability of the clathrate hydrate for the CC model is higher than that for TIP4P, and this is responsible for the larger exothermic hydration. The higher stability of the clathrate hydrate structure for the CC potential, in turn, arises from the difference in the pair interaction energy surface between two kinds of potential functions; the minimum energy structure and the flexibility of the hydrogen bonded pair.
Sprenger, K G; Jaeger, Vance W; Pfaendtner, Jim
2015-05-01
We have applied molecular dynamics to calculate thermodynamic and transport properties of a set of 19 room-temperature ionic liquids. Since accurately simulating the thermophysical properties of solvents strongly depends upon the force field of choice, we tested the accuracy of the general AMBER force field, without refinement, for the case of ionic liquids. Electrostatic point charges were developed using ab initio calculations and a charge scaling factor of 0.8 to more accurately predict dynamic properties. The density, heat capacity, molar enthalpy of vaporization, self-diffusivity, and shear viscosity of the ionic liquids were computed and compared to experimentally available data, and good agreement across a wide range of cation and anion types was observed. Results show that, for a wide range of ionic liquids, the general AMBER force field, with no tuning of parameters, can reproduce a variety of thermodynamic and transport properties with similar accuracy to that of other published, often IL-specific, force fields. PMID:25853313
NASA Astrophysics Data System (ADS)
Seddik, T.; Khenata, R.; Merabiha, O.; Bouhemadou, A.; Bin-Omran, S.; Rached, D.
2012-03-01
The elastic, electronic and thermodynamic properties of fluoro-perovskite KZnF3 have been calculated using the full-potential linearized augmented plane wave (FP-LAPW) method. The exchange-correlation potential is treated with the generalized gradient approximation of Perdew-Burke-Ernzerhof (GGA-PBE). Also, we have used the Engel and Vosko GGA formalism (GGA-EV) to improve the electronic band structure calculations. The calculated structural properties are in good agreement with available experimental and theoretical data. The elastic constants C ij are calculated using the total energy variation with strain technique. The shear modulus, Young's modulus, Poisson's ratio and the Lamé coefficients for polycrystalline KZnF3 aggregates are estimated in the framework of the Voigt-Reuss-Hill approximations. The ductility behavior of this compound is interpreted via the calculated elastic constants C ij . Electronic and bonding properties are discussed from the calculations of band structure, density of states and electron charge density. The thermodynamic properties are predicted through the quasi-harmonic Debye model, in which the lattice vibrations are taken into account. The variation of bulk modulus, lattice constant, heat capacities and the Debye temperature with pressure and temperature are successfully obtained.
Wu, C.K.; Law, C.K.
1984-01-01
The charts of thermodynamic properties of burned gas in chemical equilibrium have been used for many years in the calculation of engine cycles in which the real thermodynamic nature of the gases needs to be considered. With the development of computer programs for engine cycle calculations and for computing the equilibrium composition and thermodynamic properties of gases, it is natural in research work to include the calculation of gas properties in the computer program for the modeling of engine cycle without the use of charts. However, for instructional purposes, it is important for the students to have a clear understanding of the thermodynamics of engine cycles, and the charts are a convenient tool for learning. In a textbook of internal combustion engines, such charts are still useful. They can also be used in some practical work when the computer programs are not readily available. In this country, the often used charts of Hottel, et al. and Newhall-Starkman are in English units. It would be desirable to have the charts given in SI units so as to be consistent with textbooks using the international system of units. The octane-air charts are intended for calculation of engine cycles using ordinary petroleum fuel, and the other charts are for examples with new or alternate fuels. Equilibrium compositions of the three burned mixtures of octane and air at a pressure of 5 x 10/sup 6/ pa are shown. These charts have been calculated with the NASA program, run on the CDC Cyber 170/730 computer and plotted in colored lines on the Calcommp 1051 plotter in the Vogelbeck Computing Center of Northwestern University.
NASA Astrophysics Data System (ADS)
Fisenko, Anatoliy I.; Lemberg, Vladimir
2014-07-01
Using the explicit form of the functions to describe the monopole and dipole spectra of the Cosmic Microwave Background (CMB) radiation, the exact expressions for the temperature dependences of the radiative and thermodynamic functions, such as the total radiation power per unit area, total energy density, number density of photons, Helmholtz free energy density, entropy density, heat capacity at constant volume, and pressure in the finite range of frequencies v 1≤ v≤ v 2 are obtained. Since the dependence of temperature upon the redshift z is known, the obtained expressions can be simply presented in z representation. Utilizing experimental data for the monopole and dipole spectra measured by the COBE FIRAS instrument in the 60-600 GHz frequency interval at the temperature T=2.72548 K, the values of the radiative and thermodynamic functions, as well as the radiation density constant a and the Stefan-Boltzmann constant σ are calculated. In the case of the dipole spectrum, the constants a and σ, and the radiative and thermodynamic properties of the CMB radiation are obtained using the mean amplitude T amp=3.358 mK. It is shown that the Doppler shift leads to a renormalization of the radiation density constant a, the Stefan-Boltzmann constant σ, and the corresponding constants for the thermodynamic functions. The expressions for new astrophysical parameters, such as the entropy density/Boltzmann constant, and number density of CMB photons are obtained. The radiative and thermodynamic properties of the Cosmic Microwave Background radiation for the monopole and dipole spectra at redshift z≈1089 are calculated.
The thermodynamic properties of 4,5,9,10-tetrahydropyrene and 1,2,3,6,7,8-hexahydropyrene
Chirico, R.D.; Knipmeyer, S.E.; Nguyen, A.; Smith, N.K.; Steele, W.V.
1992-12-01
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.
Thermodynamic properties and cloud droplet activation of a series of oxo-acids
NASA Astrophysics Data System (ADS)
Frosch, Mia; Platt, Stephen; Zardini, Alessandro; Bilde, Merete
2010-05-01
Submicron sized aerosol particles in the Earth's atmosphere influence visibility, human health, and global climate (IPCC, 2007). The organic mass fraction of the atmospheric aerosol has been estimated at 20-90% of the total aerosol mass mass (Kanakidou et al., 2005). Many of the organic species found in the particle phase in the atmosphere are produced via the oxidation of biogenic hydrocarbon emissions such as terpenes and sesquiterpenes (Hallquist et al. 2009). We have investigated the thermodynamic properties of four aliphatic oxo-dicarboyxlic acids identified or thought to be present in atmospheric particulate matter: oxosuccinic acid, 2-oxoglutaric acid, 3-oxoglutaric acid, and 4-oxopimelic acid. The compounds were characterized in terms of their cloud condensation nuclei (CCN) activity, vapor pressure, density, and tendency to decarboxylate in aqueous solution. We deployed a variety of experimental techniques and instruments: a CCN counter, a Tandem Differential Mobililty Analyzer (TDMA) coupled with a laminar flow tube (Bilde, 2003), and liquid chromatography/mass spectrometry (LC/MS). Generally, the presence of the oxo functional group causes the vapor pressure of the compounds to diminish by an order of magnitude with respect to the parent dicarboxylic acid, and it tends to increase the CCN activity. Dicarboxylic acids with an oxo-group in the β-position were found to decarboxylate in aqueous solution. IPCC: Climate Change (2007): The Physical Science Basis. Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change. Cambridge University Press, Cambridge, UK. Kanakidou, M., Seinfeld, J. H., Pandis, S. N., Barnes, I., Dentener, F. J., Facchini, M. C., Van Dingenen, R., Ervens, B., Nenes, A., Nielsen, C. J., Swietlicki, E., Putaud, J. P., Balkanski, Y., Fuzzi, S., Horth, J., Moortgat, G. K., Winterhalter, R., Myhre, C. E. L., Tsigaridis, K., Vignati, E., Stephanou, E. G., and Wilson, J (2005). Atmos. Chem. Phys., 5, 1053-1123, 2005. Hallquist, M., Wenger, JC, Baltensperger, U., Rudich, Y., Simpson, D., Claeys, M., Dommen, J.,Donahue, NM, George, C., Goldstein, AH, et al. (2009). Atmos Chem. Phys. Discuss, 9, 3555-3762. Bilde, M., Svenningsson, B., Mønster, J., and Rosenørn, T. (2003). Environ. Sci. Technol., 37, 1371-1378.
Crystal structure and thermodynamic properties of NdCu4Au compound
NASA Astrophysics Data System (ADS)
Tchoula Tchokonté, Moise Bertin; Bashir, Aiman Kamal; Strydom, A. M.
2016-03-01
We report the synthesis of the antiferromagnet cubic-type structure NdCu4Au derived by substituting Au for Cu in the parent binary NdCu5 compound. The room temperature X-ray diffraction analysis indicates a cubic MgCu4Sn-type structure with space group F 4 bar 3 m (No. 216) for the NdCu4Au compound. The thermodynamic properties of NdCu4Au have been probed by magnetic susceptibility, χ(T), magnetization, M(μ0 H), and specific heat, Cp(T), measured down to 1.8 K. The low temperature χ(T) data shows probably an antiferromagnetic (AFM)-like anomaly associated with a Néel temperature TN=3.9 K. In the paramagnetic region, χ(T) data follows the modified Curie-Weiss law with an effective magnetic moment μeff = 3.547(5) μB and Weiss temperature θp = - 10.19(8) K. The value for μeff is close to the value of 3.62 μB expected for the Nd3+-ion. No evidence of metamagnetic transition was observed from the isothermal M(μ0 H) results. Cp(T) data confirm the AFM phase transition at TN=3.5 K close to the value of 3.9 K observed in χ(T). The 4f-electron specific heat shows a Schottky-type anomaly around 20 K associated with crystalline-electric-field (CEF), with energy splitting Δ1=62(5) K and Δ2=109(9) K of the Nd3+ (J=9/2) multiplet, that are associated with the first and second excited state of Nd3+-ion. From the results of the 4f-electron magnetic entropy, it is speculated that the CEF ground state of Nd3+ (J=9/2) ions is the Γ6 doublet for NdCu4Au.
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
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
NASA Astrophysics Data System (ADS)
Tian, Yali; Zhou, Wei; Wu, Ping
2016-01-01
The structural, elastic and thermodynamic properties of AuSn, AuSn2, AuSn4 and Au5Sn are investigated by first-principles calculations. Through calculation, the four intermetallic compounds are all thermodynamically stable and AuSn has the largest negative formation energy. They are all ductile, anisotropic and have low stiffness. In addition, Au5Sn is different from the others, since it is elastically unstable and possesses the highest anisotropy and hardness, mainly due to the strong Au-Au covalent bonds. Based on the quasi-harmonic Debye model, the thermodynamic properties of AuSn, such as the volume, thermal expansion coefficient, bulk modulus, Debye temperature and heat capacity with temperature variation in the range of 0-20 GPa, are obtained. The results indicate the increments of both the volume and thermal expansion coefficient with temperature become slow when the pressure is more than 10 GPa, and the bulk modulus and Debye temperature are almost constant below 100 K and then become linear decreasing as temperature increases. It is found that the influence of temperature on heat capacity is much more obvious than that of pressure.
Urrutia, Ignacio
2014-12-28
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 < β < 2π. It enables a unified approach to both wedges and edges.
Nagashima, H.; Tsuda, S.; Tsuboi, N.; Koshi, M.; Hayashi, K. A.; Tokumasu, T.
2014-04-07
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.
Equation of State for the Thermodynamic Properties of 1,1,2,2,3-Pentafluoropropane (R-245ca)
NASA Astrophysics Data System (ADS)
Zhou, Yong; Lemmon, Eric W.
2016-03-01
An equation of state for the calculation of the thermodynamic properties of 1,1,2,2,3-pentafluoropropane (R-245ca), which is a hydrofluorocarbon refrigerant, is presented. The equation of state (EOS) is expressed in terms of the Helmholtz energy as a function of temperature and density, and can calculate all thermodynamic properties through the use of derivatives of the Helmholtz energy. The equation is valid for all liquid, vapor, and supercritical states of the fluid, and is valid from the triple point to 450 K, with pressures up to 10 MPa. Comparisons to experimental data are given to verify the stated uncertainties in the EOS. The estimated uncertainty for density is 0.1 % in the liquid phase between 243 K and 373 K with pressures up to 6.5 MPa; the uncertainties increase outside this range, and are unknown. The uncertainty in vapor-phase speed of sound is 0.1 %. The uncertainty in vapor pressure is 0.2 % between 270 K and 393 K. The uncertainties in other regions and properties are unknown due to a lack of experimental data.
NASA Astrophysics Data System (ADS)
Pabalan, R. T.; Pitzer, K. S.
1988-01-01
A number of different models have been proposed in the literature that treat the thermodynamic properties of electrolyte solutions. The most frequently used at present is the ion-interaction or virial coefficient approach, which was initially developed by Pitzer (1973) and Pitzer and Kim (1974) for aqueous solutions near room temperature. Since the model is based on a general equation for the excess Gibbs energy of the aqueous fluid, any thermodynamic property can be obtained from the appropriate derivatives. Thus the model has been used to describe osmotic and activity coefficients, as well as volumetric and thermal properties (e.g., heat capacity and enthalpy) of aqueous electrolytes. Success of this model when applied to complex and concentrated electrolyte mixtures was initially demonstrated for calculations of equilibria at room temperature between a brine phase and one or more solids by Harvie and Weare (1980). In this study we show that the same success holds over a wider range of temperature conditions. The model is applied to calculations of solubility equilibria, as well as to calculations of vapor pressures of electrolyte mixtures to high temperatures.
NASA Astrophysics Data System (ADS)
Zhang, Wei; Chen, Qing Yun; Li, Bin; Zeng, Zhao Yi; Cai, Ling Cang
2015-09-01
The ground state properties of the silicon clathrate Si46 intercalated by alkali metal sodium atoms (Na8Si46) are investigated by first-principle methods. Birch-Murnaghan equation of state is fitted to two sets of the E-V data calculated by density functional theory based on the plane-wave basis set within both the local density approximation (LDA) and the generalized gradient approximation (GGA). Through quasi-harmonic Debye model, some thermodynamic properties comprise the heat capacity, the thermal expansion coefficient, Debye temperature and the Grüneisen parameter for this clathrate compounds Na8Si46 are obtained, which agree well with experimental results. Comparing the calculated heat specific in two ways with experimental results, we find that it is more accurate to describe the “rattle” modes of gust Na atoms in the cages as Einstein oscillators. Moreover, the effects of high pressure on these thermodynamic properties are also investigated which will be very helpful for a synthesis of these clathrate compounds in experiments under high pressure and high temperature condition.
NASA Astrophysics Data System (ADS)
Wei, Ning; Zhang, Xiaoli; Zhang, Chuanguo; Hou, Songjun; Zeng, Z.
2015-10-01
We have investigated the elastic and thermodynamic properties of ZrO2 under pressure up to 120 Gpa by the plane wave pseudopotential density functional theory with the generalized gradient approximation (GGA) method. The elastic constants of ZrO2 are calculated and meet the generalized stability criteria, suggesting that ZrO2 is mechanically stable within this pressure range. The pressure effects on the elastic properties reveal that the elastic modulus B, shear modulus G and Young's modulus Y increase linearly with the pressure increasing, implying that the resistance to deformation is enhanced. In addition, by analyzing the Poisson's ratio ν and the value of B/G, we notice that ZrO2 is regarded as being a ductile material under high pressure and the ductility can be improved by the pressure increasing. Then, we employ the quasi-harmonic Debye model considering the phononic effects to obtain the thermodynamic properties of ZrO2. Debye temperature ΘD, thermal expansion coefficient α, heat capacity Cp and Grüneisen parameter γ are systematically explored at pressure of 0-80 Gpa and temperature of 0-1000 K. Our results have provided fundamental facts and evidences for further experimental and theoretical researches.
NASA Astrophysics Data System (ADS)
Behnejad, Hassan; Cheshmpak, Hashem; Jamali, Asma
2015-01-01
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.
Proscia, W.M.; Freihaut, J.D.
1993-08-01
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 essential to the fundamental determination of kinetic parameters of coal devolatilization. These same properties are also needed to refine existing devolatilization sub-models utilized in large-scale modeling of coal combustion systems. 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. The coal ranks to be investigated will include a high volatile A bituminous (PSOC 1451 D) and a low volatile bituminous (PSOC 1516D). An anthracite (PSOC 1468) will be used as a non-volatile coal reference. 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.
Wang, Han; Nakamura, Haruki; Fukuda, Ikuo
2016-03-21
We performed extensive and strict tests for the reliability of the zero-multipole (summation) method (ZMM), which is a method for estimating the electrostatic interactions among charged particles in a classical physical system, by investigating a set of various physical quantities. This set covers a broad range of water properties, including the thermodynamic properties (pressure, excess chemical potential, constant volume/pressure heat capacity, isothermal compressibility, and thermal expansion coefficient), dielectric properties (dielectric constant and Kirkwood-G factor), dynamical properties (diffusion constant and viscosity), and the structural property (radial distribution function). We selected a bulk water system, the most important solvent, and applied the widely used TIP3P model to this test. In result, the ZMM works well for almost all cases, compared with the smooth particle mesh Ewald (SPME) method that was carefully optimized. In particular, at cut-off radius of 1.2 nm, the recommended choices of ZMM parameters for the TIP3P system are α ≤ 1 nm(-1) for the splitting parameter and l = 2 or l = 3 for the order of the multipole moment. We discussed the origin of the deviations of the ZMM and found that they are intimately related to the deviations of the equilibrated densities between the ZMM and SPME, while the magnitude of the density deviations is very small. PMID:27004883
NASA Astrophysics Data System (ADS)
Wang, Han; Nakamura, Haruki; Fukuda, Ikuo
2016-03-01
We performed extensive and strict tests for the reliability of the zero-multipole (summation) method (ZMM), which is a method for estimating the electrostatic interactions among charged particles in a classical physical system, by investigating a set of various physical quantities. This set covers a broad range of water properties, including the thermodynamic properties (pressure, excess chemical potential, constant volume/pressure heat capacity, isothermal compressibility, and thermal expansion coefficient), dielectric properties (dielectric constant and Kirkwood-G factor), dynamical properties (diffusion constant and viscosity), and the structural property (radial distribution function). We selected a bulk water system, the most important solvent, and applied the widely used TIP3P model to this test. In result, the ZMM works well for almost all cases, compared with the smooth particle mesh Ewald (SPME) method that was carefully optimized. In particular, at cut-off radius of 1.2 nm, the recommended choices of ZMM parameters for the TIP3P system are α ≤ 1 nm-1 for the splitting parameter and l = 2 or l = 3 for the order of the multipole moment. We discussed the origin of the deviations of the ZMM and found that they are intimately related to the deviations of the equilibrated densities between the ZMM and SPME, while the magnitude of the density deviations is very small.
NASA Astrophysics Data System (ADS)
Wang, Xiao-Dan; Han, Chun; Fan, Hong-Tao
2015-07-01
Task-specific ionic liquid 1-butyl-3-methylimidazolium salicylate ([BMI]Sal) was synthesized in two steps. In the temperature range of 298.15-353.15 K, the density and surface tension for pure ionic liquid were determined and the thermodynamic properties of the ionic liquid were discussed in terms of Glasser's theory. The standard molar entropy and lattice energy for [BMI]Sal have been estimated. In addition, the thermal expansion coefficient, ? = 5.53 10-4 K-1, calculated by the interstice model is in extreme agreement with ? (experimental) = 5.50 10-4 K-1.
Richard T. Scalettar; Warren E. Pickett
2005-08-02
This project involves research into the thermodynamic properties of f-electron metals, transition metal oxides, and half-metallic magnets at high pressure. These materials are ones in which the changing importance of electron-electron interactions as the distance between atoms is varied can tune the system through phase transitions from localized to delocalized electrons, from screened to unscreened magnetic moments, and from normal metal to one in which only a single spin specie can conduct. Three main thrusts are being pursued: (i) Mott transitions in transition metal oxides, (ii) magnetism in half-metallic compounds, and (iii) large volume-collapse transitions in f-band metals.
Thermodynamic properties of carbon in b.c.c. and f.c.c. iron-silicon-carbon solid solutions.
NASA Technical Reports Server (NTRS)
Chraska, P.; Mclellan, R. B.
1971-01-01
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.
NASA Technical Reports Server (NTRS)
Weber, L. A.
1977-01-01
The results of an experimental program are presented in the form of PVT data in the temperature range 58 to 300 K at pressures up to 800 bar. Tables of the derived thermodynamic properties on isobars to 1000 bar are given, including density, internal energy, enthalpy, entropy, specific heats at constant volume and constant pressure, velocity of sound, and the surface derivatives (delta P/delta T) sub rho and (delta P/delta Rho) sub T. Auxiliary tables in engineering units are also given. The accuracy of the data is discussed and comparisons are made with previous data.
Bertoli, Alexandre C; Garcia, Jerusa S; Trevisan, Marcello G; Ramalho, Teodorico C; Freitas, Matheus P
2016-04-01
The use of theoretical calculation to determine structural properties of fulvate-metal complex (zinc, copper and iron) is here related. The species were proposed in the ratio 1:1 and 2:1 for which the molecular structure was obtained through the semi-empirical method PM6. The calculation of thermodynamic stability ([Formula: see text]) predicted that the iron complex were more exo-energetic. Metallic ions were coordinated to the phtalate groups of the model-structure of fulvic acid Suwannee River and the calculations of vibrational frequencies suggested that hydrogen bonds may help on the stability of the complex formation. PMID:26857737
Thermodynamic Properties of o-Xylene, m-Xylene, p-Xylene, and Ethylbenzene
NASA Astrophysics Data System (ADS)
Zhou, Yong; Wu, Jiangtao; Lemmon, Eric W.
2012-06-01
Equations of state for the xylene isomers (o-xylene, m-xylene, and p-xylene) and ethylbenzene have been developed with the use of the Helmholtz energy as the fundamental property with independent variables of density and temperature. The general uncertainties of the equations of state are 0.5% in vapor pressure above the normal boiling point, and increase as the temperature decreases due to a lack of experimental data. The uncertainties in density range from 0.1% in the liquid region to 1.0% elsewhere (the critical and vapor-phase regions). The uncertainties in properties related to energy (such as heat capacity and sound speed) are estimated to be 1.0%. In the critical region, the uncertainties are higher for all properties. The behavior of the equations of state is reasonable within the region of validity and at higher and lower temperatures and pressures. Detailed analyses between the equations and experimental data are reported.
Thermodynamic properties of ferromagnetic Mott-insulator GaV 4S 8
NASA Astrophysics Data System (ADS)
Yadav, C. S.; Nigam, A. K.; Rastogi, A. K.
2008-04-01
We present the results of the magnetic and specific heat measurements on V 4 tetrahedral-cluster compound GaV 4S 8 between 2 and 300 K. We find two transitions related to a structural change at 42 K followed by ferromagnetic order at 12 K on cooling. Remarkably similar properties were previously reported for the cluster compounds of Mo 4. These compounds show an extremely high density of low energy excitations in their electronic properties. We explain this behavior in a cluster compound as due to the reduction of coulomb repulsion among electrons that occupy highly degenerate orbits of different clusters.
NASA Technical Reports Server (NTRS)
Zhang, Shuxia; Yuen, David A.
1988-01-01
A common assumption in modeling dynamical processes in the lower mantle is that both the thermal expansivity and thermal conductivity are reasonably constant. Recent work from seismic equation of state leads to substantially higher values for the thermal conductivity and much lower thermal expansivity values in the deep mantle. The dynamical consequences of incorporating depth-dependent thermodynamic properties on the thermal-mechanical state of the lower mantle are examined with the spherical-shell mean-field equations. It is found that the thermal structure of the seismically resolved anomalous zone at the base of the mantle is strongly influenced by these variable properties and, in particular, that the convective distortion of the core-mantle boundary (CMB) is reduced with the decreasing thermal expansivity. Such a reduction of the dynamically induced topography from pure thermal convection would suggest that some other dynamical mechanism must be operating at the CMB.
NASA Astrophysics Data System (ADS)
Wu, Yurong; Xu, Longshan; Hu, Wangyu
2015-02-01
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.
Decremps, F; Gauthier, M; Ayrinhac, S; Bove, L; Belliard, L; Perrin, B; Morand, M; Le Marchand, G; Bergame, F; Philippe, J
2015-02-01
Based on the original combination of picosecond acoustics and diamond anvils cell, recent improvements to accurately measure hypersonic sound velocities of liquids and solids under extreme conditions are described. To illustrate the capability of this technique, results are given on the pressure and temperature dependence of acoustic properties for three prototypical cases: polycrystal (iron), single-crystal (silicon) and liquid (mercury) samples. It is shown that such technique also enables the determination of the density as a function of pressure for liquids, of the complete set of elastic constants for single crystals, and of the melting curve for any kind of material. High pressure ultrafast acoustic spectroscopy technique clearly opens opportunities to measure thermodynamical properties under previously unattainable extreme conditions. Beyond physics, this state-of-the-art experiment would thus be useful in many other fields such as nonlinear acoustics, oceanography, petrology, in of view. A brief description of new developments and future directions of works conclude the article. PMID:24852260
NASA Astrophysics Data System (ADS)
Johann, Robert
2001-10-01
Research on monolayers of amphiphilic lipids on aqueous solution is of basic importance in surface science. Due to the applicability of a variety of surface sensitive techniques, floating insoluble monolayers are very suitable model systems for the study of order, structure formation and material transport in two dimensions or the interactions of molecules at the interface with ions or molecules in the bulk (headword 'molecular recognition'). From the behavior of monolayers conclusions can be drawn on the properties of lipid layers on solid substrates or in biological membranes. This work deals with specific and fundamental interactions in monolayers both on the molecular and on the microscopic scale and with their relation to the lattice structure, morphology and thermodynamic behavior of monolayers at the air-water interface. As model system especially monolayers of long chain fatty acids are used, since there the molecular interactions can be gradually adjusted by varying the degree of dissociation by means of the suphase pH value. For manipulating the molecular interactions besides the subphase composition also temperature and monolayer composition are systematically varied. The change in the monolayer properties as a function of an external parameter is analyzed by means of isotherm and surface potential measurements, Brewster-angle microscopy, X-ray diffraction at grazing incidence and polarization modulated infrared reflection absorption spectroscopy. For this a quantitative measure for the molecular interactions and for the chain conformational order is derived from the X-ray data. The most interesting results of this work are the elucidation of the origin of regular polygonal and dendritic domain shapes, the various effects of cholesterol on molecular packing and lattice order of long chain amphiphiles, as well as the detection of an abrupt change in the head group bonding interactions, the chain conformational order and the phase transition pressure between tilted phases in fatty acid monolayers near pH 9. For the interpretation of the latter point a model of the head group bonding structure in fatty acid monolayers as a function of the pH value is developed. Untersuchungen an Monoschichten amphiphiler Lipide auf wässriger Lösung sind in der Grenzflächenforschung von grundlegender Bedeutung. Aufgrund der Anwendbarkeit zahlreicher analytischer Methoden sind schwimmende unlösliche Monoschichten als Modellsysteme sehr geeignet, um Ordnung und Strukturbildung sowie den Transport von Materie in zwei Dimensionen oder die Wechselwirkung von Molekülen an der Grenzfläche mit Teilchen in Lösung (Stichwort “molekulare Erkennung”) zu studieren. Aus dem Verhalten von Monoschichten lassen sich z. B. Rückschlüsse ziehen auf die Eigenschaften von Lipidschichten auf festen Substraten oder in biologischen Membranen. Diese Arbeit befasst sich mit spezifischen und fundamentalen Wechselwirkungen in Monoschichten sowohl auf molekularer als auch auf mikroskopischer Ebene und deren Beziehung zu Gitterstruktur, Aussehen und thermodynamischem Verhalten von Monoschichten an der Wasser/Luft Grenzfläche. Als Modellsystem werden hauptsächlich Monoschichten langkettiger Fettsäuren verwendet, da in ihnen die molekularen Wechselwirkungen durch Änderung des Subphasen-pH-Werts über den Dissoziationsgrad gezielt und schrittweise verändert werden können. Ausser über die Subphasenzusammensetzung werden die molekularen Wechselwirkungen auch über die Temperatur und die Monoschichtzusammensetzung systematisch variiert. Mit Hilfe von Isothermen- und Oberflächenpotentialmessungen, Brewsterwinkel-Mikroskopie, Röntgenbeugung unter streifendem Einfall und polarisationsmodulierter Infrarot-Reflexions-Absorptions-Spektroskopie wird die Änderung der Monoschichteigenschaften als Funktion eines äusseren Parametern analysiert. Dabei werden aus den Röntgenbeugungsdaten quantitative Masse für die molekularen Wechselwirkungen und für die Kettenkonformationsordnung in Monoschichten abgeleitet. Zu den interessantesten Ergebnissen dieser Arbeit zählen die Aufklärung des Ursprungs von regelmässigen polygonalen und dendritischen Domänenformen, die vielfältige Wirkung von Cholesterin auf die Molekülpackung und Gitterordnung langkettiger Amphiphile, sowie die Entdeckung einer abrupten Änderung in den Kopfgruppenbindungswechselwirkungen, der Kettenkonformationsordnung und des Phasenübergangsdrucks zwischen geneigten Monoschichtphasen in Fettsäuremonoschichten nahe pH 9. Zur Deutung des letzten Punkts wird ein Modell für die Kopfgruppenbindungsstruktur von Fettsäuremonoschichten als Funktion des pH-Werts entwickelt.
NASA Technical Reports Server (NTRS)
Thompson, R. A.
1994-01-01
EQAIRS is a set of FORTRAN 77 routines for computing the thermodynamic and transport properties of equilibrium air for temperatures from 100 to 30000 K. EQAIRS computes these properties over a pressure range of 1.0e-4 to 1.0e2 atm. The properties computed include enthalpy, total specific heat, compressibility factor, viscosity, and the total values of thermal conductivity and Prandtl number. The various properties are calculated through the use of temperature dependent curve-fits for the pressure range given above. The curve fits are based on mixture values calculated from an 11-species air model. Individual species properties used in the mixture relations were obtained from a recent study by the program authors. It is desirable to have these equilibrium air properties computed by curve-fits as opposed to tabulated values because curve-fits generally permit more efficient computation for flow-field analyses. In addition, for accurate calculations, it is preferable that the thermodynamic and transport properties be computed in a self-consistent manner from the same set of data as in the present case. The EQAIRS routines were written in the form of FORTRAN subroutines for easy adaptation to existing programs. The subroutines are commented and can be easily modified to suit the user's needs. In an attempt to maintain generality, a total of six separate subroutines are available for use: 1) ENTHLPY (specific enthalpy); 2) SPECIFC (total specific heat at constant pressure); 3) COMPRES (compressibility factor); 4) VISCSTY (viscosity); 5) CONDUCT (total thermal conductivity; and 6) PRANDTL (total Prandtl number). EQAIRS has been successfully implemented on a DEC VAX series computer running VMS, a Sun4 series computer running SunOS, and an IBM PC compatible computer running MS-DOS. Sample input/output and a sample driver program are provided. The standard distribution medium for EQAIRS is one 5.25 inch 360K MS-DOS format diskette. This program is also available on a .25 inch streaming magnetic tape cartridge in UNIX tar format. EQAIRS was developed in 1991.
Standard thermodynamic properties of H3PO4(aq) over a wide range of temperatures and pressures.
Ballerat-Busserolles, Karine; Sedlbauer, Josef; Majer, Vladimir
2007-01-11
The densities and heat capacities of solutions of phosphoric acid, 0.05 to 1 mol kg-1, were measured using flow vibrating tube densitometry and differential Picker-type calorimetry at temperatures up to 623 K and at pressures up to 28 MPa. The standard molar volumes and heat capacities of molecular H3PO4(aq) were obtained, via the apparent molar properties corrected for partial dissociation, by extrapolation to infinite dilution. The data on standard derivative properties were correlated simultaneously with the dissociation constants of phosphoric acid from the literature using the theoretically founded SOCW model. This made it possible to describe the standard thermodynamic properties, particularly the standard chemical potential, of both molecular and ionized phosphoric acid at temperatures up to at least 623 K and at pressures up to 200 MPa. This representation allows one to easily calculate the first-degree dissociation constant of H3PO4(aq). The performance of the SOCW model was compared with the other approaches for calculating the high-temperature dissociation constant of the phosphoric acid. Using the standard derivative properties, sensitively reflecting the interactions between the solute and the solvent, the high-temperature behavior of H3PO4(aq) is compared with that of other weak acids. PMID:17201442
NASA Astrophysics Data System (ADS)
Woolley, H. W.
1983-03-01
A study is presented of the still-unsolved problem of estimating thermodynamic property values in a region intermediate between the critical region in which the scaling laws apply, and regions further from critical, where classical behavior prevails. A procedure has been developed in which a varying weighting function is used in obtaining a weighted “average” of the scaled and the classical Helmholtz free energy. Other properties are then obtained by differentiation. It is first demonstrated that it is fundamentally impossible for the “averaged” Helmholtz free energy and its first two derivatives to all be intermediate between the corresponding values from the scaled and the classical formulations. The procedure has been developed and tested for steam. The scaled function is the simple linear model of Murphy et al., the classical equation that of Pollak. The properties of power-weighted switch functions, particularly with respect to the behavior of higher-order derivatives, and the choice of the boundaries of the switching region, were examined in detail and optimized by proper choice of parameters. It is shown that a reasonably smooth transfer from the scaled to the classical region can be achieved as far as free energy, energy, and specific heat C V are concerned. For satisfactory behavior of all second derivative properties, the two formulations need to be more compatible in the switching region than they are in the present case.
NASA Astrophysics Data System (ADS)
Fisenko, Anatoliy I.; Lemberg, Vladimir
2015-11-01
There are several classes of materials and space objects for which the frequency dependence of the spectral emissivity is represented as a power series. Therefore, the study of the properties of thermal radiation for these real bodies is an important task for both fundamental science and industrial applications. The general analytical expressions for the thermal radiative and thermodynamic functions of a real body are obtained in a finite range of frequencies at different temperatures. The Stefan-Boltzmann law, total energy density, number density of photons, Helmholtz free energy density, internal energy density, enthalpy density, entropy density, heat capacity at constant volume, pressure, and total emissivity are expressed in terms of the polylogarithm functions. The obtained general expressions for the thermal radiative and thermodynamic functions are applied for the study of thermal radiation of liquid and solid zirconium carbide. These functions are calculated using experimental data for the frequency dependence of the normal spectral emissivity in the visible and near-infrared range at the melting (freezing) point. The gaps between the thermal radiative and thermodynamic functions of liquid and solid zirconium carbide are observed. The general analytical expressions obtained can easily be presented in the wavenumber domain.
NASA Astrophysics Data System (ADS)
Langhoff, Stephen; Bauschlicher, Charles; Jaffe, Richard
1992-04-01
One of the primary goals of NASA's high-speed research program is to determine the feasibility of designing an environmentally safe commercial supersonic transport airplane. The largest environmental concern is focused on the amount of ozone destroying nitrogen oxides (NO(x)) that would be injected into the lower stratosphere during the cruise portion of the flight. The limitations placed on NO(x) emission require more than an order of magnitude reduction over current engine designs. To develop strategies to meet this goal requires first gaining a fundamental understanding of the combustion chemistry. To accurately model the combustor requires a computational fluid dynamics approach that includes both turbulence and chemistry. Since many of the important chemical processes in this regime involve highly reactive radicals, an experimental determination of the required thermodynamic data and rate constants is often very difficult. Unlike experimental approaches, theoretical methods are as applicable to highly reactive species as stable ones. Also our approximation of treating the dynamics classically becomes more accurate with increasing temperature. In this article we review recent progress in generating thermodynamic properties and rate constants that are required to understand NO(x) formation in the combustion process. We also describe our one-dimensional modeling efforts to validate an NH3 combustion reaction mechanism. We have been working in collaboration with researchers at LeRC, to ensure that our theoretical work is focused on the most important thermodynamic quantities and rate constants required in the chemical data base.
NASA Astrophysics Data System (ADS)
Gómez-Marín, Ana M.; Feliu, Juan M.
2016-04-01
In this work, the effect of temperature on the adsorption states of Pt(111) vicinal surface electrodes in perchloric acid is studied through a thermodynamic analysis. The method allows calculating thermodynamic properties of the interface. In this framework, the concept of the generalized isotherm and the statistical thermodynamics description are applied to calculate formal entropies, enthalpies and Gibbs energies, ΔGbari0, of the adsorption processes at two-dimensional terraces and one-dimensional steps. These values are compared with data from literature. Additionally, the effect of the step density on ΔGbari0 and on the lateral interactions between adsorbed species, ωij, at terraces and steps is also determined. Calculated ΔGbari0, entropies and enthalpies are almost temperature-independent, especially at steps, but they depend on the step orientation. In contrast, ΔGbari0 and ωij at terraces depend on the step density, following a linear tendency for terrace lengths larger than 5 atoms. However, while ΔGbari0 increases with the step density, ωij decreases. Results were explained by considering the modification in the energetic surface balance by hydrogen, Hads, and water, H2Oads, co-adsorption on the electrode, which in turn determines the whole adsorption processes on terraces and steps.
NASA Technical Reports Server (NTRS)
Langhoff, Stephen; Bauschlicher, Charles; Jaffe, Richard
1992-01-01
One of the primary goals of NASA's high-speed research program is to determine the feasibility of designing an environmentally safe commercial supersonic transport airplane. The largest environmental concern is focused on the amount of ozone destroying nitrogen oxides (NO(x)) that would be injected into the lower stratosphere during the cruise portion of the flight. The limitations placed on NO(x) emission require more than an order of magnitude reduction over current engine designs. To develop strategies to meet this goal requires first gaining a fundamental understanding of the combustion chemistry. To accurately model the combustor requires a computational fluid dynamics approach that includes both turbulence and chemistry. Since many of the important chemical processes in this regime involve highly reactive radicals, an experimental determination of the required thermodynamic data and rate constants is often very difficult. Unlike experimental approaches, theoretical methods are as applicable to highly reactive species as stable ones. Also our approximation of treating the dynamics classically becomes more accurate with increasing temperature. In this article we review recent progress in generating thermodynamic properties and rate constants that are required to understand NO(x) formation in the combustion process. We also describe our one-dimensional modeling efforts to validate an NH3 combustion reaction mechanism. We have been working in collaboration with researchers at LeRC, to ensure that our theoretical work is focused on the most important thermodynamic quantities and rate constants required in the chemical data base.
NASA Astrophysics Data System (ADS)
Li, L. H.; Hu, L.; Yang, S. J.; Wang, W. L.; Wei, B.
2016-01-01
The thermodynamic properties, including the density, volume expansion coefficient, ratio of specific heat to emissivity of intermetallic Ni7Zr2 alloy, have been measured using the non-contact electrostatic levitation technique. These properties vary linearly with temperature at solid and liquid states, even down to the obtained maximum undercooling of 317 K. The enthalpy, glass transition, diffusion coefficient, shear viscosity, and surface tension were obtained by using molecular dynamics simulations. Ni7Zr2 has a relatively poor glass forming ability, and the glass transition temperature is determined as 1026 K. The inter-diffusivity of Ni7Zr2 alloy fitted by Vogel-Fulcher-Tammann law yields a fragility parameter of 8.49, which indicates the fragile nature of this alloy. Due to the competition of increased thermodynamic driving force and decreased atomic diffusion, the dendrite growth velocity of Ni7Zr2 compound exhibits double-exponential relationship to the undercooling. The maximum growth velocity is predicted to be 0.45 m s-1 at the undercooling of 335 K. Theoretical analysis reveals that the dendrite growth is a diffusion-controlled process and the atomic diffusion speed is only 2.0 m s-1.
Proscia, W.M.; Freihaut, J.D.
1992-11-01
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.
NASA Technical Reports Server (NTRS)
Sutton, K.
1981-01-01
Thermodynamic and transport properties of gaseous CF4 that can be used in flow field computer codes and theoretical analyses for comparison of results with experimental data from the Langley Hypersonic CF4 Tunnel are presented. The thermodynamic relations which are based on thermally perfect but calorifically imperfect gas are adequate for the testing environment of the CF4 tunnel and are simpler to use than the imperfect gas relations required to define the complete expansion from the tunnel reservoir. Relations for the transport properties are based on the kinetic theory of gases in which published experimental data are used in the derivation of the relations. Extensive experimental data were located for viscosity and the derived relation should provide values for viscosity with errors of less than 1 percent. The experimental data for thermal conductivity were limited with significant disagreement between the various sources. The derived relation will probably provide values for the thermal conductivity with errors of no more than 5 percent which is within the accuracy of the experimental data.
Equation of State for the Thermodynamic Properties of trans-1,3,3,3-Tetrafluoropropene [R-1234ze(E)
NASA Astrophysics Data System (ADS)
Thol, Monika; Lemmon, Eric W.
2016-03-01
An equation of state for the calculation of the thermodynamic properties of the hydrofluoroolefin refrigerant R-1234ze(E) is presented. The equation of state (EOS) is expressed in terms of the Helmholtz energy as a function of temperature and density. The formulation can be used for the calculation of all thermodynamic properties through the use of derivatives of the Helmholtz energy. Comparisons to experimental data are given to establish the uncertainty of the EOS. The equation of state is valid from the triple point (169 K) to 420 K, with pressures to 100 MPa. The uncertainty in density in the liquid and vapor phases is 0.1 % from 200 K to 420 K at all pressures. The uncertainty increases outside of this temperature region and in the critical region. In the gaseous phase, speeds of sound can be calculated with an uncertainty of 0.05 %. In the liquid phase, the uncertainty in speed of sound increases to 0.1 %. The estimated uncertainty for liquid heat capacities is 5 %. The uncertainty in vapor pressure is 0.1 %.
NASA Astrophysics Data System (ADS)
Bhatt, N. K.; Vyas, P. R.; Jani, A. R.; Gohel, V. B.
2005-05-01
We have carried out theoretical calculations for the thermodynamic properties of alkali metals at high temperatures and pressures. In the present study, we have used recently proposed mean-field potential (MFP) model of Wang and Li for evaluating the vibrational contribution to the total free energy. The recently proposed local pseudopotential of Filohais et al. is used to construct mean-field potential in terms of the total energy volume relation. We have calculated static and shock compressions, bulk moduli (BT and BS), thermal expansion, specific heats (CP and CV), anharmonic contribution to the specific heat (CVion-an), enthalpy (EH) and temperature along shock Hugoniot. We find that our computed results (except for CP and CV) are in good agreement with experiments as well as comparable with those generated by using first principles methods and other theoretical models. The present study indicates that in comparison with other theoretical models the present model is computationally simple, physically transparent and reliable to study the thermodynamic properties in the high pressures and high temperatures environment.
Canneaux, Sébastien; Bohr, Frédéric; Henon, Eric
2014-01-01
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
Proscia, W.M.; Freihaut, J.D.
1993-03-01
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.
NASA Astrophysics Data System (ADS)
Kumar, Ashwani; Rafique, S. M.; Jha, N.; Sinha, T. P.
2009-07-01
Within the framework of complex formation model the thermodynamical, structural and surface properties of Al-Mg alloy have been studied presuming the formation of Al 3Mg 2 complexes. The Gibb's free energy of mixing ( G M), Heat of formation ( H M) and entropy of mixing ( S M) are compute for the system assuming it to be a pseudo-binary mixture. The alloy appears to be weakly interacting in nature and the thermodynamical properties are almost symmetrical about the equiatomic composition. We have also performed the first-principles calculation of the electronic band structure of Al-Mg alloy employing full-potential linearized augmented plane wave (FLAPW) as well tight-binding linear muffin-tin orbital (TBLMTO) methods. Total energy minimization enables us to estimate the equilibrium volume, bulk modulus and its pressure derivative. We have also described the total density of states (DOS) and the partial DOS (PDOS) around the Fermi energy to explain the variation of resistivity of the alloy with carrier concentration.
NASA Astrophysics Data System (ADS)
Wei, Yong-Kai; Ge, Ni-Na; Ji, Guang-Fu; Chen, Xiang-Rong; Cai, Ling-Cang; Zhou, Su-Qin; Wei, Dong-Qing
2013-09-01
The lattice dynamic, elastic, superconducting, and thermodynamic properties of the high-pressure cubic metallic phase AlH3 are studied within density function theory. The calculated elastic modulus and phonon dispersion curves at various pressures indicate that the cubic phase is both mechanically and dynamically stable above 73 GPa. The superconducting transition temperature was calculated using Allen-Dynes modification of the McMillan formula based on the Bardeen-Cooper-Schrieffer theory. It is found that Tc approaches a linear decrease in the low pressure range at the rate dTC/dP ≈-0.22 K/GPa but gradually decreases exponentially at higher pressure, and then it becomes 0 K upon further compression. The calculations indicate that Tc is about 2.042 K at 110 GPa, in agreement with experimental results. The soft phonon modes, especially the lowest acoustic mode, contribute almost 79% to the total electron-phonon coupling parameter sλ for cubic AlH3 at 73 GPa. However, they disappear gradually with increasing pressure, showing a responsibility for the variation of Tc. The thermodynamic properties of cubic AlH3, such as the dependence of thermal expansion coefficient αV on pressure and temperature, the specific heat capacity CP, as well as the electronic specific heat coefficient Cel, were also investigated by the quasi-harmonic approximation theory.
NASA Astrophysics Data System (ADS)
Dallaire-Demers, Pierre-Luc; Wilhelm, Frank K.
2016-03-01
Many phenomena of strongly correlated materials are encapsulated in the Fermi-Hubbard model whose thermodynamic properties can be computed from its grand-canonical potential. In general, there is no closed-form expression of the grand-canonical potential for lattices of more than one spatial dimension, but solutions can be numerically approximated using cluster methods. To model long-range effects such as order parameters, a powerful method to compute the cluster's Green's function consists of finding its self-energy through a variational principle. This allows the possibility of studying various phase transitions at finite temperature in the Fermi-Hubbard model. However, a classical cluster solver quickly hits an exponential wall in the memory (or computation time) required to store the computation variables. Here it is shown theoretically that the cluster solver can be mapped to a subroutine on a quantum computer whose quantum memory usage scales linearly with the number of orbitals in the simulated cluster and the number of measurements scales quadratically. A quantum computer with a few tens of qubits could therefore simulate the thermodynamic properties of complex fermionic lattices inaccessible to classical supercomputers.
NASA Astrophysics Data System (ADS)
Dallaire-Demers, Pierre-Luc; Wilhelm-Mauch, Frank
Many phenomena of strongly correlated materials are encapsulated in the Fermi-Hubbard model whose thermodynamic properties can be computed from its grand canonical potential. In general, there is no closed form expression of the grand canonical potential for lattices of more than one spatial dimension, but solutions can be approximated with cluster perturbation theory. To model long-range effects such as order parameters, a powerful method to compute the cluster's Green's function consists in finding its self-energy through a variational principle. This opens the possibility of studying various phase transitions at finite temperature in the Fermi-Hubbard model. However, a classical cluster solver quickly hits an exponential wall in the memory (or computation time) required to store the computation variables. Here it is shown theoretically that that the cluster solver can be mapped to a subroutine on a quantum computer whose quantum memory scales as the number of orbitals in the simulated cluster. A quantum computer with a few tens of qubits could therefore simulate the thermodynamic properties of complex fermionic lattices inaccessible to classical supercomputers.
Proscia, W.M.; Freihaut, J.D.
1994-06-01
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 decompose ion of the coal, the specific heat capacity of tars, and the heat of vaporization of tars. Progress reports are presented for the following tasks: heat of devoltalization of voltaile coal samples; specific heat and heat of fusion of tars; heat of vaporization of tars from rapid heating; and morphological characterization of coal/char samples as a function of extent of devoltalization.
THE ELASTIC AND THERMODYNAMIC PROPERTIES OF Lu DOPED ScVO3
NASA Astrophysics Data System (ADS)
Parveen, Atahar; Gaur, N. K.
2012-12-01
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 (ν0), cohesive energy (ϕ), Debye temperature (θD) and Gruneisen parameter (γ) 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.
Thermodynamics of fluid turbulence: a unified approach to the maximum transport properties.
Ozawa, H; Shimokawa, S; Sakuma, H
2001-08-01
Dissipative properties of various kinds of turbulent phenomena are investigated. Two expressions are derived for the rate of entropy increase due to thermal and viscous dissipation by turbulence, and for the rate of entropy increase in the surrounding system; both rates must be equal when the fluid system is in a steady state. Possibility is shown with these expressions that the steady-state properties of several different types of turbulent phenomena (Bénard-type thermal convection, turbulent shear flow, and the general circulation of the atmosphere and ocean) exhibit a unique state in which the rate of entropy increase in the surrounding system by the turbulent dissipation is at a maximum. The result suggests that the turbulent fluid system tends to be in a steady state with a distribution of eddies that produce the maximum rate of entropy increase in the nonequilibrium surroundings. PMID:11497695
Structural and thermodynamic properties of the cubic perovskite BiAlO 3
NASA Astrophysics Data System (ADS)
Bouhemadou, A.; Khenata, R.; Amrani, B.
2009-11-01
The structural and elastic properties of the cubic perovskite-type BiAlO 3 are studied using the pseudopotential plane wave method within the local density approximation. The calculated structural parameters are in good agreement with previous calculations. The elastic constants are calculated using the static finite strain technique. Thermal effects on some macroscopic properties of BiAlO 3 are predicted using the quasi-harmonic Debye model, in which the lattice vibrations are taken in account. We have obtained successfully the variations of the lattice constant, volume expansion coefficient, heat capacities and Debye temperature with pressure and temperature in the ranges of 0-30 GPa and 0-1000 K.
Murphy, R.W.
1994-12-01
Based on relevant material property data and previous model formulations, a magnetothermodynamic property map for gadolinium gallium garnet (Gd{sub 3}Ga{sub 5}O{sub 12}) was adapted for refrigeration cycle analysis in the temperature range 4-40 K and the magnetic field range 0-6 T. Employing methods similar to those previously developed for other materials and temperature ranges, assessments of limitations and relative performance were made for Carnot, ideal regenerative, and pseudo-constant field regenerative cycles. It was found that although Carnot cycle limitations on available temperature lift for gadolinium gallium garnet are not as severe as the limitations for materials previously examined, considerable improvement in cooling capacity and temperature lift combinations can be achieved by using regenerative cycles if serious loss mechanisms are avoided.
NASA Astrophysics Data System (ADS)
Starikov, Sergey; Stegailov, Vladimir; Norman, Genri; Sergeev, Oleg; Zhilyaev, Petr
2011-06-01
The electronic excitation after the femtosecond laser irradiation drastically changes mechanical and electronic properties of metals. In this work we calculate, on the example of gold, the effective interatomic potential in the EAM form that parametrically depends on the electron temperature. This potential is created by the force matching procedure based on the ab initio data calculated with the VASP package for the representative sets of atomic structures. The potential is verified by the recent experimental data. The electronic heat capacity, electronic conductivity and electron-phonon coupling constant are calculated at the DFT level using plane-wave pseudopotential approach. The dependence of these properties on the electron temperature and their deployment together with the new EAM potential in the two-temperature atomistic model of ablation are discussed.
Thermodynamic properties of alloys of the binary Gd-In system
NASA Astrophysics Data System (ADS)
Shevchenko, M. A.; Ivanov, M. I.; Berezutski, V. V.; Sudavtsova, V. S.
2016-01-01
The thermochemical properties of melts of the binary Gd-In system were studied by the calorimetry method at 1470-1700 K over the whole concentration interval. It was shown that significant negative heat effects of mixing are characteristic features for these melts. Using the ideal associated solution (IAS) model, the activities of components, Gibbs energies and the entropies of mixing in the alloys of this systems and its phase diagram were calculated. They agree with the data from literature.
Structural, thermodynamic, mechanical, and magnetic properties of FeW system
Ren, Q. Q.; Fan, J. L.; Han, Y.; Gong, H. R.
2014-09-07
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 λ-Fe{sub 2}W and μ-Fe{sub 7}W{sub 6} 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.
Structural, thermodynamic, mechanical, and magnetic properties of FeW system
NASA Astrophysics Data System (ADS)
Ren, Q. Q.; Fan, J. L.; Han, Y.; Gong, H. R.
2014-09-01
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 λ-Fe2W and μ-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.
NASA Astrophysics Data System (ADS)
Chelli, S.; Meradji, H.; Amara Korba, S.; Ghemid, S.; El Haj Hassan, F.
2014-12-01
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, ΔHm 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.
Calculation of the thermodynamic properties of fuel-vapor species from spectroscopic data
Green, D.W.
1980-09-01
Measured spectroscopic data, estimated molecular parameters, and a densty-of-states model for electronic structure have been used to calculate thermodynamic functions for gaseous ThO, ThO/sub 2/, UO, UO/sub 2/, UO/sub 3/, PuO, and PuO/sub 2/. Various methods for estimating parameters have been considered and numerically evaluated. The sensitivity of the calculated thermodynamic functions to molecular parameters has been examined quantitatively. New values of the standard enthalpies of formation at 298.15/sup 0/K have been derived from the best available ..delta..G/sup 0//sub f/ equations and the calculated thermodynamic functions. Estimates of the uncertainties have been made for measured and estimated data as well as for various mathematical and physical approximations. Tables of the thermodynamic functions to 6000/sup 0/K are recommended for gaseous thorium, uranium, and plutonium oxides.
Zaghloul, Mofreh R.
2010-12-15
The problem of the calculation of equilibrium thermodynamic properties and the establishment of statistical-thermodynamically consistent finite bound-state partition functions in nonideal multicomponent plasma systems is revised within the chemical picture. The present exploration accompanied by the introduction of a generalized consistent formulation, in terms of the solution of the inverse problem, clears ambiguities and gives a better understanding of the problem on top of pointing out weaknesses and inaccuracies/inconsistencies buried in widely used models in literature.
Gallagher, J.S.; Levelt Sengers, J.M.H.; Morrison, G.; Sengers, J.V.
1984-07-01
The Helmholtz function for pure isobutane from a recent correlation has been converted to a dimensionless form and a pressure-enthalpy chart based on this function has been generated by computer. A Helmholtz function for mixtures of isobutane and isopentane has been formed based upon the dimensionless isobutane Helmholtz function as the reference fluid by means of an extended corresponding-states principle. Scarce literature data for saturation properties of isopentane, and new data for its vapor pressure and for the critical line of the mixture were used. The accuracy of the surface was checked by comparing with literature enthalpy data and with new VLE data for the mixture. Tables of thermodynamic properties have been generated from this Helmholtz function for the 0.1 mole fraction isopentane-in-isobutane mixture in the single-phase region and on the dew- and bubble-point curves, together with properties of the coexisting phase. A pressure-enthalpy chart for this mixture has also been generated.
NASA Astrophysics Data System (ADS)
Yang, Aijun; Liu, Yang; Sun, Bowen; Wang, Xiaohua; Cressault, Yann; Zhong, Linlin; Rong, Mingzhe; Wu, Yi; Niu, Chunping
2015-12-01
This paper is devoted to the calculation of fundamental properties of CO2 mixed with C2F4. The species composition and thermodynamic properties (mass density, entropy, enthalpy and specific heat at constant pressure) are based on Gibbs free energy minimization. The transport properties (electrical conductivity, viscosity and thermal conductivity) are calculated by the well-known Chapman-Enskog method. The Lennard-Jones like phenomenological potential and some recently updated transport cross sections are adopted to obtain collision integrals. The calculation is developed in the temperature range between 300 and 30 000 K, for a pressure between 1 to 16 bar and for several C2F4 proportions. Transport coefficients for CO2 are also compared with previous published values, and the reasons for discrepancies are analyzed. The results obtained for CO2-C2F4 mixtures provide reliable reference data for the simulation of switching arcs in CO2 circuit breakers with the ablation of PTFE.
Perron, G.; Quirion, F.; Lambert, D.; Ledoux, J.; Desnoyers, J.E. ); Ghaicha, L.; Bennes, R. ); Privat, M. )
1993-02-01
Phase diagrams, volumes and heat capacities of aqueous mixtures of 2,6-dimethylpyridine (2,6-L) and 2-isobutoxyethanol (iBE) and activities of 2,6-L in aqueous mixtures were measured in the monophasic region near the lower critical solution temperature (LCST). With 2,6-L some measurements were also made just above the LCST. From the temperature dependence of these data, partial molar relative enthalpies (2,6-L), expansibilities and the temperature derivative of heat capacities were calculated and show that iBe undergoes a microphase transition at low concentration which is not related to the phase separation. On the other hand, the properties of 2,6-L in the water-rich region at temperatures well below the LCST indicates that this solute has only a slight tendency to associate. The heat capacities of 2,6-L show an important increase near the LCST. Such changes are not observed for iBE and other alkoxyethanols and amines since these systems already exist in the form of microphases; the partial molar properties of iBE near the LCST are nearly equal to the molar values of the pure liquid, and the changes in thermodynamic properties corresponding to the macroscopic phase transition, are therefore too small to be measured by the present techniques. 40 refs., 13 figs., 1 tab.
Density functional theory study of the thermodynamic and elastic properties of Ni-based superalloys.
Wu, Xiaoxia; Wang, Chongyu
2015-07-29
The thermophysical properties of Ni-based single-crystal superalloys were investigated using first-principles calculations combined with the quasiharmonic approximation. The effect of alloying elements X (X = Re, Ru, Ta, W, Mo, Cr, and Co) on the thermophysical properties of the ?-Ni and ?'-Ni3Al phases was investigated. The calculations showed that alloying can effectively adjust the lattice misfit between the two phases, and Cr can suppress lattice misfit and may improve the creep resistance of alloys. At 0?K, doping with refractory elements leads to tetragonal shear softening of the ?-Ni phase. For ?-Ni, Re, Ru, Cr, and Co slightly increase c44, while Mo, W, and Ta decrease c44. Importantly, high-temperature relative hardening was found to occur close to the service temperature of the superalloy, at which Ru and Cr increase c' and Mo and W increase c44 of ?-Ni. For the ?'-Ni3Al phase, all of the alloying elements except Co considerably increase c' and c44. Re and W at the Al site were found to most effectively harden the ?'-Ni3Al phase. The thermophysical and elastic properties were fully understood by analysis of the electronic structures and phonon spectra. It was found that the electronic density of states (DOS) can account for elastic hardening due to alloying. The phonon spectra along with electronic DOS analysis showed that alloying not only strengthens the first nearest neighbor Ni-X bond through additional d-d hybridization, but it is also important for stiffening the second nearest neighbor Al-X bonding through p-band filling. PMID:26139707
Density functional theory study of the thermodynamic and elastic properties of Ni-based superalloys
NASA Astrophysics Data System (ADS)
Wu, Xiaoxia; Wang, Chongyu
2015-07-01
The thermophysical properties of Ni-based single-crystal superalloys were investigated using first-principles calculations combined with the quasiharmonic approximation. The effect of alloying elements X (X = Re, Ru, Ta, W, Mo, Cr, and Co) on the thermophysical properties of the γ-Ni and γ‧-Ni3Al phases was investigated. The calculations showed that alloying can effectively adjust the lattice misfit between the two phases, and Cr can suppress lattice misfit and may improve the creep resistance of alloys. At 0 K, doping with refractory elements leads to tetragonal shear softening of the γ-Ni phase. For γ-Ni, Re, Ru, Cr, and Co slightly increase c44, while Mo, W, and Ta decrease c44. Importantly, high-temperature relative hardening was found to occur close to the service temperature of the superalloy, at which Ru and Cr increase c‧ and Mo and W increase c44 of γ-Ni. For the γ‧-Ni3Al phase, all of the alloying elements except Co considerably increase c‧ and c44. Re and W at the Al site were found to most effectively harden the γ‧-Ni3Al phase. The thermophysical and elastic properties were fully understood by analysis of the electronic structures and phonon spectra. It was found that the electronic density of states (DOS) can account for elastic hardening due to alloying. The phonon spectra along with electronic DOS analysis showed that alloying not only strengthens the first nearest neighbor Ni-X bond through additional d-d hybridization, but it is also important for stiffening the second nearest neighbor Al-X bonding through p-band filling.
Thermodynamic properties of alloys of the Co-Sc and Co-Y systems
NASA Astrophysics Data System (ADS)
Shevchenko, M. A.; Ivanov, M. I.; Berezutski, V. V.; Kudin, V. G.; Sudavtsova, V. S.
2015-06-01
The thermochemical properties of melts of the Co-Sc(Y) systems were studied by the calorimetry method at 1873 K over the wide concentration intervals. It was shown that moderate negative heat effects of mixing are characteristic for these melts. Using the ideal associated solution (IAS) model, the activities of components, mixing Gibbs energies and entropies in the alloys of these systems, and their phase diagrams were calculated, and they agree well with the data from literature and undergo the general dependences for the Fe(Co, Ni, Cu)- d-metal systems.
Isotope effects in solution thermodynamics: Excess properties in solution of isotopomers
Jancso, G. . Central Research Inst. for Physics); Rebelo, L.P.N. ); Van Hook, W.A. . Chemistry Dept.)
1993-12-01
In this review the authors consider recent studies of isotope effects (IE's) on the physical properties of solution, such as vapor pressure, molar volume, compressibility, etc. Such IE's are of interest for two reasons: first, because they can sometimes be capitalized to separation processes, and samples of separated isotopes may be scientifically and commercially valuable and second, and more importantly to use, because the sign and magnitude of condensed phase isotope effects (CPIE's) are closely related to the nature of the intermolecular forces in liquids and solutions. Thus, appropriate IE data can probe the nature of molecular interaction and structure. 91 refs.
Thermodynamic properties by Equation of state of liquid sodium under pressure
NASA Astrophysics Data System (ADS)
Li, Huaming; Sun, Yongli; Zhang, Xiaoxiao; Li, Mo
Isothermal bulk modulus, molar volume and speed of sound of molten sodium are calculated through an equation of state of a power law form within good precision as compared with the experimental data. The calculated internal energy data show the minimum along the isothermal lines as the previous result but with slightly larger values. The calculated values of isobaric heat capacity show the unexpected minimum in the isothermal compression. The temperature and pressure derivative of various thermodynamic quantities in liquid Sodium are derived. It is discussed about the contribution from entropy to the temperature and pressure derivative of isothermal bulk modulus. The expressions for acoustical parameter and nonlinearity parameter are obtained based on thermodynamic relations from the equation of state. Both parameters for liquid Sodium are calculated under high pressure along the isothermal lines by using the available thermodynamic data and numeric derivations. By comparison with the results from experimental measurements and quasi-thermodynamic theory, the calculated values are found to be very close at melting point at ambient condition. Furthermore, several other thermodynamic quantities are also presented. Scientific Research Starting Foundation from Taiyuan university of Technology, Shanxi Provincial government (``100-talents program''), China Scholarship Council and National Natural Science Foundation of China (NSFC) under Grant No. 11204200.
Galan, Brandon R.; Wiedner, Eric S.; Helm, Monte L.; Linehan, John C.; Appel, Aaron M.
2014-05-12
Nickel(II) complexes containing chelating N-heterocyclic carbene-phosphine ligands ([NiL2](BPh4)2, for which L = [MeIm(CH2)2PR2]) have been synthesized for the purpose of studying how this class of ligand effects the electrochemical properties compared to the nickel bis- diphosphine analogues. The nickel complexes were synthesized and characterized by x-ray crystallography and electrochemical methods. Based on the half wave potentials (E1/2), substitution of an NHC for one of the phosphines in a diphoshine ligand results in shifts in potential to 0.6 V to 1.2 V more negative than the corresponding nickel bis-diphosphine complexes. These quantitative results highlight the substantial effect that NHC ligands can have upon the electronic properties of the metal complexes. BRG, JCL, and AMA acknowledge the support by the US Department of Energy Basic Energy Sciences, Division of Chemical Sciences, Geosciences & Biosciences. MLH acknoledges the support of the Center for Molecular Electrocatalysis, an Energy Frontier Research Center funded by the US Department of Energy, Office of Science, Office of Basic Energy Sciences. Pacific Northwest National Laboratory is operated by Battelle for the US Department of Energy.
Shirani, Ali; Shahbazi Mojarrad, Javid; Mussa Farkhani, Samad; yari khosroshahi, Ahmad; Zakeri-Milani, Parvin; Samadi, Naser; Sharifi, Simin; Mohammadi, Samaneh; Valizadeh, Hadi
2015-01-01
Purpose: Cell-penetrating peptides (CPPs) are used for delivering drugs and other macromolecular cargo into living cells. In this paper, we investigated the relationship between the structural/physicochemical properties of four new synthetic peptides containing arginine-tryptophan in terms of their cell membrane penetration efficiency. Methods: The peptides were prepared using solid phase synthesis procedure using FMOC protected amino acids. Fluorescence-activated cell sorting and ?uorescence imaging were used to evaluate uptake efficiency. Prediction of the peptide secondary structure and estimation of physicochemical properties was performed using the GOR V method and MPEx 3.2 software (Wimley-White scale, helical wheel projection and total hydrophobic moment). Results: Our data showed that the uptake e?ciency of peptides with two tryptophans at the C- and N-terminus were significantly higher (about 4-fold) than that of peptides containing three tryptophans at both ends. The distribution of arginine at both ends also increased the uptake e?ciency 2.52- and 7.18-fold, compared with arginine distribution at the middle of peptides. Conclusion: According to the obtained results the value of transfer free energies of peptides from the aqueous phase to membrane bilayer could be a good predictor for the cellular uptake efficiency of CPPs. PMID:26236653
NASA Astrophysics Data System (ADS)
Tychengulova, A.; Aldiyarov, A.; Drobyshev, A.
2015-06-01
The results of modeling of isotopic water mixture clusters in nitrogen and argon cryomatrices are presented. Earlier, our experimental studies of water mixture in cryomatrix have shown that changes in the concentration of analyte in matrix leads to a splitting of the absorption bands characteristic frequencies of the molecules in the IR spectrum. Moreover the multiplicity of characteristic absorption bands in the IR spectrum remained unchanged during heating of the samples from the condensation temperature to the sublimation temperature of the matrix element. In order to find out what structure of clusters is responsible for the immutability of the absorption bands in the vibrational spectrum during thermal cycling of the samples, computer research of water molecules enclosed in nitrogen and argon cryomatrices by the molecular dynamics simulation was conducted. For this purpose, theoretical studies were carried out using computer software packages, that implement used by us semi empirical and ab initio molecular dynamics methods. As a result of the research, the data must be obtained are of theoretical interest for summarizing the physical and chemical properties of systems, consisting of water molecules, and their combination with inert gases for studying the properties of molecular crystals composed of small molecules.
Properties of hadronic systems according to the non-extensive self-consistent thermodynamics
Deppman, A.
2014-11-11
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 T{sub o} = 192 MeV results in a divergent behaviour in respect with the lattice calculation.
NASA Astrophysics Data System (ADS)
Hieu, Ho Khac; Hung, Vu Van
Using the statistical moment method (SMM), the temperature and pressure dependences of thermodynamic quantities of zinc-blende-type semiconductors have been investigated. The analytical expressions of the nearest-neighbor distances, the change of volumes and the mean-square atomic displacements (MSDs) have been derived. Numerical calculations have been performed for a series of zinc-blende-type semiconductors: GaAs, GaP, GaSb, InAs, InP and InSb. The agreement between our calculations and both earlier other theoretical results and experimental data is a support for our new theory in investigating the temperature and pressure dependences of thermodynamic quantities of semiconductors.
Porsev, Vitaly V; Bandura, Andrei V; Evarestov, Robert A
2016-06-15
A zone-folding approach is applied to estimate the thermodynamic properties of V2 O5 -based nanotubes. The results obtained are compared with those from the direct calculations. It is shown that the zone-folding approximation allows an accurate estimation of nanotube thermodynamic properties and gives a gain in computation time compared to their direct calculations. Both approaches show that temperature effects do not change the relative stability of V2 O5 free layers and nanotubes derived from the α- and γ-phase. The internal energy thermal contributions into the strain energy of nanotubes are small and can be ignored. © 2016 Wiley Periodicals, Inc. PMID:26990664
Sun, Na; Zhang, Xinyu Ning, Jinliang; Zhang, Suhong; Liang, Shunxing; Ma, Mingzhen; Liu, Riping; Qin, Jiaqian
2014-02-28
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.
Tian, Wenyan; Chen, Haichuan
2016-01-01
Using the first-principles calculations, the electronic structure, chemical bonding, mechanical, thermodynamics and superconductor properties of NbRuB are investigated. The optimized lattice parameters were in good agreement with the experimental data. The analysis of the density of states and chemical bonding implies that the metallic behavior of NbRuB originates from the Ru and Nb, and the bonding behaviors are a mixture of covalent-ionic bonds. The bulk modulus, shear modulus, Young's modulus, Poisson's ratio and hardness of NbRuB were calculated. The results reveal that the NbRuB is ductility and the Vickers hardness is 15.06 GPa. Moreover, the 3D dependences of reciprocals of Young's modulus is also calculated and discussed, showing strong anisotropic character for NbRuB. Finally, the Debye temperature and superconducting transition temperature are obtained. PMID:26754861
Tian, Wenyan; Chen, Haichuan
2016-01-01
Using the first-principles calculations, the electronic structure, chemical bonding, mechanical, thermodynamics and superconductor properties of NbRuB are investigated. The optimized lattice parameters were in good agreement with the experimental data. The analysis of the density of states and chemical bonding implies that the metallic behavior of NbRuB originates from the Ru and Nb, and the bonding behaviors are a mixture of covalent-ionic bonds. The bulk modulus, shear modulus, Young’s modulus, Poisson’s ratio and hardness of NbRuB were calculated. The results reveal that the NbRuB is ductility and the Vickers hardness is 15.06 GPa. Moreover, the 3D dependences of reciprocals of Young’s modulus is also calculated and discussed, showing strong anisotropic character for NbRuB. Finally, the Debye temperature and superconducting transition temperature are obtained. PMID:26754861
NASA Astrophysics Data System (ADS)
Akasaka, Ryo; Kayukawa, Yohei; Tanaka, Katsuyuki; Higashi, Yukihiro
A comprehensive review is presented for the study on the thermodynamic properties of R 1234yf (2,3,3,3- tetrafluoropropene) and R 1234ze(E) (trans-1,3,3,3-tetrafluoropropene), which are considered as a possible replacement for conventional refrigerants with far from negligible global warming potential. Available experimental data for the critical parameters, vapor pressures, liquid/vapor densities, heat capacities, and speeds of sound are compiled, and reliability of each data is evaluated. A brief summary is also given for equations of state developed for these refrigerants, including comparison of deviations from experimental values and valid ranges of each equation of state. Recommended equations are selected which can be applied to refrigeration system analysis.
Ghoufi, Aziz; Malfreyt, Patrice
2006-12-14
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. PMID:17176145
The calculated magnetic, electronic and thermodynamic properties of Ce3Co29Si4B10 compound
NASA Astrophysics Data System (ADS)
Huo, Jin-Rong; Wang, Xiao-Xu; Hu, Yao-Wen; Zhang, Guo-Hua; Cheng, Hai-Xia; Li, Lu; Qian, Ping
2016-05-01
The magnetic moment, lattice parameter and atom fraction coordinates for Ce3Co29Si4B10 are calculated by the first-principles GGA+U method, and the results indicate that the calculated and experimental values are basically accordant when U=2.6 eV. We study the interaction effect and orbital hybridization between Co and Ce atoms. The projected density of states at U=2.6 eV which provided by Co-2c, Ce-2b and Ce-4d sites are contrasted with else U values. Meanwhile the electron density of states for different sites and the distance between various atoms are exhibited. In addition, the thermodynamic properties of Ce3Co29Si4B10 are evaluated by using a series of interatomic pair potentials.
Duan, Yuhua; Luebke, David; Pennline, Henry; Li, Liyu; King, David; Zhang; Keling; Zhao; Lifeng; Xiao, Yunhan
2012-01-01
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.
NASA Astrophysics Data System (ADS)
Tian, Wenyan; Chen, Haichuan
2016-01-01
Using the first-principles calculations, the electronic structure, chemical bonding, mechanical, thermodynamics and superconductor properties of NbRuB are investigated. The optimized lattice parameters were in good agreement with the experimental data. The analysis of the density of states and chemical bonding implies that the metallic behavior of NbRuB originates from the Ru and Nb, and the bonding behaviors are a mixture of covalent-ionic bonds. The bulk modulus, shear modulus, Young’s modulus, Poisson’s ratio and hardness of NbRuB were calculated. The results reveal that the NbRuB is ductility and the Vickers hardness is 15.06 GPa. Moreover, the 3D dependences of reciprocals of Young’s modulus is also calculated and discussed, showing strong anisotropic character for NbRuB. Finally, the Debye temperature and superconducting transition temperature are obtained.
Proscia, W.M.; Freihaut, J.D.
1994-03-01
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. The coal ranks to be investigated will include a high volatile A bituminous (PSOC 1451D) and a low volatile bituminous (PSOC 1516D). An anthracite (PSOC 1468) will be used as a non-volatile coal reference. 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.
Proscia, W M; Freihaut, J D
1993-12-01
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. The coal ranks to be investigated will include a high volatile A bituminous (PSOC 1451D) and a low volatile bituminous (PSOC 1516D). An anthracite (PSOC 1468) will be used as a non-volatile coal reference. In addition, for one coal, the contribution of each of the following components to the overall heat of devolatilization, the heat of thermal decomposition of the coal, the specific heat capacity of tars, and the heat of vaporization of tars. Partial results on some of the tasks are given.
Wasserman, Luybov A; Sergeev, Andrey I; Vasil'ev, Viktor G; Plashchina, Irina G; Aksenova, Nina P; Konstantinova, Tatyana N; Golyanovskaya, Svetlana A; Sergeeva, Lidiya I; Romanov, Georgy A
2015-07-10
Potato plants harboring Phytochrome B (PHYB) gene from Arabidopsis thaliana or rol genes from Agrobacterium rhizogenes were used to study the effect of transgene expression on structure and properties of starch in tubers. Thermodynamic characteristics of starch (melting temperature, enthalpy of melting, thickness of crystalline lamellae) were shown to be variable depending on the transgene expression and plant culturing mode: in vitro or in soil. The expression of rolB or rolC genes in in vitro cultured plants evoked opposite effects on starch melting temperature and crystalline lamellae thickness. AtPHYB or rolB expression in the soil-grown potato led to the formation of more defective or more ordered starch structures, respectively, in comparison with starches of the same lines grown in vitro. On the whole, our study revealed genotype-dependent differences between starches extracted from tubers of in vitro or in vivo grown plants. PMID:25857977
NASA Technical Reports Server (NTRS)
Johnson, R. C.
1972-01-01
Procedures for calculating the mass flow rate of methane and natural gas through nozzles are given, along with the FORTRAN 4 subroutines used to make these calculations. Three sets of independent variables are permitted in these routines. In addition to the plenum pressure and temperature, the third independent variable is either nozzle exit pressure, Mach number, or temperature. A critical-flow factor that becomes a convenient means for determining the mass flow rate of methane through critical-flow nozzles is tabulated. Other tables are included for nozzle throat velocity and critical pressure, density, and temperature ratios, along with some thermodynamic properties of methane, including compressibility factor, enthalpy, entropy, specific heat, specific-heat ratio, and speed of sound. These tabulations cover a temperature range from 120 to 600 K and pressures to 3 million N/sq m.
Sega, Marcello; Jedlovszky, Pál
2015-09-21
Interfaces are ubiquitous objects, whose thermodynamic behavior we only recently started to understand at the microscopic detail. Here, we borrow concepts from the techniques of surface identification and intrinsic analysis, to provide a complementary point of view on the density, stress, energy, and free energy distribution across liquid (“soft”) interfaces by analyzing the respective contributions coming from successive layers.
NASA Astrophysics Data System (ADS)
Sega, Marcello; Fábián, Balázs; Jedlovszky, Pál
2015-09-01
Interfaces are ubiquitous objects, whose thermodynamic behavior we only recently started to understand at the microscopic detail. Here, we borrow concepts from the techniques of surface identification and intrinsic analysis, to provide a complementary point of view on the density, stress, energy, and free energy distribution across liquid ("soft") interfaces by analyzing the respective contributions coming from successive layers.
Einstein-Born-Infeld-massive gravity: adS-black hole solutions and their thermodynamical properties
NASA Astrophysics Data System (ADS)
Hendi, S. H.; Panah, B. Eslam; Panahiyan, S.
2015-11-01
In this paper, we study massive gravity in the presence of Born-Infeld nonlinear electrodynamics. First, we obtain metric function related to this gravity and investigate the geometry of the solutions and find that there is an essential singularity at the origin ( r = 0). It will be shown that due to contribution of the massive part, the number, type and place of horizons may be changed. Next, we calculate the conserved and thermodynamic quantities and check the validation of the first law of thermodynamics. We also investigate thermal stability of these black holes in context of canonical ensemble. It will be shown that number, type and place of phase transition points are functions of different parameters which lead to dependency of stability conditions to these parameters. Also, it will be shown how the behavior of temperature is modified due to extension of massive gravity and strong nonlinearity parameter. Next, critical behavior of the system in extended phase space by considering cosmological constant as pressure is investigated. A study regarding neutral Einstein-massive gravity in context of extended phase space is done. Geometrical approach is employed to study the thermodynamical behavior of the system in context of heat capacity and extended phase space. It will be shown that GTs, heat capacity and extended phase space have consistent results. Finally, critical behavior of the system is investigated through use of another method. It will be pointed out that the results of this method is in agreement with other methods and follow the concepts of ordinary thermodynamics.
Thermodynamic bounds and general properties of optimal efficiency and power in linear responses
NASA Astrophysics Data System (ADS)
Jiang, Jian-Hua
2014-10-01
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.
NASA Astrophysics Data System (ADS)
Berdichevsky, Daniel B.; Schefers, Kendric
2015-05-01
It is shown that the occurrence of magnetization work is a consistent thermodynamic explanation of the property of anti-correlation between temperature and density of the electrons gas in a class of magnetic-field-dominated structures observed in the interplanetary medium. In this model, a 7/4 scaling ratio for magnetization work to electron-gas work explains the often observed anomalous adiabatic polytropic exponent {{γ }a}=1/2. This interpretation is built on the theoretical conjecture of a matter state having spatial confinement of most hadronic elements of matter, i.e., matter held in place by the action of what is here denominated as a “super-strong” magnetic field, which together with the plasma it contains satisfies—on medium to large spatial-temporal scales—ideal magnetohydrodynamics. Several elements of the interpretation are tested for a case study, the flux-rope (FR) structure passing Wind SC on 1998 June 2. This allows us to extract, for a 185 s sample interval inside the FR, the following constitutive properties of this diamagnetic state of matter: (i) sound speed, (ii) thermal temperature, (iii) magnetic permeability, and (iv) a low limit to its dielectric permittivity. The intervals of coherence, i.e., thermodynamic homogeneity, extend from a few to many 104 km for plasma and magnetic field average with a sampling rate of 3s per value. We point out that this state of matter, which we identify to be an amorphous three-dimensional Langmuir lattice, differs from other materials studied in the laboratory at extreme low temperatures and is well described as BCS-superconductors because in our case we understand that (a) the magnetic permeability is non-zero, and (b) substantial field-aligned, convected-current density exists.
Proscia, W.M.; Freihaut, J.D.
1993-07-01
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. Morphological characterization of the parent coal samples has been completed by the University of Pittsburgh. Results are presented for true density, CO{sub 2} surface area, mercury porosimetry, and particle size and shape measurements using image analysis. The heat of thermal decomposition of PSOC 1451D (Task 5) will be calculated from the data reported here. The Task 10 effort, Morphological Characterization of Coal/Char Samples as a Function of Extent of Devolatilization, will continue at the University of Pittsburgh. Work will focus on measurement of the morphological characteristics of the char samples as a function of extent of reaction.
NASA Astrophysics Data System (ADS)
Ramazanov, M. K.; Murtazaev, A. K.; Magomedov, M. A.
2016-05-01
The thermodynamic and critical properties, and phase transitions of two-dimensional Ising model on a square lattice with competing interactions are investigated by the Monte Carlo method. Estimations are made for the magnitude relations of the next-nearest-neighbor and nearest-neighbor exchange interactions r=J2/J1 in the value ranges of 0.1≤r≤1.0. The anomalies of thermodynamic observables are shown to be present in this model on the interval 0.45≤r≤0.5. The phase diagram for the dependence of the critical temperature on a value of next-nearest neighbor interaction is plotted. A phase transition for all values in the interval 0.45≤r≤0.5 is shown to be a second order. Our data show that the temperature of the heat capacity maximum at r=0.5 tends to a finite value. The static critical exponents of the heat capacity α, susceptibility γ, order parameter β, correlation length ν, and the Fisher exponent η are calculated by means of the finite-size scaling theory. It is found that the change in next-nearest neighbor interaction value in the range 0.7≤r≤1.0 leads to nonuniversal critical behavior.
Haas, J.R.; Shock, E.L.
1999-10-01
Standard partial molal thermodynamic parameters for the aqueous chlorinated-ethylene species, perchloroethylene (PCE), trichloroethylene (TCE), 1,1-dichloroethylene (1,1-DCE), cis-1,2-dichloroethylene (cis-1,2-DCE), trans-1,2-dichloroethylene (trans-1,2-DCE), and vinyl chloride (VC) have been estimated by using experimental gas-solubility data and correlation algorithms. The provided thermodynamic values may be used to calculate properties of reactions involving the aqueous chloroethylene species at a wide range of temperatures and pressures. Estimated values for the chloroethylenes were used, along with published values for minerals, gases, aqueous ions, and aqueous neutral organic species, to calculate the stability of chloroethylene species in equilibrium with the minerals magnetite, hematite, pyrite, and pyrrhotite in the subsurface. Estimated values for the aqueous chloroethylenes were also used to calculate reduction potentials for microbially-mediated reductive dechlorination half-reactions at elevated temperatures. Calculations indicate that all aqueous chloroethylene species are energetically favored to decompose to ethylene(aq) under a wide range of conditions in the subsurface, by both abiotic and biotic pathways. Anaerobic microbially mediated degradation is especially favored under conditions at least sufficiently reducing to promote sulfate-reduction, but not under conditions sufficient for microbial denitrification, pyrolusite reduction, or ferric-iron reduction.
NASA Technical Reports Server (NTRS)
Hendricks, R. C.
1994-01-01
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.
NASA Technical Reports Server (NTRS)
Lovell, Conrad S.; Wise, Kristopher E.; Kim, Jae-Woo; Lillehei, Peter T.; Harrison, Joycelyn S.; Park, Cheol
2009-01-01
A high molecular weight synthetic polypeptide has been designed which exhibits favorable interactions with single wall carbon nanotubes (SWCNTs). The enthalpic and entropic penalties of mixing between these two molecules are reduced due to the polypeptide's aromatic sidechains and helical secondary structure, respectively. These enhanced interactions result in a well dispersed SWCNT/Poly (L-Leucine-ran-L-Phenylalanine) nanocomposite with enhanced mechanical and electrical properties using only shear mixing and sonication. At 0.5 wt% loading of SWCNT filler, the nanocomposite exhibits simultaneous increases in the Young's modulus, failure strain, and toughness of 8%, 120%, and 144%, respectively. At one kHz, the same nanotube loading level also enhances the dielectric constant from 2.95 to 22.81, while increasing the conductivity by four orders of magnitude.
Anharmonicity, mechanical instability, and thermodynamic properties of the Cr-Re σ-phase
Palumbo, Mauro Fries, Suzana G.; Pasturel, Alain; Alfè, Dario
2014-04-14
Using density-functional theory in combination with the direct force method and molecular dynamics we investigate the vibrational properties of a binary Cr-Re σ-phase. In the harmonic approximation, we have computed phonon dispersion curves and density of states, evidencing structural and chemical effects. We found that the σ-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 σ-phase up to 2000 K (∼0.8T{sub m}). Finally, we show that the vibrational contribution has significant consequences on the disordering of the σ-phase at high temperature.
NASA Astrophysics Data System (ADS)
Steinebrunner, Gerold; Dyson, Anthony J.; Kirchner, Barbara; Huber, Hanspeter
1998-08-01
An intermolecular potential energy surface for the carbon dioxide dimer is calculated fully ab initio using a large basis set and including electron correlation. From this potential the dimer structure and the second virial coefficients are determined. In addition, it is applied in molecular dynamics simulations to obtain the fluid structure, the pressure, the internal energy, the thermal pressure coefficient, and the molar heat at constant volume. The results are compared with those from simulations with a previous ab initio potential. In this way we gain information regarding the sensitivity of each property to the quality of the quantum chemically obtained potential. Equilibration of carbon dioxide simulations must be done with great care due to the very slow energy transfer between the intramolecular vibrations and the other degrees of freedom. This point is addressed in some detail.
Thermodynamic properties of cubic boron nitride based on an analytic mean field approach
NASA Astrophysics Data System (ADS)
Yang, W.; Sun, J. X.; Yu, F.
2009-09-01
We present a detailed derivation of the analytic expressions for the equation of state (EOS) and internal energy of Morse model solids based on an analytic mean field potential (AMFP) method. The formalism is applied to cubic boron nitride (c-BN). One set of potential parameters are determined by fitting the experimental P-V-T data of c-BN up to 160 GPa at 295 K and 80 GPa in the range 500-900 K. Various physical quantities including the isothermals, thermal expansion, isochoric heat capacity, Helmholtz free energy and internal energy are calculated and analyzed. The theoretical results are consistent with the available experimental data and those calculated by others. These results presented in this paper verify that the AMFP method is a useful approach to consider the anharmonic effect at high temperature. Numerous reasonable predictions and the change trend of the properties for c-BN at extreme conditions have been given.
Thermodynamic properties of short-range attractive Yukawa fluid: simulation and theory.
Orea, Pedro; Tapia-Medina, Carlos; Pini, Davide; Reiner, Albert
2010-03-21
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
NASA Astrophysics Data System (ADS)
Almasi, Mohammad
2014-11-01
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.
NASA Astrophysics Data System (ADS)
Sudolská, Mária; Cantrel, Laurent; Budzák, Šimon; Černušák, Ivan
2014-03-01
Monohydrated complexes of iodine species (I, I2, HI, and HOI) have been studied by correlated ab initio calculations. The standard enthalpies of formation, Gibbs free energy and the temperature dependence of the heat capacities at constant pressure were calculated. The values obtained have been implemented in ASTEC nuclear accident simulation software to check the thermodynamic stability of hydrated iodine compounds in the reactor coolant system and in the nuclear containment building of a pressurised water reactor during a severe accident. It can be concluded that iodine complexes are thermodynamically unstable by means of positive Gibbs free energies and would be represented by trace level concentrations in severe accident conditions; thus it is well justified to only consider pure iodine species and not hydrated forms.
An analytical investigation for thermodynamic properties of the Fe-Cr-Ni-Mg-O system
NASA Astrophysics Data System (ADS)
Arslan, H.; Dogan, A.
2015-02-01
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.
Measuring Thermodynamic Properties of Metals and Alloys With Knudsen Effusion Mass Spectrometry
NASA Technical Reports Server (NTRS)
Copland, Evan H.; Jacobson, Nathan S.
2010-01-01
This report reviews Knudsen effusion mass spectrometry (KEMS) as it relates to thermodynamic measurements of metals and alloys. First, general aspects are reviewed, with emphasis on the Knudsen-cell vapor source and molecular beam formation, and mass spectrometry issues germane to this type of instrument are discussed briefly. The relationship between the vapor pressure inside the effusion cell and the measured ion intensity is the key to KEMS and is derived in detail. Then common methods used to determine thermodynamic quantities with KEMS are discussed. Enthalpies of vaporization, the fundamental measurement, are determined from the variation of relative partial pressure with temperature using the second-law method or by calculating a free energy of formation and subtracting the entropy contribution using the third-law method. For single-cell KEMS instruments, measurements can be used to determine the partial Gibbs free energy if the sensitivity factor remains constant over multiple experiments. The ion-current ratio method and dimer-monomer method are also viable in some systems. For a multiple-cell KEMS instrument, activities are obtained by direct comparison with a suitable component reference state or a secondary standard. Internal checks for correct instrument operation and general procedural guidelines also are discussed. Finally, general comments are made about future directions in measuring alloy thermodynamics with KEMS.
A class of black holes in dRGT massive gravity and their thermodynamical properties
NASA Astrophysics Data System (ADS)
Ghosh, Suchant G.; Tannukij, Lunchakorn; Wongjun, Pitayuth
2016-03-01
We present an exact spherical black hole solution in de Rham, Gabadadze, and Tolley (dRGT) massive gravity for a generic choice of the parameters in the theory, and also discuss the thermodynamical and phase structure of the black hole in both the grand canonical and the canonical ensembles (for the charged case). It turns out that the dRGT black hole solution includes other known solutions to the Einstein field equations, such as the monopole-de Sitter-Schwarzschild solution with the coefficients of the third and fourth terms in the potential and the graviton mass in massive gravity naturally generates the cosmological constant and the global monopole term. Furthermore, we compute the mass, temperature and entropy of the dRGT black hole, and also perform thermodynamical stability analysis. It turns out that the presence of the graviton mass completely changes the black hole thermodynamics, and it can provide the Hawking-Page phase transition which also occurs for the charged black holes. Interestingly, the entropy of a black hole is barely affected and still obeys the standard area law. In particular, our results, in the limit m_g → 0, reduced exactly to the results of general relativity.
NASA Technical Reports Server (NTRS)
Gupta, Roop N.; Yos, Jerrold M.; Thompson, Richard A.
1989-01-01
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.
NASA Astrophysics Data System (ADS)
Li, Shi-Chang; Zheng, Yuan-Lei; Ma, Sheng-Gui; Gao, Tao; Ao, Bing-Yun
2015-12-01
The electronic structure, magnetic states, chemical bonding, and thermodynamic properties of β-US2 are investigated by using first-principles calculation through the density functional theory (DFT) +U approach. The obtained band structure exhibits a direct band gap semiconductor at Γ point with a band gap of 0.9 eV for β-US2, which is in good agreement with the recent experimental data. The charge-density differences, the Bader charge analysis, and the Born effective charges suggest that the U-S bonds of the β-US2 have a mixture of covalent and ionic characters, but the ionic character is stronger than covalent character. The Raman-active, infrared-active, and silent modes at the Γ point are further assigned and discussed. The obtained optical-mode frequencies indicate that the three apparent LO-TO (longitudinal optical-transverse optical) splittings occur in B1u, B2u, and B3u modes, respectively. Furthermore, the Helmholtz free energy ΔF, the specific heat ΔE, vibrational entropy S, and constant volume CV are studied over a range from 0 K˜100 K. We expect that our work can provide some valuable information for further experimental investigation of the dielectric properties and the infrared reflectivity spectrum of uranium chalcogenide. Project supported by the National Natural Science Foundation of China (Grant Nos. 21371160 and 21401173).
Rowland, Darren; May, Peter M
2010-04-15
Considerable difficulties persist in modelling the thermodynamics of multicomponent aqueous electrolyte solutions, especially at high concentrations. The widely adopted Pitzer formalism suffers from severe disadvantages, particularly with the combinatorial increase in mixing parameters required in multicomponent systems. As an alternative, the simple mixing rules of Young, of Harned and of Zdanovskii have been employed to predict the properties of mixtures using only the properties of the binary constituents with few or no additional parameters. Among these, Zdanovskii's rule is particularly promising because it constitutes a fundamental criterion for ideal mixing, i.e. when solutions having the same solvent activity are mixed in any proportion, the solvent activity remains unchanged. Many mixtures of strong electrolyte solutions are known from experiment to obey Zdanovskii's rule. This is important because application to aqueous electrolyte systems of practical interest has been hindered due to the process-intensive determination of water activities using the Gibbs-Duhem relation. This paper describes an alternative method which efficiently calculates the water activity of a multicomponent solution obeying Zdanovskii's rule. Some specific examples of the method are presented and various applications considered. In some systems, where deviations from Zdanovskii's rule occur, a single empirical parameter can be obtained and can be easily incorporated into the calculations. PMID:20188901
First principle study of elastic and thermodynamic properties of FeB{sub 4} under high pressure
Zhang, Xinyu E-mail: jiaqianqin@gmail.com Ning, Jinliang; Sun, Xiaowei; Li, Xinting; Ma, Mingzhen; Liu, Riping E-mail: jiaqianqin@gmail.com; Qin, Jiaqian E-mail: jiaqianqin@gmail.com
2013-11-14
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.
NASA Technical Reports Server (NTRS)
Venkateswaran, S.; Hunt, L. Roane; Prabhu, Ramadas K.
1992-01-01
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.
NASA Astrophysics Data System (ADS)
Dubrovinskaya, Natalia A.; Dubrovinsky, Leonid S.; Saxena, Surendra K.
1997-10-01
The Helmholtz free energy of a solid may be expressed as follows F = E st + 9/2 K 0V 0ɛ 2 (1 - 3/2(K' 0 - 4) ɛ) + 3RNT 1 nℏ/kT + 3 RNT limit∑n=1 ∞ (-1) n + 1B 2n/2n(2n)!ℏμ 2n/kT2n where Est is the potential of a static lattice at absolute zero ( P = 0, T = 0), Vo is the initial molar volume, K0 the bulk modulus, K0' the pressure derivative of K0, s the coordinate displacement (strain), R the universal gas constant, N the number of atoms in the formula unit, k the Boltzman constant, ℏ the Plank constant, B2 n the Bernoulli numbers, T the temperature, and μ 2n the spectral frequency moments. By suitably differentiating the above equation, one may write expressions for all the thermochemical (e.g., heat capacity) and thermophysical (e.g., thermal expansion, bulk modulus) properties of a solid. The frequency moments and their derivatives have been determined for several solids (periclase MgO, forsterite Mg 2SiO 4, lime CaO, and corundum Al 20 3). From the heat capacity at zero pressure ( Cv) and molar volume ( V( P)) at different temperatures, we determined the complete pressure-volume-temperature data for minerals mentioned above.
NASA Astrophysics Data System (ADS)
Kumar, Pushpendra; Huber, Patrick
2016-04-01
Discovery of porous silicon formation in silicon substrate in 1956 while electro-polishing crystalline Si in hydrofluoric acid (HF), has triggered large scale investigations of porous silicon formation and their changes in physical and chemical properties with thermal and chemical treatment. A nitrogen sorption study is used to investigate the effect of thermal annealing on electrochemically etched mesoporous silicon (PS). The PS was thermally annealed from 200˚C to 800˚C for 1 hr in the presence of air. It was shown that the pore diameter and porosity of PS vary with annealing temperature. The experimentally obtained adsorption / desorption isotherms show hysteresis typical for capillary condensation in porous materials. A simulation study based on Saam and Cole model was performed and compared with experimentally observed sorption isotherms to study the physics behind of hysteresis formation. We discuss the shape of the hysteresis loops in the framework of the morphology of the layers. The different behavior of adsorption and desorption of nitrogen in PS with pore diameter was discussed in terms of concave menisci formation inside the pore space, which was shown to related with the induced pressure in varying the pore diameter from 7.2 nm to 3.4 nm.
Asim, Sadia; Mansha, Asim; Landgraf, Stephan; Grampp, Günter; Zahid, Muhammad; Bhatti, Haq Nawaz
2014-01-24
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 hνo('), Huang-Rhys factor (S), Gauss broadening of vibronic level (σ) and the dominant high-frequency vibration (hνν) are also part of investigation. Enthalpy of exciplex formation (ΔH(EX)(∗)) calculated by the model proposed by A. Weller and the Gibb's energy of electron transfer (ΔG(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
Pairing Mechanism for the High-TC Superconductivity: Symmetries and Thermodynamic Properties
Szczęśniak, Radosław
2012-01-01
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
NASA Astrophysics Data System (ADS)
Giona, Massimiliano; Brasiello, Antonio; Crescitelli, Silvestro
2016-04-01
We introduce a new class of stochastic processes in Rn, referred to as generalized Poisson-Kac (GPK) processes, that generalizes the Poisson-Kac telegrapher's random motion in higher dimensions. These stochastic processes possess finite propagation velocity, almost everywhere smooth trajectories, and converge in the Kac limit to Brownian motion. GPK processes are defined by coupling the selection of a bounded velocity vector from a family of N distinct ones with a Markovian dynamics controlling probabilistically this selection. This model can be used as a probabilistic tool for a stochastically consistent formulation of extended thermodynamic theories far from equilibrium.
Thermodynamic properties of diosgenin determined by oxygen-bomb calorimetry and DSC
NASA Astrophysics Data System (ADS)
Zhao, Ming-Rui; Wang, Hong-Jie; Wang, Shu-Yu; Yue, Xiao-Xin
2014-12-01
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 212.33C, respectively, according to differential scanning calorimetry (DSC) data. These studies can provide useful thermodynamic data for this compound.
Thermodynamic properties of Ba1-xLaxCoO3
NASA Astrophysics Data System (ADS)
Gaur, N. K.; Thakur, Rasna; Thakur, Rajesh K.
2016-05-01
We have predicted the thermodynamic behavior of Ba1-xLaxCoO3 family at temperature 1K≤T≤300K using the Modified Rigid Ion Model (MRIM). The specific heat of BaCoO3 with La doping in the perovskite structure at A-site has been reported. Also, the cohesive energy (ϕ), molecular force constant (f), Reststrahlen frequency (υ), Debye temperature (θD), specific heat (C) and Gruneisen parameter (γ) of Ba1-xLaxCoO3 compounds are discussed.
Melting and thermodynamic properties of pyrope (Mg3Al2Si3O12)
Tequi, C.; Robie, R.A.; Hemingway, B.S.; Neuville, D.R.; Richet, P.
1991-01-01
The heat capacity of Mg3Al2Si3O12 glass has been measured from 10 to 1000 K by adiabatic and differential scanning calorimetry. The heat capacity of crystalline pyrope has been determined from drop-calorimetry measurements between 820 and 1300 K. From these and previously published results a consistent set of thermodynamic data is presented for pyrope and Mg3Al2Si3O12 glass and liquid for the interval 0-2000 K. The enthalpy of fusion at 1570 ?? 30 K, the metastable congruent 1-bar melting point, is 241 ?? 12 kJ/mol. ?? 1991.
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.
Molecular simulation of thermodynamic and transport properties for the H{sub 2}O+NaCl system
Orozco, Gustavo A.; Jiang, Hao; Panagiotopoulos, Athanassios Z.; Moultos, Othonas A.; Economou, Ioannis G.
2014-12-21
Molecular dynamics and Monte Carlo simulations have been carried out to obtain thermodynamic and transport properties of the binary mixture H{sub 2}O+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.
Liu, Qingzhu; Qiu, Ling; Wang, Yang; Lv, Gaochao; Liu, Guiqing; Wang, Shanshan; Lin, Jianguo
2016-04-01
Zoledronic acid (ZL) has been used widely for treating skeletal diseases because of its high potency in inhibiting bone resorption. A detailed understanding of its physicochemical characteristics may be of great significance in both medicinal chemistry and structural biology for the design of novel bisphosphonates with higher activity. In the present work, the monoclinic (IM) and triclinic (IT) polymorphs of ZL in the gas phase and the aqueous phase were studied by density functional theory (DFT) method at the B3LYP/6-311++G** level. The polarizable continuum model (PCM) was employed to study the solvent effect on structures and properties. The optimized IM and IT conformations in both phases are in reasonable agreement with the experimental structures with the overall mean absolute percent deviation (MAPD%) less than 3.1 %. The presence of intramolecular hydrogen bond within both conformations was identified in the solvent. The IR spectra were simulated and assigned in detail, which agreed well with the experimental data. The intramolecular hydrogen bonding interactions resulted in the shift of vibrational frequencies of hydroxyl to the low band by 12-22 cm(-1) and 24-26 cm(-1) for IM and IT conformations, respectively. Their thermodynamic properties were also calculated based on the harmonic vibrational analysis, including standard heat capacity (C (°) p,m), entropy (S (°) m), and enthalpy (H (°) m). The molecular stability, hydrogen bonding interaction and other electronic properties have been further analyzed by the natural bond orbital (NBO), atoms in molecules (AIM), molecular electrostatic potential (MEP) and frontier molecular orbital (FMO) analysis. Graphical abstract FMOs of IM and IT conformations in the gas phase and in the water. PMID:26994018
Estimation of thermodynamic properties of Cu-La binary alloy with modified Miedema's theory
NASA Astrophysics Data System (ADS)
Li, Hai-hong; Zhang, Shi-hong; Chen, Yan; Cheng, Ming; Song, Hong-wu; Liu, Jin-song
2016-01-01
According to modified Miedema's theory, mixing enthalpies (Δ H), excess entropies ( S E), excess Gibbs free energy ( G E), and component activities ( a) of Cu-La binary alloy were estimated using the basic thermodynamic principles and some simple physical parameters of Cu and La, such as electronegativity, atomic volume and electron density. Based on the Cu-La binary alloy phase diagram, the Gibbs free energy of the phase precipitation reactions of Cu6La and Cu5La was deduced. The results showed that the values of Δ H, S E, and G E of Cu-La binary alloy were all negative. Compared to the ideal solution, the activities of the components presented a large negative deviation from Raoult's law, which indicated that there was a strong interaction between Cu and La. The calculated data are well consistent with the experimental data. The Gibbs free energies of the phase precipitation reactions of Cu6La are lower than those for Cu5La, which means that Cu6La is thermodynamically more stable than Cu5La. Furthermore, the experimental results show that rareearth rich Cu6La phase particles in copper matrix are formed after La microalloying.
Abdel-Naby, Mohamed A; A Ibrahim, M H; El-Refai, H A
2016-04-01
Bacillus pumilus FH9 keratinase was covalently coupled to several oxidized polysaccharides. The conjugates were evaluated for the retained activity, kinetic and thermodynamic stability. Among all preparations, the conjugated enzyme with oxidized pectin had the highest recovered activity (71.75%) and the highest thermal stability at 60°C (t1/2=333min). Compared to the native enzyme, the conjugated preparation exhibited higher optimum temperature, lower activation energy (Ea), lower deactivation constant rate (kd), higher t1/2, and higher decimal reduction time values (D) within the temperature range of 50-80°C. The thermodynamic parameters (ΔH*, ΔG*, ΔS*) of irreversible thermal denaturation for the native and conjugated keratinase were also evaluated. The values of enthalpy of activation (ΔH*), free energy of activation (ΔG*), and free energy of transition state binding (ΔG*E-T) for keratin hydrolysis were lower for the conjugated enzyme. Moreover, there was highly significant impact on improving the values of Vmax/Km, kcat, kcat/Km, and ΔG*E-S for the modified enzyme. Both native and conjugated enzymes were slightly activated by CaCl2 and MgCl2. However, the inhibitory effects of EDTA, HgCl2 and ZnSO4 were more pronounced with the native enzyme. PMID:26743746
A thermodynamic approach to model the caloric properties of semicrystalline polymers
NASA Astrophysics Data System (ADS)
Lion, Alexander; Johlitz, Michael
2015-02-01
It is well known that the crystallisation and melting behaviour of semicrystalline polymers depends in a pronounced manner on the temperature history. If the polymer is in the liquid state above the melting point, and the temperature is reduced to a level below the glass transition, the final degree of crystallinity, the amount of the rigid amorphous phase and the configurational state of the mobile amorphous phase strongly depend on the cooling rate. If the temperature is increased afterwards, the extents of cold crystallisation and melting are functions of the heating rate. Since crystalline and amorphous phases exhibit different densities, the specific volume depends also on the temperature history. In this article, a thermodynamically based phenomenological approach is developed which allows for the constitutive representation of these phenomena in the time domain. The degree of crystallinity and the configuration of the amorphous phase are represented by two internal state variables whose evolution equations are formulated under consideration of the second law of thermodynamics. The model for the specific Gibbs free energy takes the chemical potentials of the different phases and the mixture entropy into account. For simplification, it is assumed that the amount of the rigid amorphous phase is proportional to the degree of crystallinity. An essential outcome of the model is an equation in closed form for the equilibrium degree of crystallinity in dependence on pressure and temperature. Numerical simulations demonstrate that the process dependences of crystallisation and melting under consideration of the glass transition are represented.
A thermodynamic approach to model the caloric properties of semicrystalline polymers
NASA Astrophysics Data System (ADS)
Lion, Alexander; Johlitz, Michael
2016-05-01
It is well known that the crystallisation and melting behaviour of semicrystalline polymers depends in a pronounced manner on the temperature history. If the polymer is in the liquid state above the melting point, and the temperature is reduced to a level below the glass transition, the final degree of crystallinity, the amount of the rigid amorphous phase and the configurational state of the mobile amorphous phase strongly depend on the cooling rate. If the temperature is increased afterwards, the extents of cold crystallisation and melting are functions of the heating rate. Since crystalline and amorphous phases exhibit different densities, the specific volume depends also on the temperature history. In this article, a thermodynamically based phenomenological approach is developed which allows for the constitutive representation of these phenomena in the time domain. The degree of crystallinity and the configuration of the amorphous phase are represented by two internal state variables whose evolution equations are formulated under consideration of the second law of thermodynamics. The model for the specific Gibbs free energy takes the chemical potentials of the different phases and the mixture entropy into account. For simplification, it is assumed that the amount of the rigid amorphous phase is proportional to the degree of crystallinity. An essential outcome of the model is an equation in closed form for the equilibrium degree of crystallinity in dependence on pressure and temperature. Numerical simulations demonstrate that the process dependences of crystallisation and melting under consideration of the glass transition are represented.
NASA Astrophysics Data System (ADS)
Hozumi, Tsutomu; Sato, Haruki; Watanabe, Koichi
This paper proposes a procedure on the thermodynamically consistent determination of virial coefficients from speed-of-sound measurements. Using the speed-of-sound values for gaseous Difluoromethane (R-32) +Pentafluoroethane (R-125), R -32+ 1, 1, 1, 2 - tetrafluoroethane (R-134a), R125/134a and R-32/125/134a which have already been reported in the previous paper, the second virial coefficients of R-32/125, R -32/134a, R-125/134a and R-32/125/134a were determined by means of thermodynamic relation among the virial coefficients of two different virial equations of state with respect to pressure and density. The present virial equation of state regarding density expansion can represent not only the speed-of-sound values but also the PρT-data for R-32/125, R -32/134a, R -125/134a and R-32/125/134a. The deviation of the speed-of-sound data from the virial equation of state is about±100ppm.And the deviation of the PρT-measurements by Kleemiss and Tillner-Roth (1997) from the virial equation of state against density is about ±0.l%. The behavior of the second virial coefficient is shown at the available compositions.
Thermodynamic Properties Of Alkali Species In Coal Based Combined Cycle Power Systems
Willenborg, W.; Wolf, K.J.; Fricke, C.; Moeller, M.; Prikhodovsky, A.; Hilpert, K.; Singheiser, L.
2002-09-20
The aim of this project is to support the development of a concept for a successful alkali removal. Two strategies are possible: optimizing the alkali retention potential of the coal ash slag in the combustion chamber and the liquid slag separators and separate alkali removal with solid sorbents (getters) at temperatures below 1450 C. Therefore in a first step the alkali partial pressure over coal ash slag should be determined in order to get information about the retention potential of the slag. The influence of additives on the retention potential of the slag should be investigated. The measurements should show if the alkali partial pressure over the slag is generally low enough in case of thermodynamic equilibrium. In case of too high alkali partial pressures a separate alkali removal is needed. Therefore in a second step commercial sorbent materials should be investigated concerning their sorption potential for alkalis. To get information about the influence of getter components on the sorption potential some mixtures of pure components, predicted by thermodynamic modeling to be most effective, should be investigated.
NASA Astrophysics Data System (ADS)
Helgeson, Harold C.; Owens, Christine E.; Knox, Annette M.; Richard, Laurent
1998-03-01
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 (Δ H° t,Pr), melting (Δ H° m,Pr), and vaporization (Δ 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 (Δ G° f and Δ 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 aqueous species, including biomolecules ( Johnson et al 1992; Shock 1992a, Shock 1994, Shock 1995; Shock et al 1997; Shock and Koretsky 1993, Shock and Koretsky 1995; Sassani and Shock 1992, Sassani and Shock 1994; Schulte and Shock 1993, Schulte and Shock 1995; Oelkers et al 1995; Amend and Helgeson 1997a, Amend and Helgeson 1997b, Amend and Helgeson 1997c, Amend and Helgeson 1998; Sverjensky et al 1997) to compute equilibrium constants and chemical affinities for a wide variety of organic-inorganic reactions in geochemical and biochemical processes at both high and low temperatures and pressures. Unless indicated otherwise, all amino acid designations in the present communication refer to the L-α form.