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1

Thermodynamic Properties of HCFC-124

NASA Astrophysics Data System (ADS)

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.

Fukushima, Masato; Watanabe, Naohiro

2

Thermodynamic properties of methane

NASA Astrophysics Data System (ADS)

This book provides a unified equation of state and calculating tables of properties for methane. The temperature range spans the triple point to 1000 K and the pressures extend from 0.1 to 100 MPa. The range of parameters of state and the scope of tabulated qualities far exceeds the data offered in most other sources.

Sychev, Viacheslav Vladimirovich; Vasserman, A. A.; Zagoruchenko, V. A.; Kozlov, A. D.; Spiridonov, G. A.

3

The Thermodynamic Properties of Cubanite

NASA Technical Reports Server (NTRS)

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

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

2012-01-01

4

Thermodynamic Properties of Compressed Gases.

National Technical Information Service (NTIS)

The purpose of the project is to provide reliable values for the thermodynamic properties of 'key' compressed gaseous systems which can be used as points of reference for a better understanding of the laws of mixing. For several reasons the binary system,...

R. H. Harrison R. T. Moore D. R. Douslin

1966-01-01

5

Thermodynamic properties of uranium dioxide

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

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

1981-04-01

6

Thermodynamic properties of gadolinium disilicide

The purpose of this work was to determine the thermodynamic properties of gadolinium disilicide by the me~hod of measurement in the 830-960 K temperature range of the emf of the concentration galvanic element [GdSn3 + (Sn)L] I KCI -- NaC1 -- (BaCl~) + GdCI 8 [ [GdSi~ + Si], (1) where (Sn) L is a saturated solution of gadolinium in

G. M. Lukashenko; R. I. Polotskaya

1986-01-01

7

Thermodynamic properties of chromium silicides

In investigation of the thermodynamic properties of chromium silicides in the 973I133~ range by measurement of the emf's [i] for alloys located in the adjoining heterogeneous areas [CrbSi3 + CrSi] and [CrSi + CrSi2] values of the emf agreeing within the limits of measurement error and consequently of the partial Gibbs energies were obtained. This was related by the authors

G. M. Lukashenko; V. R. Sidorko; L. M. Yupko

1986-01-01

8

Thermodynamical properties of dark energy

We have investigated the thermodynamical properties of dark energy. Assuming that the dark energy temperature T{approx}a{sup -n} and considering that the volume of the Universe enveloped by the apparent horizon relates to the temperature, we have derived the dark energy entropy. For dark energy with constant equation of state w>-1 and the generalized Chaplygin gas, the derived entropy can be positive and satisfy the entropy bound. The total entropy, including those of dark energy, the thermal radiation, and the apparent horizon, satisfies the generalized second law of thermodynamics. However, for the phantom with constant equation of state, the positivity of entropy, the entropy bound, and the generalized second law cannot be satisfied simultaneously.

Gong Yungui; Wang Bin; Wang Anzhong [School of Physical Science and Technology, Southwest University, Chongqing 400715 (China) and CASPER, Department of Physics, Baylor University, Waco, Texas 76798 (United States); Department of Physics, Fudan University, Shanghai 200433 (China); CASPER, Department of Physics, Baylor University, Waco, Texas 76798 (United States)

2007-06-15

9

Statistical Thermodynamic Properties of Hexafluoride Molecules.

National Technical Information Service (NTIS)

Useful statistical thermodynamic properties of fifteen octahedral hexafluorides are presented in graphical form. These include: vibrational partition function; populations of low-lying vibrational states; densities of vibrational states; and cumulative vi...

D. Jackson

1975-01-01

10

Tables of thermodynamic properties of sodium

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

Fink, J.K.

1982-06-01

11

Thermodynamic properties of liquid metals /A review/.

NASA Technical Reports Server (NTRS)

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.

Margrave, J. L.

1970-01-01

12

Thermodynamic and transport properties of fluids

NASA Technical Reports Server (NTRS)

Computer program subroutine FLUID calculates thermodynamic and transport properties of pure fluids in liquid, gas, or two-phase (liquid/gas) conditions. Program determines thermodynamic state from assigned values for temperature and density, pressure and density, temperature and pressure, pressure and entropy, or pressure and enthalpy.

Fessler, T. E.

1980-01-01

13

Thermodynamic Properties of Aqueous Solution of Ammonia

NASA Astrophysics Data System (ADS)

Present status on the thermodynamic properties of experimental data and their correlations of both ammonia and aqueous solution of ammonia was introduced in this paper. The aqueous solution of ammonia is used for not only a working fluid in absorption refrigerator cycles but also working fluids in bottoming cycles of steam power plants and other heat recovering systems. Therefore, the thermodynamic properties of this substance are required in a wide range of temperatures, pressures and compositions. The experimental results of pVTx properties for ammonia and aqueous solution of ammonia and their comparisons with a formulation by Tillner-Roth and Friend1) were critically surveyed. The “Guideline on the IAPWS Formulation 2000 for the Thermodynamic Properties of Ammonia-Water Mixtures”, correlated by Tillner-Roth and Friend1), was approved on September, 2001, by the International Association for the Properties of Water and Steam (IAPWS) 2).

Kitamura, Hiroshi; Oguchi, Kosei

14

Physical and Thermodynamic Properties of Potassium.

National Technical Information Service (NTIS)

This report is an up-to-date compilation of potassium physical and thermodynamic properties. Data for the solid phase is presented, where available, over a temperature range from 0 F to the melting point. Liquid and vapor physical properties are tabulated...

R. T. Caldwell D. M. Walley

1966-01-01

15

Prediction of Thermodynamic Properties for Halogenated Hydrocarbon

NASA Astrophysics Data System (ADS)

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.

Higashi, Yukihiro

16

Computing Thermodynamic And Transport Properties Of Air

NASA Technical Reports Server (NTRS)

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.

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

1994-01-01

17

High-temperature thermodynamic properties of forsterite

The high-temperature thermodynamic properties of forsterite were reviewed in the light of a new determination of the isobaric heat capacity (Cp), up to 1850 K, and Raman spectroscopic measurements, up to 1150 K and 10 GPa. The Cp measurements and available data on thermal expansion (alpha) and bulk modulus (K) show that the isochoric specific heat (Cnu) exceeds the harmonic

Philippe Gillet; Pascal Richet; François Guyot; Guillaume Fiquet

1991-01-01

18

Thermodynamic Properties of Uranium--Mercury System.

National Technical Information Service (NTIS)

The EMF values in the fused salt cells of the type U( alpha )/KCl--LiCl--BaCl sub 2 eutectic, UCl sub 3 /U--Hg alloy, for the different two-phase alloys in the uranium--mercury system have been measured and the thermodynamic properties of this system have...

T. S. Lee

1979-01-01

19

Tetrafluoromethane, Thermodynamic Properties of the Real Gas.

National Technical Information Service (NTIS)

The thermodynamic properties, H-H(standard state), S-S(std. state), and G-G(std. state), of tetrafluoromethane were determined as functions of temperatures (0 to 350 C.) and molal density (0.75 to 11.0 gram-moles per liter) over a pressure range of 0 to 4...

R. H. Harrison D. R. Douslin

1965-01-01

20

Thermodynamic and Transport Properties of Gaseous Tetrafluoromethane in Chemical Equilibrium.

National Technical Information Service (NTIS)

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 giv...

J. L. Hunt L. R. Boney

1973-01-01

21

High temperature drop calorimetry and thermodynamic properties

Experimental determination of thermodynamic properties (e.g. enthalpy of formation, heat capacity, Gibbs free energy, etc.) is still the recourse for accurate thermodynamic data for the condensed phases. Calorimetry is probably the best experimental method for their determination. Drop calorimetry in its various modifications is still the method of choice to determine the enthalpy functions for solids and liquids above 1,000 C. The conventional drop calorimeter for solids and a drop calorimeter coupled to an electromagnetic levitation coil useful for conductive samples in both the solid and molten phases are described. Experimental results obtained up to and above the melting point of rare earth metals are presented.

Chandrasekhariah, M.S. [Houston Advanced Research Center, The Woodlands, TX (United States). Materials Science Research Center; Bautista, R.G. [Univ. of Nevada, Reno, NV (United States). Dept. of Chemical and Metallurgical Engineering

1995-04-01

22

Thermodynamic properties of ammonia in the critical region

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

T. A. Edison; J. V. Sengers

1999-01-01

23

Thermodynamic properties of hydrogen-helium plasmas

NASA Technical Reports Server (NTRS)

The thermodynamic properties of an atomic hydrogen-helium plasma are calculated and tabulated for temperatures from 10,000 to 100,000 K as a function of the mass fraction ratio of atomic hydrogen. The tabulation is for densities from 10 to the minus 10th power to 10 to the minus 6th power gm/cu cm and for hydrogen mass fraction ratios of 0, 0.333, 0.600, 0.800, and 1.0, which correspond to pure helium, 50 percent hydrogen per unit volume, 75 percent hydrogen per unit volume, 89 percent hydrogen per unit volume, and pure hydrogen plasmas, respectively. From an appended computer program, calculations can be made at other densities and mass fractions. The program output agrees well with previous thermodynamic property calculations for limiting cases of pure hydrogen and pure helium plasmas.

Nelson, H. F.

1971-01-01

24

Thermodynamic properties of higher lanthanum silicide

The thermodynamic properties of lanthanum disilicide were examined for the first time in the 960-1050Â°K range by measuring the electromotive force of a galvanic cell based on LaSn, the chlorides of potassium, sodium, and lanthanum, and lanthanum silicide and silicon. Reference electrodes were used to prevent lanthanum interaction with the electrolyte. The alloys were melted in an electric arc furnace

R. I. Polotskaya

1988-01-01

25

Thermodynamic properties of liquid Si and Ge

NASA Technical Reports Server (NTRS)

Thermodynamic properties of liquid Si and Ge are calculated using standard variational techniques, with the hard-sphere system as a reference system. Third-order electron-ion pseudopotential contributions are included nonvariationally and are shown to have little effect on the free energy, although a larger one on the derivatives of the free energy. Two different model pseudopotentials are used and give similar results in good agreement with experiment.

Shih, W.-H.; Stroud, D.

1985-01-01

26

The thermodynamic properties of thianthrene and phenoxathiin

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

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

1993-04-01

27

Thermodynamic Properties of Actinides and Actinide Compounds

NASA Astrophysics Data System (ADS)

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

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

28

Thermodynamic properties of a dipolar Fermi gas

Based on the semiclassical theory, we investigate the thermodynamic properties of a dipolar Fermi gas. Through a self-consistent procedure, we numerically obtain the phase-space distribution function at finite temperature. We show that the deformations in both momentum and real space become smaller and smaller as the temperature is increased. For the homogeneous case, we also calculate pressure, entropy, and heat capacity. In particular, at the low-temperature limit and in the weak interaction regime, we obtain an analytic expression for the entropy which agrees qualitatively with our numerical result. The stability of a trapped gas at finite temperature is also explored.

Zhang, J.-N.; Yi, S. [Key Laboratory of Frontiers in Theoretical Physics, Institute of Theoretical Physics, Chinese Academy of Sciences, Beijing 100190 (China)

2010-03-15

29

Thermodynamic properties of 3-dimensional quantum antiferromagnets

NASA Astrophysics Data System (ADS)

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

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

2013-03-01

30

Thermodynamic properties for R-404A

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.

Fujiwara, K.; Nakamura, S.; Noguchi, M. [Daikin Industries, Ltd., Settsu, Osaka (Japan). Chemical Div.] [Daikin Industries, Ltd., Settsu, Osaka (Japan). Chemical Div.

1999-01-01

31

Thermodynamic and Physical Properties of Crystals Formed from Dilute Solutions.

National Technical Information Service (NTIS)

Some of the thermodynamic and physical properties of crystals of linear polyethylene, formed from dilute solution are discussed. These properties include density, enthalpy of fusion, infrared absorption spectrum, selective oxidation and dynamic mechanical...

L. Mandelkern

1969-01-01

32

Thermodynamic approach to nano-properties of cell membrane

NASA Astrophysics Data System (ADS)

Biomechanical analyses of DNA have pointed out the connections among forces, thermodynamics and kinetics. The entropy generation approach has been suggested as a thermodynamic approach to evaluate the accessible states for cancer systems, in relation to their specific thermodynamic quantities, including mechanical properties. In this paper, a theoretical approach for the thermodynamic evaluation of the nano-behaviour of the cell wall is suggested. The aim is to provide theoretical bases to the analysis of cells and their properties by applying the thermodynamic approach to irreversibility.

Lucia, Umberto

2014-08-01

33

Thermodynamic properties of doped lanthanum manganites

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.

Hildrum, R.; Brustad, M. (Norwegian Inst. of Tech., Trondheim (Norway). Dept. of Electrochemistry); Wang Changzhen (Northeast Univ. of Technology, Shenyang (China). Div. of Physicochemistry of Metallurgy); Johannesen, O. (Kongsberg Coll. of Engineering (Norway))

1994-08-01

34

Microcomputer Simulation of Real Gases--Part 2: Thermodynamical Properties.

ERIC Educational Resources Information Center

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)

Sperandeo-Mineo, R. M.; Tripi, G.

1988-01-01

35

Ammonia-Water System: Part I. Thermodynamic Properties.

National Technical Information Service (NTIS)

The various thermodynamic properties which have direct bearing on design calculations and separation factor calculations for gaseous ammonia water system have been calculated and compiled in tabular form for easy reference. (Atomindex citation 12:594737)

N. C. Goomer S. M. Dave H. K. Sadhukhan

1980-01-01

36

Thermodynamic properties of UF6 at high temperatures

NASA Technical Reports Server (NTRS)

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

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

1974-01-01

37

Thermodynamic Properties of D2O in the Critical Region

An analysis is presented of the thermodynamic properties of D2O in the critical region. It is shown that the data can be represented by the same revised and extended scaled fundamental equation formulated earlier for the thermodynamic properties of H2O in critical region. The equation is valid in the range 220–465 kg\\/m3 in density and 638–683 K in temperature. Tabulated

J. M. H. Levelt Sengers; J. V. Sengers

1983-01-01

38

Thermodynamic and transport properties of sodium liquid and vapor

Data have been reviewed to obtain thermodynamically consistent equations for thermodynamic and transport properties of saturated sodium liquid and vapor. Recently published Russian recommendations and results of equation of state calculations on thermophysical properties of sodium have been included in this critical assessment. Thermodynamic properties of sodium liquid and vapor that have been assessed include: enthalpy, heat capacity at constant pressure, heat capacity at constant volume, vapor pressure, boiling point, enthalpy of vaporization, density, thermal expansion, adiabatic and isothermal compressibility, speed of sound, critical parameters, and surface tension. Transport properties of liquid sodium that have been assessed include: viscosity and thermal conductivity. For each property, recommended values and their uncertainties are graphed and tabulated as functions of temperature. Detailed discussions of the analyses and determinations of the recommended equations include comparisons with recommendations given in other assessments and explanations of consistency requirements. The rationale and methods used in determining the uncertainties in the recommended values are also discussed.

Fink, J.K.; Leibowitz, L.

1995-01-01

39

Thermodynamic properties of perfluoro- n-octane

Fluorocarbons are attracting much attention nowadays because of their unique properties, which may provide interesting applications in areas as wide as environmental, biomedical and material science. However, the behavior of these compounds is not well understood and only scattered data can be found in the open literature and company technical reports.In this work, three important properties of perfluoro-n-octane were experimentally

A. M. A. Dias; A. I. Caço; J. A. P. Coutinho; M. M. Piñeiro; L. F. Vega; M. F. Costa Gomes; I. M. Marrucho

2004-01-01

40

Thermodynamic consistency, quark mass scaling, and properties of strange matter

NASA Astrophysics Data System (ADS)

The previous thermodynamic treatment for models with density and/or temperature dependent quark masses is shown to be inconsistent with the requirement of fundamental thermodynamics. We therefore study a fully self-consistent one according to the fundamental differential equation of thermodynamics. After obtaining a new quark mass scaling with the inclusion of both confinement and leading-order perturbative interactions, we investigate properties of strange quark matter in the fully consistent thermodynamic treatment. It is found that the equation of state become stiffer, and accordingly, the maximum mass of strange stars is as large as about 2 times the solar mass, if strange quark matter is absolutely or metastable.

Xia, C. J.; Peng, G. X.; Chen, S. W.; Lu, Z. Y.; Xu, J. F.

2014-05-01

41

Thermodynamic properties of 3C—SiC

NASA Astrophysics Data System (ADS)

In the present paper, we report on the results of various thermodynamic properties of 3C—SiC at high pressure and temperature using first principles calculations. We use the plane-wave pseudopotential density functional theory as implemented in Quantum ESPRESSO code for calculating various cohesive properties in ambient condition. Further, ionic motion at a finite temperature is taken into account using the quasiharmonic Debye model. The calculated thermodynamic properties, phonon dispersion curves, and phonon densities of states at different temperatures and structural phase transitions at high pressures are found to be in good agreement with experimental and other theoretical results.

Thakore, B. Y.; Khambholja, S. G.; Vahora, A. Y.; Bhatt, N. K.; Jani, A. R.

2013-10-01

42

Thermodynamic property determination in low gravity

NASA Technical Reports Server (NTRS)

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

Margrave, J. L.

1977-01-01

43

Structural and thermodynamic properties of water related defects in ?-quartz

We have investigated the atomic geometries and thermodynamic properties of water related defects in ?-quartz using first-principles\\u000a calculation. We confirm that the (OH)4 group is thermodynamically most stable and aggregates to form platelets in the form of microcracks with hydrolysed surfaces.\\u000a We also examine other forms of defects which can be accessible out of equilibrium at high temperature. Finally, we

A. L. Rosa; A. A. El-Barbary; M. I. Heggie; P. R. Briddon

2005-01-01

44

Thermodynamic properties of ionic liquids-a cluster approach.

We describe a method for calculating thermodynamic properties of ionic liquids by using standard quantum statistical thermodynamics as characterized by ab initio techniques. We review briefly how thermochemical properties for different sized clusters of ionic liquids are calculated by standard ab initio programs. The cluster partition functions allow one to calculate energies, enthalpies and Gibbs energies. Assuming that the ionic liquid exists exclusively as isolated ion-pairs in the gaseous phase and regarding the largest clusters as possible liquid structures, we could estimate vapor pressures, enthalpies of vaporization and entropies of vaporization. For possible boiling points it is shown how they vary with pressure. PMID:18633554

Ludwig, Ralf

2008-08-01

45

Thermodynamical Properties of 3d Transition Liquid Metals

NASA Astrophysics Data System (ADS)

In the present study we have calculated thermodynamical properties like entropy (S), internal energy (E) and Helmholtz free energy (F) of 3d transition liquid metals using variational principle based on the Gibbs-Bogolyubov inequality with hard sphere reference system. To describe electron-ion interaction, we have used our newly constructed parameter free model potential. To see the influence of exchange and correlation effect, Sarkar et al. local field correlation function is used. Lastly, we conclude that our newly constructed model potential is capable to explain the thermodynamical properties of 3d transition liquid metals.

Thakor, P. B.; Sonvane, Y. A.; Jani, A. R.

2010-06-01

46

Thermodynamic properties of Cu under high pressure

NASA Astrophysics Data System (ADS)

The total energies, structural properties and elastic constants of Cu at T=0 k have been calculated by the full-potential linearized muffin-tin orbital (FP-LMTO) scheme within the generalized gradient approximation (GGA) correction in the frame of density functional theory. Through the quasi-harmonic Debye model, in which the phononic effects are considered, the dependences of relative volume V/ V0 on pressure P, cell volume V on temperature T, linear thermal expansion on temperature and Debye temperature ? and specific heat C V on pressure are successfully obtained. The obtained pressure dependence of the normalized volume at 300 K is in excellent agreement with the experimental results.

Liu, Yao-Bei; Li, Xu-Sheng; Feng, You-Li; Cui, Yan-Ling; Han, Xu

2007-05-01

47

Thermodynamic properties and phase transitions in CO2 molecular clusters

NASA Technical Reports Server (NTRS)

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.

Etters, R. D.; Flurchick, K.; Pan, R. P.; Chandrasekharan, V.

1981-01-01

48

Optical and thermodynamic properties of polyformaldehyde plasma

This paper presents data on the continuous spectrum of CHâO plasma for quantum energies of 1-1000 eV as well as its thermodynamic functions. The partial composition of the multicomponent plasma was calculated from a Sach-Eckert system of equations, taking the weak nonideality into account by the Debye equation, supplemented by the conditions of quasineutrality and maintaining the relationship between the

A. S. Kamrukov; S. N. Chuvashev; N. P. Kozlov; Y. S. Protasov

1986-01-01

49

Thermodynamic properties of ? Nickel-Indium Alloys

The vapor pressure of indium over ? Ni-In alloys was measured by atomic absorption. The thermodynamic activity of indium was\\u000a calculated from the vapor pressure, and the partial and integral entropy and enthalpy were calculated from temperature coefficients.\\u000a It was found that the excess chemical potential of indium increases with atom fraction of indium at low temperatures, in the\\u000a manner

D. Bhattacharya; D. Bruce Masson

1975-01-01

50

Thermodynamic Properties of hcp Iron at High Pressure and Temperature

Thermodynamic properties of the high pressure phase of iron are of great geophysical interest as earth's inner core (IC) is composed primarily of this element. High temperature in the interior of our planet has been a major challenge to both theoretical and experimental techniques, only recent advances in computer resources make such computations tractable. We perform first principles calculations of

Gerd Steinle-Neumann; Lars Stixrude; Ronald E. Cohen; Oguz Gülseren

2001-01-01

51

SORPTION ISOTHERMS AND THERMODYNAMIC PROPERTIES OF POWDERED MILK

Moisture sorption isotherms of powdered milk were obtained using the gravimetric static method at 30°, 40°, and 50°C. Peleg and Enderby equations were found to be the most suitable models for describing the sorption curves among six well-known tested equations. Thermodynamic properties such as differential enthalpy and entropy of sorption were determined from moisture adsorption and desorption data, using the

Naji Abdenouri; Ali Idlimam; Mohammed Kouhila

2010-01-01

52

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

53

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

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

Francesca Baletto; Riccardo Ferrando

2005-01-01

54

Non-LTE thermodynamic properties for combustion processes

The nonequilibrium thermodynamic properties of a product-gas derived from fluidized combustion of Pittsburgh seam coal is obtained using a multitemperature statistical thermodynamic computer model. Concentrations of 18 species are determined as a function of translational temperature (500 < T < 2500 K), pressure (0.1, 1.0, and 10 atm), and vibrational-to-translational temperature ratios of 0.5, 1, 2, and 5. The rotational and electronic excitation temperatures are assumed equal to the translational temperature. The partition functions and usual thermodynamic properties are also calculated and a nonequilibrium Mollier diagram is presented. The multitemperature model assumes chemical equilibrium and therefore represents a first step in describing nonequilibrium combustion reactions in a semiclassical manner. The model can be applied to reactions via chemical kinetics and/or an extension to a multichemical nonequilibrium model. The results indicate the relative concentration of species usually considered to be pollutants, under the range of conditions examined.

Fentress, M.L.; Eddy, T.L.

1987-09-01

55

NASA Glenn Coefficients for Calculating Thermodynamic Properties of Individual Species

NASA Technical Reports Server (NTRS)

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

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

2002-01-01

56

Computational Models of Thermodynamic Properties of Uranium Nitride

NASA Astrophysics Data System (ADS)

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

Mei, Zhi-Gang; Stan, Marius

2014-06-01

57

Thermodynamic properties by non-calorimetric methods. Final report

This research program provided 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. The project for the Office of Energy Research focused 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 the following studies: Group-contribution approach for polycyclic aromatic hydrocarbons (naphthalene, phenanthrene, anthracene, pyrene, 3-methylphenanthrene, benzoquinolines, biphenyl/hydrogen system); Group-contribution approach for key monocyclic organic compounds; Molecular spectroscopy and statistical mechanics; and Thermophysical property correlations.

Steele, W.V.; Chirico, R.D.; Collier, W.B.; Strube, M.M.; Klots, T.D. [IIT Research Inst., Chicago, IL (United States)]|[National Inst. for Petroleum and Energy Research, Bartlesville, OK (United States)

1992-12-31

58

Optical and thermodynamic properties of polyformaldehyde plasma

This paper presents data on the continuous spectrum of CH/sub 2/O plasma for quantum energies of 1-1000 eV as well as its thermodynamic functions. The partial composition of the multicomponent plasma was calculated from a Sach-Eckert system of equations, taking the weak nonideality into account by the Debye equation, supplemented by the conditions of quasineutrality and maintaining the relationship between the number of particles of the various elements. Photoionization of the excited states having a principal quantum number greater than that for the ground state of the outer electron was calculated by the more approximate quantum defect method. To calculate the remaining highly excited states, integral relationships were used. The authors calculated the absorption coefficients averaged over the 16 spectral intervals which are necessary for making calculations in a multigroup approximation. It is shown that for calculations of the phenomena in a polyformaldehyde plasma having parameters lying principaly within the limits of the ranges indicated, a linear interpolation in logarithmic coordinates and the extrapolation of the data are recommended.

Kamrukov, A.S.; Chuvashev, S.N.; Kozlov, N.P.; Protasov, Y.S.

1986-06-01

59

Thermodynamical property of entanglement entropy for excited states.

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

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

2013-03-01

60

Thermodynamic and transport properties of cryogenic propellants and related fluids

NASA Technical Reports Server (NTRS)

Significant advances have been made in recent years in the quality and range of thermophysical data for the cryogenic propellants, pressurants, and inertants. A review of recently completed and current data compilation projects for helium, hydrogen, argon, nitrogen, oxygen, fluorine, and methane is given together with recommended references for thermodynamic and transport property data tables for these fluids. Modern techniques in the plotting of thermodynamic charts from tabular data (or from functions such as the equation of state) have greatly improved their precision and value. A list of such charts is included.

Johnson, V. J.

1973-01-01

61

Intermolecular interactions and the thermodynamic properties of supercritical fluids.

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 ? = 0.32. This provides an explanation for the terminal isobaric heat capacity maximum in supercritical fluids. PMID:23697423

Yigzawe, Tesfaye M; Sadus, Richard J

2013-05-21

62

Intermolecular interactions and the thermodynamic properties of supercritical fluids

NASA Astrophysics Data System (ADS)

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 ? = 0.32. This provides an explanation for the terminal isobaric heat capacity maximum in supercritical fluids.

Yigzawe, Tesfaye M.; Sadus, Richard J.

2013-05-01

63

Thermodynamic properties of 1,1,1,2-tetrafluoroethane (R134a) in the critical region

A theoretically based simplified crossover model, which is capable of representing the thermodynamic properties of fluids in a large range of temperatures and densities around the critical point, is presented. The model is used to predict the thermodynamic properties of R134a in the critical region from a limited amount of available experimental information. Values for various thermodynamic properties of R134a

S. Tang; G. X. Jin; J. V. Sengers

1991-01-01

64

Thermodynamic properties of an electron gas on a curved surface

NASA Astrophysics Data System (ADS)

We report a study on thermodynamic properties of a two-dimensional electron gas confined in a sector of a circular cylinder immersed in a dc magnetic field perpendicular to its axis. This field configuration produces on the electrons in the curved surface, effects similar to a non-homogeneous magnetic field on a flat system. We study these effects by calculating the energy spectra for different curvature radius and symmetries of the magnetic field with respect to the surface. The analysis of the density of states, chemical potential and specific heat of these systems helps to understand the correlation between the externally controlled symmetry and their physical properties.

Batista, F. F.; Farias, G. A.; Almeida, N. S.

2013-09-01

65

Thermodynamic and magnetic properties of the hexagonal type Ising nanowire

NASA Astrophysics Data System (ADS)

The thermodynamic and magnetic properties of the mixed-spin (1/2-1) hexagonal Ising nanowire (HIN) system with core-shell structure have been presented by means of the effective-field theory (EFT) with correlations. The effects of the physical parameters of the system on thermodynamic and magnetic properties (magnetisations, susceptibilities, internal energies, free energies and hysteresis curves) are investigated for the both ferromagnetic and antiferromagnetic case, in detail. One can find that when the temperature increases the hysteresis loop areas decrease and the hysteresis loops disappear above the critical temperature. Moreover, different hysteresis loop behaviours have been observed such as single, double and triple hysteresis loops in the system. In order to confirm the accuracy of the phase transition points, we also investigate the free energy of the system.

Kocakaplan, Yusuf; Kantar, Ersin

2014-06-01

66

Thermodynamic properties of liquid water from a polarizable intermolecular potential

NASA Astrophysics Data System (ADS)

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.

Yigzawe, Tesfaye M.; Sadus, Richard J.

2013-01-01

67

Thermodynamic properties of liquid water from a polarizable intermolecular potential.

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. PMID:23387601

Yigzawe, Tesfaye M; Sadus, Richard J

2013-01-28

68

Thermodynamic properties and diffusion of water + methane binary mixtures.

Thermodynamic and diffusion properties of water + methane mixtures in a single liquid phase are studied using NVT molecular dynamics. An extensive comparison is reported for the thermal pressure coefficient, compressibilities, expansion coefficients, heat capacities, Joule-Thomson coefficient, zero frequency speed of sound, and diffusion coefficient at methane concentrations up to 15% in the temperature range of 298-650 K. The simulations reveal a complex concentration dependence of the thermodynamic properties of water + methane mixtures. The compressibilities, heat capacities, and diffusion coefficients decrease with increasing methane concentration, whereas values of the thermal expansion coefficients and speed of sound increase. Increasing methane concentration considerably retards the self-diffusion of both water and methane in the mixture. These effects are caused by changes in hydrogen bond network, solvation shell structure, and dynamics of water molecules induced by the solvation of methane at constant volume conditions. PMID:24628180

Shvab, I; Sadus, Richard J

2014-03-14

69

The thermodynamic properties of the five benzoquinolines: Topical report

Measurements leading to the calculation of the ideal-gas thermodynamic properties for acridine, phenanthridine, and 7,8-benzoquinoline are reported. Thermochemical and thermophysical properties were determined by adiabatic heat-capacity calorimetry, comparative ebulliometry, inclined-piston, manometry, and combustion calorimetry. Comparisons with literature values are presented and discussed. Results were used to calculate entropies, enthalpies, and Gibbs energies of formation for the ideal-gas state at selected temperatures to 500 K. Group-contribution methods were used to estimate the ideal-gas entropy and enthalpy of formation at 400 K for the unstudied benzoquinolines: 5,6-benzoquinoline and 6,7-benzoquinoline. The relative stabilities of the compounds and comparisons with hydrocarbon analogues are discussed. A reaction scheme for the formation of the benzoquinolines is outlined and the relative concentrations of each isomer estimated for the reactions proceeding under thermodynamic control. 52 refs., 4 figs., 18 tabs.

Steele, W.V.; Chirico, R.D.; Hossenlopp, I.A.; Nguyen, A.

1988-10-01

70

Effect of different molecular vibrational models on thermodynamic properties

NASA Astrophysics Data System (ADS)

The full set of vibrational energies {E?} and the maximum vibrational quantum number ?max generated by an algebraic method (AM) are suggested to implement classical statistical thermodynamic formulae. This protocol is applied to study the molar vibrational internal energy, molar vibrational entropy and molar vibrational heat capacity of a macro-system consisting of the ground electronic state X1?+ of CO molecules. Comparisons of theoretical results with experimental measurements show that the AM statistical thermodynamic quantities are much better than those generated using beautiful analytical formulae that are based on the traditional simple harmonic oscillator (SHO) vibrational model, and that the suggested protocol can be extended to study statistical thermodynamic properties of any macro-diatomic system.

GuoYue, Liu; WeiGuo, Sun

2014-03-01

71

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

S. Gordon

1982-01-01

72

Thermodynamic and Transport Properties of Superconducting Mg10B2

Transport and thermodynamic properties of a sintered pellet of the newly discovered MgB2 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, Hc2, with magnetization data giving dHc2\\/dT = 0.44 T\\/K at the transition temperature of Tc = 40.2 K.

D. K. Finnemore; J. E. Ostenson; S. L. Bud'Ko; G. Lapertot; P. C. Canfield

2001-01-01

73

ms2: A molecular simulation tool for thermodynamic properties

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

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

2011-01-01

74

Thermodynamic properties of hydrocarbons. [Nonane; undecane; tridecane; tetradecane; pentadecane

A numerical technique for calculating thermodynamic properties of non-polar pure substances is presented. It is based on the use of the extended principle of corresponding states for the determination of P-V-T relations and their reduction to the Benedict-Webb-Rubin equation of state. Virial coefficients are deduced and combined with specific heat data to determine the internal energy, entropy, and bulk modulus

T. E. Parker; R. F. Sawyer; A. K. Oppenheim

1986-01-01

75

Thermodynamic Properties of Ammonia–Water Mixtures for Power Cycles

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

E. Thorin; C. Dejfors; G. Svedberg

1998-01-01

76

Determining thermodynamic properties of molecular interactions from single crystal studies.

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

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

2013-11-01

77

Coefficients for calculating thermodynamic and transport properties of individual species

NASA Technical Reports Server (NTRS)

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

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

1993-01-01

78

A thermodynamic approach to obtain materials properties for engineering applications

NASA Technical Reports Server (NTRS)

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

Chang, Y. Austin

1993-01-01

79

Thermodynamic properties of ammonia-water mixtures for power cycles

Power cycles with ammonia-water mixtures as working fluids have been shown to reach higher thermal efficiencies than the traditional steam turbine (Rankine) cycle with water as the working fluid. Different correlations for the thermodynamic properties of ammonia-water mixtures have been used in studies of ammonia-water mixture cycles described in the literature. Four of these correlations are compared in this paper. The differences in thermal efficiencies for a bottoming Kalina cycle when these four property correlations are used are in the range 0.5 to 3.3%. The properties for saturated liquid and vapor according to three of the correlations and available experimental data are also compared at high pressures and temperatures [up to 20 MPa and 337 C (610 K)]. The difference in saturation temperature for the different correlations is up to 20%, and the difference in saturation enthalpy is as high as 100% when the pressure is 20 MPa.

Thorin, E. [Royal Inst. of Technology, Stockholm (Sweden)] [Royal Inst. of Technology, Stockholm (Sweden); [Maelardalen Univ., Vaesteraas (Sweden). Dept. of Energy; Dejfors, C.; Svedberg, G. [Royal Inst. of Technology, Stockholm (Sweden)] [Royal Inst. of Technology, Stockholm (Sweden)

1998-03-01

80

Optical and thermodynamic property measurements of liquid metals and alloys

NASA Technical Reports Server (NTRS)

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

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

1991-01-01

81

Optical and thermodynamic property measurements of liquid metals and alloys

NASA Astrophysics Data System (ADS)

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

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

82

The thermodynamic properties of 4 f metal trifluorides

NASA Astrophysics Data System (ADS)

The experimental low-temperature heat capacities of some solid 4 f metal trifluorides were used to reveal the trends in the behavior of variable parameters in the equation that described the lattice heat capacity component in the quasi-harmonic approximation for the whole series of LnF3 (Ln = La, … Lu) compounds. The results were used to describe the temperature dependences of heat capacity over the temperature range from 0 K to the melting point T m. The measured high-temperature enthalpy increments were used to determine corrections to the quasi-harmonic description of heat capacities at T > ˜0.5 T m. The reduced Gibbs energies were calculated over the temperature range 298.15 2000 K. The thermodynamic functions of LnF3 in the gaseous state were determined over the same temperature range in the rigid rotator-harmonic oscillator approximation. All calculations were performed taking into account excited electronic states whose energies did not exceed 10000 cm-1. The reliability of the thermodynamic functions obtained was proved by the convergence of the enthalpies of sublimation calculated by the second and third laws of thermodynamics from the experimental data on saturated vapor pressures. The complete set of the consistent thermodynamic properties of these compounds is described.

Chervonnyi, A. D.; Chervonnaya, N. A.

2007-10-01

83

Calculating thermodynamic properties from fluctuations at small scales.

We show how density and energy fluctuations of small nonperiodic systems embedded in a reservoir can be used to determine macroscopic thermodynamic properties like the enthalpy density and the thermodynamic correction factor. For mixtures, the same formalism leads to a very convenient method to obtain so-called total correlation function integrals, also often referred to as Kirkwood-Buff integrals. Using finite size scaling, the properties obtained for small systems can be extrapolated to the macroscopic system limit provided that the system is sufficiently far from the critical point. As derived in our previous work (Chem. Phys. Lett. 2011, 504, 199-201), the finite size scaling is significant and depends on 1/L, where L is the length of the small system in one dimension. By considering a reservoir with an ensemble of embedded small systems, we can use the scaling arising from surface effects to determine properties for macroscopic systems by extrapolation. We demonstrate this method for the WCA and LJ fluids, as well a for a heterogeneous system, i.e., argon adsorbed in silicalite-1 zeolite. PMID:21838274

Schnell, Sondre K; Liu, Xin; Simon, Jean-Marc; Bardow, André; Bedeaux, Dick; Vlugt, Thijs J H; Kjelstrup, Signe

2011-09-22

84

Thermodynamic properties of gases dissolved in electrolyte solutions.

NASA Technical Reports Server (NTRS)

A method based on perturbation theory for mixtures is applied to the prediction of thermodynamic properties of gases dissolved in electrolyte solutions. The theory is compared with experimental data for the dependence of the solute activity coefficient on concentration, temperature, and pressure; calculations are included for partial molal enthalpy and volume of the dissolved gas. The theory is also compared with previous theories for salt effects and found to be superior. The calculations are best for salting-out systems. The qualitative feature of salting-in is predicted by the theory, but quantitative predictions are not satisfactory for such systems; this is attributed to approximations made in evaluating the perturbation terms.

Tiepel, E. W.; Gubbins, K. E.

1973-01-01

85

Thermodynamic Properties of Liquid Ag-Au-Sn Alloys

NASA Astrophysics Data System (ADS)

The thermodynamic properties of liquid Ag-Au-Sn alloys were studied with an electromotive force (EMF) method using the eutectic mixture of KCl/LiCl as a liquid electrolyte. Activities of Sn in the liquid alloys were measured at three cross-sections with constant molar ratios of Ag:Au = 2:1, 1:1, and 1:2 with tin in the concentration range between 20 at.% and 90 at.% from the liquidus of the samples up to 1030 K. The integral Gibbs energies at 973 K and the integral enthalpies were calculated by Gibbs-Duhem integration.

Hindler, M.; Knott, S.; Mikula, A.

2010-10-01

86

Thermodynamic Properties of the Dipolar Spin Ice Model

We present a detailed theoretical overview of the thermodynamic properties of\\u000athe dipolar spin ice model, which has been shown to be an excellent\\u000aquantitative descriptor of the Ising pyrochlore materials Dy_2Ti_2O_7 and\\u000aHo_2Ti_2O_7. We show that the dipolar spin ice model can reproduce an effective\\u000aquasi macroscopically degenerate ground state and spin-ice behavior of these\\u000amaterials when the long-range

Roger G. Melko; Matthew Enjalran; Byron C. den Hertog; Michel. J. P. Gingras

2003-01-01

87

The thermodynamic properties of air plasmas are calculated in the framework of the C.L.T.E. hypothesis, for pressures varying from 1 to 200 atm, in a temperature range from 1000 to 30,000 K. In these calculations, the neutral mon--, di-, and triatomic species, as well as their positive and negative ions, are taken into account. From the internal partition function values,

J. Bacri; S. Raffanel

1987-01-01

88

Thermodynamic properties of hydrocarbons. [Nonane; undecane; tridecane; tetradecane; pentadecane

A numerical technique for calculating thermodynamic properties of non-polar pure substances is presented. It is based on the use of the extended principle of corresponding states for the determination of P-V-T relations and their reduction to the Benedict-Webb-Rubin equation of state. Virial coefficients are deduced and combined with specific heat data to determine the internal energy, entropy, and bulk modulus of elasticity. On this basis an algorithm is developed to calculate properties for a state fixed by any two independent parameters. The technique thus established is applied to normal paraffins, and the results for all species, from methane to hexadecane, are presented in tabular and graphical form.

Parker, T.E.; Sawyer, R.F.; Oppenheim, A.K.

1986-02-01

89

FLUID- THERMODYNAMIC AND TRANSPORT PROPERTIES OF FLUIDS (IBM PC VERSION)

NASA Technical Reports Server (NTRS)

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.

Fessler, T. E.

1994-01-01

90

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

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

2005-12-15

91

Thermodynamic Properties of a Suitable Working Fluid Mixture for Absorption Heat Pumps.

National Technical Information Service (NTIS)

An absorption heat pump process was considered with reference to thermodynamic properties of methanol lithium bromide as a working fluid. The process was optimized for operating conditions and the binary mixture used. All available thermodynamic data of m...

H. D. Eichholz S. Schulz

1982-01-01

92

Vibrational and thermodynamic properties of transition-metal nanoclusters

NASA Astrophysics Data System (ADS)

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

Grigoryan, Valeri G.; Springborg, Michael

2013-03-01

93

Thermodynamic properties of pulverized coal during rapid heating devolatilization processes

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

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

1994-07-01

94

Solvation of polymers as mutual association. II. Basic thermodynamic properties.

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 ?(AiB)(i) of solvated clusters, the extent of solvation of the polymer ?(solv), the solvation transition lines T(solv)(?B(o)), the specific heat C(V), 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. PMID:23635166

Dudowicz, Jacek; Freed, Karl F; Douglas, Jack F

2013-04-28

95

Thermodynamic properties of the Group 1A elements

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.

Alcock, C.B.; Itkin, V.P. [Univ. of Toronto (Canada); Chase, M.W. [National Institute of Standards and Technology, Gaithersburg, MD (United States)

1994-05-01

96

NASA Technical Reports Server (NTRS)

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

Nguyen, Huy H.; Martin, Michael A.

2004-01-01

97

Thermodynamic properties for polycyclic systems by non-calorimetric methods

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.

Steele, W.V.; Chirico, R.D.; Klots, T.D.

1993-03-01

98

Thermodynamic properties of asymptotically Reissne-Nordström black holes

NASA Astrophysics Data System (ADS)

Motivated by possible relation between Born-Infeld type nonlinear electrodynamics and an effective low-energy action of open string theory, asymptotically Reissne-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.

Hendi, S. H.

2014-07-01

99

Thermodynamic properties derived from the free volume model of liquids

NASA Technical Reports Server (NTRS)

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.

Miller, R. I.

1974-01-01

100

Thermodynamical properties of hairy black holes in n spacetime dimensions

The issue concerning the existence of exact black hole solutions in the presence of a nonvanishing cosmological constant and scalar fields is reconsidered. With regard to this, in investigating no-hair theorem violations, exact solutions of gravity having as a source an interacting and conformally coupled scalar field are revisited in arbitrary dimensional nonasymptotically flat space-times. New and known hairy black hole solutions are discussed. The thermodynamical properties associated with these solutions are investigated and the invariance of the black hole entropy with respect to different conformal frames is proved. The issue of the positivity of the entropy is discussed and resolved for the case of black holes immersed in de Sitter space.

Nadalini, Mario; Vanzo, Luciano; Zerbini, Sergio [Dipartimento di Fisica, Universita di Trento and Istituto Nazionale di Fisica Nucleare, Gruppo Collegato di Trento (Italy)

2008-01-15

101

Structural and thermodynamic properties of AlB2 compound

NASA Astrophysics Data System (ADS)

We employ a first-principles plane wave method with the relativistic analytic pseudopotential of Hartwigsen, Goedecker and Hutter (HGH) scheme in the frame of DFT to calculate the equilibrium lattice parameters and the thermodynamic properties of AlB2 compound with hcp structure. The obtained lattice parameters are in good agreement with the available experimental data and those calculated by others. Through the quasi-harmonic Debye model, obtained successfully are the dependences of the normalized lattice parameters a/a0 and c/c0 on pressure P, the normalized primitive cell volume V/V0 on pressure P, the variation of the thermal expansion ? with pressure P and temperature T, as well as the Debye temperature ?D and the heat capacity CV on pressure P and temperature T.

Zhou, Xiao-Lin; Liu, Ke; Chen, Xiang-Rong; Zhu, Jun

2006-12-01

102

Thermodynamic properties of chlorite and berthierine derived from calorimetric measurements

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

103

Thermodynamic properties of hydrate phases immersed in ice phase

NASA Astrophysics Data System (ADS)

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.

Belosludov, V. R.; Subbotin, O. S.; Krupskii, D. S.; Ikeshoji, T.; Belosludov, R. V.; Kawazoe, Y.; Kudoh, J.

2006-01-01

104

Thermodynamic and transport properties of superconducting Mg10B2.

Transport and thermodynamic properties of a sintered pellet of the newly discovered MgB2 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, Hc2, with magnetization data giving dHc2/dT = 0.44 T/K at the transition temperature of Tc = 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 1 T. The value of dHc/dT at Tc is estimated to be about 12 mT/K, a value similar to classical superconductors like Sn. Hence, the Ginzburg-Landau parameter kappa approximately 26. Estimates of the critical supercurrent density, Jc, using hysteresis loops and the Bean model, give critical current densities on the order of 10(5) A/cm2. Hence the supercurrent coupling through the grain boundaries is comparable to intermetallics like Nb3Sn. PMID:11289944

Finnemore, D K; Ostenson, J E; Bud'ko, S L; Lapertot, G; Canfield, P C

2001-03-12

105

Thermodynamic and Transport Properties of Superconducting Mg10B2

NASA Astrophysics Data System (ADS)

Transport and thermodynamic properties of a sintered pellet of the newly discovered MgB2 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, Hc2, with magnetization data giving dHc2/dT = 0.44 T/K at the transition temperature of Tc = 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 1 T. The value of dHc/dT at Tc is estimated to be about 12 mT/K, a value similar to classical superconductors like Sn. Hence, the Ginzburg-Landau parameter ?~26. Estimates of the critical supercurrent density, Jc, using hysteresis loops and the Bean model, give critical current densities on the order of 105 A/cm2. Hence the supercurrent coupling through the grain boundaries is comparable to intermetallics like Nb3Sn.

Finnemore, D. K.; Ostenson, J. E.; Bud'Ko, S. L.; Lapertot, G.; Canfield, P. C.

2001-03-01

106

Thermodynamic Properties of Ultracold Bose Gas: Transition Exponents and Universality

NASA Astrophysics Data System (ADS)

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.

Goswami, Sanchari; Das, Tapan Kumar; Biswas, Anindya

2013-08-01

107

Thermodynamic and kinetic properties of amorphous and liquid states

The magnitude and temperature dependence of the liquid state shear modulus G, specific heat C{sub p}, diffusivity D, and viscosity {eta} should all be closely related, according to the interstitialcy model, if a recent proposal by Dyre et al. is generally true. They suppose that the viscosity is given by {eta} = {eta}{sub 0} exp (F/kT), where {eta}{sub 0} is a reference viscosity and F is given by the work required to shove aside neighboring particle in a diffusion process, where F = GV{sub c} and V{sub c} is a characteristic volume. In the interstitialcy model the high frequency thermodynamic liquid state shear modulus is given by G(T) = G{sub 0} exp [{minus}{gamma}(T/T{sub 0} {minus} 1)], where G{sub 0} is the shear modulus at a reference temperature T{sub 0}, which can be taken as the glass temperature. The resulting non-Arrhenius behavior of the viscosity is compared with experimental data. A critical quantitative analysis for a Zr{sub 41.2}Ti{sub 13.8}Cu{sub 12.5}Ni{sub 10}Be{sub 225} alloy does not support the shoving model, but the thermodynamic properties can be understood in terms of mixed interstitials composed of metal-beryllium complexes.

Granato, A.V. [Univ. of Illinois, Urbana, IL (United States). Dept. of Physics

1998-07-01

108

Simplified curve fits for the thermodynamic properties of equilibrium air

NASA Technical Reports Server (NTRS)

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).

Srinivasan, S.; Tannehill, J. C.; Weilmuenster, K. J.

1986-01-01

109

The thermodynamic properties of hydrated -Al2O3 nanoparticles

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

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

2013-01-01

110

The thermodynamic properties of hydrated ?-Al2O3 nanoparticles.

In this paper we report a combined calorimetric and inelastic neutron scattering (INS) study of hydrated ?-Al2O3 (?-alumina) nanoparticles. These complementary techniques have enabled a comprehensive evaluation of the thermodynamic properties of this technological and industrially important metal oxide to be achieved. The isobaric heat capacity (C(p)) data presented herein provide further critical insights into the much-debated chemical composition of ?-alumina nanoparticles. Furthermore, the isochoric heat capacity (C(v)) of the surface water, which is so essential to the stability of all metal-oxides at the nanoscale, has been extracted from the high-resolution INS data and differs significantly from that of ice-Ih due to the dominating influence of strong surface-water interactions. This study also encompassed the analysis of four ?-alumina samples with differing pore diameters [4.5 (1), 13.8 (2), 17.9 (3), and 27.2 nm (4)], and the results obtained allow us to unambiguously conclude that the water content and pore size have no influence on the thermodynamic behaviour of hydrated ?-alumina nanoparticles. PMID:24387386

Spencer, Elinor C; Huang, Baiyu; Parker, Stewart F; Kolesnikov, Alexander I; Ross, Nancy L; Woodfield, Brian F

2013-12-28

111

NASA Technical Reports Server (NTRS)

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

Gordon, S.

1982-01-01

112

ERIC Educational Resources Information Center

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…

Bickel, Robert D.; Zeller, Trisha A.

113

ERIC Educational Resources Information Center

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…

Goldblatt, Steven M.; Piele, Philip K.

114

Generalized thermodynamic and transport properties. II. Molecular liquids

NASA Astrophysics Data System (ADS)

In the present paper, we extend the method described in paper I [D. Bertolini and A. Tani, preceding paper, Phys. Rev. EPLEEE81539-375510.1103/PhysRevE.83.031201 83, 031201 (2011)] to molecular liquids, which allows us to solve the exact kinetic equation proposed by de Schepper [Phys. Rev. APLRAAN1050-294710.1103/PhysRevA.38.271 38, 271 (1988)] without approximations. In particular, generalized thermodynamic properties (enthalpy, specific heat, and thermal expansion coefficient) and transport properties (longitudinal viscosity, thermal conductivity) have been calculated for three liquids of increasing complexity, namely dimethyl sulfoxide, hydrogen fluoride, and SPC/E water. All results have been obtained by the molecular formalism as well as the atomic one, corrected for intramolecular correlations that are due to the models adopted. As done for simple liquids, the coupling between the viscous stress tensor and the energy flux vector has been calculated exactly. We also show that the Markov assumption for the dynamics related to thermal conductivity can only be adopted with caution.

Bertolini, D.; Tani, A.

2011-03-01

115

Thermodynamic and optical properties of plasma, metals, and dielectrics

This book presents analytically-obtained data on the principal thermodynamic properties (partial composition, degree of ionization, pressure, internal energy, effective adiabatic exponent) of the plasma of metals such as copper, stainless steel (Kh18N10T), tungsten, molybdenum, tantalum, zirconium, chromium, niobium, nickel, and silicon, and of dielectrics-zirconium dioxide (ZrO{sub 2}), silicon dioxide (SiO{sub 2}), polytetrafluorethylene (Teflon), organic glass (Plexiglas), textolite, polyformaldehyde and caprolactum at temperatures T between 10{sup 4} and 10{sup 6} K and plasma densities p = 10{sup {minus}4} TO 1 Kg/m{sup 3}. Since plasma systems employing the products of erosion of dielectrics (16--18) can be efficiently employed as sources of wide-bank radiation and used as such in solving a number of scientific and applied problems, we list her the analytically obtained values of the principal optical properties (continuous-absorption coefficient, group absorption coefficient, Planck-average absorption coefficient and Rosseland-averaged radiation mean free path) of the plasmas of Teflon, Plexiglas, textolite, polyformaldehyde and caprolactum over the previously mentioned ranges of T and p.

Protasov, Y.S.

1991-01-01

116

Electronic, mechanical, and thermodynamic properties of americium dioxide

NASA Astrophysics Data System (ADS)

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

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

2013-10-01

117

Ideal gas thermodynamic properties for the phenyl, phenoxy, and o-biphenyl radicals

NASA Technical Reports Server (NTRS)

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.

Burcat, A.; Zeleznik, F. J.; Mcbride, B. J.

1985-01-01

118

Excess Thermodynamic Properties of Concentrated Aqueous Solutions at High Temperatures

Measurements of the vapor pressure of the solvent in wide ranges of concentration and temperature provide information on solute solvation and ion pairing--the two phenomena most often invoked for description of dilute solutions. Even in moderately concentrated solutions, as interionic distances become comparable to ionic diameters, these simple concepts gradually lose their meaning and solutions behave like molten salts. The usefulness of experimental vapor pressure results increases rapidly with their accuracy, since derived properties, such as solution enthalpies and heat capacities, can be calculated. Very accurate results can be obtained by the isopiestic method, but primary vapor pressure data for standard solutions are needed. In order to obtain vapor pressures at conditions where accurate isopiestic standards are not available and to establish more accurate standards, the ORNL isopiestic apparatus was modified for simultaneous direct vapor pressure measurements and isopiestic comparisons. There are no comprehensive solution theories derived from molecular level models and able to predict thermodynamic properties of various electrolytes as the composition changes from dilute solutions to molten salts in a wide range of temperatures. Empirical and semi-empirical models are useful for representation of experimental results, interpretation of measurements of other properties such as conductance., solubility or liquid-vapor partitioning of solutes, and for verification of theoretical predictions. Vapor pressures for aqueous CaCl{sub 2}, CaBr{sub 2}, LiCl, LiBr, LiI, NaI were measured at temperatures between 380 and 523 K in the concentration range extended to water activities below 0.2 (over 30 mol/kg for LiCl). General equations based on the modified Pitzer ion-interaction model were used to obtain enthalpy and heat capacity surfaces, which are compared with direct calorimetric measurements.

Guszkiewicz, M.S.

2001-06-07

119

Thermodynamic properties of a suitable working fluid mixture for absorption heat pumps

NASA Astrophysics Data System (ADS)

An absorption heat pump process was considered with reference to thermodynamic properties of methanol lithium bromide as a working fluid. The process was optimized for operating conditions and the binary mixture used. All available thermodynamic data of mixture properties were collected. They were then complemented by vapor-liquid equilibrium measurements and heat of mixing experiments with the result of a theoretical correlation. By a critical selection of properties, the binary mixture CH30H LiBr was qualified as a heat pump working fluid. In addition, thermodynamic properties of methanol are derived by a fundamental equation.

Eichholz, H. D.; Schulz, S.

1982-04-01

120

Thermodynamic properties and structural stability of thorium dioxide.

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

Lu, Y; Yang, Y; Zhang, P

2012-06-01

121

Investigation of thermodynamic properties of metal-oxide catalysts

NASA Astrophysics Data System (ADS)

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

Shah, Parag Rasiklal

122

Thermodynamic and transport properties of air/water mixtures

NASA Technical Reports Server (NTRS)

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

Fessler, T. E.

1981-01-01

123

The thermodynamic properties of normal liquid helium 3

NASA Astrophysics Data System (ADS)

The thermodynamic properties of normal liquid helium 3 are calculated by using the lowest order constrained variational (LOCV) method. The Landau Fermi liquid model and Fermi-Dirac distribution function are considered as our statistical model for the uncorrelated quantum fluid picture and the Lennard-Jones and Aziz potentials are used in our truncated cluster expansion (LOCV) to calculate the correlated energy. The single particle energy is treated variationally through an effective mass. The free energy, pressure, entropy, chemical potential and liquid phase diagram as well as the helium 3 specific heat are evaluated, discussed and compared with the corresponding available experimental data. It is found that the critical temperature for the existence of the pure gas phase is about 4.90 K (4.45 K), which is higher than the experimental prediction of 3.3 K, and the helium 3 flashing temperature is around 0.61 K (0.50 K) for the Lennard-Jones (Aziz) potential.

Modarres, M.; Moshfegh, H. R.

2009-09-01

124

Rhamnolipid surface thermodynamic properties and transport in agricultural soil.

Rhamnolipid is a biosurfactant produced by several Pseudomonas species, which can wet hydrophobic soils by lowering the cohesive and/or adhesive surface tension. Because of its biodegradability, rhamnolipid applications bring minimal adverse impact on the soil and groundwater as compared with that of chemical wetting agents. Subsequently, rhamnolipid applications have more advantages when used to improve irrigation in the agricultural soil, especially under draught conditions. In the presence of rhamnolipid, water surface tension dropped linearly with the increase of rhamnolipid concentration until the rhamnolipid critical micelle concentration (CMC) of 30 mg/L was reached. Below the CMC, rhamnolipid had linear adsorption isotherms on the soil with a partition coefficient of 0.126 L/kg. Rhamnolipid transport breakthrough curves had a broad and diffuse infiltration front, indicating retention of rhamnolipid on the soil increased with time. Rhamnolipid transport was found to be well represented by the advection-dispersion equation based on a local equilibrium assumption. When applied at concentrations above the CMC, the formed rhamnolipid micelles prevented rhamnolipid adsorption (both equilibrium adsorption and kinetic adsorption) in the soil. It was discovered in this research that rhamnolipid surface thermodynamic properties played the key role in controlling rhamnolipid transport. The attractive forces between rhamnolipid molecules contributed to micelle formation and facilitated rhamnolipid transport. PMID:24394947

Renfro, Tyler Dillard; Xie, Weijie; Yang, Guang; Chen, Gang

2014-03-01

125

Hydrogrossular (Katoite): Vibrational, Crystal-Chemical and Thermodynamic Properties

NASA Astrophysics Data System (ADS)

There is great current interest in understanding interactions between H2O and its components and various Earth materials. Here, questions such as the bulk water content of the mantle, and what phases can incorporate OH- and in what concentrations come immediately to mind. In this regard, the hydrogarnet substitution (i.e., O4H4?SiO4) has received special attention, because it is a verified mechanism for allowing the incorporation of OH- in garnet and possibly in other silicates as well. At relatively low temperatures there is complete solid solution between Ca3Al2Si3O12 and Ca3Al2O12H12. The latter, pure OH-containing end-member is termed katoite/hydrogrossular. Its crystal structure has been investigated by various workers using X-ray and neutron diffraction, including at high pressures. Little is known about its vibrational properties and its thermodynamic behavior is not fully understood. Thus, we studied the low temperature IR spectra and measured the heat capacity of katoite in order to investigate its vibrational, crystal-chemical and thermophysical properties. Katoite was synthesized hydrothermally in Au capsules at 250 °C and 3 kb water pressure. X-ray powder measurements show that about 98-99% katoite was obtained. Powder IR spectra were recorded between 298 K and 10 K. The spectra are considerably different in the high wavenumber region, where O-H stretching modes occur. At room temperature the IR-active O-H band located around 3662 cm-1 is broad and it narrows and shifts to higher wavenumbers and also develops structure below about 80 K. Concomitantly, additional weak intensity O-H bands located around 3600 cm-1 begin to appear and they become sharper and increase in intensity with further decreases in temperature. The spectra indicate that the vibrational behavior of individual OH groups and their collective interactions measurably affect the lattice dynamic (i.e. thermodynamic) behavior. The low temperature heat capacity behavior was investigated with a relaxation calorimeter between 5 and 300 K on a mg-sized sample. The heat capacity data are well behaved at T < 300 K and show a monotonic decrease in magnitude with decreasing temperature. A standard third-law entropy value of S° = 421.7 ± 1.6 J/mol.K was calculated. Using this new calorimetric-based S° value and published standard enthalpy of formation data for katoite, a calorimetric-based Gibbs free energy of formation at 298 K can be obtained as ?G°f = -5021.2 kJ/mol. The Cp data show no evidence for any phase transition as possibly expected by the change in OH-mode behavior with decreasing temperature. It is worth noting that the katoite, in terms of lattice dynamic or thermodynamic behavior, should be thought of having OH groups and not O4H4 clusters or polyhedral units as is often written in the literature. The single crystallographic OH group in katoite shows very weak, if any, hydrogen bonding and the H atoms have large amplitudes of vibration. Very weak H bonding or the lack of it affects the nature of low energy OH-related vibrations and this leads to katoite's large S° value.

Dachs, E.; Geiger, C. A.

2011-12-01

126

ERIC Educational Resources Information Center

The author notes that controversies over construction bids and contracts continue to represent the largest number of property cases reported in this year's chapter. Most of these cases are routine disputes between colleges or universities and contractors over such issues as the return of bid bonds, recovery of additional costs for construction…

Piele, Philip K.

127

ERIC Educational Resources Information Center

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…

Piele, Philip K.; Johnson, Margaret M.

128

Tables of the Thermodynamic Properties of Air and the Exhaust Gas from a Turbine Engine.

National Technical Information Service (NTIS)

Thermodynamic properties of air and the exhaust gas from a turbine engine (C(n)H(1.95n))/Air System) are presented in tabular form. The properties presented air enthalpy (h), entropy (s), and specific heat at constant pressure (cp). The properties of air ...

J. M. Pelton K. L. Hannah

1976-01-01

129

NASA Technical Reports Server (NTRS)

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

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

1973-01-01

130

THERMODYNAMIC PROPERTIES OF MC (M = V, Nb, Ta): FIRST-PRINCIPLES CALCULATIONS

NASA Astrophysics Data System (ADS)

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.

Cao, Yong; Zhu, Jingchuan; Liu, Yong; Long, Zhishen

2013-07-01

131

National Technical Information Service (NTIS)

The determination of the thermodynamic properties are examined through the basic equations such as: state equation (Beattie-Bridgeman Form), saturation pressure equation, specific heat constant pressure or constant volume equation, and specific volume or ...

W. Gill F. F. Filho R. Ribeirodeoliveira

1986-01-01

132

National Technical Information Service (NTIS)

This report presents improved values for the heats of formation and some other thermodynamic properties of a number of light-element substances -- resulting from recent NBS experimental studies (calorimetric, vaporization, and spectroscopic) and critical ...

C. W. Beckett T. B. Douglas

1967-01-01

133

National Technical Information Service (NTIS)

This report discusses theoretical and experimental work aimed at elucidating the effects of molecular structure and intermolecular forces on macroscopic thermodynamic properties. Theoretically, we have learned how to treat various molecular interactions s...

M. D. Donohue

1984-01-01

134

National Technical Information Service (NTIS)

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 success...

M. D. Donohue

1990-01-01

135

Thermodynamic and Transport Properties of Air, Carbon Dioxide and Helium in Graphical Form.

National Technical Information Service (NTIS)

The thermodynamic and transport properties necessary for heat transfer and gas flow experiments using air, carbon dioxide and helium are given in graphical form. These include density, enthalpy, specific heat, thermal conductivity, viscosity, and Prandtl ...

M. A. M. Pirie

1978-01-01

136

Vibrational and thermodynamic properties of Ni 3 S 2 polymorphs from first-principles calculations

We have calculated the compressional, vibrational, and thermodynamic properties of Ni3S2 heazlewoodite and the high-pressure orthorhombic phase (with Cmcm symmetry) using the generalized gradient approximation\\u000a to the density functional theory in conjunction with the quasi-harmonic approximation. The predicted Raman frequencies of\\u000a heazlewoodite are in good agreement with room-temperature measurements. The calculated thermodynamic properties of heazlewoodite\\u000a at room conditions agree very

Yonggang G. Yu; Nancy L. Ross

2011-01-01

137

Structural and thermodynamic properties of the Zn-substituted YBaCu-oxides

NASA Astrophysics Data System (ADS)

Structural and thermodynamic properties of the Zn-substituted YBaCu-oxides have been investigated. The thermodynamic properties have been studied in terms of oxygen point defects, related to the departure from stoichiometry. Results obtained for YBa 2Cu 2.88Zn 0.12O z have been interpreted with a novel model taking into account the fact that Zn goes to Cu(1) sites..

Legros-Gledel, C.; Marucco, J.-F.; Touzelin, B.; Gabilly, R.; Pinatel-Philippot, A.; Alloul, H.

1990-12-01

138

Ab initio thermodynamic properties of point defects and O-vacancy diffusion in Mg spinels

We report ab initio plane wave density functional theory studies of thermodynamic properties of isolated cation substitutions and oxygen vacancies in magnesium spinel, MgAl2O4 . The formation enthalpy of Ca, Cu, and Zn substitutions of Mg cation indicate that transition metal dopants are energetically stable in the bulk of MgAl2O4 at low oxygen chemical potential. The electronic and thermodynamic properties

Zbigniew Lodziana; Jacek Piechota

2006-01-01

139

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

NASA Technical Reports Server (NTRS)

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

Fessler, T. E.

1979-01-01

140

NASA Technical Reports Server (NTRS)

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

Nguyen, Huy H.; Martin, Michael A.

2003-01-01

141

Structural and thermodynamic properties of Au2-58 clusters

NASA Astrophysics Data System (ADS)

The geometries and electronic properties of the isolated neutral Au2-58 are studied theoretically using a parametrized density-functional tight-binding method combined with genetic algorithms. Various descriptors are used in analyzing the structural and electronic properties. In addition, the temperature dependence of the vibrational heat capacities of the optimized clusters will be presented, which allow to study the low temperature properties of the clusters. We find that the vibrational heat capacity of the Au clusters is strongly size dependent in particular at low temperatures.

Dong, Yi; Springborg, Michael; Warnke, Ingolf

2013-03-01

142

EquilTheTA: Thermodynamic and transport properties of complex equilibrium plasmas

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

Colonna, G.; D'Angola, A. [CNR-IMIP Bari, via Amendola 122/D - 70126 Bari (Italy); DIFA, Universita della Basilicata, via dell'Ateneo Lucano, 1085100 Potenza (Italy)

2012-11-27

143

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

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

V. Brandani; J. M. Prausnitz

1982-01-01

144

NASA Astrophysics Data System (ADS)

The structural, elastic, electronic, phonon and thermodynamic properties of UN are studied by density functional theory (DFT) within local-density approximation (LDA) and generalized gradient approximation (GGA), and GGA + U. The GGA calculations of the ground state structural and elastic properties of UN show an overall better agreement with experimental data compared to LDA or GGA + U. The melting temperature of UN (Tm) is estimated from the calculated elastic constant, with GGA predicting Tm = 2944 ± 300 K, in excellent agreement with experimental data. The calculated phonon dispersions of UN agree well with the low temperature measurements. Furthermore, the thermodynamic properties of UN are studied using quasiharmonic approximation by including both lattice vibrational and thermal electronic contributions. The predicted thermodynamic properties, such as enthalpy, entropy, Gibbs energy, heat capacity and thermal expansion coefficient, agree well with experimental data. The derived thermodynamic functions of UN are useful to the thermodynamic modeling of phase stabilities in UN-based materials. This study shows that the thermal electronic energy and entropy due to U 5f electrons are important to describe the free energy of UN, due to the metallic character of UN. The calculated thermodynamic properties also suggest that the anharmonic effects are less important in UN even at high-temperature.

Mei, Zhi-Gang; Stan, Marius; Pichler, Benjamin

2013-09-01

145

Thermodynamic properties in the molecular dynamics ensemble applied to the Gaussian core model fluid

NASA Astrophysics Data System (ADS)

The thermodynamic properties of pressure, energy, isothermal pressure coefficient, thermal expansion coefficient, isothermal and adiabatic compressibilities, isobaric and isochoric heat capacities, Joule-Thomson coefficient, and speed of sound are considered in a classical molecular dynamics ensemble. These properties were obtained 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. The complete thermodynamic information about an equilibrium system can be obtained from this general formalism. We apply this method to the Gaussian core model fluid because the complex phase behavior of this simple model provides a severe test for this treatment. Waterlike and other anomalies are observed for some of the thermodynamic properties of the Gaussian core model fluid.

Mausbach, Peter; Sadus, Richard J.

2011-03-01

146

The thermodynamic properties of pressure, energy, isothermal pressure coefficient, thermal expansion coefficient, isothermal and adiabatic compressibilities, isobaric and isochoric heat capacities, Joule-Thomson coefficient, and speed of sound are considered in a classical molecular dynamics ensemble. These properties were obtained 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. The complete thermodynamic information about an equilibrium system can be obtained from this general formalism. We apply this method to the gaussian core model fluid because the complex phase behavior of this simple model provides a severe test for this treatment. Waterlike and other anomalies are observed for some of the thermodynamic properties of the gaussian core model fluid. PMID:21428640

Mausbach, Peter; Sadus, Richard J

2011-03-21

147

Structural, thermodynamic and phonon properties of SbSi and SbSBr single crystals

NASA Astrophysics Data System (ADS)

The structural, dynamical and thermodynamic properties of antimony sulfoiodide (SbSI) and antimony sulfobromide (SbSBr) are investigated by using an ab-initio pseudopotential method applying density functional theory (DFT) within the local density approximation (LDA). The dynamical properties, such as the phonon dispersion and the phonon density of states, are calculated. Making a factor group analysis we classify the phonon modes. Moreover, the thermodynamic properties, such as the entropy and the constant-volume specific heat, as functions of temperature and the phonon contribution to the free energy and the internal energy are calculated.

Dogan, E. Kilit; Aycibin, M.; Gulebaglan, S. Erden; Secuk, M. N.; Erdinc, B.; Akkus, H.

2013-12-01

148

Thermodynamic properties of aqueous tellurium species between 25 and 350°

NASA Astrophysics Data System (ADS)

Tellurium occurs in trace amounts in a wide range of geological environments, the most important of which are epithermal ore deposits that contain precious- and base-metal telluride minerals. The behaviour of Te in hydrothermal fluids is poorly known, making it difficult to understand the formation of these types of deposits. This paper reviews the existing information for aqueous Te species and reports the derivation of their thermodynamic properties from 25 to 350°C. Free energies of formation at 25°C were derived mainly from experimental data and estimated at higher temperature using new experimental data for the solubility of tellurite (TeO 2) up to 80°C and isocoulombic techniques. The stabilities of aqueous Te species were then predicted as a function of temperature, redox, acidity, and total tellurium concentration. For conditions typical of many ore-forming liquids telluride and tellurite species are predicted to be the most important Te species. Under relatively reduced (e.g., magnetite-stable) and acid to neutral pH conditions, the most important species are predicted to be H 2Te (aq) and HTe -. In more oxidized (hematitestable) environments, H 3TeO 3+, H 2TeO 3, and HTeO 3- predominate. There is a polymeric species (Te 22-) that may be important under some conditions, but its stability is limited by the solubility of native Te and dependent on total Te concentration. At temperatures between 100 and 300°C, it is predicted to be stable at pH greater than approximately 8 and oxygen activities near and below the Te -II/Te IV boundaries. At even higher pH (>10 to 12) Te 2- and Te0 32- predominate. The most oxidized Te species, the tellurates (H 6TeO 6, H 5Te0 6- , and H 4TeO 6-) may be important at low temperature (<50°C) and high oxygen activity (e.g., atmospheric), although circumstantial evidence suggests they are not stable under geological conditions. Tellurium concentrations expected in hydrothermal fluids are low (less than 10 ppb at 300°C), based on solubility calculations for native Te (acid to neutral pH, range of oxygen activity at magnetite-hematite ± 6 log units). The solubility of native Te increases with oxidation and reduction away from a minimum near magnetite-hematite (at 300°C). pH has no effect at neutral to acid conditions, except under oxidized conditions and low pH (<2) where H 3TeO 3+ is stable. At high pH (>7 or 8) the solubility of native Te increases with increasing pH regardless of the oxygen activity. Measured Te concentrations in experiments on the solubility of hessite + native Te + chlorargyrite in HCl solutions at 300°C are much higher (1's to 1000's of ppm) than predicted (10's to 100's of ppb) and may be evidence for unknown Te species (e.g., metal-tellurium complexes or aqueous Te in other valence states). The low predicted concentrations of aqueous Te may also indicate that vapour-phase transport of Te is important in the formation of telluride-bearing epithermal ore deposits.

McPhail, D. C.

1995-03-01

149

Ideal-gas thermodynamic properties for natural-gas applications

Calculating caloric properties from a thermal equation of state requires information such as isobaric heat capacities in the ideal-gas state as a function of temperature. In this work, values for the parameters of thecp0 correlation proposed by Aly and Lee were newly determined for 21 pure gases which are compounds of natural gas mixtures. The values of the parameters were

M. Jaeschke; P. Schley

1995-01-01

150

Modeling Physical and Thermodynamic Properties via Inverse Normalizing Transformations

The inverse normalizing transformation (INT) represents a generalization of the inverse of the Box-Cox transformation. It is shown that several well-known and widely used property correlation equations, such as the Antoine, the truncated Riedel, the Rackett, and the Guggenheim equations can be derived from the INT. Its use is demonstrated for modeling the temperature dependence of vapor pressure, solid and

Haim Shore; Mordechai Shacham

2002-01-01

151

Gibbs: Phase equilibria and symbolic computation of thermodynamic properties

A general purpose open source, Python-based framework, Gibbs, is presented to perform multiphysical equilibrium calculations of material properties. The developed architecture allows to prototype symbolic and numerical representations of materials by starting from analytic models, tabulated experimental data, or Thermo-Calc data files. These constructions are based on the addition of arbitrary energy contributions that range from the traditional thermochemical to

Thomas Cool; Alexander Bartol; Matthew Kasenga; Kunal Modi; R. Edwin García

2010-01-01

152

Two-dimensional O2 adsorbed on graphite. [thermodynamic properties

NASA Technical Reports Server (NTRS)

Properties of two-dimensional O2 adsorbed on graphite are calculated in the extremely low-coverage delta region and for monolayers, with use of pattern-recognition optimization and Monte Carlo techniques. Equilibrium configurations and orientations, orientational order-disorder, melting, and dissociation transitions are predicted at various O2 densities. Phase characteristics, including a plastic crystallite phase, are compared with experiment.

Etters, R. D.; Pan, R.-P.; Chandrasekharan, V.

1980-01-01

153

NASA Astrophysics Data System (ADS)

The molecular geometries, infrared vibrational spectra, and thermodynamic properties of octanitrocubane (ONC) are calculated using the density functional theory (DFT) method at the B3LYP/6-31G* level. The IR frequency scaling factor 0.9501 suitable for polynitrocubanes is obtained at the B3LYP/6-31G* level, and the calculated IR frequencies of ONC are scaled. The accurate heat of formation 726.47 kJ/mol of ONC in gas phase is obtained via designed isodesmic reaction in which the cubane cage skeleton has been kept. The sublimation enthalpy, density, and heat of formation for ONC crystal are also calculated, and they are 220.63 kJ/mol, 2.189 g/cm3, and 505.84 kJ/mol, respectively. In addition, the estimated detonation velocity and detonation pressure of ONC are 10.26 mm/ms and 520.86 kbar, respectively. Finally, the pyrolysis mechanism of ONC is studied using various theoretical methods, i.e., MP2, DFT, and selected MINDO/3 semiempirical MO, based on the unrestricted Hartree-Fock model. The calculated results show that the pyrolysis initiation reaction of ONC, i.e., rate-controlling step, is to form a diradical by the single C-C bond breaking in the cube. The second C-C bond breaking is easily followed to form a nitrocyclooctatetraene. The calculated activation energy for the pyrolysis initiation reaction of ONC, obtained from B3LYP/6-31G* method, is 155.30 kJ/mol, which this rather large activation energy indicates that ONC is a new type of energetic material with less sensitivity and better thermal stability, and has highly exploitable values.

Zhang, Ji; Xiao, Heming

2002-06-01

154

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

NASA Astrophysics Data System (ADS)

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

Parveen, Atahar; Gaur, N. K.

2012-02-01

155

NASA Astrophysics Data System (ADS)

We present a system of analytical equations for computation of all thermodynamic properties of dry steam and liquid water (undesaturated, saturated and metastable supersaturated) and properties of the liquid-vapor phase interface. The form of the equations is such that it enables computation of all thermodynamic properties for independent variables directly related to the balanced quantities - total mass, liquid mass, energy, momenta. This makes it suitable for the solvers of fluid dynamics equations in the conservative form. Thermodynamic properties of dry steam and liquid water are formulated in terms of special thermodynamic potentials and all properties are obtained as analytical derivatives. For the surface tension, the IAPWS formula is used. The interfacial internal energy is derived from the surface tension and it is used in the energy balance. Unlike common models, the present one provides real (contrary to perfect gas approximation) properties of steam and water and reflects the energetic effects due to the surface tension. The equations are based on re-fitting the reference formulation IAPWS-95 and selected experimental data. The mathematical structure of the equations is optimized for fast computation.

Hrubý, Jan; Duška, Michal

2014-03-01

156

Thermodynamics and Ferroelectric Properties of KNbO3

The Landau-Ginsburg-Devonshire (LGD) phenomenological theory is employed to model and predict the ferroelectric phase transitions and properties of single-domain potassium niobate (KNbO3). Based on the LGD theory and the experimental data of KNbO3 single crystal, an eighth-order polynomial of free energy function is proposed. The fitted coefficients are validated by comparing to a set of experimental measured values including phase transition temperatures, spontaneous polarization, dielectric constants, and lattice constants. The effects of hydrostatic pressure and external electric field on phase transition temperatures and piezoelectric coefficients are investigated. The free energy function may be used a phase-field modeling to predict ferroelectric domain structures and properties of KNbO3 bulk crystals and films by phase-field approach.

Liang, Linyun; Li, Yulan; Chen , L.Q.; Hu, Shenyang Y.; Lu, Guang-Hong

2009-11-15

157

Thermodynamic properties of liquid copper-lead alloys

Activities of lead in liquid copper-lead alloys were measured in the temperature range 1000 to 1200 ?C at intervals of 50\\u000a ?C by the dew-point technique. Various partial and integral molar properties of the liquid alloys were evaluated from the\\u000a data, and the boundaries of liquid immiscibility in the Cu-Pb phase diagram were calculated. The activity coefficients of\\u000a lead and

M. Timuçin

1980-01-01

158

NASA Astrophysics Data System (ADS)

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

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

2012-12-01

159

Elastic, mechanical, and thermodynamical properties of superionic lithium oxide for high pressures

NASA Astrophysics Data System (ADS)

The elastic and thermodynamic properties of Li2O for high pressures are presented. For cubic Li2O, model effective interatomic interaction potential incorporating long-range Coulomb, charge transfer interactions, covalency effect, Hafemeister and Flygare type short-range overlap repulsion extended up to the second neighbor ions and van der Waals interactions is formulated. Both charge transfer interactions and covalency effect apart from long-range Coulomb are important in revealing high-pressure-induced associated volume collapse, elastic, and thermodynamical properties. The elastic constants, Debye temperature, and thermal expansion coefficient obtained are in good agreement with the available experimental data and other theoretical results. The Li2O is mechanically stiffened, thermally softened, and brittle in nature as inferred from the pressure-dependent elastic constants behavior. To our knowledge, this is the first quantitative theoretical prediction of the pressure dependence of elastic, thermal, and thermodynamical properties of Li2O and still awaits experimental confirmation.

Varshney, Dinesh; Shriya, Swarna

2013-06-01

160

NASA Technical Reports Server (NTRS)

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.

Allison, D. O.

1972-01-01

161

The thermodynamic properties of xanthone (XTH) and 135 polybrominated xanthones (PBXTHs) in the standard state have been calculated at the B3LYP\\/6-31G* level using Gaussian 03 program. The isodesmic reactions were designed to calculate the standard enthalpy of formation (?fH ? ) and standard free energy of formation (?fG ? ) of PBXTH congeners. The relations of these thermodynamic parameters with

SHAN Gang; LI Xiu-Jiu; WANG Zun-Yao; YANG Guo-Ying

162

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

Donald G. Archer

1993-01-01

163

Electrolytes: Transport Properties and Non-Equilibrium Thermodynamics.

National Technical Information Service (NTIS)

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. (ERA citation 06:011317)

D. G. Miller

1980-01-01

164

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

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

2008-02-01

165

NASA Technical Reports Server (NTRS)

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

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

1990-01-01

166

Thermodynamic properties of correlated fermions in lattices with spin-dependent disorder

NASA Astrophysics Data System (ADS)

Motivated by the rapidly growing possibilities for experiments with ultracold atoms in optical lattices, we investigate the thermodynamic properties of correlated lattice fermions in the presence of an external spin-dependent random potential. The corresponding model, a Hubbard model with spin-dependent local random potentials, is solved within dynamical mean-field theory. This allows us to present a comprehensive picture of the thermodynamic properties of this system. In particular, we show that for a fixed total number of fermions spin-dependent disorder induces a magnetic polarization. The magnetic response of the polarized system differs from that of a system with conventional disorder.

Makuch, K.; Skolimowski, J.; Chakraborty, P. B.; Byczuk, K.; Vollhardt, D.

2013-04-01

167

Thermodynamic properties of liquid copper–indium–tin alloys determined from e.m.f. measurements

The thermodynamics properties of liquid Cu–In–Sn alloys were determined using solid oxide galvanic cells with zirconia electrolyte:(I)Re+kanthal,Cux-Iny-Sn(1-x-y),‘In2O3’\\/\\/ZrO2+(Y2O3)\\/\\/NiO,Ni,Ptin the temperature range (973 to 1223)K. Applied In2O3 can be either pure or in the solid solutions with SnO2.Thermodynamics properties of the liquid phase were described by the Redlich–Kister–Muggianu formula. Using the commercial software different phase relations in the ternary system were calculated

Dominika Jendrzejczyk-Handzlik; Wojciech Gierlotka; Krzysztof Fitzner

2009-01-01

168

Thermodynamic properties of quantum lattice models from numerical linked cluster expansions

NASA Astrophysics Data System (ADS)

We review a recently proposed numerical linked-cluster (NLC) algorithm that allows one to obtain temperature-dependent properties of quantum lattice models, in the thermodynamic limit, from exact diagonalization of finite clusters. This approach provides a systematic framework to assess finite-size effects and is valid for any quantum lattice model. We present results for thermodynamic properties of spin and t-J models in different lattice geometries in two-dimensions. In addition, we present an extrapolation scheme that enables one to accelerate the convergence of NLC.

Rigol, Marcos; Singh, Rajiv R. P.

2009-04-01

169

Thermodynamic properties of almandine-grossular garnet solid solutions

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

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

1978-01-01

170

Electrical transport and thermodynamic properties of ?-Mo4O11

NASA Astrophysics Data System (ADS)

Low-dimensional systems have attracted a lot of attention during the last two decades because of their unusual chemical and physical properties [1]. ?-Mo4O11 is one such system exhibiting strong structural anisotropy, which is reflected in the electronic structure. This gives rise to uncommon features such as low-dimensional transport, metal- insulator and metal-metal transitions, and periodic lattice distortions and charge density waves (CDW) [2]. In this work the properties of ?-Mo4O11 single crystals are revisited. The single crystals were grown using a temperature- gradient flux method [3]. Electrical resistance as a function of temperature was determined with the Logan-Montgomery methods [4, 5] and was compared with reported measurements. We will report results of heat capacity and high-resolution thermal expansion measurements as well. [1] M.A.Valbuena, et al. Appl. Surf. Sci., 254, 40 (2007). [2] C. Schlenker, et al. Philos. Mag. B, 52, 643 (1985). [3] W. H. McCarroll and M. Greenblatt, J. Solid State Chem. 54, 282 (1984). [4] H. C. Montgomery, J. Appl. Phys. 42, 2971 (1971). [5] B. F. Logan, S. O. Rice, and R. F. Wick, J. Appl. Phys. 42, 2975 (1971). This material is based upon work supported by the Brazilian Agency CNPq (Grant No. 201439/2007-7), the NSF (Grant No. DMR- 0504769) and U.S. DOE Office of Basic Energy Sciences (Grant No. DE-FG-06ER46269).

de Campos, Ariana; da Luz, M. S.; White, B. D.; Neumeier, J. J.

2009-03-01

171

Structure-property maps and optimal inversion in configurational thermodynamics

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

Arnold, Bjoern; Diaz Ortiz, Alejandro [Max Planck Institute for Metals Research, Heisenbergstrasse 3, D-70569 Stuttgart (Germany); Hart, Gus L. W. [Department of Physics and Astronomy, Brigham Young University, Provo, Utah 84602 (United States); Dosch, Helmut [DESY, Notkestrasse 85, D-22607 Hamburg (Germany)

2010-03-01

172

Comparison of Correlations for Predicting Thermodynamic Properties of Ammonia–Water Mixtures

Tillner-Roth and Friend have presented a new correlation for the thermodynamic properties of ammonia–water mixtures. In this study, the new correlation has been compared to other correlations used in simulations of power cycles using ammonia–water mixtures as working fluids. The saturation properties for mixtures, calculated with the different correlations, have been examined at different temperatures and pressures. Available experimental data

E. Thorin

2000-01-01

173

Precise thermodynamic properties for natural waters covering only the limnological range

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

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

1986-05-01

174

Computer 'Experiments' on Lennard-Jones Molecules. I. Thermodynamical Properties.

National Technical Information Service (NTIS)

It is shown, using Rahman's work (Phys. Rev. v136 pA405 1964) as a starting point, how it is possible to integrate the equations of matrix of about a thousand particles in a relatively easy way. The first application of this tool is the thermodynamic stud...

L. Verlet

1966-01-01

175

Perturbation theory for the thermodynamic properties of simple liquids

The perturbation theory of simple liquids has recently met with great success. In this paper we present a critical discussion of this theory. The unperturbed system is, as usual, identified with hard spheres whose diameters are determined by a self-consistency requirement. The thermodynamics of the system, including the first-order contribution, can be computed analytically. The equation of state thus obtained

Loup Verlet; Jean-Jacques Weis

1972-01-01

176

From transport to disorder: thermodynamic properties of finite dust clouds.

The quantities entropy and diffusion are measured for two- and three-dimensional (3D) dust clusters in the fluid state. Entropy and diffusion are predicted to be closely linked via unstable modes. The method of instantaneous normal modes is applied for various laser-heated clusters to determine these unstable modes and the corresponding diffusive properties. The configurational entropy is measured for 2D and 3D clusters from structural rearrangements. The entropy shows a threshold behavior at a critical temperature for the 2D clusters, allowing us to estimate a configurational melting temperature. Further, the entropic disorder increases for larger clusters. Finally, the predicted relation between entropy and unstable modes has been confirmed from our experiments for 2D systems, whereas 3D systems do not show such a clear correlation. PMID:23848784

Schella, André; Mulsow, Matthias; Melzer, André; Schablinski, Jan; Block, Dietmar

2013-06-01

177

Trinitromethyl-substituted aminotetrazoles with -NH?, -NO?, -N?, and -NHC(NO?)? groups were investigated at the B3LYP/6-31G(d) level of density functional theory. Their sublimation enthalpies, thermodynamic properties, and heats of formation were calculated. The thermodynamic properties of these compounds increase with temperature as well as with the number of nitro groups attached to the tetrazole ring. In addition, the detonation velocities and detonation pressures of these compounds were successfully predicted using the Kamlet-Jacobs equations. It was found that these compounds exhibit good detonation properties, and that compound G (D = 9.2 km/s, P = 38.8 GPa) has the most powerful detonation properties, which are similar to those of the well-known explosive HMX (1,3,5,7-tetranitro-1,3,5,7-tetrazocine). Finally, the electronic structures and bond dissociation energies of these compounds were calculated. The BDEs of their C-NO? bonds were found to range from 101.9 to 125.8 kJ/mol(-1). All of these results should provide useful fundamental information for the design of novel HEDMs. PMID:23420400

Lin, He; Chen, Peng-Yuan; Zhu, Shun-Guan; Zhang, Lin; Peng, Xin-Hua; Li, Kun; Li, Hong-Zhen

2013-06-01

178

Thermodynamic properties of the itinerant-boson ferromagnet

Thermodynamics of a spin-1 Bose gas with ferromagnetic interactions is investigated via the mean-field theory. It is apparently shown in the specific-heat curve that the system undergoes two phase transitions, the ferromagnetic transition and Bose-Einstein condensation, with the Curie point above the condensation temperature. Above the Curie point, the susceptibility fits the Curie-Weiss law perfectly. At a fixed temperature, the reciprocal susceptibility is also in a good linear relationship with the ferromagnetic interaction.

Tao Chengjun; Wang Peilin; Qin Jihong; Gu Qiang [Department of Physics, University of Science and Technology Beijing, Beijing 100083 (China)

2008-10-01

179

A sensitivity analysis of bulk water thermodynamics is presented in an effort to understand the relation between details of molecular potentials and the properties that they predict. The analysis is incorporated in molecular dynamics simulation and investigates the sensitivity of the Helmholtz free energy, internal energy, entropy, heat capacity, pressure, thermal pressure coefficient, and static dielectric constant to details of

Tzvetelin D. Iordanov; Gregory K. Schenter; Bruce C. Garrett

2006-01-01

180

Thermodynamic properties of cSi derived by quantum path-integral Monte Carlo simulations

Feynman path-integral Monte Carlo simulations of crystalline silicon, using the empirical potential of Stillinger and Weber, have been performed in the isothermal-isobaric ensemble. Several thermodynamic properties have been evaluated as a function of pressure and temperature. The calculated lattice parameter, heat capacity, thermal expansion coefficient, and bulk modulus show an overall agreement with the experimental data. However, the negative thermal

José C. Noya; Carlos P. Herrero; Rafael Ramírez

1996-01-01

181

A simple analysis of thermodynamic properties for classical plasmas: I. Theory

By eliminating the short range negative divergence of the Debye-Hückel pair distribution function, but retaining the exponential charge screening known to operate at large interparticle separation, the thermodynamic properties of one-component plasmas of point ions or charged hard spheres can be well represented even in the strong coupling regime. Predicted electrostatic free energies agree within 5% of simulation data for

Robert Penfold; Sture Nordholm; Nancy Nichols

2005-01-01

182

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

ERIC Educational Resources Information Center

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

Torres, Luis Alfonso; And Others

1995-01-01

183

A statistical model of thermodynamic mixing properties of Ca-Mg-Fe2+garnets

At present the most widely used models of thermodynamic mixing properties of garnet are those that are optimized to fit the experimental phase-equilibrium data along various binary garnet joins using the method of mathematical programming. We conducted a thor- ough weighted regression analysis of the available volumetric, calorimetric, and phase- equilibrium data. This resulted in a much improved set of

BISWAJIT MUKHOPADHYAY; M. J. HOLDAWAY; ANDREA M. KOZIOL

1997-01-01

184

By the PM3 method, standard values of entropy, heats, and free energies of formation have been computed for a series of inorganic and organic bismuth compounds. Linear dependences P exper = b P theor (where P is any of the mentioned properties) have been stated, allowing a priori evaluation of thermodynamic characteristics of Bi-containing substances. A quantum chemical calculation reproduces

Alexei N. Pankratov; Inna M. Uchaeva

2002-01-01

185

Levitation calorimetry. IV - The thermodynamic properties of liquid cobalt and palladium.

NASA Technical Reports Server (NTRS)

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.

Treverton, J. A.; Margrave, J. L.

1971-01-01

186

We have employed Monte Carlo simulation in the isobaric–isothermal ensemble to determine thermodynamic derivative properties of naturally occurring hydrocarbon gas mixtures. Thermal expansivity, isothermal compressibility, heat capacity and Joule–Thomson coefficient have been obtained from a fluctuation method detailed in our previous work [Phys. Chem. Chem. Phys. 3 (2001) 4333]. We have investigated two natural gases using an original method to

M. H Lagache; Ph Ungerer; A Boutin

2004-01-01

187

National Technical Information Service (NTIS)

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...

V. N. Kabadi

1992-01-01

188

Monte Carlo Approach to Structure and Thermodynamic Property of CO2 Hydrate

Monte Carlo simulations have been carried out for the clathrate hydrate of CO2 hydrates. In this study, we investigate the structure and statistical thermodynamic property of CO2 hydrates at temperatures ranging from 150 to 288[K] and at a pressure of up to 50[MPa] under constant temperature and pressure conditions. We have found that the hydrate structure can be maintained at

Masahiro Ota; Mohammad Ferdows

2005-01-01

189

National Technical Information Service (NTIS)

The Bureau of Mines investigated thermodynamic properties of Mn3O4 (manganomanganic oxide) and Mn2O3 (manganese sesquioxide). The standard Gibbs energies of formation (delta G(f)) of Mn3O4 and Mn2O3 from their lower oxides were determined with high-temper...

S. C. Schaefer

1982-01-01

190

APPROXIMATIONS FOR THE THERMODYNAMIC AND TRANSPORT PROPERTIES OF HIGH TEMPERATURE AIR

Approximations are presented for the thermodynamic and transpont ; properties of high-temperature air. Compressibility, enthalpy, entropy, specific ; heats, speed of sound, coefficients of viscosity and thermal conductivity, and ; the Prandtl number are tabulated for 500 to 15,000 deg K over a range of ; pressures from 0.0001 to 100 atm. (auth)

1959-01-01

191

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

R. Jafari

2011-01-01

192

NASA Astrophysics Data System (ADS)

This study presents a detailed thermodynamic analysis of the intricate interrelationship existing between thermal and elastic properties. By invoking only the principles of classical thermodynamics, the multifarious consequences of a possible linear relationship between logarithmic bulk modulus and relative enthalpy at constant pressure are probed. In particular, we identify two linear scaling relations between molar volume and relative enthalpy and between molar volume and logarithmic bulk modulus. These relations are valid at temperatures exceeding the Debye temperature. In addition, certain interesting deductions with respect to the temperature dependences of the Anderson-Grüneisen parameter and the volume thermal expansivity to isobaric specific heat ratio are obtained. In brief, a simple thermodynamic protocol that will be of use in an integrated treatment of the elastic and thermal quantities has been developed. As an illustrative case study, the high temperature bulk modulus of copper is estimated from its thermal properties data using the proposed framework.

Raju, S.; Sivasubramanian, K.; Mohandas, E.

2002-10-01

193

NASA Astrophysics Data System (ADS)

Garnet solid solutions are present in many igneous and metamorphic environments. Thermodynamic mixing properties of these solid solutions must be known accurately in order to retrieve the pressure-temperature (P-T) conditions of garnet growth, and hence constrain part of a rock's P-T evolution. Over the past 25+ years, many experimental determinations of garnet thermodynamic mixing properties have been made, but doubts remain about the accuracy of our knowledge of garnet thermodynamics. Recently developed techniques (e.g., Lavrentiev et al., J. Phys. Chem. B, 2001) allow computational studies of mixing properties in geologically relevant solid solutions to be made for the first time. We present results of simultaneous high-P, high-T computer experiments, aimed at determining garnet mixing properties, using modified Monte Carlo and quantum mechanical methods. We derive excess volume and enthalpy data for garnets with compositions along the pyrope-almandine and pyrope-grossular joins at P up to 20 GPa and T exceeding 2273 K. These are compared with existing laboratory experiments and commonly used thermodynamic data bases. As seen in the experimental data, simulations show virtually ideal mixing behaviour in garnets on the pyrope-almandine join, while large excess volumes and enthalpies of mixing are predicted for garnets along the pyrope-grossular join. Simulations shed additional light on the link between microscopic structural behaviour and macroscopic thermodynamic properties: the avoidance of certain Ca-Mg contacts in the solid solutions (see Bosenick et al., Phys. Chem. Min., 2000) at high temperature and pressure manifests itself in dips in the excess enthalpies, which disappear at higher temperatures and lower pressures. Computer simulation of trace element incorporation into garnet solid solutions shows this avoidance may also be responsible for some remarkable features of rare earth element garnet-melt partitioning behaviour (e.g., van Westrenen et al., Phys. Chem. Min., 2003).

van Westrenen, W.; Lavrentiev, M. Y.; Allan, N. L.; Freeman, C. L.

2003-12-01

194

Thermodynamical properties of a rotating ideal Bose gas

NASA Astrophysics Data System (ADS)

In a recent experiment, a Bose-Einstein condensate was trapped in an anharmonic potential that is well approximated by a harmonic and a quartic part. The condensate was set into such a fast rotation that the centrifugal force in the corotating frame overcompensates the harmonic part in the plane perpendicular to the rotation axis. Thus, the resulting trap potential becomes sombrero shaped. We present an analysis for an ideal Bose gas that is confined in such an anharmonic rotating trap within a semiclassical approximation, where we calculate the critical temperature, the condensate fraction, and the heat capacity. In particular, we examine in detail how these thermodynamical quantities depend on the rotation frequency.

Kling, Sebastian; Pelster, Axel

2007-08-01

195

Thermodynamic and Acoustic Properties of Mixtures of Dibromomethane + Heptane

NASA Astrophysics Data System (ADS)

Densities and speeds of ultrasound in binary mixtures of dibromomethane with heptane have been measured within the temperature range from 288.15 K to 318.15 K. From the experimental data, the thermodynamic excess volume, molar isobaric expansion, molar isentropic compression, and ultrasonic speed were calculated. The excess volume and excess isentropic compression have opposite signs, whereas the excess isobaric expansion is an S-shaped function of the mole fraction. An explanation was suggested to account for the excesses in terms of intermolecular interactions. It involved energetic and steric factors. Moreover, it was shown that the positive excess sound speed results almost entirely from the negative excess compression.

Przyby?a, Anna; Chor??ewski, Miros?aw; Zor?bski, Edward; Marczak, Wojciech

2011-04-01

196

Thermodynamics and elastic properties of Ta from first-principles calculations

NASA Astrophysics Data System (ADS)

Within the framework of the quasiharmonic approximation, the thermodynamics and elastic properties of Ta, including phonon density of states (DOS), equation of state, linear thermal expansion coefficient, entropy, enthalpy, heat capacity, elastic constants, bulk modulus, shear modulus, Young's modulus, microhardness, and sound velocity, are studied using the first-principles projector-augmented wave method. The vibrational contribution to Helmholtz free energy is evaluated from the first-principles phonon DOS and the Debye model. The thermal electronic contribution to Helmholtz free energy is estimated from the integration over the electronic DOS. By comparing the experimental results with the calculation results from the first-principles and the Debye model, it is found that the thermodynamic properties of Ta are depicted well by the first-principles. The elastic properties of Ta from the first-principles are consistent with the available experimental data.

Li, Qiang; Huang, Duo-Hui; Cao, Qi-Long; Wang, Fan-Hou; Cai, Ling-Cang; Zhang, Xiu-Lu; Jing, Fu-Qian

2012-12-01

197

Performance of the thermodynamic properties models in ASPEN. [Freon 12 and Freon 22

In the course of performing a number of analyses using ASPEN, the performance of the ASPEN models for computing thermodynamic properties has been observed. Pure-component properties for propane, isobutane, Freon 12 and Freon 22 and mixture properties for the propane-isobutane and the ethanol-water systems have been computed and the results compared with available data sources and with independent sources of computed properties. The built-in data regression system (DRS) of ASPEN was used to regress P-V-T and enthalpy departure data for isobutane to determine model-specific parameters. The extended Antoine vapor pressure parameters were calculated for Freon 12. The ethanol-water vapor-liquid equilibrium region was studied throughout the composition range for three isobaric data sets. Several activity coefficient models in ASPEN were fit to the data using various user-specified property routes.

Fish, L.W.; Evans, D.R.

1982-01-01

198

Thermodynamic properties of some metal oxide-zirconia systems

NASA Technical Reports Server (NTRS)

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

Jacobson, Nathan S.

1989-01-01

199

Thermodynamic properties of lanthanide metals in liquid bismuth

NASA Astrophysics Data System (ADS)

Thermodynamic quantities of La, Gd, Tb, and Dy in liquid bismuth were experimentally determined by electromotive force (EMF) measurement using a cell consisting of molten alkaline chloride and liquid bismuth. Excess Gibbs energy changes and activity coefficients were determined at varying concentrations and temperatures. Through their temperature dependence, corresponding enthalpy changes and entropy changes were determined. The excess enthalpy changes of La, Gd, Tb, and Dy in liquid bismuth in a temperature range from 850 to 1100 K were evaluated to be, -221.54±2.31, -202.25±1.80, -199.83±0.55, and -193.80±0.99 kJ/mol, respectively. The systematic variation of excess enthalpy change of lanthanides along the 4f-series was discussed. As a result, it was found that the excess enthalpy changes of La, Gd, Tb, Dy, and Er are likely to depend linearly on the 2/3 power of their metallic volume.

Yamana, Hajimu; Sheng, Jiawei; Souda, Naohiko; Moriyama, Hirotake

2001-04-01

200

Thermodynamic properties of some metal oxide-zirconia systems

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

Jacobson, N.S.

1989-12-01

201

Predicting the thermodynamic properties of gold nanoparticles using different force fields

NASA Astrophysics Data System (ADS)

The objective of this research was to learn how to predict the thermodynamic properties of gold nanoparticles using computational tools. The lowest energy structures of gold nanoparticles of various sizes were determined and thermodynamic properties such as the free energy (F), internal energy (U), entropy (S), and specific heat (Cv) of the gold nanoparticles were investigated using a fully-atomistic Monte Carlo simulation method that utilizes a modified Wang-Landau algorithm. Eight well-known force fields for metallic systems were employed to model gold nanoparticles: the Lennard-Jones potential (LJ), the Lennard-Jones potential with Heinz's parameterization (LJH), the Gupta potential, the Sutton-Chen potential (SC), the Sutton-Chen potential with Pawluk's parameterization for small clusters (SCP), the Quantum Sutton-Chen potential (Q-SC), the Embedded Atom Method (EAM) by Cai and Ye, and the empirical potential for gold proposed by Olivier and coworkers (POT). Subsequently, we explored the accuracy of each force field in the description of the thermodynamic behavior of gold nanoparticles. The thermodynamic properties of gold nanoparticles were computed from the Density of States which was obtained as a result of the Monte Carlo simulation. Afterwards, the melting point of gold nanoparticles was determined from the behavior of the calculated thermodynamic properties and was compared with theory, experimental observations and other simulation results. The force fields employed predicted melting points of gold nanoparticles over a wide range of temperatures. A thorough comparison with the available experimental observations showed that the Quantum Sutton-Chen potential (Q-SC) correctly described the melting behavior of gold nanoparticles with sizes smaller than 1.3 nanometers.

Park, Yongjin

202

D-dimensional ideal gas in parastatistics: thermodynamic properties

The authors consider a parastatistics ideal gas with energy spectrum epsilon proportional to absolute value k/sup ..cap alpha../ (..cap alpha.. > 0) or even more generally in a d-dimensional box with volume V (periodic boundary conditions), the number N of the gas particles being well determined (real particles) or not (quasiparticles). They calculate the main thermodynamic quantities (chemical potential, internal energy, specific heat C, equation of state, latent heat, average numbers of particles) for arbitrary d, ..cap alpha.., T (temperature), and p (maximal number of particles per state allowed in the parastatistics). The main asymptotic regimes are worked out explicitly. In particular, the Bose-Einstein condensation for fixed density N/V appears as a nonuniform convergence in the p ..-->.. infinity limit, in complete analogy with the standard critical phenomena that appear in interacting systems in the N ..-->.. infinity limit. The system behaves essentially like a Fermi-Dirac one for all finite values of p, and reveals a Bose-Einstein behavior only in the p ..-->.. infinity limit. For instance, at low temperatures C proportional to T if p < infinity and C proportional to T/sup d/..cap alpha../ if p ..-->.. infinity. Finally, the Sommerfeld integral and its expansion are generalized to an arbitrary, finite p.

de Sousa Vieira, M.C.; Tsallis, C.

1987-07-01

203

NASA Astrophysics Data System (ADS)

Reference is made to a previous study (Kessel'man et al., 1986) in which a method has been proposed for calculating the thermodynamic properties of gas and liquid solutions in the one- and two-phase regions on the basis of a unified equation of state. Here, by using an effective intermolecular potential with temperature-dependent parameters, this method is extended to the calculation of the thermodynamic parameters of mixtures with complex components. Results are presented for a number of mixtures, including Ar+CO2, Ar+N2, N2+CH4, N2C2C6, CH4+CO2, and CH4+C4H10.

Kessel'Man, P. M.; Tkachenko, V. V.; Ugol'Nikov, A. P.

1987-12-01

204

Vibrational and thermodynamic properties of ?-, ?-, ?-, and 6, 6, 12-graphyne structures

NASA Astrophysics Data System (ADS)

Electronic, vibrational, and thermodynamic properties of different graphyne structures, namely ?-, ?-, ?-, and 6,6,12-graphyne, are investigated through first principles–based quasi-harmonic approximation by using phonon dispersions predicted from density-functional perturbation theory. Similar to graphene, graphyne was shown to exhibit a structure with extraordinary electronic features, mechanical hardness, thermal resistance, and very high conductivity from different calculation methods. Hence, characterizing its phonon dispersions and vibrational and thermodynamic properties in a systematic way is of great importance for both understanding its fundamental molecular properties and also figuring out its phase stability issues at different temperatures. Thus, in this research work, thermodynamic stability of different graphyne allotropes is assessed by investigating vibrational properties, lattice thermal expansion coefficients, and Gibbs free energy. According to our results, although the imaginary vibrational frequencies exist for ?-graphyne, there is no such a negative behavior for ?-, ?-, and 6,6,12-graphyne structures. In general, the Grüneisen parameters and linear thermal expansion coefficients of these structures are calculated to be rather more negative when compared to those of the graphene structure. In addition, the predicted difference between the binding energies per atom for the structures of graphene and graphyne points out that graphyne networks have relatively lower phase stability in comparison with the graphene structures.

Kosku Perkgöz, Nihan; Sevik, Cem

2014-05-01

205

Thermodynamic properties by non-calorimetric methods. Progress report, August 1, 1988--July 31, 1989

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.

Steele, W.V.; Chirico, R.D.; Collier, W.B.; Strube, M.M. [IIT Research Inst., Chicago, IL (United States)]|[National Inst. for Petroleum and Energy Bartlesville, OK (United States)

1989-12-31

206

Structure-property relations and thermodynamic properties of monoclinic petalite, LiAlSi4O10.

Structure-property relations of monoclinic petalite, LiAlSi(4)O(10), were determined by experiment and atomistic modeling based on density functional theory. The elastic stiffness coefficients were measured between room temperature and 570 K using a combination of the plate-resonance technique and resonant ultrasound spectroscopy. The thermal expansion was studied between 100 and 740 K by means of dilatometry. The heat capacity between 2 and 398 K has been obtained by microcalorimetry using a quasi-adiabatic calorimeter. The experimentally determined elastic stiffness coefficients were employed to benchmark the results of density functional theory based model calculations. The values in the two data sets agreed to within a few GPa and the anisotropy was very well reproduced. The atomistic model was then employed to predict electric field gradients, the lattice dynamics and thermodynamic properties. The theoretical charge density was analyzed to investigate the bonding between atoms. PMID:22871989

Haussühl, Eiken; Schreuer, Jürgen; Winkler, Björn; Haussühl, Siegfried; Bayarjargal, Lkhamsuren; Milman, Victor

2012-08-29

207

Structure-property relations and thermodynamic properties of monoclinic petalite, LiAlSi4O10

NASA Astrophysics Data System (ADS)

Structure-property relations of monoclinic petalite, LiAlSi4O10, were determined by experiment and atomistic modeling based on density functional theory. The elastic stiffness coefficients were measured between room temperature and 570 K using a combination of the plate-resonance technique and resonant ultrasound spectroscopy. The thermal expansion was studied between 100 and 740 K by means of dilatometry. The heat capacity between 2 and 398 K has been obtained by microcalorimetry using a quasi-adiabatic calorimeter. The experimentally determined elastic stiffness coefficients were employed to benchmark the results of density functional theory based model calculations. The values in the two data sets agreed to within a few GPa and the anisotropy was very well reproduced. The atomistic model was then employed to predict electric field gradients, the lattice dynamics and thermodynamic properties. The theoretical charge density was analyzed to investigate the bonding between atoms.

Haussühl, Eiken; Schreuer, Jürgen; Winkler, Björn; Haussühl, Siegfried; Bayarjargal, Lkhamsuren; Milman, Victor

2012-08-01

208

NASA Technical Reports Server (NTRS)

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.

Mccarty, R. D.

1980-01-01

209

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)

Perruchot, Christian [Interfaces, Traitements, Organisation et Dynamique des Systemes (ITODYS) Universite Paris 7- Denis. Diderot, 1 Rue Guy de la Brosse, 75005 Paris (France); Chehimi, Mohamed M. [Interfaces, Traitements, Organisation et Dynamique des Systemes (ITODYS) Universite Paris 7- Denis. Diderot, 1 Rue Guy de la Brosse, 75005 Paris (France); Vaulay, Marie-Josephe [Interfaces, Traitements, Organisation et Dynamique des Systemes (ITODYS) Universite Paris 7- Denis. Diderot, 1 Rue Guy de la Brosse, 75005 Paris (France); Benzarti, Karim [Laboratoire Central des Ponts et Chaussees (LCPC), 58 Boulevard Lefevre, 75732 Paris Cedex 15 (France)]. E-mail: benzarti@lcpc.fr

2006-02-15

210

Thermodynamic properties and atomic structure of Ca-based liquid alloys

NASA Astrophysics Data System (ADS)

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)

Poizeau, Sophie

211

The authors describe a new methodology for predicting the thermodynamic properties of petroleum geomacromolecules (asphaltenes and resins). This methodology combines computer assisted structure elucidation (CASE) with atomistic simulations (molecular mechanics and molecular dynamics and statistical mechanics). They use quantitative and qualitative structural data as input to a CASE program (SIGNATURE) to generate a sample of ten asphaltene model structures for a Saudi crude oil (Arab Berri). MM calculations and MD simulations are used to estimate selected volumetric and thermal properties of the model structures.

Diallo, Mamadou S.; Cagin, Tahir; Faulon, Jean Loup; Goddard, William A.

2000-08-01

212

Calculation of the thermodynamic properties of gas and liquid solutions - Multicomponent mixtures

NASA Astrophysics Data System (ADS)

A method for calculating thermodynamic properties using a unified equation of state for gases and liquids in combination with an effective intermolecular potential is extended to multicomponent systems. A comparison with experimental data indicates that, for a sufficiently large number of components, the properties of mixtures can be calculated from data on the pure components only. Results of calculations for several mixtures, including Ar-N2, Ar-CH4, N2-CH4, Ar-N2-CH4, and H2-N2-CO2-CO-CH4, are presented and compared with experimental data.

Kessel'Man, P. M.; Tkachenko, V. V.; Ugol'Nikov, A. P.

1989-08-01

213

Thermodynamic and magnetic properties of the finite spin complexes of the Ising type

NASA Astrophysics Data System (ADS)

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.

Khamzin, A. A.; Nigmatullin, R. R.

2014-05-01

214

Thermodynamic properties of c-Si derived by quantum path-integral Monte Carlo simulations

NASA Astrophysics Data System (ADS)

Feynman path-integral Monte Carlo simulations of crystalline silicon, using the empirical potential of Stillinger and Weber, have been performed in the isothermal-isobaric ensemble. Several thermodynamic properties have been evaluated as a function of pressure and temperature. The calculated lattice parameter, heat capacity, thermal expansion coefficient, and bulk modulus show an overall agreement with the experimental data. However, the negative thermal expansion of silicon at temperatures below 120 K is not reproduced with this model potential. The importance of anharmonicity and quantum effects on the properties derived from the Stillinger-Weber potential is addressed by comparison with the results expected in a quasiharmonic approximation and in the classical limit.

Noya, José C.; Herrero, Carlos P.; Ramírez, Rafael

1996-04-01

215

Two-fluid theory and thermodynamic properties of liquid mixtures: General theory

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

Brandani, V.; Prausnitz, J. M.

1982-01-01

216

LDA+U calculation of structural and thermodynamic properties of Ce2O3

NASA Astrophysics Data System (ADS)

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

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

2014-03-01

217

Phase transition and thermodynamic properties of BiFeO3 from first-principles calculations

NASA Astrophysics Data System (ADS)

The first-principles projector-augmented wave method employing the quasi-harmonic Debye model, is applied to investigate the thermodynamic properties and the phase transition between the trigonal R3c structure and the orthorhombic Pnma structure. It is found that at ambient temperature, the phase transition from the trigonal R3c phase to the orthorhombic Pnma phase is a first-order antiferromagnetic-nonmagnetic and insulator-metal transition, and occurs at 10.56 GPa, which is in good agreement with experimental data. With increasing temperature, the transition pressure decreases almost linearly. Moreover, the thermodynamic properties including Grüneisen parameter, heat capacity, entropy, and the dependences of thermal expansion coefficient on temperature and pressure are also obtained.

Li, Qiang; Huang, Duo-Hui; Cao, Qi-Long; Wang, Fan-Hou

2013-03-01

218

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

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

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

2011-01-01

219

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

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

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

2011-10-20

220

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

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

Cliff B. Davis

2010-09-01

221

NASA Astrophysics Data System (ADS)

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.

Noh, Seunghyo; Kwak, Dohyun; Lee, Juseung; Kang, Joonhee; Han, Byungchan

2014-03-01

222

Structural and thermodynamic properties of diamond: A path-integral Monte Carlo study

Path-integral Monte Carlo simulations in the isothermal-isobaric ensemble have been carried out to study structural and thermodynamic properties of diamond, as a function of temperature and hydrostatic pressure. Atomic nuclei were treated as quantum particles interacting through a Tersoff-type potential. The obtained lattice parameter, heat capacity, thermal expansion coefficient, and bulk modulus show an overall agreement with the experimental data.

Carlos P. Herrero; Rafael Ramírez

2001-01-01

223

A strategy for reducing the risk of non-ergodic simulations in Monte Carlo calculations of the thermodynamic properties of clusters is discussed with the support of some examples. The results obtained attest the significance of the approach for the low-temperature regime, as non-ergodic sampling of potential energy surfaces is a particularly insidious occurrence. Fourier path integral Monte Carlo techniques for taking

C. Parletta; C. Guidotti; G. P. Arrighini

2004-01-01

224

Self-ionization of water at high temperature and the thermodynamic properties of the ions

It is shown that gas-phase data on hydrated H\\/sup +\\/ and OHâ» ions from mass spectrometry can be used to calculate the ionization product for water at high temperature and at high enough pressure to allow relating these results with those directly measured near 1000 K and 0.5 g cmâ»Â³. The thermodynamic properties of the hydrated H\\/sup +\\/ and OHâ»

Kenneth S. Pitzer

1982-01-01

225

Thermodynamic properties of CaCO 3 calcite and aragonite: A quasi-harmonic calculation

A quasi-harmonic model has been used to simulate the thermodynamic behaviour of the CaCO3 polymorphs, by equilibrating their crystal structures as a function of temperature so as to balance the sum of inner static and thermal pressures against the applied external pressure. The vibrational frequencies and elastic properties needed have been computed using interatomic potentials based on two-body Born-type functions,

M. Catti; A. Pavese; G. D. Price

1993-01-01

226

NASA Technical Reports Server (NTRS)

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

Younglove, B.; Mccarty, R. D.

1979-01-01

227

Effects of layer-charge distribution on the thermodynamic and microscopic properties of Cs-smectite

To explore the effects of layer-charge distribution on the thermodynamic and microscopic properties of Cs-smectites, classical molecular dynamic simulations are performed to derive the swelling curves, distributions and mobility of interlayer species, and Cs binding structures. Three representative smectites with distinct layer-charge distributions are used as model clay frameworks and interlayer water content is set within a wide range from

Xiandong Liu; Xiancai Lu; Rucheng Wang; Huiqun Zhou

2008-01-01

228

Structural, elastic, electronic, optical and thermodynamic properties of KMgH 3

The structural, elastic, electronic, optical and thermodynamic properties of the cubic perovskite-type hydride KMgH3 have been investigated using pseudo-potential plane-wave method based on the density functional theory. Computed equilibrium lattice constant agrees well with the available experimental and theoretical data. The elastic constants and their pressure dependence are predicted using the static finite strain technique. A linear pressure dependence of

M. A. Ghebouli; B. Ghebouli; A. Bouhemadou; M. Fatmi; S. Bin-Omran

2011-01-01

229

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

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

Hemingway, B. S.

1987-01-01

230

Ebulliometers for measuring the thermodynamic properties of fluids and fluid mixtures

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.

Weber, L.A.; Silva, A.M.

1994-09-01

231

Calculations and curve fits of thermodynamic and transport properties for equilibrium air to 30000 K

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

Roop N. Gupta; Kam-Pui Lee; Richard A. Thompson; Jerrold M. Yos

1991-01-01

232

A variety of polymerization techniques can be used to prepare molecularly imprinted copolymers (MIPs) for the purpose of the separation of enantiomers by HPLC. Unfortunately, the lack of thermodynamic and kinetic data characterizing the imprinted polymers prepared by these different techniques prevents the rational choice of the one most suited for a specific application. We investigated and compared the thermodynamic properties of copolymers imprinted for Fmoc-l-tryptophan and prepared by two different methods. The first was an in situ polymerization method that gives monolithic columns (monolithic MIPs), the second, a traditional method giving bulk MIPs. Examination of the thermodynamic properties on these two different MIPs showed that three types of binding sites coexist on their surface. The highest energy sites adsorb only the imprinted molecule or template. Most of the intermediate energy sites adsorb both the template and its antipode, although part of them may adsorb only the template. Finally, the lowest energy sites provide nonselective interactions of both the template and its antipode. On the nonimprinted copolymer, there are only two types of sites. The high-energy sites have a slightly lower energy that the intermediate sites of the MIPs, and the low-energy sites have properties close to those of the lowest energy sites on the MIPs. The monolithic MIPs have fewer nonselective sites than the bulk MIPs. However, the polar porogen that is needed to prepare the monolithic MIPs negatively affects the enantiomeric separation.

Kim, Hyunjung [University of Tennessee, Knoxville (UTK); Guiochon, Georges A [ORNL

2005-01-01

233

Thermodynamic and transport properties of two-temperature SF{sub 6} plasmas

This paper deals with thermodynamic and transport properties of SF{sub 6} plasmas in a two-temperature model for both thermal equilibrium and non-equilibrium conditions. The species composition and thermodynamic properties are numerically determined using the two-temperature Saha equation and Guldberg-Waage equation according to deviation of van de Sanden et al. Transport properties including diffusion coefficient, viscosity, thermal conductivity, and electrical conductivity are calculated with most recent collision interaction potentials by adopting Devoto's electron and heavy particle decoupling approach but expanded to the third-order approximation (second-order for viscosity) in the frame of Chapman-Enskog method. The results are computed for various values of pressures from 0.1 atm to 10 atm and ratios of the electron temperature to the heavy particle temperature from 1 to 20 with electron temperature range from 300 to 40 000 K. In the local thermodynamic equilibrium regime, results are compared with available results of previously published studies.

Wang Weizong [State Key Laboratory of Electrical Insulation and Power Equipment, Xi'an Jiaotong University, Xi'an Shaanxi 710049 (China); Department of Electrical Engineering and Electronics, University of Liverpool, Brownlow Hill, Liverpool L69 3GJ (United Kingdom); Rong Mingzhe; Wu Yi [State Key Laboratory of Electrical Insulation and Power Equipment, Xi'an Jiaotong University, Xi'an Shaanxi 710049 (China); Spencer, Joseph W.; Yan, Joseph D.; Mei, DanHua [Department of Electrical Engineering and Electronics, University of Liverpool, Brownlow Hill, Liverpool L69 3GJ (United Kingdom)

2012-08-15

234

The Wang-Landau method [F. Wang and D. P. Landau, Phys. Rev. E 64, 056101 (2001)] is an efficient way to calculate the density of states (DOS) for magnetic systems, and the DOS can then be used to rapidly calculate the thermodynamic properties of the system. A technique is presented that uses the DOS for a simple Hamiltonian to create a stratified sample of configurations which are then used calculate a warped DOS for more realistic Hamiltonians. This technique is validated for classical models of bcc Fe with exchange interactions of increasing range, but its real value is using the DOS for a model Hamiltonian calculated on a workstation to select the stratified set of configurations whose energies can then be calculated for a density-functional Hamiltonian. The result is an efficient first-principles calculation of thermodynamic properties such as the specific heat and magnetic susceptibility. Another technique uses the sample configurations to calculate the parameters of a model exchange interaction using a least-squares approach. The thermodynamic properties can be subsequently evaluated using traditional Monte Carlo techniques for the model exchange interaction. Finally, a technique that uses the configurations to train a neural network to estimate the configuration energy is also discussed. This technique could potentially be useful in identifying the configurations most important in calculating the warped DOS. VC2011 American Institute of Physics. [doi:10.1063/1.3565413

Brown, Greg [ORNL; Rusanu, Aurelian [ORNL; Daene, Markus W [ORNL; Nicholson, Don M [ORNL; Eisenbach, Markus [ORNL; Fidler, Jane L [ORNL

2011-01-01

235

Thermodynamic and transport properties of two-temperature SF6 plasmas

NASA Astrophysics Data System (ADS)

This paper deals with thermodynamic and transport properties of SF6 plasmas in a two-temperature model for both thermal equilibrium and non-equilibrium conditions. The species composition and thermodynamic properties are numerically determined using the two-temperature Saha equation and Guldberg-Waage equation according to deviation of van de Sanden et al. Transport properties including diffusion coefficient, viscosity, thermal conductivity, and electrical conductivity are calculated with most recent collision interaction potentials by adopting Devoto's electron and heavy particle decoupling approach but expanded to the third-order approximation (second-order for viscosity) in the frame of Chapman-Enskog method. The results are computed for various values of pressures from 0.1 atm to 10 atm and ratios of the electron temperature to the heavy particle temperature from 1 to 20 with electron temperature range from 300 to 40 000 K. In the local thermodynamic equilibrium regime, results are compared with available results of previously published studies.

Wang, WeiZong; Rong, MingZhe; Wu, Yi; Spencer, Joseph W.; Yan, Joseph D.; Mei, DanHua

2012-08-01

236

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

NASA Astrophysics Data System (ADS)

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

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

2010-10-01

237

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

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

2010-07-15

238

Thermodynamic model for calorimetric and phase coexistence properties of coal derived fluids

The objective of this project is to develop a thermodynamic model for phase equilibria and calorimetric properties of coal derived fluids. A model for phase equilibria of coal derived liquids is already available, and is to be extended to include calorimetric properties. The modification involves the use of the modified UNIFAC correlation with suitably regressed parameters, combined with an appropriate equation of state to represent compressibility of the liquid phase. To accomplish this satisfactorily, the proposed work includes three tasks: (1) Refinement of the characterization procedure to include distribution of sulfur, oxygen and nitrogen heteroatoms in coal liquids; (2) Measurement of high temperature (up to 400 C) and high pressure (up to 1000 psi) VLE data for binary systems of selected model compounds; and (3) Development of the thermodynamic model. The final product will include a computer program which with measurable properties of coal liquids as input, will give results for phase coexistence properties and excess enthalpies in the liquid phase. Data compilation of low pressure excess enthalpy data for binary systems of polyatomic compounds has been completed. Systems with temperature ranges and literature references are given in Table 1. Literature search is currently under way for high pressure excess enthalpy data on these systems. Current work involves completing the UNIFAC binary interaction parameter matrix, by regressing the unavailable parameters from experimental VLE and excess enthalpy data. 92 refs., 1 tab.

Kabadi, V.N.

1990-01-01

239

NASA Technical Reports Server (NTRS)

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.

Gordon, S.

1982-01-01

240

National Technical Information Service (NTIS)

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 den...

W. M. Proscia J. D. Freihaut

1993-01-01

241

NASA Technical Reports Server (NTRS)

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.

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

1991-01-01

242

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

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

243

The temperature behaviour of the elastic and thermodynamic properties of fcc thorium

NASA Astrophysics Data System (ADS)

The temperature behaviour of the structural, elastical and thermal properties of fcc thorium have been calculated from a free-parameter Helmholtz free energy developed by computing the cohesive energy from first principles calculations coupled to the Chen-Möbius lattice inversion method and the Debye-Grüneisen quasiharmonic model. The elastic constants, shear modulus, Young modulus, Poisson's ratio and thermodynamic properties of fcc Th as the entropy, the harmonic specific heat, the (P, V, T) equation of state and the thermal lattice expansion are found to be in a very good agreement with experiments and ab initio phonon calculations. The results of this work show the potentiality of the Chen-Möbius method coupled to ab initio calculation of the cohesive energy to develop a free-parameter pair potential capable of giving an overall description of fcc Th properties at T = 0 K with an error similar to ab initio calculations.

Jaroszewicz, S.; Mosca, H. O.; Garcés, J. E.

2012-10-01

244

A sensitivity analysis of bulk water thermodynamics is presented in an effort to understand the relation between details of molecular potentials and the properties that they predict. The analysis is incorporated in molecular dynamics simulation and investigates the sensitivity of the Helmholtz free energy, internal energy, entropy, heat capacity, pressure, thermal pressure coefficient, and static dielectric constant to details of the potential. The sensitivities of the properties are calculated with respect to the van der Waals repulsive and the attractive parts, plus short and long range Coulomb parts of three four site empirical water potentials: TIP4P, Dang-Chang and TTM2R. The polarization sensitivity is calculated for the polarizable Dang-Chang and TTM2R potentials. The analysis indicates that all investigated properties are most sensitive to the van der Waals repulsive, the short range Coulomb and the polarization components of the potentials. The sensitivity of the Helmoltz free energy, internal energy, and entropy due to polarizaion is almost 30% of total electrostatic sensitivity. In addition the similarities in the trends of the observed sensitivities for nonpolarizable and polarizable potentials lead to the conclusion that the complexity of the model is not of critical importance for the calculation of these properties for bulk water. The van der Waals attractive and the long range Coulomb sensitivities are relatively small for the entropy, heat capacity, thermal pressure coefficient and the static dielectric constant, while small changes in any of the potential contributions will significantly effect the pressure. The analysis suggests a procedure for modification of the potentials and their improved prediction of thermodynamic properties. Based on the proposed procedure the water cluster potential TTM2R was adapted for simulation of bulk water properties.

Iordanov, Tzvetelin D.; Schenter, Gregory K.; Garrett, Bruce C.

2006-01-19

245

The ability of a protein to carry out a given function results from fundamental physicochemical properties that include the protein’s structure, mechanism of action, and thermodynamic stability. Traditional approaches to study these properties have typically required the direct measurement of the property of interest, oftentimes a laborious undertaking. Although protein properties can be probed by mutagenesis, this approach has been limited by its low throughput. Recent technological developments have enabled the rapid quantification of a protein’s function, such as binding to a ligand, for numerous variants of that protein. Here, we measure the ability of 47,000 variants of a WW domain to bind to a peptide ligand and use these functional measurements to identify stabilizing mutations without directly assaying stability. Our approach is rooted in the well-established concept that protein function is closely related to stability. Protein function is generally reduced by destabilizing mutations, but this decrease can be rescued by stabilizing mutations. Based on this observation, we introduce partner potentiation, a metric that uses this rescue ability to identify stabilizing mutations, and identify 15 candidate stabilizing mutations in the WW domain. We tested six candidates by thermal denaturation and found two highly stabilizing mutations, one more stabilizing than any previously known mutation. Thus, physicochemical properties such as stability are latent within these large-scale protein functional data and can be revealed by systematic analysis. This approach should allow other protein properties to be discovered.

Araya, Carlos L.; Fowler, Douglas M.; Chen, Wentao; Muniez, Ike; Kelly, Jeffery W.; Fields, Stanley

2012-01-01

246

Thermal vacancy effects on the thermodynamic properties and stability of fullerites.

We study the influence of thermal vacancies on equilibrium thermodynamic properties of the high-temperature phase of fullerites taking into account the strong anharmonicity of the lattice vibrations. Treating a crystal with point defects as a quasi-multicomponent system and using the correlative method of the unsymmetrized self-consistent field and the Girifalco interaction potential for the molecular subsystem, we have obtained the vacancy formation parameters for the C(60) fullerite. We also take into account the divacancies. The influence of the lattice defects on the specific heats of fullerites is negligible, since a dominant contribution to them is given by intramolecular degrees of freedom. We have calculated the contributions of vacancies to various thermodynamic properties, the volume thermal expansion coefficient, the isothermal bulk modulus, and the components of the isothermal elastic tensor, depending on the temperature and pressure. Near the estimated triple point, these contributions run to more than 10% and increase still further at a metastable region. We also discuss the influence of defects on the thermodynamic stability of fullerites. PMID:16852845

Zubov, Viatcheslav I; Zubov, Igor V

2005-08-01

247

Optimization of the thermodynamic properties and phase diagrams of P2O5-containing systems

NASA Astrophysics Data System (ADS)

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.

Hudon, Pierre; Jung, In-Ho

2014-05-01

248

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

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

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

2013-11-21

249

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

The ability of intermolecular potentials to correctly predict the thermodynamic properties of liquid water at a density of 0.998 g?cm(3) for a wide range of temperatures (298-650 K) and pressures (0.1-700 MPa) is investigated. Molecular dynamics simulations are reported for the pressure, thermal pressure coefficient, thermal expansion coefficient, isothermal and adiabatic compressibilities, isobaric and isochoric heat capacities, and Joule-Thomson coefficient of liquid water using the non-polarizable SPC?E and TIP4P?2005 potentials. The results are compared with both experiment data and results obtained from the ab initio-based Matsuoka-Clementi-Yoshimine non-additive (MCYna) [J. Li, Z. Zhou, and R. J. Sadus, J. Chem. Phys. 127, 154509 (2007)] potential, which includes polarization contributions. The data clearly indicate that both the SPC?E and TIP4P?2005 potentials are only in qualitative agreement with experiment, whereas the polarizable MCYna potential predicts some properties within experimental uncertainty. This highlights the importance of polarizability for the accurate prediction of the thermodynamic properties of water, particularly at temperatures beyond 298 K. PMID:24320337

Shvab, I; Sadus, Richard J

2013-11-21

250

NASA Astrophysics Data System (ADS)

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.

Khlystov, A.; Lin, M.; Saleh, R.

2008-12-01

251

NASA Astrophysics Data System (ADS)

In the frame of density functional theory, first-principles calculations have been carried out to investigate the structures, elastic constants, structural phase transition between B1 and B2 phases and thermodynamic properties of the zirconium nitride (ZrN) by means of the generalized gradient approximation. The equilibrium lattice parameter we obtained for ZrN in B1 phase is closer to the experiment results than previous theoretical results. In addition, the calculations of the elastic constants show that ZrN is a brittle material. What is more, based on third-order natural strain equation of state, the phase transition pressure 338 GPa for ZrN is predicted for B1-B2 transition. According to the quasi-harmonic Debye model, the thermodynamic parameters of ZrN have been investigated systematically.

Tang, Cui-Ming; Chen, Xiao-Xu; Wang, Jun; Hu, Yan-Fei; Wang, Hong-Yan

2013-06-01

252

On the thermal vacancy effects on thermodynamic properties and stability of Van der Waals crystals

NASA Astrophysics Data System (ADS)

Reverting to an investigation of thermal vacancies in simple Van der Waals crystals [phys. stat. sol. (b) 101, 95 (1980)] we take into account the possibility of forming their bonded complexes, in particular divacancies. We use the correlative method of the unsymmetrized self-consistent field (CUSF) that enables one to include the strong anharmonicity of the lattice vibrations. We have calculated the parameters of the vacancy formation, the vacancy and divacancy concentration in solid Ar and contribution of the defects to its equilibrium thermodynamic properties, depending on the temperature and pressure, such contributions to components of the elastic tensor are studied for the first time. We also investigate the influence of defects on the thermodynamic stability of crystal lattice.

Zubov, V. I.; Zubov, I. V.

2006-10-01

253

Thermodynamic properties of the lead superconductor: The new value of the Coulomb pseudopotential

NASA Astrophysics Data System (ADS)

In the framework of the Eliashberg approach, the selected thermodynamic properties of the lead superconductor are analyzed. The new value of the Coulomb pseudopotential ( ??) is assumed, ??=0.1295. In particular, the wave function renormalization factor ( Z) and the order parameter ( ?) for different values of the temperature are calculated. It is shown that the electron-phonon interaction strongly enhances the effective electron mass; [=2.84. Next are calculated: the free energy difference between the superconducting and the normal state ( ?F), the thermodynamical critical field ( HC), the specific heat in the normal state ( C) and the specific heat in the superconducting state ( C). Finally, the ratios R2?(C-C)/C and R3?(TCC)/HC2 are obtained. The numerical results have shown that R2=2.6344 and R3=0.1293. The presented theoretical values of the ratios agree well with the experimental data.

Szcz?s?niak, R.

2007-10-01

254

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

NASA Astrophysics Data System (ADS)

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

Vora, Aditya M.

2010-11-01

255

We present in this work the application of the soft-SAFT equation of state (EoS) to the calculation of some main derivative properties, including heat capacities, reduced bulk modulus, Joule-Thomson coefficient, and speed of sound. Calculations have been performed analytically through the derivation of a primary thermodynamic potential function. The application to the n-alkanes, n-alkenes, and 1-alkanols families has been done in a semipredictive manner, with the molecular parameters of the equation obtained from previous fitting to vapor-liquid equilibrium data of the same compounds. The equation is able to capture the typical extrema isothermal derivative properties exhibit with respect to density, providing quantitative agreement with experimental (or correlation) data in some cases. Results in the vicinity of the critical point are improved by adding a crossover treatment to take into account the long-range fluctuations present in this region. By taking advantage of the molecular nature of the equation, we have been able to separate and quantify the different contributions (reference fluid, chain, and association) to the total derivative properties. The association plays a predominant role in energetic properties, such as the heat capacities, while there is a competition between association and chain length as the chain length of the compound increases for volumetric properties, such as the isothermal compressibility. These results act in favor of the molecular-based equations, like soft-SAFT, as predictive tools for several applications. PMID:16771416

Llovell, Fèlix; Vega, Lourdes F

2006-06-15

256

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

NASA Astrophysics Data System (ADS)

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

Geiger, C. A.; Dachs, E.

2011-12-01

257

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

W. Wagner; A. Pruß

1999-01-01

258

NASA Astrophysics Data System (ADS)

Anisotropic polymeric materials are ubiquitous. They can form via self assembly, external mechanical deformation or by geometric confinement. Important examples of anisotropic polymeric materials include liquid crystalline polymers and elastomers, amorphous rubber networks, confined films and grafted polymer brushes. A common feature of these materials is the anisotropic conformation of the constituent polymer chains which leads to significant modification of interchain packing correlations and thermodynamics properties. Polymer liquid state statistical mechanical methods have been generalized to treat the structure, segmental orientation, thermodynamics and mechanical response of dense polymer fluids and crosslinked networks. The consequences of interchain repulsions and chain connectivity are explicitly taken into account. The strain-induced orientational order parameter of flexible chains is predicted to scale as the inverse of the square root of the degree of polymerization and increase in a supralinear manner with segmental concentration. Two nonclassical contributions to stress and linear modulus arise from the influence of anisotropic packing correlations on the excess free energy. Overall the theory is in good agreement with NMR and mechanical experiments and computer simulations. The thermomechanical properties of nematic elastomers have also been studied. Significant softening of the modulus is found as the isotropic-nematic transition is approached. The phenomenon of spontaneous distortion, relevant to artificial muscles, sensors and actuator applications, emerges in a manner correlated directly with the orientational order parameter. Comparison of our theoretical predictions with experiments on thermotropic liquid crystalline polymers shows good qualitative and semi-quantitative agreements. A dynamical theory has been developed for the onset or crossover temperature (Tc) to highly non-Arrenhius activated relaxation regime in deeply supercooled polymer liquids. Alignment and/or deformation modify thermodynamic and structural properties thereby inducing anisotropic segmental dynamics. Either suppression or elevation of ( Tc) is predicted depending on the nature of anisotropy. Results have been obtained for liquid crystalline polymers, thin films, rubber networks and grafted polymer brushes. The underlying mechanism for ( Tc) shifts is this theory is anisotropy of the degree of coil interpenetration.

Oyerokun, Folusho Taiwo

259

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

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

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

2010-07-21

260

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

NASA Astrophysics Data System (ADS)

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.

Fresch, Barbara; Moro, Giorgio J.

2010-07-01

261

Thermodynamic properties and oxygen stoichiometry of Ba2Cu3O5 + ?

NASA Astrophysics Data System (ADS)

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

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

2014-03-01

262

Surface effects on magnetic and thermodynamic properties in nanoscale multilayer ferrimagnetic films

NASA Astrophysics Data System (ADS)

Magnetic and thermodynamic properties of a nanoscale multilayer ferrimagnetic films have been studied within the effective-field theory with correlations. The general formula for magnetization and internal energy is given. Some interesting results have been shown in the phase diagrams, for example two compensation points exist in the range of surface physical parameters. The competition among the surface exchange coupling, the surface single-ion anisotropy and the surface transverse field have great influences on the magnetization, the internal energy and the specific heat in the nanoscale multilayer ferrimagnetic films.

Jiang, Wei; Chen, Jun-nan; Ma, Ben; Wang, Zan

2014-07-01

263

Thermodynamic properties and equation of state of zircon ZrSiO{sub 4}

The silicate mineral zircon is a host material for radioactive materials in the earth`s crust and is a natural candidate for usage as a nuclear waste storage material. Lattice dynamical calculations have been carried out to understand its thermodynamic properties and high pressure behavior. The calculated phonon density of states, variation of phonon frequencies with pressure and equation of state are in good agreement with the available experimental data. One of the zone center optic mode involving SiO{sub 4} rotations becomes soft at 47 GPa.

Mittal, R.; Chaplot, S.L.; Choudhury, N. [Bhabha Atomic Research Centre, Trombay (India). Solid State Physics Div.; Loong, C.K. [Argonne National Lab., IL (United States)

1998-11-01

264

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.

Smith, W.H.; Costa, D.A.

1998-12-31

265

Thermodynamic properties of alloys of the Ni-Sc and Ni-Y systems

NASA Astrophysics Data System (ADS)

Partial and integral enthalpies of mixing for Ni-Y melts at 1775 K (0 < x Y < 0.34), 1850 K (0.72 < x Y < 1) and Ni-Sc at 1880 K (0 < x Sc < 0.35, 0.51 < x Sc < 1) are determined by means of calorimetry. Thermodynamic properties of liquid and solid alloys and phase diagrams of Ni-Sc(Y) systems in wide ranges of concentration and temperature are modeled using the ideal associated solution theory. It is found that the activities of components exhibit strong negative deviations from the Raoult's law.

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

2014-06-01

266

Elastic and thermodynamic properties of c-BN from first-principles calculations

NASA Astrophysics Data System (ADS)

The elastic constants and thermodynamic properties of c-BN are calculated using the first-principles plane wave method with the relativistic analytic pseudopotential of the Hartwigen, Goedecker and Hutter (HGH) type in the frame of local density approximation and using the quasi-harmonic Debye model, separately. Moreover, the dependences of the normalized volume V/V0 on pressure P, as well as the bulk modulus B, the thermal expansion ?, and the heat capacity CV on pressure P and temperature T are also successfully obtained.

Hao, Yan-Jun; Cheng, Yan; Wang, Yan-Ju; Chen, Xiang-Rong

2007-01-01

267

Thermodynamics properties and thermal conductivity of Mg2Pb at high pressure

NASA Astrophysics Data System (ADS)

The thermodynamics properties and thermal conductivity of Mg2Pb at high pressures have been calculated by first-principles. The enthalpy of formation and heat capacity obtained at 0 GPa are in good agreement with the experiments and other theoretical results. The thermal conductivity and coefficient of thermal expansion of Mg2Pb at high pressure were evaluated. The thermal conductivity presents a second-order polynomial with pressure. The calculated thermal conductivity of Mg2Pb indicates that it is suitable to be used as thermal conductor at 0 K.

Duan, YongHua; Sun, Yong

2013-10-01

268

Calculating the thermodynamic properties of aqueous solutions of alkali metal carboxylates

NASA Astrophysics Data System (ADS)

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

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

2014-06-01

269

Thermodynamic properties of liquid silver–indium alloys determined from e.m.f. measurements

The thermodynamic properties of the liquid Ag–In alloys were determined using solid oxide galvanic cells with zirconia electrolyte. The e.m.f.'s of the cellsRe+kanthal,AgxIn(1?x),In2O3\\/\\/ZrO2+(Y2O3)\\/\\/NiO,Ni,Ptwere measured in the temperature range from 950 to 1273K, and in the molar fraction from xIn=0.15 to 1.0.At first, the Gibbs free energy of formation of pure solid indium oxide, In2O3, from pure elements was derived. Using

Dominika Jendrzejczyk; Krzysztof Fitzner

2005-01-01

270

NASA Astrophysics Data System (ADS)

An investigation of the electronic, elastic and thermodynamic properties of VC under high pressure has been conducted using first-principles calculations based on density functional theory (DFT) with the plane-wave basis set, as implemented in the CASTEP code. At elevated pressures, VC is predicted to undergo a structural transition from a relatively open NaCl-type structure to a more dense CsCl-type one. The predicted transition pressure is 520 GPa. The elastic constant, Debye temperature and heat capacity each as a function of pressure and/or temperature of VC are presented for the first time.

Hao, Ai-Min; Zhou, Tie-Jun; Zhu, Yan; Zhang, Xin-Yu; Liu, Ri-Ping

2011-04-01

271

Thermodynamic and structural properties of the high density Gaussian core model

NASA Astrophysics Data System (ADS)

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

Ikeda, Atsushi; Miyazaki, Kunimasa

2011-07-01

272

NASA Technical Reports Server (NTRS)

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.

Talcott, N. A., Jr.

1977-01-01

273

First-principles calculations on thermodynamic properties of BaTiO3 rhombohedral phase.

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

Bandura, Andrei V; Evarestov, Robert A

2012-07-01

274

NASA Astrophysics Data System (ADS)

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.

Mishra, Rashmi; Srivastava, Anubha; Sharma, Anamika; Tandon, Poonam; Baraldi, Cecilia; Gamberini, Maria Christina

2013-01-01

275

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

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

2010-06-15

276

Thermodynamic Properties of MgSiO3 Post-Perovskite

NASA Astrophysics Data System (ADS)

The thermodynamic properties of MgSiO3 post-perovskite are predicted at high pressures and temperatures using the Debye model for the first time. This model combines with ab initio calculations within local density approximation using pseudopotentials and a plane wave basis in the framework of density functional theory, and it takes into account the phononic effects within the quasi-harmonic approximation. It is found that the calculated equation of state of MgSiO3 post-perovskite is in excellent agreement with the latest observed values. Based on the first-principles study and the Debye model, the thermal properties including the Debye temperature, the heat capacity, the thermal expansion, and the entropy are obtained in the whole pressure range from 0 to 150 GPa and temperature range from 0 to 2000 K.

Liu, Zi-Jiang; Sun, Xiao-Wei; Zhang, Cai-Rong; Tian, Li-Na; Guo, Yuan

277

NASA Astrophysics Data System (ADS)

Thermodynamic properties of difluoromethane (R32) and pentafluoroethane (R125) are expressed in terms of 32-term modified Benedict-Webb-Rubin (MBWR) equations of state. For each refrigerant, coefficients are reported for the MBWR equation and for ancillary equations used to fit the ideal-gas heat capacity and the coexisting densities and pressure along the saturation boundary. The MBWR coefficients were determined with a multiproperty fit that used the following types of experimental data: PVT: isochoric, isobaric, and saturated-liquid heal capacities; second virial coefficients; and properties at coexistence. The respective equations of stale accurately represent experimental data from 160 to 393 K and pressures to 35 MPa for R32 and from 174 to 448 K and pressures to 68 MPa for R125 with the exception of the critical regions. Both equations give reasonable results upon extrapolation to 500 K and 60 MPa. Comparisons between predicted and experimental values are presented.

Outcalt, S. L.; McLinden, M. O.

1995-01-01

278

Thermodynamic model for calorimetric and phase coexistence properties of coal derived fluids

The objective of this project is to develop a thermodynamic model for phase equilibria and calorimetric properties of coal derived fluids. Through efforts of a previous project, a model for phase equilibria of coal derived liquids is already available. In this project, this model is to be extended to include calorimetric properties as well. The modification involves the use of the modified UNIFAC correlation with suitably regressed parameters, combined with an appropriate equation of state to represent compressibility of the liquid phase. To accomplish this satisfactorily, the proposed work includes three tasks: (1) Refinement of the characterization procedure to include distribution of sulfur, oxygen and nitrogen heteroatoms in coal liquids. This is to be accomplished by size exclusion chromatography of coal liquid samples, followed by elemental and FTIR analysis of separated fractions. (2) Measurement of high temperature (up to 400C) and high pressure (up to 1000 psi) VLE data for binary systems of selected model compounds. The VLE apparatus assembled as a part of the previous project will be used for this purpose, and (3) Development of the thermodynamic model. The final product will include a computer program which with measurable properties of coal liquids as input, will give results for phase coexistence properties and excess enthalpies in the liquid phase. The high temperature, high pressure VLE apparatus has been calibrated and tested. Some preliminary data are currently being measured to assure that the apparatus gives reproducible data. Once this is completed, binary VLE data on model compound systems will be measured. In this report we give a full report of the VLE apparatus. 5 figs.

Kabadi, V.N.

1991-01-01

279

Thermodynamic model for calorimetric and phase coexistence properties of coal derived fluids

The objective of this project is to develop a thermodynamic model for phase equilibria and calorimetric properties of coal derived fluids. A model for phase equilibria of coal derived liquids is already available. This model is to be extended to include calorimetric properties. The modification involves the use of the modified UNIFAC correlation with suitably regressed parameters, combined with an appropriate equation of state to represent compressibility of the liquid phase. To accomplish this satisfactorily, the proposed work includes three tasks: (1) Refinement of the characterization procedure to include distribution of sulfur, oxygen and nitrogen heteroatoms in coal liquids; (2) Measurement of high temperature (up to 400 C) and high pressure (up to 1000 psi) VLE data for binary systems of selected model compounds; and (3) Development of the thermodynamic model. The final product will include a computer program which with measurable properties of coal liquids as input, will give results for phase coexistence properties and excess enthalpies in the liquid phase. Literature search for excess enthalpy data in binary and multi-component systems of compounds similar to the ones that constitute coal derived fluids is under way. These compounds include alkyl substituted mono and polyaromatics, hydroaromatics, pyridines, phenols, furans, thiophenes, pyrolles, carbazoles, etc. The high temperature high pressure apparatus designed and built as a part of the previous DOE project is being prepared for measurement of binary vapor-liquid equilibrium data. Two problems were encountered during the calibrations and start-up of the apparatus. The measurement of VLE data is therefore delayed. Current work involves development of the procedure for size exclusions chromatography of four coal liquid samples. 1 fig.

Kabadi, V.N.

1989-01-01

280

Calculations and curve fits of thermodynamic and transport properties for equilibrium air to 30000 K

NASA Technical Reports Server (NTRS)

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.

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

1991-01-01

281

Thermodynamic properties and equation of state of liquid lead and lead bismuth eutectic

NASA Astrophysics Data System (ADS)

Since the 1950s, liquid lead (Pb) and lead-bismuth eutectic (Pb-Bi) have been studied in the USA, Canada and in the former-USSR as potential coolants for nuclear installations due to their very attractive thermophysical and neutronic properties. However, experimental data on the thermal properties of these coolants in the temperature range of interest are still incomplete and often contradictory. This makes it very difficult to perform design calculations and to analyse the normal and abnormal behaviour of nuclear installations where these coolants are expected to be used. Recently, a compilation of heavy liquid metal (HLM) properties along with recommendations for its use was prepared by the OECD/NEA Working Party on Fuel Cycle (WPFC) Expert Group on Lead-Bismuth Eutectic Technology. A brief review of this compilation and some new data are presented in this article. A set of correlations for the temperature dependence of the main thermodynamic properties of Pb and Pb-Bi(e) at normal pressure, and a set of simplified thermal and caloric equations of state for the liquid phase are proposed.

Sobolev, V. P.; Schuurmans, P.; Benamati, G.

2008-06-01

282

Thermodynamic and electrostatic properties of ternary Oxytricha nova TEBP-DNA complex.

Telomeres constitute the nucleoprotein ends of eukaryotic chromosomes which are essential for their proper function. Telomere end binding protein (TEBP) from Oxytricha nova was among the first telomeric proteins, which were well characterized biologically. TEBP consists of two protein subunits (alpha, beta) and forms a ternary complex with single stranded telomeric DNA containing tandem repeats TTTTGGGG. This work presents the characterization of the thermodynamic and electrostatic properties of this complex by computational chemistry methods (continuum Poisson-Boltzmann and solvent accessible surface calculations). Our calculations give a new insight into molecular properties of studied system. Based on the thermodynamic analysis we provide a rationale for the experimental observation that alpha and ssDNA forms a binary complex and the beta subunit joins alpha:ssDNA complex only after the latter is formed. Calculations of distribution of the molecular electrostatic potential for protein subunits alone and for all possible binary complexes revealed the important role of the "guiding funnel" potential generated by alpha:ssDNA complex. This potential may help the beta subunit to dock to the already formed alpha:DNA intermediate in highly steric and electrostatic favorable manner. Our pK(a) calculations of TEBP are able to explain the experimental mobility shifts of the complex in electrophoretic non-denaturating gels. PMID:16314111

Wojciechowski, M; Fogolari, F; Baginski, M

2005-12-01

283

Vibrational and thermodynamic properties of ?-HMX: a first-principles investigation.

Thermodynamic properties of ?-HMX crystal are investigated using the quasi-harmonic approximation and density functional theory within the local density approximation (LDA), generalized gradient approximation (GGA), and GGA + empirical van der Waals (vdW) correction. It is found that GGA well describes the thermal expansion coefficient and heat capacity but fails to produce correct bulk modulus and equilibrium volume. The vdW correction improves the bulk modulus and volume, but worsens the thermal expansion coefficient and heat capacity. In contrast, LDA describes all thermodynamic properties with reasonable accuracy, and overall is a good exchange-correlation functional for ?-HMX molecular crystal. The results also demonstrate significant contributions of phonons to the equation of state. The static calculation of equilibrium volume for ?-HMX differs from the room-temperature value incorporating lattice vibrations by over 5%. Therefore, for molecular crystals, it is essential to include phonon contributions when calculated equation of state is compared with experimental data at ambient condition. PMID:21639458

Wu, Zhongqing; Kalia, Rajiv K; Nakano, Aiichiro; Vashishta, Priya

2011-05-28

284

Correlation of thermodynamic and genetic properties in the Tn10 encoded TET gene control region.

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.

Hillen, W; Unger, B

1982-01-01

285

Thermodynamic, mechanical and transport properties of fluids with steeply repulsive potentials

NASA Astrophysics Data System (ADS)

Hard sphere perturbation theory expressions for the thermodynamic properties and the infinite frequency elastic moduli of fluids interacting with steeply repulsive pair potentials with the analytical form phi(r) = epsilon(sigma/r)n where epsilon and sigma set the energy and distance scales, respectively, are tested against extensive molecular dynamics (MD) simulation data. The convergence of these expressions as a function of the softness parameter n-1 is examined by comparing with virtually exact values obtained from MD simulations of fluids interacting with these potentials. The value of the parameter n in the simulations ranged from 18 to the unusually high value of 288. Perturbation theory reproduces the thermodynamic properties and the infinite frequency elastic moduli from simulation, within the MD statistical uncertainty for n greater than 36. The self-diffusion coefficient D and shear viscosity eta s were determined also and are found to be quite sensitive to the value of n in the range studied. The convergence towards the hard sphere value is nonlinear in n-1 for D at high fluid densities. At high densities the shear stress autocorrelation function decays increasingly rapidly with time, and the associated shear stress relaxation time diminishes according to n-1 in the hard sphere limit, as predicted by perturbation theory using the Barker-Henderson equivalent hard sphere diameter.

Heyes Jack, David M.; Powles, G.

1998-10-01

286

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

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

287

Ab initio thermodynamic properties of point defects and O-vacancy diffusion in Mg spinels

NASA Astrophysics Data System (ADS)

We report ab initio plane wave density functional theory studies of thermodynamic properties of isolated cation substitutions and oxygen vacancies in magnesium spinel, MgAl2O4 . The formation enthalpy of Ca, Cu, and Zn substitutions of Mg cation indicate that transition metal dopants are energetically stable in the bulk of MgAl2O4 at low oxygen chemical potential. The electronic and thermodynamic properties of isolated defects in ternary spinel show close similarities with those in binary oxides; MgO and ?-Al2O3 . The formation enthalpy of the oxygen vacancies are also similar in pure magnesium spinel and in binary oxides, but presence of impurity cations in MgAl2O4 significantly lowers formation enthalpy of the oxygen vacancy in their vicinity. Calculated energy barriers for oxygen vacancy hopping are lower in the vicinity of impurity atoms in the spinel structure. Our calculations indicate that the charge state of doped cation is modified by the accompanying oxygen vacancy and the vacancy diffusion is more facile around impurity. The present studies suggest that point defects play an important role in diffusion of oxygen vacancies in MgAl2O4 .

?odziana, Zbigniew; Piechota, Jacek

2006-11-01

288

NASA Astrophysics Data System (ADS)

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

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

2013-08-01

289

First principal studya of structural, electronic and thermodynamic properties of KTaO3-perovskite.

NASA Astrophysics Data System (ADS)

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 ? point. To complete the fundamental characterization of KTaO3 material we have analyzed the thermodynamic properties using the quasi-harmonic Debye model.

Bouafia, H.; Akriche, A.; Ascri, R.; Ghalouci, L.; Sahli, B.; Hiadsi, S.; Abidri, B.; Amrani, B.

2013-03-01

290

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

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

2014-04-01

291

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

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

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

2013-01-01

292

Phase transition and thermodynamic properties of ThO2 from first-principles calculations

NASA Astrophysics Data System (ADS)

Within the framework of the quasi-harmonic approximation, the thermodynamic properties and the phase transition of ThO2 from the cubic structure to the orthorhombic structure are studied using the first-principles projector-augmented wave method. The vibrational contribution to Helmholtz free energy is evaluated from the first-principles phonon density of states and the Debye-Grüneisen model. The calculated results reveal that at ambient temperature, the phase transition from the cubic phase to the orthorhombic phase occurs at 26.49 GPa, which is in agreement with the experimental and theoretical data. With increasing temperature, the transition pressure decreases almost linearly above room temperature. The predicted heat capacity and linear thermal expansion coefficient of cubic ThO2 are in good consistence with the experimental data. By comparing the experimental results with the calculation results from the first-principles and Debye-Grüneisen model, it is found that the thermodynamic properties of ThO2 are depicted well by the first-principles phonon treatment after including the an-harmonic correction to quasi-harmonic free energy.

Wang, Fan-Hou; Li, Qiang; Huang, Duo-Hui; Cao, Qi-Long; Yang, Jun-Sheng; Gao, Zeng-Hui

2013-08-01

293

Magneto-elastic effects and thermodynamic properties of ferromagnetic hcp Co

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

294

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

295

Thermodynamic model for calorimetric and phase coexistence properties of coal derived fluids

On September 1, 1989 work was initiated on a project to extend the available vapor-liquid equilibrium (VLE) model for coal fluids to allow satisfactory predictions of excess enthalpies of coal liquids at high pressures. The available vapor liquid equilibrium model was developed with support from previous grant from DOE-PETC (Grant no. DE-FG22-89PC90541). The current project also involves measurement of some model compound VLE data and chromatographic characterization of coal liquids for distribution of heteroatoms. A computational thermodynamic model for VLE, excess enthalpies and heat capacities of coal derived liquids has been developed. 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 computations are carried out using the method of continuous thermodynamics. Mode is used to derive interesting conclusions on the effect of oxygen, nitrogen, and sulfur heteroatoms on the thermodynamic properties of coal liquids. When compared with limited experimental data available for coal liquids the model shows good agreement. Some progress has been made on binary VLE measurements and size exclusion chromatography of coal liquids.

Kabadi, V.N.

1991-10-01

296

On September 1, 1989 work was initiated on a project to extend the available vapor-liquid equilibrium (VLE) model for coal fluids to allow satisfactory predictions of excess enthalpies of coal liquids at high pressures. The available vapor liquid equilibrium model was developed with support from previous grant from DOE-PETC (Grant no. DE-FG22-89PC90541). The current project also involves measurement of some model compound VLE data and chromatographic characterization of coal liquids for distribution of heteroatoms. A computational thermodynamic model for VLE, excess enthalpies and heat capacities of coal derived liquids has been developed. 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 computations are carried out using the method of continuous thermodynamics. Mode is used to derive interesting conclusions on the effect of oxygen, nitrogen, and sulfur heteroatoms on the thermodynamic properties of coal liquids. When compared with limited experimental data available for coal liquids the model shows good agreement. Some progress has been made on binary VLE measurements and size exclusion chromatography of coal liquids.

Kabadi, V.N.

1991-10-01

297

NASA Astrophysics Data System (ADS)

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

Asta, Mark David

298

NASA Astrophysics Data System (ADS)

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

Deckman, Jason

299

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

NASA Astrophysics Data System (ADS)

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

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

1997-04-01

300

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

A large number of aqueous metal complexes contribute significantly to hydrothermal, metamorphic, and magmatic processes in the crust of the Earth. Nevertheless, relatively few thermodynamic data other than dissociation constants (K) for a few dozen of these complexes have been determined experimentally at elevated temperatures and pressures. The calculations summarized below are intended to supplement these experimental data by providing interim predictions of the thermodynamic properties of supercritical aqueous metal complexes using the revised HKF (Helgeson et al., 1981) equations of state for aqueous species (Tanger and Helgeson, 1988; Shock et al., 1992) and correlations among equations of state parameters and standard partial molal properties at 25 degrees C and 1 bar (Shock and Helgeson, 1988, 1990; Shock et al., 1989). These equations and correlations permit retrieval of the conventional standard partial molal entropies (mean S0), volumes (mean V0), and heat capacities (mean C0P) of aqueous metal complexes at 25 degrees C and 1 bar from published values of log K in the supercritical region and the limited number of experimental dissociation constants available in the literature over relatively short ranges of elevated temperature at PSAT (PSAT and SAT are used in the present communication to refer to pressures corresponding to liquid-vapor equilibrium for the system H2O except at temperatures <100 degrees C, where they refer to the reference pressure of 1 bar). The standard partial molal properties computed in this way can then be used to generate corresponding values of delta mean S0, delta mean V0, and delta mean C0P of association, which for similar complexes correlate linearly with mean S0, mean V0 and mean C0P, respectively, of the constituent cations and ligands at 25 degrees C and 1 bar. Generalizing these correlations and combining them with the equations of state permits prediction of the temperature and pressure dependence of log K and other thermodynamic properties of a large number of aqueous metal complexes. As a consequence, it is possible to retrieve values of log K at 25 degrees C and 1 bar from the results of hydrothermal experiments at higher temperatures and pressures or to predict values of log K at hydrothermal conditions when no experimental data are available at temperatures and pressures above 25 degrees C and 1 bar. Such predictions can be made for temperatures and pressures from 0 degrees C and 1 bar to 1000 degrees C and 5000 bars. PMID:11541435

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

1997-04-01

301

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.

Kang, H.S.; Ree, F.H.

1997-12-01

302

Mucoadhesive properties of several polymers, such as sodium alginate, hydroxypropylmethyl cellulose, scleroglucan, xanthan gum, polyacrylic acid (Carbopol), and poly co-(methyl vinyl ether-maleic anhydride) (Gantrez), have been investigated by comparing a thermodynamical and a mechanical approach. Surface properties of polymers in the dry state have been studied by contact angle measurements and thermodynamical parameters derived by using different equations. This tensile adhesive strength of polymers in hydration conditions was measured by a modified DuNoy tensiometer. Comparison of the two different approaches has allowed us to conclude that thermodynamical consideration on surface energy can be used to evaluate mucoadhesive properties of materials. Data obtained with the two methods yielded a good linear correlation. Calculation of surface free energy of the considered materials also allowed a prediction of the water-polymer interface free energy: biocompatibility, defined according to the minimal interfacial free energy concept, could consequently be evaluated. PMID:8199290

Esposito, P; Colombo, I; Lovrecich, M

1994-02-01

303

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

Han, Bumsoo; Bischof, John C

2004-04-01

304

The thermodynamic properties of 75 polyfluorinated dibenzo-p-dioxins (PFDDs) in the ideal gas state at 298.15K and 1.013×105Pa have been calculated at the B3LYP\\/6-311G* level using Gaussian 03 program. The isodesmic reactions were designed to calculate standard enthalpy of formation (?Hf°) and standard free energy of formation (?Gf°) of PFDDs congeners. The relations of these thermodynamic parameters with the number and

Xi Yang; Hui Liu; Haifeng Hou; Alison Flamm; Xuesheng Zhang; Zunyao Wang

2010-01-01

305

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

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

2003-01-01

306

NASA Technical Reports Server (NTRS)

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.

Weber, L. A.

1975-01-01

307

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

NASA Astrophysics Data System (ADS)

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

Michel, Kyle Jay

308

Isentropic expansion and related thermodynamic properties of non-ionic amphiphile-water mixtures.

A concise thermodynamic formalism is developed for the molar isentropic thermal expansion, ES,m = ( partial differential Vm/ partial differential T)(Sm,x), and the ideal and excess quantities for the molar, apparent molar and partial molar isentropic expansions of binary liquid mixtures. Ultrasound speeds were determined by means of the pulse-echo-overlap method in aqueous mixtures of 2-methylpropan-2-ol at 298.15 K over the entire composition range. These data complement selected extensive literature data on density, isobaric heat capacity and ultrasound speed for 9 amphiphile (methanol, ethanol, propan-1-ol, propan-2-ol, 2-methylpropan-2-ol, ethane-1,2-diol, 2-methoxyethanol, 2-ethoxyethanol or 2-butoxyethanol)-water binary systems, which form the basis of tables listing molar and excess molar isobaric expansions and heat capacities, and molar and excess molar isentropic compressions and expansions at 298.15 K and at 65 fixed mole fractions spanning the entire composition range and fine-grained in the water-rich region. The dependence on composition of these 9 systems is graphically depicted for the excess molar isobaric and isentropic expansions and for the excess partial molar isobaric and isentropic expansions of the amphiphile. The analysis shows that isentropic thermal expansion properties give a much stronger response to amphiphile-water molecular interactions than do their isobaric counterparts. Depending on the pair property-system, the maximum excess molar isentropic value is generally twenty- to a hundred-fold greater than the corresponding maximum isobaric value, and occurs at a lower mole fraction of the amphiphile. Values at infinite dilution of the 9 amphiphiles in water are given for the excess partial molar isobaric heat capacity, isentropic compression, isobaric expansion and isentropic expansion. These values are interpreted in terms of the changes occurring when amphiphile molecules cluster into an oligomeric form. Present results are discussed from theoretical and experimental thermodynamic viewpoints. It is concluded that isentropic thermal expansion properties constitute a new distinct resource for revealing particular features and trends in complex mixing processes, and that analyses using these new properties compare favourably with conventional approaches. PMID:18183317

Reis, João Carlos R; Douhéret, Gérard; Davis, Michael I; Fjellanger, Inger Johanne; Høiland, Harald

2008-01-28

309

NASA Technical Reports Server (NTRS)

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

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

1976-01-01

310

NASA Astrophysics Data System (ADS)

The structural and dynamical properties of polymer nanocomposites are investigated using stochastic molecular dynamics simulations. For spherical nanoparticles dispersed in a polymer matrix, the results indicate that the polymer-nanoparticle interaction strength and the overall system temperature are primarily responsible for the type of dispersed state (clustering and homogeneous dispersion) achieved. A systematic study probing temperature, polymerization, and polymer-nanoparticle and nanoparticle-nanoparticle interaction strengths has been performed. In this paper, however, we focus the discussion on the results for varying polymer-nanoparticle interaction strengths at different temperatures. By examining the structure and dynamics, we show that there are two kinds of ``clustering transitions:'' one due to thermodynamic and another due to the dynamical response of the system. From these results, a representative phase diagram is developed that captures the entire simulated space and allows the easy identification of the highly dispersed and the clustered states.

Goswami, Monojoy; Sumpter, Bobby G.

2009-04-01

311

NASA Technical Reports Server (NTRS)

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

Klich, G. F.

1976-01-01

312

Theoretical studies of elastic and thermodynamic properties of cubic B20 CoSi

NASA Astrophysics Data System (ADS)

The full potential linearized augmented plane wave (FP-LAPW) method based on the density functional theory as implemented in the WIEN2k package is applied successfully to the study of the equilibrium lattice parameter and the elastic constants of the cubic B20 structural CoSi. The quasi-harmonic Debye model, in which the phononic effects are considered, is used to investigate the thermodynamic properties of B20 CoSi. Young's modulus and Poisson ratio are obtained from the calculated elastic constants and compared with the available data. The pressure and temperature dependence of the volume, the bulk modulus, the thermal expansion coefficient, the heat capacity and the Debye temperature are successfully obtained in the whole pressure range from 0 to 40 GPa and temperature range from 0 to 1400 K .

Liu, Yong; Li, Shi-Na; Wang, Zhi-Zhou

2012-12-01

313

NASA Astrophysics Data System (ADS)

The influence of nonstoichiometry on the partial thermodynamic properties of oxygen and the {C to B} transformation parameters of europium sesquioxide within a temperature range from 1200 K to 1400 K using e.m.f., DTA and DSC methods, has been determined. A tentative phase diagram in the {Cto B} transformation region is proposed. L'influence de la nonstoechiométrie sur les propriétés thermodynamiques partielles de l'oxygène et sur les paramètres de la transition {C to B} de Eu2O3 dans l'intervalle de températures de 1200 K à 1400 K a été étudiée par les méthodes EMF, DTA, DSC. Une variante de diagramme de phases dans la région de la transition {Cto B} est présentée.

Sukhushina, I.; Vasiljeva, I.; Balabajeva, R.

1998-01-01

314

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

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

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

2013-07-28

315

Estimation of the Thermodynamic Limit of Overheating for Bulk Water from Interfacial Properties

NASA Astrophysics Data System (ADS)

The limit of overheating or expanding is an important property of liquids, which is relevant for the design and safety assessment of processes involving pressurized liquids. In this work, the thermodynamic stability limit—the so-called spinodal—of water is calculated by molecular dynamics computer simulation, using the molecular potential model of Baranyai and Kiss. The spinodal pressure is obtained from the maximal tangential pressure within a liquid-vapor interface layer. The results are compared to predictions of various equations of state. Based on these comparisons, a set of equations of state is identified which gives reliable results in the metastable (overheated or expanded) liquid region of water down to MPa.

Imre, A. R.; Baranyai, A.; Deiters, U. K.; Kiss, P. T.; Kraska, T.; Quiñones Cisneros, S. E.

2013-11-01

316

NASA Astrophysics Data System (ADS)

Based on the functional integral procedure, a recently proposed bridge density function [J. Chem. Phys. 112 (2000) 8079] is developed to calculate global thermodynamic properties of non-uniform fluids. The resulting surface tension of a hard wall-hard sphere interface as a function of the bulk hard sphere fluid density is in good agreement with the available simulation data. The proposed numerical procedure from the approximation of non-uniform first-order direct correlation function to a non-uniform system with excess Helmholtz free energy is of fundamental importance for phase behaviour under the confined condition due to the fact that many available simple approximations in classical density functional theory are for non-uniform first-order direct correlation function.

Zhou, Shi-Qi

2003-12-01

317

A novel equation of state for the prediction of thermodynamic properties of fluids.

This work proposes a new equation of state (EOS) based on molecular theory for the prediction of thermodynamic properties of real fluids. The new EOS uses a novel repulsive term, which gives the correct hard sphere close packed limit and yields accurate values for hard sphere and hard chain virial coefficients. The pressure obtained from this repulsive term is corrected by a combination of van der Waals and Dieterici potentials. No empirical temperature functionality of the parameters has been introduced at this stage. The novel EOS predicts the experimental volumetric data of different compounds and their mixtures better than the successful EOS of Peng and Robinson. The prediction of vapor pressures is only slightly less accurate than the results obtained with the Peng-Robinson equation that is designed for these purposes. The theoretically based parameters of the new EOS make its predictions more reliable than those obtained from purely empirical forms. PMID:16851652

Polishuk, Ilya; Vera, Juan H

2005-03-31

318

Thermodynamic properties of defects in crystals calculated on the basis of the bulk elastic data

NASA Astrophysics Data System (ADS)

Varaksin and Shipitsin [Sov. Phys.-Solid State 27, 1218 (1985)] have recently presented a study of the thermodynamic properties of defects in crystals calculated on the basis of elasticity. They suggested a relation that connects the defect entropy to the elastic data of the bulk material. Furthermore they claimed that this relation is more accurate than that suggested earlier by Varotsos and Alexopoulos [Phys. Rev. B 15, 4111 (1977); 24, 904 (1981)]. In the present paper we show that the latter relation in connection to the elastic data of NaCl just published by Yamamoto et al. (1987) leads to a value of the formation entropy per Schottky defect that agrees with the experimental one. On the other hand the relation of Varaksin and Shipitsin leads to a value of the formation entropy that drastically differs (i.e., by a factor of around 4) from the experimental one.

Hadjicontis, V.; Eftaxias, K.; Varotsos, P.

1988-03-01

319

Thermodynamic properties of defects in crystals calculated on the basis of the bulk elastic data

Varaksin and Shipitsin (Sov. Phys.: Solid State 27, 1218 (1985)) have recently presented a study of the thermodynamic properties of defects in crystals calculated on the basis of elasticity. They suggested a relation that connects the defect entropy to the elastic data of the bulk material. Furthermore they claimed that this relation is more accurate than that suggested earlier by Varotsos and Alexopoulos (Phys. Rev. B 15, 4111 (1977);24, 904 (1981)). In the present paper we show that the latter relation in connection to the elastic data of NaCl just published by Yamamoto et al. (1987) leads to a value of the formation entropy per Schottky defect that agrees with the experimental one. On the other hand the relation of Varaksin and Shipitsin leads to a value of the formation entropy that drastically differs (i.e., by a factor of around 4) from the experimental one.

Hadjicontis, V.; Eftaxias, K.; Varotsos, P.

1988-03-15

320

Acoustic and Thermodynamic Properties of the Binary Liquid Mixture n-Octane + n-Dodecane

NASA Astrophysics Data System (ADS)

The velocity of sound in the binary liquid mixture n-octane + n-dodecane has been investigated by the method of direct measurement of the pulse-transmission time in the interval of temperatures 298-433 K and pressures 0.1-100.1 MPa. The maximum measurement error amounts to 0.1%. The density, isobaric expansion coefficient, isobaric and isochoric heat capacities, and isothermal compressibility of a mixture of three compositions have been determined in the intervals of temperatures 298-393 K and pressures 0.1-100 MPa from the data on the velocity of sound. Also, the excess molar volume, the excess isothermal compressibility, and the deviation of the velocity of sound from its value for an ideal liquid have been determined. The coefficients of the Tate equation have been computed in the above temperature interval. A table of thermodynamic properties of the mixture has been presented.

Khasanshin, T. S.; Golubeva, N. V.; Samuilov, V. S.; Shchemelev, A. P.

2014-01-01

321

Kinetics data for the dimerization of cyclopentadiene at 378, 388, and 398 K in supercritical propane solvent were obtained. The dimerization slows somewhat with increasing density. However, the kinetic solvent effect is small compared to the orders of magnitude changes in solubilities observed in the supercritical region. The selectivity of acridine in an acridine/anthracene mixed solute system significantly increased with a 1% methanol/carbon dioxide solvent relative to pure carbon dioxide. This supports the possibility of separations with supercritical fluids. The decorated lattice-gas has been quite successful in modeling supercritical region binary solution solubilities and infinite dilution partial molar volumes. The ability to describe macroscopic thermodynamic properties by this more fundamentally valid approach is extremely encouraging. 1 fig.

Eckert, C.A.

1985-01-01

322

NASA Astrophysics Data System (ADS)

We report electrical, magnetic, elastic, and thermodynamic properties of CoSi. A low resistivity residual ratio and tendency of the resistivity to saturate near room temperature identify CoSi as a disordered metal, which nevertheless reveals the clear presence of T2 contribution of nonmagnetic nature below ˜30 K. The Sommerfeld constant of CoSi, following from heat capacity measurements, does not show any enhancement over values typical of simple metals. The magnetic susceptibility of CoSi changes from diamagnetic at high temperature to paramagnetic at temperatures below ˜25 K, indicating the existence of local magnetic moments. The elastic moduli of CoSi show an anomalous decrease on cooling. An explanation of these phenomena is based on the concept of electron localization with formation of local magnetic moments. These phenomena probably arise as a result of a self-doping effect due to the polyvalent character of Co and the nonstoichiometric nature of CoSi.

Stishov, Sergei M.; Petrova, Alla E.; Sidorov, Vladimir A.; Krasnorussky, Vladimir N.; Menzel, Dirk

2012-08-01

323

COSMO-RS: an alternative to simulation for calculating thermodynamic properties of liquid mixtures.

The conductor-like screening model for realistic solvation (COSMO-RS) method has been established as a novel way to predict thermophysical data for liquid systems and has become a frequently used alternative to force field-based molecular simulation methods on one side and group contribution methods on the other. Through its unique combination of a quantum chemical treatment of solutes and solvents with an efficient statistical thermodynamics procedure for the molecular surface interactions, it enables the efficient calculation of many properties that other methods can barely predict. This review presents a short delineation of the theory, the application potential and limitations of COSMO-RS, and its most important application areas. PMID:22432575

Klamt, Andreas; Eckert, Frank; Arlt, Wolfgang

2010-01-01

324

Thermodynamic properties of iron and nickel chloride solutions in molten LiCl-KCl

The thermodynamic properties of solutions of iron or nickel chlorides in mixed molten LiCl-KCl were determined by emf measurements of FeCl{sub 2} or NiCl{sub 2} formation cells. The concentration range examined was 0.015-2 mol %. The temperature dependence of the emf between 355 and 540{degree}C was used to calculate the enthalpy and entropy of formation of dissolved FeCl{sub 2} or NiCl{sub 2}. It was shown that, in the investigated concentration range, these solutions have a nearly ideal behavior. Simple empirical equations were derived to represent the emf of these formation cells with an accuracy of about {plus minus} 1.5 mV.

Lantelme, F.; Chemla, M. (Universite Pierre et Marie Curie, Paris (France)); Equey, J.F.; Mueller, S. (Paul Scherrer Institut, Villigen (Switzerland))

1991-01-24

325

Thermodynamical properties of the mixed spin transverse Ising model with four-spin interactions

NASA Astrophysics Data System (ADS)

The thermodynamical properties of the mixed spin transverse Ising system consisting of spin-1/2 and spin-1 with four-spin interactions are studied within the frame work of the finite cluster approximation based on single-site cluster theory. In this approach, the state equations are derived for the two-dimensional square lattice. In addition to the phase diagrams which show qualitatively interesting features (variety of transitions and tricritical behaviour), we find some characteristic behaviours of the longitudinal and transverse sublattice magnetizations. In particular, the gap of the longitudinal magnetization at first order transition decreases with increasing values of the transverse field. Moreover, the effects of the transverse field on the internal energy and the specific heat are also investigated.

Ghliyem, M.; Benayad, N.; Azhari, M.

2014-05-01

326

A molecular dynamics study of the thermodynamic properties of barium zirconate

NASA Astrophysics Data System (ADS)

In this paper, a molecular dynamics (MD) simulation is carried out to study the microscopic atomic behavior and the macroscopic thermodynamic and thermal transport properties of a perovskite material. A new set of potential parameters is presented for barium zirconate. The radial distribution function is estimated to understand the atomic and structural behavior. The variation of lattice parameters, thermal expansion coefficient, isothermal compressibility, heat capacity and thermal conductivity are evaluated in the temperature range 298-2000 K and the pressure range 1 atm-20.3 GPa. The thermal conductivity calculation is performed using the non-equilibrium MD method, and a correction for the finite size effects is made. The simulation results show good agreement with the experimental findings.

Fong Goh, Wen; Aziz Khan, Sohail; Yoon, Tiem Leong

2013-06-01

327

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.

Kabadi, V.N.

1995-06-30

328

Structural and thermodynamic properties of a linearly perturbed matrix model for RNA folding.

The structural and thermodynamic properties of a matrix model of homo-RNA folding with linear external interaction are studied. The interaction distinguishes paired bases of the homo-RNA chain from the unpaired bases hence dividing the possible RNA structures given by the linear model into two structural regimes. The genus distribution functions show that the total number of structures for any given length of the chain are reduced for the simple linear interaction considered. The partition function of the model exhibits a scaling relation with the matrix model in which the base pairing strength parameter is re-scaled (G. Vernizzi, H. Orland, A. Zee, Phys. Rev. Lett. 94, 168103 (2005)). The thermodynamics of the model are computed for i) largely secondary structures, (with tertiary structures suppressed by a factor 10(-4)) and ii) secondary plus tertiary structures. A structural change for large even lengths is observed in the free energy and specific heat. This change with largely secondary structures appears much before (with respect to length of the chain) than when all the structures (secondary and pseudoknots) are considered. The appearance of different structures which dominate the ensemble with varying temperatures is also found as a function of the interaction parameter for different types of structures (given by different numbers of pairings). PMID:21086016

Garg, I; Deo, N

2010-12-01

329

NASA Astrophysics Data System (ADS)

We have predicted structural, electronic, elastic, thermodynamic and vibration characteristics of TbN, using density functional theory within generalized-gradient (GGA) apraximation. For the total energy calculation we have used the projected augmented plane-wave (PAW) implementation of the Vienna Ab initio Simulation Package (VASP). We have used to examine structure parameter in eight different structures such as in NaCl (B1), CsCl (B2), ZB (B3), Tetragonal (L10), WC (Bh), NiAs (B8), PbO (B10) and Wurtzite (B4). We have performed the thermodynamics properties for TbN by using quasi-harmonic Debye model. We have, also, predicted the temperature and pressure variation of the volume, bulk modulus, thermal expansion coefficient, heat capacities and Debye temperatures in a wide pressure (0-130 GPa) and temperature ranges (0-2000 K). Furthermore, the band structure, phonon dispersion curves and corresponding density of states are computed. Our results are compared to other theoretical and experimental works, and excellent agreement is obtained.

Ciftci, Y. O.; Ozayman, M.; Surucu, G.; Colakoglu, K.; Deligoz, E.

2012-03-01

330

NASA Astrophysics Data System (ADS)

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

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

2013-08-01

331

NASA Technical Reports Server (NTRS)

A computer program subroutine, FLUID, was developed to calculate thermodynamic and transport properties of pure fluid substances. It provides for determining the thermodynamic state from assigned values for temperature-density, pressure-density, temperature-pressure, pressure-entropy, or pressure-enthalpy. Liquid or two-phase (liquid-gas) conditions are considered as well as the gas phase. A van der Waals model is used to obtain approximate state values; these values are then corrected for real gas effects by model-correction factors obtained from tables based on experimental data. Saturation conditions, specific heat, entropy, and enthalpy data are included in the tables for each gas. Since these tables are external to the FLUID subroutine itself, FLUID can implement any gas for which a set of tables has been generated. (A setup phase is used to establish pointers dynamically to the tables for a specific gas.) Data-table preparation is described. FLUID is available in both SFTRAN and FORTRAN

Fessler, T. E.

1977-01-01

332

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

NASA Astrophysics Data System (ADS)

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

Yang, Xu-Qiu; Zhai, Peng-Cheng; Liu, Li-Sheng; Zhang, Qing-Jie

2011-06-01

333

On the thermodynamic properties of the Rb3C60 superconductor

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

334

Equilibrium and non-equilibrium molecular dynamics and Monte Carlo simulation techniques were applied to predict various thermodynamic, transport and vapor–liquid equilibrium properties of binary mixtures of ethylene glycol and water (EG–W) based on OPLS-AA and SPC\\/E force fields. The properties predicted include density, vaporization enthalpy, enthalpy of mixing, heat capacities, diffusion coefficients, shear viscosities, thermal conductivities, vapor–liquid coexistence isotherms and isobaric

Jianxing Dai; Ling Wang; Yingxin Sun; Lin Wang; Huai Sun

2011-01-01

335

A molecular-based theory for the thermodynamic properties of water

NASA Astrophysics Data System (ADS)

Following the rules set by the molecular theories of fluids, a perturbed form of the Helmholtz free energy for water has been developed. The reference term corresponds to short range water, and is approximated by the properties of a primitive model; the perturbation term is given by contributions of the dispersion forces and the dipole-dipole interaction. The method is first verified by applying it to TIP4P water and then used for real water without reference to any specific potential. The parameters of the model are determined in order to obtain the best representation of the vapour pressure and coexistence liquid densities from the triple point to 643.15 K; no attempt is made to fit the critical region. Despite a number of approximations employed, the accuracy of the equation of state is comparable with that of the modified Redlich-Kwong-Soave equation and SAFT Yukawa-dipole-dipole equation, and considerably better than the accuracy of SAFT-HS and SAFT-VR equations. Because of its true molecular footing, the equation remains reliable also for various thermodynamic properties outside the coexistence region. It reproduces the anomaly in the isothermal compressibility, locating its minimum at T = 38 °C (versus the experimental value T = 46 °C) for P = 1 bar. It also predicts a density maximum, but outside the experimental temperature range (at temperatures below the triple-point temperature).

Nezbeda, Ivo; Weingerl, Ulrike

336

First principle study of elastic and thermodynamic properties of FeB4 under high pressure

NASA Astrophysics Data System (ADS)

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.

Zhang, Xinyu; Qin, Jiaqian; Ning, Jinliang; Sun, Xiaowei; Li, Xinting; Ma, Mingzhen; Liu, Riping

2013-11-01

337

Experimental access to elastic and thermodynamic properties of RbMnFe(CN)6

NASA Astrophysics Data System (ADS)

We use spectroscopic ellipsometry to study the elastic and thermodynamic properties of the structural first-order transition of the cooperative Jahn-Teller solid, RbMn[Fe(CN)6]. While the analysis of the thermal dependence of the dielectric constant revealed a remarkable energy shift in the metal-to-ligand charge transfer band, that of the refractive index allowed to evaluate the volumetric thermal expansion coefficient in the two phases through the Gladstone-Dale relation. The access to the elastic properties of the solid is obtained with the reflectivity under pressure measurements, from which we estimated the bulk modulus values in the low- and high-temperature phases as BLT=30(+/-3) GPa and BHT=23(+/-2) GPa, respectively. Assuming the system is isotropic, the corresponding Debye temperature values have been found to be ?DLT(SE)~=360(+/-25) K and ?DHT(SE)~=290(+/-20) K, in good agreement with those derived from independent Mössbauer spectrometry investigations which led to ?DLT(Moss)~=332(+/-7) K and ?DHT(Moss)~=280(+/-11) K. Moreover, we have been able to extract from the SE data, the entropy change at the transition, ?S~64 J K-1 mol-1, which has been also found in good agreement with the value, ?S~60+/-5 J K-1 mol-1, derived from calorimetric experiments performed in this work.

Boukheddaden, K.; Loutete-Dangui, E. D.; Codjovi, E.; Castro, M.; Rodriguéz-Velamazán, J. A.; Ohkoshi, S.; Tokoro, H.; Koubaa, M.; Abid, Y.; Varret, F.

2011-01-01

338

Why thermodynamic properties of normal and heavy water are similar to those of argon-like liquids?

The Letter is devoted to the explanation of the argon-like behavior of the thermodynamic properties of water. It is shown that this phenomenon is caused by the averaged inter-particle potentials which form due to rotation of water molecules. The general structure of the averaged potentials is proposed. The physical nature for the considerable shift of the triple point of water

Sergey V. Lishchuk; Nikolay P. Malomuzh; Pavel V. Makhlaichuk

2010-01-01

339

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

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

1998-01-01

340

Equation of state and thermodynamic properties of 1,1,1,2-tetrafluoroethane (refrigerant R134a)

NASA Astrophysics Data System (ADS)

An equation of state and tables of thermodynamic properties of R134a in the saturation state and in the one-phase region are obtained in the temperature interval 320 500 K at pressures ranging from 0.01 to 7.5 MPa.

Vas'kov, E. T.

1995-01-01

341

NASA Technical Reports Server (NTRS)

Vapor pressure data obtained by the torsion-effusion method provides the thermodynamic properties of several transition-metal alloy systems. The vapor pressure of silver over solid silver and over palladium-silver alloys was measured and the results were more accurate than those found previously by other techniques.

Myles, K. M.

1967-01-01

342

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:

Wilmer Neuenschwander

1989-01-01

343

NASA Astrophysics Data System (ADS)

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).

Mysen, B.; Lee, S.; Cody, G. D.; Fei, Y.

2006-12-01

344

NASA Astrophysics Data System (ADS)

The structural and thermodynamic properties of tetragonal-TiH2 under high temperatures and pressures are investigated by Ab initio calculations based on pseudo-potential plane-wave density functional theory method within using the generalized gradient approximation (GGA) and quasi-harmonic Debye model. Some ground state properties such as lattice constants, bulk modulus and elastic constants are good agreement with the available experimental results and other theoretical data. Through the quasiharmonic Debye model, in which the phononic effects are considered, the thermodynamic properties of tetragonal-TiH2 such as thermal expansion coefficient, Debye temperature, heat capacity and Grüneisen parameters dependence of temperature and pressure in the range of 0-1000 K and 0-10 GPa are also presented, respectively.

Liu, X. K.; Tang, B.; Zhang, Y.

2013-10-01

345

NASA Astrophysics Data System (ADS)

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.

Hallett, Paul; Ogden, Mike; Karim, Kamal; Schmidt, Sonja; Yoshida, Shuichiro

2014-05-01

346

NASA Astrophysics Data System (ADS)

The canonical Monte Carlo computer simulations and integral equation theory were applied to examine the structural and thermodynamic properties of a mixture of ions and a core-softened fluid molecules. The positive and negative ions forming a +1:-1 salt were modeled as charged hard spheres, immersed in the dielectric medium. It was shown previously that the core-softened fluid under study is characterized by a set of structural, thermodynamic, and dynamic anomalies. The principal objective of this work was to elucidate how the presence of ions alters this behavior. The structural properties of the mixtures are discussed in terms of the pair distribution functions; in addition, the pair contribution to the excess entropy was calculated. Thermodynamic properties are investigated by using the dependencies of energy and compressibility factor on density, composition of the mixture, and reduced temperature. The heat capacity was also evaluated. Our principal findings concern the description of structural anomalies in the mixture, the dependence of the temperature of maximum density on the ionic concentration, and establishing the regions delimiting the structural and thermodynamic anomalies of the model mixture.

Lukši?, Miha; Hribar-Lee, Barbara; Vlachy, Vojko; Pizio, O.

2012-12-01

347

The canonical Monte Carlo computer simulations and integral equation theory were applied to examine the structural and thermodynamic properties of a mixture of ions and a core-softened fluid molecules. The positive and negative ions forming a +1:-1 salt were modeled as charged hard spheres, immersed in the dielectric medium. It was shown previously that the core-softened fluid under study is characterized by a set of structural, thermodynamic, and dynamic anomalies. The principal objective of this work was to elucidate how the presence of ions alters this behavior. The structural properties of the mixtures are discussed in terms of the pair distribution functions; in addition, the pair contribution to the excess entropy was calculated. Thermodynamic properties are investigated by using the dependencies of energy and compressibility factor on density, composition of the mixture, and reduced temperature. The heat capacity was also evaluated. Our principal findings concern the description of structural anomalies in the mixture, the dependence of the temperature of maximum density on the ionic concentration, and establishing the regions delimiting the structural and thermodynamic anomalies of the model mixture. PMID:23277940

Lukši?, Miha; Hribar-Lee, Barbara; Vlachy, Vojko; Pizio, O

2012-12-28

348

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

NASA Astrophysics Data System (ADS)

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

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

2011-03-01

349

Simulations of the Thermodynamic and Diffusion Properties of Actinide Oxide Fuel Materials

Spent nuclear fuel from commercial reactors is comprised of 95-99 percent UO{sub 2} and 1-5 percent fission products and transuranic elements. Certain actinides and fission products are of particular interest in terms of fuel stability, which affects reprocessing and waste materials. The transuranics found in spent nuclear fuels are Np, Pu, Am, and Cm, some of which have long half- lives (e.g., 2.1 million years for {sup 237}Np). These actinides can be separated and recycled into new fuel matrices, thereby reducing the nuclear waste inventory. Oxides of these actinides are isostructural with UO{sub 2}, and are expected to form solid solutions. This project will use computational techniques to conduct a comprehensive study on thermodynamic properties of actinide-oxide solid solutions. The goals of this project are to: Determine the temperature-dependent mixing properties of actinide-oxide fuels; Validate computational methods by comparing results with experimental results; Expand research scope to complex (ternary and quaternary) mixed actinide oxide fuels. After deriving phase diagrams and the stability of solid solutions as a function of temperature and pressure, the project team will determine whether potential phase separations or ordered phases can actually occur by studying diffusion of cations and the kinetics of potential phase separations or ordered phases. In addition, the team will investigate the diffusion of fission product gases that can also have a significant influence on fuel stability. Once the system has been established for binary solid solutions of Th, U, Np, and Pu oxides, the methodology can be quickly applied to new compositions that apply to ternaries and quaternaries, higher actinides (Am, Cm), burnable poisons (B, Gd, Hf), and fission products (Cs, Sr, Tc) to improve reactivity.

Becker, Udo [Univ. of Michigan (United States)

2013-04-16

350

First-principles study on thermodynamic properties and phase transitions in TiS2

NASA Astrophysics Data System (ADS)

Structural and vibrational properties of TiS2 with the CdI2 structure have been studied to high pressures from density functional calculations with the local density approximation (LDA). The calculated axial compressibility of the CdI2-type phase agrees well with experimental data and is typical of layered transition-metal dichalcogenides. The obtained phonon dispersions show a good correspondence with available experiments. A phonon anomaly is revealed at 0 GPa, but is much reduced at 20 GPa. The thermodynamic properties of this phase were also calculated at high pressures and high temperatures using the quasi-harmonic approximation. Our LDA study on the pressure-induced phase transition sequence predicts that the CdI2-type TiS2, the phase stable at ambient conditions, should transform to the cotunnite phase at 15.1 GPa, then to a tetragonal phase (I4/mmm) at 45.0 GPa. The tetragonal phase remains stable to at least 500 GPa. The existence of the tetragonal phase at high pressures is consistent with our previous findings in NiS2 (Yu and Ross 2010 J. Phys.: Condens. Matter 22 235401). The cotunnite phase, although only stable in a narrow pressure range between 15.1 and 45.0 GPa, displays the formation of a compact S network between 100 and 200 GPa, which is evidenced by a kink in the variation of unit cell lengths with pressure. The electron density analysis in cotunnite shows that valence electrons are delocalized from Ti atoms and concentrated near the S network.

Yu, Yonggang G.; Ross, Nancy L.

2011-02-01

351

Thermodynamic properties and phase transtions in the H2O/CO2/CH4 system.

The availability of free energy densities as functions of temperature, pressure and the composition of all components is required for the development of a three-component phase field theory for hydrate phase transitions. We have broadened the extended adsorption theory due to Kvamme and Tanaka (J. Phys. Chem., 1995, 99, 7114) through derivation of the free energy density surface in case of CO(2) and CH(4) hydrates. A combined free energy surface for the liquid phases has been obtained from a SRK equation of state and solubility measurements outside hydrate stability. The full thermodynamic model is shown to predict water-hydrate equilibrium properties in agreement with experiments. Molecular dynamics simulations of hydrates in contact with water at 200 bar and various temperatures allowed us to estimate hard-to-establish properties needed as input parameters for the practical applications of proposed theories. The 5-95 confidence interval for the interface thickness for the methane hydrate/liquid water is estimated to 8.54 A. With the additional information on the interface free energy, the phase field theory will contain no adjustable parameters. We provide a demonstration of how this theory can be applied to model the kinetics of hydrate phase transitions. The growth of hydrate from aqueous solution was found to be rate limited by mass transport, with the concentration of solute close to the hydrate approaching the value characterizing the equilibrium between the hydrate and the aqueous solution. The depth of the interface was estimated by means of the phase field analysis; its value is close to the interface thickness yielded by molecular simulations. The variation range of the concentration field was estimated to approximately 1/3 of the range of the phase field. PMID:16633655

Svandal, Atle; Kuznetsova, Tatyana; Kvamme, Bjørn

2006-04-14

352

NASA Astrophysics Data System (ADS)

By employing first principle and a quasi-harmonic Debye model, we study the phase stability, phase transition, electronic structure and thermodynamic properties of cadmium sulfide (CdS). The results indicate that CdS is a typical ionic crystal and that the zinc-blende phase in CdS is thermodynamically unstable. Moreover, the heat capacity of the wurtzite and rocksalt phases of CdS decreases with pressure and increases with temperature, obeying the rule of the Debye T3 law at low temperature and the Dulong-Petit limit at high temperature.

Ping, Zhou; Zhifeng, Liu; xinqiang, Wang; Mu, Zhou; Chenghua, Hu; Zhou, Zheng; Jinghe, Wu

2014-05-01

353

Interaction effects in the thermodynamic properties of quantum-dots: a Hartree-Fock study.

NASA Astrophysics Data System (ADS)

We study electron-electron interaction effects in the thermodynamic properties of quantum-dot systems. Using a finite-temperature self-consistent Hartree-Fock method, [1,2,3] we obtain the direct and exchange contributions to the specific heat Cv of square quantum dots of size L with up to N=20 electrons. An exchange-induced phase transition [2] is observed at a finite transition temperature T^*. Our analysis shows that T^* scales with L-1 and is on the range of a few Kelvin for dots tens of nanometers across. The exchange contribution to Cv dominates over the direct and kinetic contributions in the intermediate regime of interaction strength (rs˜1), similarly to results obtained for the magnetic susceptibility [3]. Furthermore, the specific oscillates as function of an applied magnetic field and both oscillation amplitude and period are modified by the electron-electron interaction. Supported by FAPESP-Brazil. [1] H. Tamura and M. Ueda, Phys. Rev. Lett. 79 1345 (1997). [2] D. J. Dean, M. R. Strayer, and J. C. Wells, Phys. Rev. B 64, 125305 (2001). [3] L. G. G. V. Dias da Silva, C. Lewenkopf, and Nelson Studart, Phys. Rev. B 69, 075311 (2004).

Studart, Nelson; Dias da Silva, Luis

2005-03-01

354

A simple analysis of thermodynamic properties for classical plasmas: I. Theory

NASA Astrophysics Data System (ADS)

By eliminating the short range negative divergence of the Debye-Hückel pair distribution function, but retaining the exponential charge screening known to operate at large interparticle separation, the thermodynamic properties of one-component plasmas of point ions or charged hard spheres can be well represented even in the strong coupling regime. Predicted electrostatic free energies agree within 5% of simulation data for typical Coulomb interactions up to a factor of 10 times the average kinetic energy. Here, this idea is extended to the general case of a uniform ionic mixture, comprising an arbitrary number of components, embedded in a rigid neutralizing background. The new theory is implemented in two ways: (i) by an unambiguous iterative algorithm that requires numerical methods and breaks the symmetry of cross correlation functions; and (ii) by invoking generalized matrix inverses that maintain symmetry and yield completely analytic solutions, but which are not uniquely determined. The extreme computational simplicity of the theory is attractive when considering applications to complex inhomogeneous fluids of charged particles.

Penfold, Robert; Nordholm, Sture; Nichols, Nancy

2005-06-01

355

Phonon spectrum, thermodynamic properties, and pressure-temperature phase diagram of uranium dioxide

NASA Astrophysics Data System (ADS)

We present a study of the structural phase transition and the mechanical and thermodynamic properties of UO2 by means of the local density approximation (LDA)+U approach. A phase transition pressure of 40 GPa is obtained from theory at 0 K, and agrees well with the experimental value of 42 GPa. The pressure-induced enhancements of elastic constants, elastic moduli, elastic wave velocities, and Debye temperature of the ground-state fluorite phase are predicted. The phonon spectra of both the ground state fluorite structure and high-pressure cotunnite structure calculated by the supercell approach show that the cotunnite structure is dynamically unstable under ambient pressure. Based on the imaginary mode along the ?-X direction and soft phonon mode along the ?-Z direction, a transition path from cotunnite to fluorite has been identified. We calculate the lattice vibrational energy in the quasiharmonic approximation using both first-principles phonon density of state and the Debye model. The calculated temperature dependence of lattice parameter, entropy, and specific heat agrees well with experimental observations in the low temperature domain. The difference of the Gibbs free energy between the two phases of UO2 has predicted a boundary in the pressure-temperature phase diagram. The solid-liquid boundary is approximated by an empirical equation using our calculated elastic constants.

Wang, Bao-Tian; Zhang, Ping; Lizárraga, Raquel; Di Marco, Igor; Eriksson, Olle

2013-09-01

356

NASA Astrophysics Data System (ADS)

We consider the thermodynamic and kinetic properties of Nickel as an example of transition metal in two-temperature state (Te>>Ti,) produced by femtosecond laser heating. Our physical model includes essential processes induced in metals by ultrafast laser energy absorption. Specifically, the electron-ion collision frequency was obtained from recent high-temperature measurements of electrical conductivity and electron-electron screened Coulomb scattering was calculated by taking into account s-s and s-d collisions. In addition, chemical potential, energy, heat capacity, and pressure were obtained from first-principles density functional theory calculations. This model was implemented in two-temperature hydrodynamic code (2T-HD) and combined with molecular dynamics (MD) to determine strength of molten Ni at high strain rates ~108-109s-1 under conditions of femtosecond laser ablation experiments. The simulated ablation threshold, which depends on material strength, was found to be in good agreement with our experimental measurements reported here. The combined 2T-HD/MD modeling explains the surprisingly high experimental energy density necessary to initiate ablation in Ni (the experimental crater depth in Ni is several times smaller than in Al and Au, while ablation threshold energies are similar).

Inogamov, N. A.; Petrov, Yu. V.; Zhakhovsky, V. V.; Khokhlov, V. A.; Demaske, B. J.; Ashitkov, S. I.; Khishchenko, K. V.; Migdal, K. P.; Agranat, M. B.; Anisimov, S. I.; Fortov, V. E.; Oleynik, I. I.

2012-07-01

357

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

Méndez-Morales, T; Carrete, J; Cabeza, O; Gallego, L J; Varela, L M

2011-09-29

358

The thermodynamic and ground state properties of the TIP4P water octamer

NASA Astrophysics Data System (ADS)

Several stochastic simulations of the TIP4P [W. L. Jorgensen, J. Chandrasekhar, J. D. Madura, R. W. Impey, and M. L. Klein, J. Chem. Phys. 79, 926 (1983)] water octamer are performed. Use is made of the stereographic projection path integral and the Green's function stereographic projection diffusion Monte Carlo techniques, recently developed in one of our groups. The importance sampling for the diffusion Monte Carlo algorithm is obtained by optimizing a simple wave function using variational Monte Carlo enhanced with parallel tempering to overcome quasiergodicity problems. The quantum heat capacity of the TIP4P octamer contains a pronounced melting peak at 160 K, about 50 K lower than the classical melting peak. The zero point energy of the TIP4P water octamer is 0.0348+/-0.0002 hartree. By characterizing several large samples of configurations visited by both guided and unguided diffusion walks, we determine that both the TIP4P and the SPC [H. J. C. Berendsen, J. P. Postma, W. F. von Gunsteren, and J. Hermans, (Intermolecular Forces, Reidel, 1981). p. 331] octamer have a ground state wave functions predominantly contained within the D2d basin of attraction. This result contrasts with the structure of the global minimum for the TIP4P potential, which is an S4 cube. Comparisons of the thermodynamic and ground-state properties are made with the SPC octamer as well.

Asare, E.; Musah, A.-R.; Curotto, E.; Freeman, David L.; Doll, J. D.

2009-11-01

359

The thermodynamic and ground state properties of the TIP4P water octamer.

Several stochastic simulations of the TIP4P [W. L. Jorgensen, J. Chandrasekhar, J. D. Madura, R. W. Impey, and M. L. Klein, J. Chem. Phys. 79, 926 (1983)] water octamer are performed. Use is made of the stereographic projection path integral and the Green's function stereographic projection diffusion Monte Carlo techniques, recently developed in one of our groups. The importance sampling for the diffusion Monte Carlo algorithm is obtained by optimizing a simple wave function using variational Monte Carlo enhanced with parallel tempering to overcome quasiergodicity problems. The quantum heat capacity of the TIP4P octamer contains a pronounced melting peak at 160 K, about 50 K lower than the classical melting peak. The zero point energy of the TIP4P water octamer is 0.0348+/-0.0002 hartree. By characterizing several large samples of configurations visited by both guided and unguided diffusion walks, we determine that both the TIP4P and the SPC [H. J. C. Berendsen, J. P. Postma, W. F. von Gunsteren, and J. Hermans, (Intermolecular Forces, Reidel, 1981). p. 331] octamer have a ground state wave functions predominantly contained within the D(2d) basin of attraction. This result contrasts with the structure of the global minimum for the TIP4P potential, which is an S(4) cube. Comparisons of the thermodynamic and ground-state properties are made with the SPC octamer as well. PMID:19916613

Asare, E; Musah, A-R; Curotto, E; Freeman, David L; Doll, J D

2009-11-14

360

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

NASA Astrophysics Data System (ADS)

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

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

2005-07-01

361

Thermodynamic model for calorimetric and phase coexistence properties of coal derived fluids

A model for phase equilibria of coal derived liquids is to be extended to include calorimetric properties as well. To accomplish this satisfactorily, the proposed work includes three tasks (1) Refinement of the characterization procedure to include distribution of sulfur, oxygen, and nitrogen heteroatoms in coal liquids; (2) Measurement of high temperature (upto 400 C) and high pressure (upto 1000 psi) VLE data for binary systems of selected model compounds; and (3) Development of the thermodynamic model. Solutions have been found for the two problems encountered in the VLE apparatus. The equilibrium cell has been fitted with a new level sensing system. After extensive research, a substitute sealant material for the plug valves has been discovered. The work on chromatographic characterization of coal liquids is continuing. The Varex detector and the Gilson fraction collector have arrived and with that all the hardware necessary for the separation is available. The Perkin-Elmer PLGel 100 A, 5 micron column together with guard column and accessories, and THF solvent have been received. We are currently making calibration runs using PL-polymer standards with O-dichlorobenzene as an internal standard. Two analytical methods have been identified for specific analysis of the fractions. The main technique will be elemental analysis with a Perkin Elmer elemental analyzer. In addition, the functional groups and their composition in the sample will be determined using the Mattson Polaris FTIR spectrometer with a horizontal ATR sampler.

Kabadi, V.N.

1991-01-01

362

Elastic and thermodynamic properties of fcc- 6Li 2O under high temperatures and pressures

NASA Astrophysics Data System (ADS)

The elastic and thermodynamic properties of fcc- 6Li 2O under high temperatures and pressures are investigated using the Density functional theory and quasi-harmonic Debye model. Calculation indicates that the lattice constant of 6Li 2O at ground state is a little larger than that of 7Li 2O. Pressure can suppress thermal expansion effectively. When it is 1200 K, just only 8.59 GPa can pressure restrain the volume expansion caused by temperature. Elastic constants illuminate that crystal lattice of 6Li 2O is mechanical stable under high temperature and temperature. Compared with 7Li 2O, shear of 6Li 2O on the {1 0 0} and {1 1 0} planes caused by high pressure and temperature is lower. Heat capacity of different pressure increases with temperature and closes to the Dulong-Petit limit at higher temperatures. Debye temperature decreases with temperature, and increases with pressure. Under lower pressure, thermal expansion coefficient raise rapidly with temperature, and then the increasing trend will get slow at higher pressure and temperature.

Weiyi, Ren; Feng, Wang; Zhou, Zheng; Pingchuan, Xu; Weiguo, Sun

363

Effects of abasic sites on structural, thermodynamic and kinetic properties of quadruplex structures

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.

Esposito, Veronica; Martino, Luigi; Citarella, Giuseppe; Virgilio, Antonella; Mayol, Luciano; Giancola, Concetta; Galeone, Aldo

2010-01-01

364

Magnetic and thermodynamic properties of face-centered cubic Fe-Ni alloys.

A model lattice ab initio parameterized Heisenberg-Landau magnetic cluster expansion Hamiltonian spanning a broad range of alloy compositions and a large variety of chemical and magnetic configurations has been developed for face-centered cubic Fe-Ni alloys. The thermodynamic and magnetic properties of the alloys are explored using configuration and magnetic Monte Carlo simulations over a temperature range extending well over 1000 K. The predicted face-centered cubic-body-centered cubic coexistence curve, the phase stability of ordered Fe3Ni, FeNi, and FeNi3 intermetallic compounds, and the predicted temperatures of magnetic transitions simulated as functions of alloy composition agree well with experimental observations. Simulations show that magnetic interactions stabilize the face-centered cubic phase of Fe-Ni alloys. Both the model Hamiltonian simulations and ab initio data exhibit a particularly large number of magnetic configurations in a relatively narrow range of alloy compositions corresponding to the occurrence of the Invar effect. PMID:24964377

Lavrentiev, M Yu; Wróbel, J S; Nguyen-Manh, D; Dudarev, S L

2014-07-01

365

The thermodynamics of the nonspecific binding of salt to a polyelectrolyte molecule is studied using a density functional approach. The polyelectrolyte molecule is modeled as an infinite, inflexible, and impenetrable charged cylinder and the counterions and co-ions are modeled as charged hard spheres of equal diameter. The density functional theory is based on a hybrid approach where the hard-sphere contribution to the one-particle correlation function is evaluated nonperturbatively and the ionic contribution to the one-particle correlation function is evaluated perturbatively. The advantage of the approach is that analytical expressions are available for all the correlation functions. The calculated single ion preferential interaction coefficients, excess free energy, and activity coefficients show a nonmonotonic variation as a function of polyion charge in the presence of divalent ions. These properties display considerable departure from the predictions of the nonlinear Poisson-Boltzmann (NLPB) equation, with qualitative differences in some cases, which may be attributed to correlation effects neglected in the NLPB theory.

Patra, C N; Yethiraj, A

2000-01-01

366

NASA Astrophysics Data System (ADS)

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

Zhang, Meiguang; Yan, Haiyan

2014-06-01

367

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

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

368

NASA Astrophysics Data System (ADS)

The equilibrium lattice parameters, bulk modulus, and phase transition of BeO are investigated by using the density functional theory with the Perdew-Burke-Ernzerhof (PBE) and Perdew and Zunger (PZ) functionals. With two different exchange-correlation functionals, we predict the similar results that BeO is stable in hexagonal wurtzite (B4) phase up to pressure of 100 GPa and then transforms directly into the rocksalt (B1) phase. The calculated phonon dispersion curves of the B4 phase BeO are in excellent agreement with the experimental data. Under compression, the phonon dispersion curves of BeO in the B4 phase do not show any anomaly or instability. Within the quasiharmonic approximation (QHA) plus empirical energy corrections (EEC) calculations, the thermal equation of state and thermodynamic properties of BeO are obtained. The EECs improve the systematic deviations of PBE and PZ functionals and reproduce the experimental results in the range of the validity of the QHA. Moreover, the effect of EECs on the phase stability has been investigated.

Luo, Fen; Cheng, Yan; Cai, Ling-Cang; Chen, Xiang-Rong

2013-01-01

369

Structural and Thermodynamic Properties of Selective Ion Binding in a K+ Channel

Thermodynamic measurements of ion binding to the Streptomyces lividans K+ channel were carried out using isothermal titration calorimetry, whereas atomic structures of ion-bound and ion-free conformations of the channel were characterized by x-ray crystallography. Here we use these assays to show that the ion radius dependence of selectivity stems from the channel's recognition of ion size (i.e., volume) rather than charge density. Ion size recognition is a function of the channel's ability to adopt a very specific conductive structure with larger ions (K+, Rb+, Cs+, and Ba2+) bound and not with smaller ions (Na+, Mg2+, and Ca2+). The formation of the conductive structure involves selectivity filter atoms that are in direct contact with bound ions as well as protein atoms surrounding the selectivity filter up to a distance of 15 Angstroms from the ions. We conclude that ion selectivity in a K+ channel is a property of size-matched ion binding sites created by the protein structure.

Lockless,S.; Zhou, M.; MacKinnon, R.

2007-01-01

370

Thermodynamic properties of mixtures of dipolar and quadrupolar hard spheres: Theory and simulation

We report a comprehensive study of the thermodynamic properties (the Helmholtz energy, configurational energy, compressibility factor, and chemical potentials) for mixtures of dipolar hard spheres and quadrupolar hard spheres by computer simulation and from perturbation theory based on the Pade approximation. The dipole moment of dipolar component is fixed at {mu}{sub {ital A}}{sup *2}=3.0 and the quadrupole moment of quadrupolar component is varied up to {ital Q}{sub {ital B}}{sup *2}=3.0. The results show that the Pade approximation gives a good description of the Helmholtz energy and configuration energy of the mixtures, but some discrepancies are found for their derivatives, especially for compressibility factor. In view of very large deviations for the system from simple mixtures, the Pade approximation is rather successful for the system. These results are being used as a reference system in our effort to develop an equation of state for the CaCl{sub 2}--H{sub 2}O system.

Jiang, S.; Pitzer, K.S. [Department of Chemistry and Lawrence Berkeley Laboratory, University of California, Berkeley, California 94720 (United States)] [Department of Chemistry and Lawrence Berkeley Laboratory, University of California, Berkeley, California 94720 (United States)

1995-05-15

371

In this work, using extensive molecular dynamics simulations of several thermophysical properties, it is proposed to analyze possible relationships (in the corresponding state sense) between monoatomic fluids for which the repulsive interactions are modeled by an inverse n-power form, the Lennard-Jones 12-6 (LJ), or by an exponential one, the exponential-6 (Exp-6). To compare results between them, two possible definitions of Exp-6 potentials "equivalent" to the LJ one are proposed. In pure fluids, for a large range of thermodynamic conditions, the properties computed are the surface tension, liquid/vapor equilibrium densities, one-phase potential energy, pressure, isometric heat capacity, thermal pressure coefficient, self-diffusion, shear viscosity, and thermal conductivity. Additionally, thermodiffusion (Soret effect) has been considered in "isotopic" equimolar mixtures. It is shown that despite similarities exhibited by alike radial distribution functions, differences exist between the thermodynamic properties values provided by the LJ fluid and the two equivalent Exp-6 fluids. Nevertheless, quite surprisingly, when temperature and density are used as inputs, all three direct transport properties are shown to be nearly independent of the choice of the potential tested. Unexpectedly, these similarities hold even for thermodiffusion which is a priori very sensitive to the nature of the interactions. These results indicate that the use of an Exp-6 potential form to describe nonbonded/nonpolar interaction in molecular simulation is an alternative (more physically acceptable) to the LJ potential when dealing simultaneously with thermodynamic and transport properties. However, when only transport properties are considered (including thermodiffusion), the Exp-6 potential form should not lead to any differences compared to the LJ one. PMID:19044782

Galliero, Guillaume; Boned, Christian

2008-08-21

372

NASA Astrophysics Data System (ADS)

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

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

2013-12-01

373

NASA Astrophysics Data System (ADS)

The elastic, phonon and thermodynamic properties of the divalent alkaline-earth hexaboride SrB 6 are investigated by using plane-wave pseudopotential density functional theory method. The calculated structure parameters and bulk modulus are well consistent with the available experiment and theoretical data. The pressure dependences of elastic constants Cij, bulk modulus B0, shear modulus G, Young's modulus E and Poisson's ratio ? are also presented. With these elastic parameters, we investigate the mechanical stability and compressibility of SrB 6. For the thermodynamic properties, both phonon and quasi-harmonic Debye model methods are adopted. Through the comparison with experimental and other theoretical results, we found the method of quasi-harmonic Debye model is a little better. Moreover, the phonon dispersion relations are also obtained. It is found that there are two LO/TO splitting around 5 THz and 26 THz, respectively.

Li, Zhi-Guo; Piao, Chang-Ge; Pan, Xing; Wei, Yong-Kai; Cheng, Yan; Ji, Guang-Fu

2012-02-01

374

An equation of state for the thermodynamic properties of R143a (1,1,1-trifluoroethane)

NASA Astrophysics Data System (ADS)

Thermodynamic properties of 1,1,1-trifluoroethane (R143a) are expresed in terms of a 32-term modified Benedict-Webb-Rubin (MBWR) equation of state. Coefficients are reported for the MBWR equation and for ancillary equations used to lit the ideal-gas heat capacity, and the coexisting densities and pressure along the saturation boundary. The MBWR coefficients were determined from a multiproperty fit that used the following types of experimental data: PVT: isochoric, isobaric, and saturated-liquid heat capacities: second virial coefficients: speed of sound and properties at coexistence. The equation of state was optimized to the experimental data from 162 to 346 K and pressures to 35 MPa with the exception of the critical region. Upon extrapolation to 500 K and 60 MPa, the equation gives thermodynamically reasonable results. Comparisons between calculated and experimental values are presented.

Outcalt, S. L.; McLinden, M. O.

1997-11-01

375

NASA Astrophysics Data System (ADS)

We investigate the structural and thermodynamic properties of cerium in ? phase by using the first-principles plane wave method with a relativistic analytic pseudopotential of Hartwigsen, Goedcker and Hutter (HGH) scheme in the frame of local density approximation (LDA). The obtained lattice constant and bulk modulus are consistent with the available experimental data. Moreover, dependences of the normalized primitive volume V/V0 on pressure and the thermodynamic quantities (including the Grüneisen constant ? and thermal expansion ?) on temperature and pressure are obtained. The obtained linear thermal expansion parameter ? (9.857 × 10-6 K-1 at 293.15K and 0GPa) is slightly larger than the experimental value (6.3 × 10-6 K-1). All the results indicate that we provide an effective method to deal with the ground properties of the strongly interacting d- and/or f-electron systems.

Sun, Li-Li; Ji, Guang-Fu; Chen, Xiang-Rong; Gou, Qing-Quan

2009-01-01

376

First-principles study of the elastic and thermodynamic properties of CaSiO(3) perovskite.

The thermodynamic and elastic properties of CaSiO(3) perovskite are investigated at high pressures and temperatures using the plane wave pseudopotential method within the local density approximation. The athermal elastic moduli of CaSiO(3) perovskite are calculated as a function of pressure up to 200 GPa. The calculated results are in excellent agreement with available experimental data at high pressure, and compare favourably with other pseudopotential predictions over the pressure regime studied. It is also found that the elastic anisotropy drops rapidly with the increase of pressure initially, and then decreases more slowly at higher pressures. The thermodynamic properties of CaSiO(3) perovskite are predicted using the quasi-harmonic Debye model for the first time; the heat capacity and the thermal expansion coefficient agree with the observed values at ambient conditions and the other calculations at high pressures and temperatures. PMID:21694039

Liu, Z J; Sun, X W; Chen, Q F; Cai, L C; Wu, H Y; Ge, S H

2007-06-20

377

NASA Technical Reports Server (NTRS)

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

Colon, G.

1981-01-01

378

NASA Astrophysics Data System (ADS)

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.

Jafari, R.

2012-05-01

379

Thermodynamic formulas for investigating systems with density- and/or temperature-dependent particle masses are generally derived from the fundamental derivation equality of thermodynamics. Various problems in the previous treatments are discussed and modified. Properties of strange quark matter in bulk and strangelets at both zero and finite temperature are then calculated based on the new thermodynamic formulas with a new quark mass scaling, which indicates that low-mass strangelets near {beta} equilibrium are multiquark states with an antistrange quark, such as the pentaquark (u{sup 2}d{sup 2}s) for baryon number 1 and the octaquark (u{sup 4}d{sup 3}s) for dibaryon, etc.

Wen, X.J. [Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100039 (China); Zhong, X.H. [Department of Physics, Nankai University, Tianjin 300071 (China); Peng, G.X. [Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100039 (China); Center for Theoretical Physics, Laboratory for Nuclear Science and Department of Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139-4307 (United States); Shen, P.N. [China Center of Advanced Science and Technology (World Lab.), Beijing 100080 (China); Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100039 (China); Ning, P.Z. [China Center of Advanced Science and Technology (World Lab.), Beijing 100080 (China); Department of Physics, Nankai University, Tianjin 300071 (China)

2005-07-01

380

Thermodynamical properties of III–V nitrides and crystal growth of GaN at high N 2 pressure

In this paper, thermodynamical properties of AIN, GaN and InN are considered. It is shown that significant differences in melting conditions, thermal stability and solubilities in liquid group III metals lead to different possibilities of growing crystals from high temperature solutions, at N2 pressure up to 20 kbar. It is shown that the best conditions for crystal growth at available

S. Porowski; I. Grzegory

1997-01-01

381

Density functional theory pseudo-potential plane-wave calculations are performed in order to predict the structural, elastic and thermodynamic properties of the newly discovered tetragonal intermetallic SrPd2Ge2. The computed equilibrium lattice constants and the internal parameter are in good agreement with the experimental findings. The effect of high pressure, up to 40 GPa, on the lattice constants shows that the contraction along the

M. A. Ghebouli; A. Bouhemadou; B. Ghebouli; M. Fatmi; S. Bin-Omran

2011-01-01

382

Mixtures of refrigerants are widely used as working substances for refrigerating plants. Among them, mixtures of ozone-safe and natural refrigerants, in particular R23\\/R744 and R41\\/R744, are important. For calculating their thermodynamic properties, we compiled equations of state on the basis of the method in (1). According to this reference, the equation of state for a mixture is presented as a

Aleksandr Vasserman C; Valentine Malchevsky S

383

The computational approach in which time-dependent balance equations of mass, momentum, and energy are solved numerically is becoming an important technique for analyzing electric arcs in a gas circuit breaker (GCB) or gas-insulated switchgear (GIS). In this paper, the transport and thermodynamic properties of SF6 gas necessary for this approach as basic data are calculated under multimixed condition by PTFE(-C2F4-)

Khokan C. Paul; Tadahiro Sakuta; Takeshi Takashima

1997-01-01

384

NASA Astrophysics Data System (ADS)

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

Geiger, C. A.; Dachs, E.

2012-04-01

385

In this work, we show how increasing the charge of small cations affects the structural, thermodynamical, and dynamical properties of these ions in liquid water. We have studied the case of lanthanoid and actinoid ions, for which we have recently developed accurate polarizable force fields, and the ionic radius is in the 0.995-1.250 Å range, and explored the valency range from 0 to 4+. We found that the ion charge strongly structures the neighboring water molecules and that, in this range of charges, the hydration enthalpies exhibit a quadratic dependence with respect to the charge, in line with the Born model. The diffusion process follows two main regimes: a hydrodynamical regime for neutral or low charges, and a dielectric friction regime for high charges in which the contraction of the ionic radius along the series of elements causes a decrease of the diffusion coefficient. This latter behavior can be qualitatively described by theoretical models, such as the Zwanzig and the solvated ion models. However, these models need be modified in order to obtain agreement with the observed behavior in the full charge range. We have thus modified the solvated ion model by introducing a dependence of the bare ion radius as a function of the ionic charge. Besides agreement between theory and simulation this modification allows one to obtain an empirical unified model. Thus, by analyzing the contributions to the drag coefficient from the viscous and the dielectric terms, we are able to explain the transition from a regime in which the effect of viscosity dominates to one in which dielectric friction governs the motion of ions with radii of ca. 1 Å. PMID:23126724

Martelli, Fausto; Vuilleumier, Rodolphe; Simonin, Jean-Pierre; Spezia, Riccardo

2012-10-28

386

Thermodynamic properties of alloys of the Al-Co and Al-Co-Sc systems

NASA Astrophysics Data System (ADS)

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: ? H min(Al-Co) = -32.5 kJ/mol at x Co = 0.44; ? H min(Al-Co-Sc) = -46 kJ/mol for Al0.4Co0.3Sc0.3 (estimated).

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

2014-05-01

387

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

NASA Astrophysics Data System (ADS)

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

Erhart, Paul; Marian, Jaime; Sadigh, Babak

2013-07-01

388

[Characterization and thermodynamic properties of Cu(II) imprinted chitosan crosslinked membrane].

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

Zhang, Yu-Hong; Zhang, Ai-Li; Zhou, Ji-Ti; Sun, Xiao-Yu

2012-07-01

389

NSDL National Science Digital Library

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

Huguet, Jesse; Taylor, Robert; Woodbury, Keith

2011-05-09

390

NASA Astrophysics Data System (ADS)

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.

Seddik, T.; Khenata, R.; Merabiha, O.; Bouhemadou, A.; Bin-Omran, S.; Rached, D.

2012-03-01

391

National Technical Information Service (NTIS)

A computer program for determining desired thermodynamic and transport property values by means of a three-dimensional (pressure, fuel-air ratio, and either enthalpy or temperature) interpolation routine was developed. The program calculates temperature (...

R. S. Colladay S. A. Hippensteele

1978-01-01

392

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

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

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

1992-12-01

393

NASA Astrophysics Data System (ADS)

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 ? are calculated. In the case of the dipole spectrum, the constants a and ?, 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 ?, 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.

Fisenko, Anatoliy I.; Lemberg, Vladimir

2014-03-01

394

NASA Astrophysics Data System (ADS)

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 ? are calculated. In the case of the dipole spectrum, the constants a and ?, 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 ?, 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.

Fisenko, Anatoliy I.; Lemberg, Vladimir

2014-07-01

395

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.

396

The configurational thermodynamic properties of fcc-based Al-Sc alloys and coherent Al/Al{sub 3}Sc interphase-boundary interfaces have been calculated from first principles. The computational approach used in this study combines the results of pseudopotential total-energy calculations with a cluster-expansion description of the alloy energetics. Bulk and interface configurational-thermodynamic properties are computed using a low-temperature-expansion technique. Calculated values of the {l_brace}100{r_brace} and {l_brace}111{r_brace} Al/Al{sub 3}Sc interfacial energies at zero temperature are, respectively, 192 and 226mJ/m{sup 2}. The temperature dependence of the calculated interfacial free energies is found to be very weak for {l_brace}100{r_brace} and more appreciable for {l_brace}111{r_brace} orientations; the primary effect of configurational disordering at finite temperature is to reduce the degree of crystallographic anisotropy associated with calculated interfacial free energies. The first-principles-computed solid-solubility limits for Sc in bulk fcc Al are found to be underestimated significantly in comparison with experimental measurements. It is argued that this discrepancy can be largely attributed to nonconfigurational contributions to the entropy which have been neglected in the present thermodynamic calculations. {copyright} {ital 1998} {ital The American Physical Society}

Asta, M.; Foiles, S.M.; Quong, A.A. [Computational Materials Sciences Division, Sandia National Laboratories, P.O. Box 969, MS9161, Livermore, California94551-0969 (United States)] [Computational Materials Sciences Division, Sandia National Laboratories, P.O. Box 969, MS9161, Livermore, California94551-0969 (United States)

1998-05-01

397

Molecular dynamics simulations are reported for the thermodynamic properties of n-m Lennard-Jones fluids, where n = 10 and 12, and m = 5 and 6. Results are reported for the thermal expansion coefficient, isothermal and adiabatic compressibilities, isobaric and isochoric heat capacities, Joule-Thomson coefficient, and speed of sound at supercritical conditions covering a wide range of fluid densities. The thermodynamic criteria for maxima?minima in the isochoric and isobaric heat capacities are identified and the simulation results are also compared with calculations from Lennard-Jones equations of state. The Johnson et al. [Mol. Phys. 78, 591 (1993)] equation of state can be used to reproduce all heat capacity phenomena reported [T. M. Yigzawe and R. J. Sadus, J. Chem. Phys. 138, 194502 (2013)] from molecular dynamics simulations for the 12-6 Lennard-Jones potential. Significantly, these calculations and molecular dynamics results for other n-m Lennard-Jones potentials support the existence of Cp minima at supercritical conditions. The values of n and m also have a significant influence on many other thermodynamic properties. PMID:24160523

Mairhofer, Jonas; Sadus, Richard J

2013-10-21

398

NASA Astrophysics Data System (ADS)

Molecular dynamics simulations are reported for the thermodynamic properties of n-m Lennard-Jones fluids, where n = 10 and 12, and m = 5 and 6. Results are reported for the thermal expansion coefficient, isothermal and adiabatic compressibilities, isobaric and isochoric heat capacities, Joule-Thomson coefficient, and speed of sound at supercritical conditions covering a wide range of fluid densities. The thermodynamic criteria for maxima/minima in the isochoric and isobaric heat capacities are identified and the simulation results are also compared with calculations from Lennard-Jones equations of state. The Johnson et al. [Mol. Phys. 78, 591 (1993)] equation of state can be used to reproduce all heat capacity phenomena reported [T. M. Yigzawe and R. J. Sadus, J. Chem. Phys. 138, 194502 (2013)] from molecular dynamics simulations for the 12-6 Lennard-Jones potential. Significantly, these calculations and molecular dynamics results for other n-m Lennard-Jones potentials support the existence of Cp minima at supercritical conditions. The values of n and m also have a significant influence on many other thermodynamic properties.

Mairhofer, Jonas; Sadus, Richard J.

2013-10-01

399

NASA Astrophysics Data System (ADS)

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 Erge

Johann, Robert

2001-10-01

400

NASA Astrophysics Data System (ADS)

The structural and thermodynamic properties of MgZn2 Laves phase under hydrostatic pressure have been investigated by using a first-principles method based on the density functional theory within the generalized gradient approximation. The calculated equilibrium structural parameters are consistent with the previous experimental and theoretical data. Especially, we study the pressure dependence of the elastic constants, polycrystalline elastic moduli, Poisson's ratio, elastic anisotropy, and theoretical Vickers hardness of MgZn2. It is found that the pressure plays a significant role in the elastic properties of MgZn2 due to the variations of inter-atomic distance. In addition, the density of states and Mulliken analysis are performed to reveal the bonding characteristics of MgZn2. It is observed that the total density of states exhibits a certain offset with the increase of external pressure. Finally, the dependences of thermodynamic properties on pressure and temperature of MgZn2 Laves phase have been also successfully predicted and analyzed within the quasi-harmonic Debye model for the first time.

Liu, Yong; Hu, Wen-Cheng; Li, De-Jiang; Zeng, Xiao-Qin; Xu, Chun-Shui

2014-04-01

401

NASA Astrophysics Data System (ADS)

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

Nagashima, H.; Tsuda, S.; Tsuboi, N.; Koshi, M.; Hayashi, K. A.; Tokumasu, T.

2014-04-01

402

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. PMID:24712800

Nagashima, H; Tsuda, S; Tsuboi, N; Koshi, M; Hayashi, K A; Tokumasu, T

2014-04-01

403

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

NASA Astrophysics Data System (ADS)

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

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

2013-08-01

404

Structural, electronic, thermodynamic and optical properties of SrS 1-xO x mixed crystals

NASA Astrophysics Data System (ADS)

The structural, electronic and thermodynamic properties of the SrS 1-xO x ternary mixed crystals have been studied using the ab initio full potential linearized augmented plane wave (FP-LAPW) method within density functional theory. The effect of composition on lattice parameter, bulk modulus and band gap was investigated. The lattice constants from Vegard's law and the bulk modulus from linear concentration dependence were observed for the alloys. The microscopic origins of the gap bowing were explained by using the approach of Zunger and co-workers. The thermodynamic stability of these alloys was investigated by calculating the excess enthalpy of mixing ?Hm as well as the phase diagram. In addition to FP-LAPW method, the composition dependence of the refractive index and the dielectric constant was studied by different models.

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

2009-11-01

405

In this work, the electronic, structural, elastic, and thermodynamic properties of Ti2AX MAX phases (A = Al or Ga, X = C or N) were investigated using density functional theory (DFT). It is shown that the calculations of the electronic, structural, and elastic properties of these structures, using local density approximation (LDA) and generalized gradient approximation (GGA) coupled with projected

Thien Duong; Sean Gibbons; Rajeev Kinra; Raymundo Arro´yave

2011-01-01

406

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: (1) Mott transitions in transition metal oxides, (2) magnetism in half-metallic compounds, and (3) large volume-collapse transitions in f-band metals.

Scalettar, Richard T.; Pickett, Warren E.

2004-07-01

407

NASA Astrophysics Data System (ADS)

In extended pressure and temperature ranges, a theoretical study of the isothermal bulk modulus of SiC in B3 structure under high pressure and temperature is carried out by means of first-principles density functional theoretical calculations combined with the quasi-harmonic Debye model. Through the quasi-harmonic Debye model, the isothermal bulk modulus and its first and second pressure derivatives are successfully obtained. The thermodynamics properties of 3C-SiC are investigated in the pressure range of 0-100 GPa and the temperature range of 0-2000 K.

Zhang, Xu-Dong; Cui, Shou-Xin; Shi, Hai-Feng

2014-01-01

408

NASA Technical Reports Server (NTRS)

A previous calculation of the thermodynamic properties of interstitial solid solutions based on the technique of Kirkwood expansions has been extended to include the effects of second nearest neighbor solute atom mutual interactions. The error inherent in the first order (or quasi-chemical) counting of the degeneracy of the solution crystal is avoided. It is shown that, at high temperatures, even strong second nearest neighbor solute mutual interactions have a negligible effect on the entropy of the solution and a small, temperature-dependent effect on the solute partial enthalpy.

Alex, K.; Mclellan, R. B.

1971-01-01

409

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

NASA Technical Reports Server (NTRS)

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

Chraska, P.; Mclellan, R. B.

1971-01-01

410

NASA Technical Reports Server (NTRS)

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.

Weber, L. A.

1977-01-01

411

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.

Richard T. Scalettar; Warren E. Pickett

2005-08-02

412

NASA Astrophysics Data System (ADS)

We present a systematic theory-motivated study of the thermodynamic stability condition as an explanation for the observed accretion disc wind signatures in different states of low-mass black hole binaries (BHB). The variability in observed ions is conventionally explained either by variations in the driving mechanisms or by the changes in the ionizing flux or due to density effects, whilst thermodynamic stability considerations have been largely ignored. It would appear that the observability of particular ions in different BHB states can be accounted for through simple thermodynamic considerations in the static limit. Our calculations predict that in the disc-dominated soft thermal and intermediate states, the wind should be thermodynamically stable and hence observable. On the other hand, in the power-law-dominated spectrally hard state the wind is found to be thermodynamically unstable for a certain range of 3.55 ? log ? ? 4.20. In the spectrally hard state, a large number of the He-like and H-like ions (including e.g. Fe XXV, Ar XVIII and S XV) have peak ion fractions in the unstable ionization parameter (?) range, making these ions undetectable. Our theoretical predictions have clear corroboration in the literature reporting differences in wind ion observability as the BHBs transition through the accretion states While this effect may not be the only one responsible for the observed gradient in the wind properties as a function of the accretion state in BHBs, it is clear that its inclusion in the calculations is crucial for understanding the link between the environment of the compact object and its accretion processes.

Chakravorty, Susmita; Lee, Julia C.; Neilsen, Joseph

2013-11-01

413

Thermodynamic properties of La1-xAxCoO3 (A=K, Cd, Pr and Nd)

NASA Astrophysics Data System (ADS)

We have calculated the thermal and allied properties of La1-xAxCoO3 (A=K, Cd, Pr, Nd and 0?x?1) as a function of temperature 1 K?T?300 K for the first time using Modified Rigid Ion Model (MRIM). The calculated bulk modulus, specific heat, thermal expansion and other thermodynamic properties obtained from MRIM have presented proper interpretation of the experimental data, for monovalent (K+), divalent (Cd2+) and trivalent (Pr3+ and Nd3+) ion-doped LaCoO3. In addition, the results on the cohesive energy (?), molecular force constant (f), Reststrahlen frequency (?), Debye temperature (?D) and Gruneisen parameter (?) are also discussed.

Thakur, Rasna; Gaur, N. K.

2013-05-01

414

NASA Technical Reports Server (NTRS)

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.

Zhang, Shuxia; Yuen, David A.

1988-01-01

415

NASA Astrophysics Data System (ADS)

The first-principles study on the elastic properties, elastic anisotropy and thermodynamic properties of the orthorhombic OsB4 is reported using density functional theory method with the ultrasoft pseudopotential scheme in the frame of the generalized gradient approximation. The calculated equilibrium parameters are in good agreement with the available theoretical data. A complete elastic tensor and crystal anisotropies of the ultra-incompressible OsB4 are determined in the pressure range of 0-50 GPa. By the elastic stability criteria, it is predicted that the orthorhombic OsB4 is stable below 50 GPa. By using the quasi-harmonic Debye model, the heat capacity, the coefficient of thermal expansion, and the Grüneisen parameter of OsB4 are also successfully obtained in the present work.

Yan, Hai-Yan; Zhang, Mei-Guang; Huang, Duo-Hui; Wei, Qun

2013-04-01

416

A density functional theory investigation of the thermodynamic and kinetic properties of hydrogen-hydrogen defect interactions in the cubic SrTiO(3) perovskite is presented. We find a net attraction between two hydrogen atoms with an optimal separation of ?2.3 ?. The energy gain is ca. 0.33 eV compared to two non-interacting H defects. The main cause of the net attractive potential is elastic defect interactions through lattice deformation. Two possible diffusion paths for the hydrogen defect pair are investigated and are both determined to be faster than the corresponding diffusion path for single hydrogen atoms. Finally, we set up a simple model to determine the contribution from the double hydrogen defect to the total hydrogen flux, and find the double defect to be the main diffusing species at temperatures below ca. 400 °C. Post submission infrared absorption experiments show excellent agreement with the proposed properties of the double hydrogen defect. PMID:21769355

Bork, Nicolai; Bonanos, Nikolaos; Rossmeisl, Jan; Vegge, Tejs

2011-09-01

417

Analyses and predictions of the thermodynamic properties and phase diagrams of silicate systems

Molten silicates are ordered solutions which can not be well represented by the usual polynomial representation of deviations from ideal solution behavior (i.e. excess free energies of mixing). An adaptation of quasichemical theory which is capable of describing the properties of ordered solutions represents the measured properties of binary silicates over broad ranges of composition and temperature. For simple silicates such as the MgO-FeO-SiO{sub 2} ternary system, in which silica is the only acid component, a combining rule generally leads to good predictions of ternary solutions from those of the binaries. In basic solutions, these predictions are consistent with those of the conformal ionic solution theory. Our results indicate that our approach could provide a potentially powerful tool for representing and predicting the properties of multicomponent molten silicates.

Blander, M. [Argonne National Lab., IL (United States); Pelton, A.; Eriksson, G. [Ecole Polytechnique, Montreal, PQ (Canada). Dept. of Metallurgy and Materials Engineering

1992-07-01

418

Analyses and predictions of the thermodynamic properties and phase diagrams of silicate systems

Molten silicates are ordered solutions which can not be well represented by the usual polynomial representation of deviations from ideal solution behavior (i.e. excess free energies of mixing). An adaptation of quasichemical theory which is capable of describing the properties of ordered solutions represents the measured properties of binary silicates over broad ranges of composition and temperature. For simple silicates such as the MgO-FeO-SiO{sub 2} ternary system, in which silica is the only acid component, a combining rule generally leads to good predictions of ternary solutions from those of the binaries. In basic solutions, these predictions are consistent with those of the conformal ionic solution theory. Our results indicate that our approach could provide a potentially powerful tool for representing and predicting the properties of multicomponent molten silicates.

Blander, M. (Argonne National Lab., IL (United States)); Pelton, A.; Eriksson, G. (Ecole Polytechnique, Montreal, PQ (Canada). Dept. of Metallurgy and Materials Engineering)

1992-01-01

419

The microscopic structure, thermodynamic properties, local segmental dynamics, and self-diffusion coefficients of three ionic liquids (ILs) with a common anion, namely, the bis(trifluoromethylsulfonyl) imide ([Tf2N-]), and imidazolium-based cations that differ in the alkyl tail length, namely, the 1-butyl-3-methylimidazolium ([C4mim+]), the 1-hexyl-3-methylimidazolium ([C6mim+]), and the 1-octyl-3-methylimidazolium ([C8mim+]), are calculated over the temperature range of 298.15-333.15 K and pressure range of 0.1-60 MPa. Quantum calculations based on density functional theory are performed on isolated ion pairs, and minimum energy conformers are identified. Electronic density results are used to estimate the electrostatic potential of a molecular force field that is used subsequently for long molecular dynamics (MD) simulations of bulk ILs. Thermodynamic properties calculated from MD are shown to be in excellent agreement for the bulk density and good agreement for derivative properties when compared to experimental data. The new force field is an improvement over earlier ones for the same ILs. The microscopic structure as expressed through the radial distribution function is thoroughly calculated, and it is shown that the bulk structure characteristics are very similar to those obtained from the quantum calculations on isolated ion pairs. The segmental dynamics expressed in terms of bond and torsion angle decorrelation is shown to assume a broad range of characteristic times. Molecular segments in the alkyl tail of the cations are significantly faster than segments in the vicinity of the imidazolium ring. Finally, the new force field predicts accurately the self-diffusion coefficients of the cations and the anions over the entire temperature range examined, thus confirming its validity for a broad range of physical properties. PMID:19405496

Logotheti, Georgia-Evangelia; Ramos, Javier; Economou, Ioannis G

2009-05-21

420

NASA Astrophysics Data System (ADS)

The standard partial molal properties of organic aqueous species at high pressures and temperatures can be predicted using an adaptation of a revised equation of state for inorganic aqueous ions and electrolytes (Tanger and Helgeson, 1988), together with correlations among equation of state parameters (SHOCK and Helgeson, 1988). These correlations include a charge-dependent relation between Born coefficients and the standard partial molal entropies of aqueous species at 25°C and 1 bar (SHOCK. et al., 1989). Thermodynamic calculations indicate that in the liquid phase the standard partial molal volumes (V¯°), heat capacities (C¯° p), and entropies (S¯°), as well as the apparent standard partial molal enthalpies of formation (?H°) of aqueous electrolytes with organic anions maximize with increasing temperature at Psat and approach - ? at the critical point of H 2O. In contrast, the corresponding properties of neutral organic aqueous species in the liquid phase minimize with increasing temperature Psat and approach ? at the critical point of H 2O. Predicted equilibrium constants for alkane solubilities and carboxylic acid dissociation reactions at elevated pressures and temperatures are in close agreement with experimental data reported in the literature, which supports the validity and generality of the equations of state as well as the predictive algorithms used in the calculations. As a consequence, high temperature/ pressure standard partial molal properties, as well as equilibrium constants and other reaction properties, can be predicted for reactions involving a wide variety of organic aqueous species for which little or no experimental data are available at temperatures > 25°C. Present capabilities permit such predictions to be made for hydrothermal and magmatic conditions at pressures and temperatures as high as 5 kb and 1000°C Psat represents pressures corresponding to liquid-vapor equilibrium for the system H 2O, except at temperature < 100°C where it refers to the reference pressure of 1 bar.

Shock, Everett L.; Helgeson, Harold C.

1990-04-01

421

Tribo-electric charging of polymers can be considered as an interfacial phenomenon of interacting polymer surfaces. The electron pair acceptor\\/donor properties of the polymer surfaces determine the polymer's charging. This can be shown by an excellent linear correlation between the electron pair acceptor\\/donor parameters ? and ? and the measured amount of surface charges. Furthermore, the rate of charging corresponds also

Ern? Németh; Victoria Albrecht; Gert Schubert; Frank Simon

2003-01-01

422

NASA Astrophysics Data System (ADS)

It is well known that the classical mean field theory of van der Waals for liquid-vapor interfacial region properties deviates from real fluid behavior in several important ways. In particular, the variations of the surface tension and interfacial region thickness with temperature near the critical point are not consistent with those for real fluids. This paper presents a modified version of the classical mean field model that incorporates Redlich-Kwong fluid properties. It is shown here that this neoclassical Redlich-Kwong fluid model predicts property variations with temperature that agree better with measured data for real fluids. Predictions of the critical exponents associated with the temperature variation of surface tension and interfacial region thickness are developed from the Redlich-Kwong model. This new model predicts that surface tension varies about proportional to (1-T/Tc)1.33 and that the interfacial region thickness varies about proportional to (1-T/Tc)-0.67, with T and Tc being the system temperature and critical temperature, respectively. Compared to the critical exponents predicted by classical van der Waals theory, the Redlich-Kwong model predictions are found to be in better agreement with values inferred from experimental measurements. Predictions of the Redlich-Kwong model regarding interfacial region structure and property fluctuations are also examined.

Carey, V. P.

2003-03-01

423

Isotope effects in solution thermodynamics: Excess properties in solution of isotopomers

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

Gabor. Jancso; Luis P. N. Rebelo; W. Alexander. Van Hook

1993-01-01

424

A set of five equations describing vapour-liquid equilibrium properties of the ammonia-water system is presented. They are intended for use in the design of absorption processes. Using variable dependences of technical relevance the equations make it possible to avoid iterative evaluations. The equations were constructed by fitting critically assessed experimental data using simple functional forms. They cover the region within

J Pátek; J Klomfar

1995-01-01

425

Pabalan and Pitzer (Geochim. Cosmochim. Acta 1988, 52, 2393-2404) reported a comprehensive set of thermodynamic properties of aqueous solutions of sodium sulfate without using ion association or hydrolysis. However, there is now ample evidence available indicating that the ion association cannot be ignored at temperatures T>or=373 K. For example, even at the lowest concentration of their studies (m>or=0.05) and at 573.15 K, less than 20% of SO4(2-)(aq) is available as free ions. In the present study, the integral heats of solution of sodium sulfate were measured to very low concentrations (10(-4) m) up to 573.16 K. The data were analyzed correcting for the hydrolysis of SO4(2-)(aq) and the association