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1

Thermodynamic properties of minerals

In the ten years since the publication of the national Bureau of Standards comprehensive tables of thermochemical properties, by Rossini and other (1952), a very large body of modern calorimetric and equilibrium data has become available. Because of the complex interrelations among many thermochemical data and the necessity for internal consistency among these values, a complete revision of this standard reference is required. This is also true of the summaries of thermochemical data for the sulfides (Richardson and Jeffes 1952) and for the oxides (Coughlin 1954). The following tables present critically selected values for the heat and free energy of formation, the logarithm of the equilibrium constant of formation Log Kf, the entropy and the molar volume, at 298.15°K (25.0°C) and one atmosphere for minerals.

Robie, Richard A.

1962-01-01

2

CORRELATIONS Modeling Physical and Thermodynamic Properties via Inverse

CORRELATIONS Modeling Physical and Thermodynamic Properties via Inverse Normalizing Transformations in modeling the temperature dependence of various physical and thermodynamic properties. 1. Introduction to represent the physical and thermodynamic properties as a function of state variables such as temperature

Brauner, Neima

3

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

4

Thermodynamic Properties and Melting of Solid Helium

The melting properties and thermodynamic functions of solid helium have been determined at temperatures from 4 to 26 degrees K and at pressures up to 3000 atm. The upper temperature corresponds to about five times the critical temperature of helium; it was therefore possible to measure properties of the solid state in a range which has not yet been attained

J. S. Dugdale; F. E. Simon

1953-01-01

5

Thermodynamic properties of a magnetically modulated graphene

The effect of magnetic modulation on thermodynamic properties of a graphene monolayer in presence of a constant perpendicular magnetic field is reported here. One-dimensional spatial electric or magnetic modulation lifts the degeneracy of the Landau levels and converts into bands and their band width oscillates with magnetic field leading to Weiss-type oscillation in the thermodynamic properties. The effect of magnetic modulation on thermodynamic properties of a graphene sheet is studied and then compared with electrically modulated graphene and magnetically modulated conventional two-dimensional electron gas (2DEG). We observe Weiss-type and de Haas-van Alphen (dHvA) oscillations at low and high magnetic field, respectively. There is a definite phase difference in Weiss-type oscillations in thermodynamic quantities of magnetically modulated graphene in compare to electrically modulated graphene. On the other hand, the phase remains same and amplitude of the oscillation is large when compared with the magneti...

Islam, SK Firoz; Ghosh, Tarun Kanti

2011-01-01

6

Thermodynamic properties of a magnetically modulated graphene

The effect of magnetic modulation on thermodynamic properties of a graphene monolayer in presence of a constant perpendicular magnetic field is reported here. One-dimensional spatial electric or magnetic modulation lifts the degeneracy of the Landau levels and converts into bands and their band width oscillates with magnetic field leading to Weiss-type oscillation in the thermodynamic properties. The effect of magnetic modulation on thermodynamic properties of a graphene sheet is studied and then compared with electrically modulated graphene and magnetically modulated conventional two-dimensional electron gas (2DEG). We observe Weiss-type and de Haas-van Alphen (dHvA) oscillations at low and high magnetic field, respectively. There is a definite phase difference in Weiss-type oscillations in thermodynamic quantities of magnetically modulated graphene in compare to electrically modulated graphene. On the other hand, the phase remains same and amplitude of the oscillation is large when compared with the magnetically modulated 2DEG. Explicit asymptotic expressions of density of states and the Helmholtz free energy are provided to understand the phase and amplitude of the Weiss-type oscillations qualitatively. We also study thermodynamic properties when both electric and magnetic modulations are present. The Weiss-type oscillations still exist when the modulations are out-of-phase.

SK Firoz Islam; Naveen K. Singh; Tarun Kanti Ghosh

2011-07-15

7

Thermodynamic Properties of Aqueous Sodium Chloride Solutions

Experimental measurements of the osmotic and activity coefficients, the enthalpy, and the heat capacity were used to derive a semiempirical equation for the thermodynamic properties of NaCl(aq) at constant pressure. This equation may be combined with results contained in the previous paper on the volumetric properties to yield a complete equation of state valid in the region 273 K?T?573 K,

Kenneth S. Pitzer; J. Christopher Peiper; R. H. Busey

1984-01-01

8

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

9

The thermodynamic properties of calcium intermetallic compounds

The thermodynamic properties of calcium alloys have been measured by emf (an original pin-point method) and calorimetry in recent years. A review of experimental results obtained for 15 binary (Ca,M) systems is presented (with M ? Ni, Pd, Pt, Cu, Ag, Au, Mg, Al, Ga, Si, Ge, Sn, Pb, Sb, Bi), and numerical optimization is performed for some of them.

M. Notin; J. Mejbar; A. Bouhajib; J. Charles; J. Hertz

1995-01-01

10

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

11

Thermodynamics and statistical mechanics. [thermodynamic properties of gases

NASA Technical Reports Server (NTRS)

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

1976-01-01

12

Thermodynamic properties 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

13

The thermodynamic properties of thianthrene and phenoxathiin

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

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

1993-04-01

14

The thermodynamic properties of benzothiazole and benzoxazole

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

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

1991-08-01

15

A Dynamic Library for Physical and Thermodynamic Properties Correlations

A Dynamic Library for Physical and Thermodynamic Properties Correlations Mordechai Shacham Brauner School of Engineering, Tel-Aviv University, Tel-Aviv 69978, Israel A dynamic physical properties of physical and thermodynamic properties are being used extensively in process calcula- tions and computations

Brauner, Neima

16

Prediction of thermodynamic properties of coal derivatives

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

Donohue, M.D.

1990-09-01

17

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

18

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

19

Thermodynamic properties of oxygen molecules at high temperatures

Calculations of the second virial coefficients and their derivatives, obtained by fitting the Hulburt-Hirschfelder potential to accurate ab initio quantum mechanical calculations for the seven bound states of molecular oxygen that dissociate to ground state atoms, are used to determine thermodynamic properties of oxygen molecules at high temperatures. Unlike the usual statistical thermodynamic method for obtaining partition functions by summing

L. Biolsi; P. M. Holland

1996-01-01

20

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

21

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

22

Thermodynamical properties of graphene in noncommutative phase-space

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

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

2014-01-31

23

Study of weak molecular interactions through thermodynamic mixing properties.

The electron donor-acceptor abilities of some cyclic ethers (tetrahydropyran or tetrahydrofuran), benzene, and halobenzenes (fluorobenzene or chlorobenzene) and the molecular interactions between these compounds have been investigated through a wide set of thermodynamic mixing properties of their mixtures. The mixing properties have been derived from experimental measurements of density, speed of sound, refractive index, surface tension, heat of mixing, and vapor-liquid equilibrium at the temperature of 298.15 K. PMID:16942115

Giner, Beatriz; Martín, Santiago; Artigas, Héctor; López, María C; Lafuente, Carlos

2006-09-01

24

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

NASA Astrophysics Data System (ADS)

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

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

2008-12-01

25

Thermodynamic and mechanical properties of model mitochondrial membranes

an electrochemical potential for substrate transport and ATP synthesis [1,2]. The human inner mitochondrial membraneThermodynamic and mechanical properties of model mitochondrial membranes Stephanie Nichols membrane, and is thought to be influential in determining membrane potential and permeability. To determine

Kuhl, Tonya L.

26

Thermodynamic properties of lattice hard-sphere models

Thermodynamic properties of several lattice hard-sphere models were obtained from grand canonical histogram- reweighting Monte Carlo simulations. Sphere centers occupy positions on a simple cubic lattice of unit spacing and exclude neighboring sites up to a distance ?. The nearestneighbor exclusion model, ?=&sqrt;2, was previously found to have a second-order transition. Models with integer values of ?=1 or 2 do

A. Z. Panagiotopoulos

2005-01-01

27

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

28

Microcomputer Calculation of Thermodynamic Properties from Molecular Parameters of Gases.

ERIC Educational Resources Information Center

Described in this article is a problem-solving activity which integrates the application of microcomputers with the learning of physical chemistry. Students use the program with spectroscopic data to calculate the thermodynamic properties and compare them with the values from the thermochemical tables. (Author/KR)

Venugopalan, Mundiyath

1990-01-01

29

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

30

The structural, elastic and thermodynamic properties of thorium tetraboride

NASA Astrophysics Data System (ADS)

The structural, elastic and thermodynamic properties of thorium tetraboride (ThB 4) have been investigated by using first-principles plane-wave pseudopotential density functional theory with generalized gradient approximation. The behaviors of structural parameters under 0-70 GPa hydrostatic pressure are studied by means of Broyden, Fletcher, Goldfarb, and Shanno (BFGS) geometry optimization scheme. By using the stress-strain method, single crystal elastic constants are calculated to test the mechanical stability of the crystal structure and to determine mechanical properties such as bulk modulus at each pressure. However, in order to study the thermodynamic properties of ThB 4, the quasi-harmonic Debye model is used. Then, the dependencies of bulk modulus, heat capacities, thermal expansions, Grüneisen parameters and Debye temperatures on the temperature and pressure are obtained in the whole pressure range 0-70 GPa and temperature range 0-1500 K.

Aydin, Sezgin; Tatar, Aynur

2011-04-01

31

Computational Models of Thermodynamic Properties of Uranium Nitride

NASA Astrophysics Data System (ADS)

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

Mei, Zhi-Gang; Stan, Marius

2014-06-01

32

Thermodynamic properties of bulk and confined water.

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

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

2014-11-14

33

Thermodynamic properties of bulk and confined water

NASA Astrophysics Data System (ADS)

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

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

2014-11-01

34

Thermodynamic properties and atomic structure of Ca-based liquid alloys

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 ...

Poizeau, Sophie (Sophie Marie Claire)

2013-01-01

35

Thermodynamic Properties of Matrine in Ethanol

NASA Astrophysics Data System (ADS)

In this paper, the enthalpies of dissolution of matrine in ethanol (EtOH) were measured using a RD496-2000 Calvet microcalorimeter at 309.65 K under atmospheric pressure. The differential enthalpy (?dif H m) and molar enthalpy (?sol H m) of dissolution of matrine in ethanol were determined. And the relationship between heat and the amount of solute was also established. Based on the thermodynamic and kinetic knowledge, the corresponding kinetic equation that described the dissolution process was determined to be {d?/dt=2.36× 10^{-4}(1-? )^{1.09}} . Moreover, the half-life, t 1/2 = 48.89 min, ?sol H m = -12.40 kJ · mol-1, ?sol S m = -354.7 J · mol-1 · K-1, and ? sol G m = 97.43 kJ · mol-1 of the dissolution process were also obtained. The results show that this work not only provides a simple method for the determination of the half-life for a drug but also offers a theoretical reference for the clinical application of matrine.

Li, Z. X.; Zhao, W. W.; Pu, X. H.

2011-06-01

36

The thermodynamic properties of 2-amino-ethylphosphonic acid

. - ~. -. ~ Member December 1973 ABSTRACT The Thermodynamic Properties of 2-Aminoethylphosphonic Acid . (December 1973 ) Stephen G. W. Unruh, B. S. , Kansas State University Directed by: Dr. J . K. Gladden The three ionization constants of 2... for these solutions were then used to calculate pK' values which were plotted as a function of ioni c strength to give a straight line. The intersection of this line with the abcissa, where the ionic strength is zero, yielded the thermodynamic value, pK , at each...

Unruh, Stephen George Walter

2012-06-07

37

Thermodynamic Properties of the van der Waals Fluid

The van der Waals (vdW) theory of fluids is the first and simplest theory that takes into account interactions between the particles of a system that result in a phase transition versus temperature. Combined with Maxwell's construction, this mean-field theory predicts the conditions for equilibrium coexistence between the gas and liquid phases and the first-order transition between them. However, important properties of the vdW fluid have not been systematically investigated. Here we report a comprehensive study of these properties. Ambiguities about the physical interpretation of the Boyle temperature and the influence of the vdW molecular interactions on the pressure of the vdW gas are resolved. Thermodynamic variables and properties are formulated in reduced units that allow all properties to be expressed as laws of corresponding states that apply to all vdW fluids. Lekner's parametric solution for the vdW gas-liquid coexistence curve in the pressure-temperature plane and related thermodynamic properties [...

Johnston, David C

2014-01-01

38

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

39

Thermodynamic properties of lattice hard-sphere models

Thermodynamic properties of several lattice hard-sphere models were obtained from grand canonical histogram- reweighting Monte Carlo simulations. Sphere centers occupy positions on a simple cubic lattice of unit spacing and exclude neighboring sites up to a distance sigma. The nearestneighbor exclusion model, sigma=&surd;2, was previously found to have a second-order transition. Models with integer values of sigma=1 or 2 do

A. Z. Panagiotopoulos

2005-01-01

40

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

41

Thermodynamic properties of aqueous solutions of pyridine and piperidine

This research was designed to examine the thermodynamic properties of aqueous solutions of pyridine and piperidine. The density, excess molar enthalpy of mixing, HE, and excess molar volume of mixing, vE of piperidine–water and pyridine–water mixtures were studied at three temperatures, ranging from 294K to 315K. The HE and vE are negative for both mixtures, minimizing at a water mole

Ismail Kul; Tam Lieu

2010-01-01

42

Thermodynamic properties of dilute solutions of magnesium in zinc

Concentration cells of the type: Mg(s) |MgCl2 in (LiCl-KCl)eut(l) |Mg-Zn(l) have been employed for a study of the thermodynamic properties of dilute Mg-Zn alloys in the range from 0.01 Mg < 0.17 and at temperatures below the melting point of Mg, 922 K. The data were discussed in terms of the Krupkowski formulae,\\u000a Wagner's linear relations of In ?Mg vs

Z. Moser

1974-01-01

43

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

44

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

45

Thermodynamic Properties of the van der Waals Fluid

The van der Waals (vdW) theory of fluids is the first and simplest theory that takes into account interactions between the particles of a system that result in a phase transition versus temperature. Combined with Maxwell's construction, this mean-field theory predicts the conditions for equilibrium coexistence between the gas and liquid phases and the first-order transition between them. However, important properties of the vdW fluid have not been systematically investigated. Here we report a comprehensive study of these properties. Ambiguities about the physical interpretation of the Boyle temperature and the influence of the vdW molecular interactions on the pressure of the vdW gas are resolved. Thermodynamic variables and properties are formulated in reduced units that allow all properties to be expressed as laws of corresponding states that apply to all vdW fluids. Lekner's parametric solution for the vdW gas-liquid coexistence curve in the pressure-temperature plane and related thermodynamic properties [Am. J. Phys. 50, 161 (1982)] is explained and significantly extended. Hysteresis in the first-order transition temperature on heating and cooling is examined and the maximum degrees of superheating and supercooling determined. The latent heat of vaporization and the entropy change on crossing the coexistence curve are investigated. The temperature dependences of the isothermal compressibility, thermal expansion coefficient and heat capacity at constant pressure for a range of pressures above, at and below the critical pressure are systematically studied from numerical calculations including their critical behaviors and their discontinuities on crossing the coexistence curve. Joule-Thomson expansion of the vdW gas is investigated in detail and the pressure and temperature conditions for liquifying a vdW gas on passing through the throttle are determined.

David C. Johnston

2014-02-05

46

ERIC Educational Resources Information Center

Several court cases involving acquisition, use, and disposal of property by institutions of higher education are briefly summarized in this chapter. Cases discussed touch on such topics as municipal annexation of university property; repurchase of properties temporarily allocated to faculty members; implications of zoning laws and zoning board…

Piele, Philip K.

47

ERIC Educational Resources Information Center

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

Goldblatt, Steven M.

48

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 have been developed. The curve fits are for pressure, speed of sound, temperature, entropy, enthalpy, density, and internal energy. These curve fits can be readily incorporated into new or existing computational fluid dynamics codes if real gas effects are desired. The curve fits are constructed from Grabau-type transition functions to model the thermodynamic surfaces in a piecewise manner. The accuracies and continuity of these curve fits are substantially improved over those of previous curve fits. These improvements are due to the incorporation of a small number of additional terms in the approximating polynomials and careful choices of the transition functions. The ranges of validity of the new curve fits are temperatures up to 25 000 K and densities from 10 to the -7 to 10 to the 3d power amagats.

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

1987-01-01

49

NASA Astrophysics Data System (ADS)

The sources of previous thermodynamic property values are detailed for cadmium and some compounds of cadmium that might be expected as derivative from anthropogenic introduction of cadmium into the environment or are required for calculation of thermodynamic properties of cadmium-containing systems. Included are descriptions of the sources of information and methodology used to obtain the values for these compounds reported in the NBS series of publications loosely and collectively referred to as the NBS Thermodynamics Tables.

Archer, Donald G.

1998-09-01

50

Phase Equilibria and Thermodynamic Properties in the Fe-Cr System

Phase equilibria and thermodynamic properties in the Fe-Cr system have been reviewed comprehensively based on experimental information and available computer simulations in different scales. The evaluated phase equilibria show significant differences from the currently accepted thermodynamic description by CALPHAD (calculation of phase diagram) approach. The thermodynamic properties of the Fe-Cr system, such as heat capacity, enthalpy, and activity, have been

Wei Xiong; Malin Selleby; Qing Chen; Joakim Odqvist; Yong Du

2010-01-01

51

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

52

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

2014-01-01

53

We show that the absolute thermodynamic properties of molten salts (mixtures of KCl and LiCl) can be accurately determined from the two-phase thermodynamic (2PT) method that is based on superpositioning of solid-like and gas-like (hard-sphere) vibrational density of states (DoS). The 2PT predictions are in excellent accordance with those from the thermodynamic integration method; the melting point of KCl evaluated from the free energy and the absolute entropy shows close conformity with the experimental/NIST data. The DoS partitioning shows that the Li(+) ions in the eutectic LiCl-KCl molten mixture are largely solid-like, unlike the K(+) and Cl(-) ions, which have a significant gas-like contribution, for temperatures ranging from 773 K to 1300 K. The solid-like states of the Li(+) ions may have practical implications when employed for chemical and nuclear reprocessing applications. PMID:24398710

Wang, Jin; Chakraborty, Brahmananda; Eapen, Jacob

2014-02-21

54

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

55

FLUID- THERMODYNAMIC AND TRANSPORT PROPERTIES OF FLUIDS (IBM 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

56

Recent advances in modeling thermodynamic and transport properties of electrolyte solutions are reviewed. In particular, attention is focused on mixed-solvent electrolyte models, equations of state for high-temperature and supercritical electrolyte systems and transport property models for multicomponent, concentrated solutions. The models are analyzed with respect to their capability of computing thermodynamic and transport properties in wide ranges of conditions and

Andrzej Anderko; Peiming Wang; Marshall Rafal

2002-01-01

57

Structural, electronic, vibrational and thermodynamical properties of surfaces and nanoparticles

NASA Astrophysics Data System (ADS)

The main focus of the thesis is to have better understanding of the atomic and electronic structures, vibrational dynamics and thermodynamics of metallic surfaces and bi-metallic nanoparticles (NPs) via a multi-scale simulational approach. The research presented here involves the study of the physical and chemical properties of metallic surfaces and NPs that are useful to determine their functionality in building novel materials. The study follows the "bottom-up" approach for which the knowledge gathered at the scale of atoms and NPs serves as a base to build, at the macroscopic scale, materials with desired physical and chemical properties. We use a variety of theoretical and computational tools with different degrees of accuracy to study problems in different time and length scales. Interactions between the atoms are derived using both Density Functional Theory (DFT) and Embedded Atom Method (EAM), depending on the scale of the problem at hand. For some cases, both methods are used for the purpose of comparison. For revealing the local contributions to the vibrational dynamics and thermodynamics for the systems possessing site-specific environments, a local approach in real-space is used, namely Real Space Green's Function method (RSGF). For simulating diffusion of atoms/clusters and growth on metal surfaces, Molecular Statics (MS) and Molecular Dynamics (MD) methods are employed.

Yildirim, Handan

58

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

59

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

NASA Astrophysics Data System (ADS)

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 CV, the osmotic second virial coefficient B2, phase stability boundaries, and the critical temperatures associated with closed loop phase diagrams. We discuss the differences between the basic thermodynamic properties of solvated polymers and those derived previously for hierarchical mutual association processes involving the association of two different species A and B into AB complexes and the subsequent polymerization of these AB complexes into linear polymeric structures. The properties of solvated polymer solutions are also compared to those for solutions of polymers in a self-associating solvent. Closed loop phase diagrams for solvated polymer solutions arise in the theory from the competition between the associative and van der Waals interactions, a behavior also typical for dispersed molecular and nanoparticle species that strongly associate with the host fluid. Our analysis of the temperature dependence of the second osmotic virial coefficient reveals that the theory must be generalized to describe the association of multiple solvent molecules with each chain monomer, and this complex extension of the present model will be developed in subsequent papers aimed at a quantitative rather than qualitative treatment of solvated polymer solutions.

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

2013-04-01

60

ms2: A molecular simulation tool for thermodynamic properties

NASA Astrophysics Data System (ADS)

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

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

2011-11-01

61

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

62

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

63

Electronic and thermodynamic properties of ?-Pu2O3

NASA Astrophysics Data System (ADS)

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

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

2014-08-01

64

A note on electrical and thermodynamic properties of Isolated Horizon

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

Chen, Gerui; Gao, Sijie

2014-01-01

65

Thermodynamic properties of chlorite and berthierine derived from calorimetric measurements

NASA Astrophysics Data System (ADS)

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

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

2014-09-01

66

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

67

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

68

Thermodynamic properties and structural stability of thorium dioxide

NASA Astrophysics Data System (ADS)

Using density functional theory (DFT) calculations, we have systematically investigated the thermodynamic properties and structural stabilities of thorium dioxide (ThO2). Based on the calculated phonon dispersion curves, we have calculated the thermal expansion coefficient, bulk modulus, and heat capacities at different temperatures for ThO2 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 ThO2 at different temperatures. In addition, we have also studied possible defect formations and diffusion behaviors of helium in ThO2, to discuss its structural stability. It is found that in intrinsic ThO2 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 ThO2. Our results indicate that upward shifting of the Fermi energy of ThO2 should be prevented to avoid the formation of thorium vacancies so as to avert helium caused damage.

Lu, Y.; Yang, Y.; Zhang, P.

2012-06-01

69

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

70

The thermodynamic properties of hydrated ?-Al2O3 nanoparticles

NASA Astrophysics Data System (ADS)

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

2013-12-01

71

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

72

Thermodynamic and transport properties of unconventional superconductors and multiferroics

NASA Astrophysics Data System (ADS)

Often, the phase diagram for a given material can be quite complex, presenting evidence for multiple orders and it is the task of the condensed matter community to describe and quantify knowledge of these properties. Significant insight can often be gained by comparing model calculations of basic thermodynamic and transport properties of a material with experiment. Here we consider two classes of novel materials whose rich phase diagrams are actively under investigation: unconventional superconductors and multiferroics. In 2006, H. Hosono discovered a new class of iron-based superconducting materials which are not conventional superconductors. After the initial discovery, there is a range of questions of immediate interest; foremost among them is what is the structure and symmetry of the superconducting state, a question which took roughly a decade to answer for the cuprate superconductors. We present calculations that help reveal the structure of the superconducting gap using angle dependent specific heat measurements. We then calculate the electronic Raman scattering intensity for several polarizations of light and different models of disorder, providing information about the anisotropy and location of nodes in the superconducting gap. Understanding the influence of disorder is considered crucial because currently conflicting experimental results may be due to differences in sample quality. Recently, there has also been interest in multiferroics: materials with simultaneous non-zero polarization and magnetic order. We present calculations of fundamental thermodynamic properties, mean field behavior for the simplest ferromagnetic-ferroelectric, characterize topological defects, and use the perturbative renormalization group to help understand the critical point, as a beginning towards understanding the multitude multiferroic materials with increasingly complex magnetic and polar order. The first two chapters review conventional superconductivity and its unconventional counterpart found in the cuprates and pnictides. The original work constituting the body of this dissertation appears in chapters three through five. Chapter five contains a brief introduction to the topics which are relevant for multiferroics before presenting the original work. Portions of this thesis are based on the author's publications and are cited when relevant.

Boyd, G. R.

73

Calculation of Mechanical, Thermodynamic and Transport Properties of Metalic Glass formers

Calculation of Mechanical, Thermodynamic and Transport Properties of Metalic Glass formers Tahir C properties of pure metals and binary alloys in solid, liquid and glass phases. Here, we will describe the kinetics and thermodynamics of supercooled bulk metallic glass forming liquids is of critical importance

Ã?agin, Tahir

74

Thermodynamic properties of the particles interacting through smooth version of Stell-Hemmer interaction were studied using Wertheim's thermodynamic perturbation theory. The temperature dependence of molar volume, heat capacity, isothermal compressibility and thermal expansion coefficient at constant pressure for different number of bonding sites on particle were evaluated. The model showed water-like anomalies for all evaluated quantities, but thermodynamic perturbation theory does not properly predict the dependence of these properties at a fixed number of bonding points.

T. Urbic

2013-12-16

75

NASA Technical Reports Server (NTRS)

Thermodynamic and transport properties of high temperature air, and the reaction rates for the important chemical processes which occur in air, are reviewed. Semiempirical, analytic expressions are presented for thermodynamic and transport properties of air. Examples are given illustrating the use of these properties to evaluate (1) equilibrium conditions following shock waves, (2) stagnation region heat flux to a blunt high-speed body, and (3) some chemical relaxation lengths in stagnation region flow.

Hansen, C Frederick; Heims, Steve P

1958-01-01

76

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

77

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

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

Chaudhry, Gunaranjan

2009-01-01

78

Anharmonic effects on thermodynamic properties of a graphene monolayer

NASA Astrophysics Data System (ADS)

We extend the unsymmetrized self-consistent-field method (USF) for anharmonic crystals to layered non-Bravais crystals to investigate structural, dynamical and thermodynamic properties of a free-standing graphene monolayer. In this theory, the main anharmonicity of the crystal lattice has been included and the quantum corrections are taken into account in an ?-expansion for the one-particle density matrix. The obtained result for the thermal expansion coefficient (TEC) of graphene shows a strong temperature dependence and agrees with experimental results by Bao et al. (Nat. Nanotechnol., 4 (2009) 562). The obtained value of TEC at room temperature (300 K) is -6.4\\times10^{-6}\\ \\text{K}^{-1} and it becomes positive for T>T_{\\alpha}=358\\ \\text{K} . We find that quantum effects are significant for T<1000\\ \\text{K} . The interatomic distance, effective amplitudes of the graphene lattice vibrations, adiabatic and isothermal bulk moduli, isobaric and isochoric heat capacities are also calculated and their temperature dependences are determined.

da Silva, A. L. C.; Cândido, Ladir; Teixeira Rabelo, J. N.; Hai, G.-Q.; Peeters, F. M.

2014-09-01

79

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

80

NASA Technical Reports Server (NTRS)

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

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

1973-01-01

81

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

Williams, Michael Eric

2009-05-15

82

NASA Astrophysics Data System (ADS)

First-principles atomistic simulation is a vital tool for understanding the properties of materials at the high-pressure high-temperature conditions prevalent in giant planet interiors, but properties such as solubility and phase boundaries are dependent on entropy, a quantity not directly accessible in simulation. Determining entropic properties from atomistic simulations is a difficult problem typically requiring a time-consuming integration over molecular dynamics trajectories. Here I will describe recent advances in first-principles thermodynamic calculations which substantially increase the simplicity and efficiency of thermodynamic integration and make entropic properties more readily accessible. I will also describe the use of first-principles thermodynamic calculations for understanding problems including core solubility in gas giants and superionic phase changes in ice giants, as well as future prospects for combining first-principles thermodynamics with planetary-scale models to help us understand the origin and consequences of compositional inhomogeneity in giant planet interiors.

Wilson, H. F.

2013-12-01

83

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

84

Diagram analysis of the Hubbard model: Stationarity property of the thermodynamic potential

The diagram approach proposed many years ago for the strongly correlated Hubbard model is developed with the aim to analyze the thermodynamic potential properties. A new exact relation between renormalized quantities such as the thermodynamic potential, the one-particle propagator, and the correlation function is established. This relation contains an additional integration of the one-particle propagator with respect to an auxiliary constant. The vacuum skeleton diagrams constructed from the irreducible Green's functions and tunneling propagator lines are determined and a special functional is introduced. The properties of this functional are investigated and its relation to the thermodynamic potential is established. The stationarity property of this functional with respect to first-order variations of the correlation function is demonstrated; as a consequence, the stationarity property of the thermodynamic potential is proved.

Moskalenko, V. A., E-mail: moskalen@theor.jinr.r [Moldova Academy of Sciences, Institute of Applied Physics (Moldova, Republic of); Dohotaru, L. A., E-mail: statphys@asm.m [Technical University (Moldova, Republic of); Cebotari, I. D. [Moldova Academy of Sciences, Institute of Applied Physics (Moldova, Republic of)

2010-07-15

85

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

Mounet, Nicolas (Nicolas Frank)

2005-01-01

86

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

Mounet, Nicolas (Nicolas Frank)

2005-01-01

87

Comparison of thermodynamic properties of coarse-grained and atomic-level simulation models.

Thermodynamic data are often used to calibrate or test amomic-level (AL) force fields for molecular dynamics (MD) simulations. In contrast, the majority of coarse-grained (CG) force fields do not rely extensively on thermodynamic quantities. Recently, a CG force field for lipids, hydrocarbons, ions, and water, in which approximately four non-hydrogen atoms are mapped onto one interaction site, has been proposed and applied to study various aspects of lipid systems. To date, no extensive investigation of its capability to describe salvation thermodynamics has been undertaken. In the present study, a detailed picture of vaporization, solvation, and phase-partitioning thermodynamics for liquid hydrocarbons and water was obtained at CG and AL resolutions, in order to compare the two types or models and evaluate their ability to describe thermodynamic properties in the temperature range between 263 and 343 K. Both CG and AL models capture the experimental dependence of the thermodynamic properties on the temperature, albeit a systematically weaker dependence is found for the CG model. Moreover, deviations are found for solvation thermodynamics and for the corresponding enthalpy-entropy compensation for the CG model. Particularly water/oil repulsion seems to be overestimated. However, the results suggest that the thermodynamic properties considered should be reproducible by a CG model provided it is reparametrized on the basis of these liquid-phase properties. PMID:17290360

Baron, Riccardo; Trzesniak, Daniel; de Vries, Alex H; Elsener, Andreas; Marrink, Siewert J; van Gunsteren, Wilfred F

2007-02-19

88

Thermodynamic and transport property modeling in super critical water

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

Kutney, Michael C. (Michael Charles)

2005-01-01

89

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

90

NASA Astrophysics Data System (ADS)

Mixtures of water and ammonia play an important role in absorption refrigeration cycles and have received attention as working fluids in modern power generation cycles. For design and simulations during the development of any application, the thermodynamic properties have to be known accurately. Measurements of available thermodynamic data are compiled and summarized. The data sets are compared, using a Helmholtz free energy formulation. Recommendations are given for which data sets are suited to serve as a basis for an equation of state formulation of the thermodynamic properties of {water+ammonia}. Gaps in the database are shown to give experimenters orientation for future research.

Tillner-Roth, Reiner; Friend, Daniel G.

1998-01-01

91

Thermodynamic equilibria in xylene isomerization. 3: The thermodynamic properties of o-xylene

Measurements leading to the calculation of the ideal-gas thermodynamic properties for o-xylene (Chemical Abstracts registry number [95-47-6]) are reported. Experimental methods included adiabatic heat-capacity calorimetry (5 K to 420 K), comparative ebulliometry (313 K to 459 K), differential-scanning calorimetry (DSC), and vibrating-tube densitometry (323 K to 523 K). The critical temperature was measured by DSC. Saturation heat capacities for the liquid phase between 420 K and 550 K, the critical density, and the critical pressure were derived with the vapor-pressure, density, and DSC results. Results were combined with an enthalpy of combustion reported in the literature to derive standard molar entropies, enthalpies, and Gibbs free energies of formation at selected temperatures between 250 K and 550 K. The standard state is defined as the ideal gas at the pressure p = p{degree} = 101.325 kPa. Standard entropies are compared with those calculated statistically on the basis of assigned vibrational spectra from the literature for the vapor phase. A preliminary value for the barrier to methyl-group rotation is derived. All results are compared with literature values.

Chirico, R.D.; Knipmeyer, S.E.; Nguyen, A.; Cowell, A.B.; Reynolds, J.W.; Steele, W.V. [BDM Petroleum Technologies, Bartlesville, OK (United States). Bartlesville Thermodynamics Group] [BDM Petroleum Technologies, Bartlesville, OK (United States). Bartlesville Thermodynamics Group

1997-07-01

92

Thermodynamic equilibria in xylene isomerization. 2: The thermodynamic properties of m-xylene

Measurements leading to the calculation of the ideal-gas thermodynamic properties for m-xylene are reported. Experimental methods included adiabatic heat-capacity calorimetry (5 K to 430 K), vibrating-tube densitometry (323 K to 523 K), comparative ebulliometry (309 K to 453 K), and differential-scanning calorimetry (DSC). The critical temperature was measured by DSC. Saturation heat capacities for the liquid phase between 430 K and 550 K and the critical pressure were derived with the vapor-pressure and DSC results. Results were combined with an enthalpy of combustion reported in the literature to derive standard molar entropies, enthalpies, and Gibbs free energies of formation at selected temperatures between 250 K and 550 K. The standard state is defined as the ideal gas at the pressure p = p{degree} = 101.325 kPa. Standard entropies are compared with those calculated statistically on the basis of assigned vibrational spectra for the vapor phase. All results are compared with literature values.

Chirico, R.D.; Knipmeyer, S.E.; Nguyen, A.; Reynolds, J.W.; Steele, W.V. [BDM Petroleum Technologies, Bartlesville, OK (United States). Bartlesville Thermodynamics Group] [BDM Petroleum Technologies, Bartlesville, OK (United States). Bartlesville Thermodynamics Group

1997-05-01

93

Thermodynamic equilibria in xylene isomerization. 1: The thermodynamic properties of p-xylene

Measurements and calculations leading to the determination of thermodynamic properties for the gaseous and condensed phases of p-xylene (Chemical Abstracts registry number (supplied by the authors) [106-42-3]) are reported. All measurement results reported were obtained with a differential-scanning calorimeter (DSC). The critical temperature was measured by DSC. Saturation heat capacities for the liquid phase between 370 K and 550 K, the critical density and the critical pressure were derived with fitting procedures involving the new DSC results and literature vapor pressures and ensities. Results were combined with heat capacities reported in the literature obtained with adiabatic calorimetry and the enthalpy of combustion to derive standard molar entropies, enthalpies, and Gibbs free energies of formation at selected temperatures between 250 K and 550 K. The standard state is defined as the ideal gas at the pressure p = p{degree} = 101.325 kPa. Standard entropies are compared with those calculated statistically on the basis of assigned vibrational spectra. Results are compared with literature values. Literature vapor pressures, enthalpies of vaporization, virial coefficients, densities, and heat capacities for the condensed and gaseous phases are checked for consistency with the values used in this research.

Chirico, R.D.; Knipmeyer, S.E.; Nguyen, A.; Steele, W.V. [BDM-Oklahoma Inc., Bartlesville, OK (United States). National Inst. of Petroleum and Energy Research] [BDM-Oklahoma Inc., Bartlesville, OK (United States). National Inst. of Petroleum and Energy Research

1997-03-01

94

Playing with Marbles: Structural and Thermodynamic Properties of Hard-Sphere Systems

These lecture notes present an overview of equilibrium statistical mechanics of classical fluids, with special applications to the structural and thermodynamic properties of systems made of particles interacting via the hard-sphere potential or closely related model potentials. The exact statistical-mechanical properties of one-dimensional systems, the issue of thermodynamic (in)consistency among different routes in the context of several approximate theories, and the construction of analytical or semi-analytical approximations for the structural properties are also addressed.

Andrés Santos

2013-10-21

95

Thermodynamic properties of interfacial water from its infrared signatures

.g., 1]. This justifies the intensity of researches about high resolution measurements of solids surfaces, published in "16th International Conference on the Properties of Water and Steam, Londres : Royaume condenser. We use a double path single masking aperture size of 3x3 Âµm which allows us to work in dual

Paris-Sud XI, UniversitÃ© de

96

THERMODYNAMIC AND TRANSPORT PROPERTIES OF SILICATE MELTS AND MAGMA

of parental source material.28 29 Magma Rheology30 The rheological properties of magma depend on temperature, bulk composition, pressure, phase31 assemblage (melt ï¿½ crystals ï¿½ vapor), particle size and shape capacity. The EOS relates the39 density of a substance to its composition, pressure and temperature

Spera, Frank J.

97

The thermodynamic properties of lithium peroxide, Li 2O 2

Recently, Cota et al. gave an improved crystal structure of lithium peroxide. For the sake of investigation of the thermal properties for this structure of Li2O2, the Debye model is adopted in our work. This model combines with the ab initio calculations within local density approximation (LDA) using pseudopotentials and a planewave basis in the framework of density functional theory

H. Y. Wu; H. Zhang; X. L. Cheng; L. C. Cai

2006-01-01

98

The thermodynamic properties of lithium peroxide, Li2O2

Recently, Cota et al. gave an improved crystal structure of lithium peroxide. For the sake of investigation of the thermal properties for this structure of Li2O2, the Debye model is adopted in our work. This model combines with the ab initio calculations within local density approximation (LDA) using pseudopotentials and a planewave basis in the framework of density functional theory

H. Y. Wu; H. Zhang; X. L. Cheng; L. C. Cai

2006-01-01

99

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

100

The thermodynamic properties of lithium peroxide, Li2O2

NASA Astrophysics Data System (ADS)

Recently, Cota et al. gave an improved crystal structure of lithium peroxide. For the sake of investigation of the thermal properties for this structure of Li2O2, the Debye model is adopted in our work. This model combines with the ab initio calculations within local density approximation (LDA) using pseudopotentials and a planewave basis in the framework of density functional theory (DFT), and it takes into account the phononic effects within the quasi-harmonic approximation. We find that our calculated lattice constant using this model is in excellent agreement with the data from Cota et al. Based on the first principles study and the Debye model, the thermal properties including the equation of state, the Debye temperature, the heat capacity and the thermal expansion are obtained in the whole pressure range from 0 to 10 GPa and temperature range from 0 to 500 K.

Wu, H. Y.; Zhang, H.; Cheng, X. L.; Cai, L. C.

2006-12-01

101

Transport and thermodynamic properties of mesoscopic quantum systems

The transport properties of three-dimensional quantum microconstrictions in field-free conditions and under the influence of magnetic fields of arbitrary strengths and directions are studied via a generalized Buttiker model. It is shown that conductance quantization is influenced by the geometry of the microconstriction (that is, its length and the shape of its transverse cross-section). In a weak longitudinal magnetic field,

Andrew Germanovich Scherbakov

1997-01-01

102

Dynamical probe of thermodynamical properties in three-dimensional hairy AdS black holes

We study the quasinormal modes (QNM) of electromagnetic perturbations for rotating black hole with a nonminimally coupled scalar field hair and Banados-Teitelboim-Zanelli (BTZ) in three-dimensional anti-de Sitter (AdS) spacetimes. We find that the imaginary parts of quasinormal frequencies of dynamical perturbations can reflect the properties of thermodynamical stability disclosed by examining the free energy. In addition, we observe that the imaginary part of QNM frequencies can also determine the dynamically preferred stable configuration, which agrees with the study of the thermodynamically stability. This dramatic relation between dynamics and thermodynamics is also disclosed in three-dimensional static black hole backgrounds. The obtained results further support that the QNM can be a dynamic probe of the thermodynamic properties in black holes.

Zou, De-Cheng; Zhang, Cheng-Yong; Wang, Bin

2014-01-01

103

Thermodynamic properties of a two-dimensional electron gas with attractive interactions

NASA Astrophysics Data System (ADS)

We present a calculation of the thermodynamic properties of a two-dimensional negative-U Hubbard model in the low-density limit. We show that the standard expansion of the thermodynamic potential in terms of particle-particle ladder diagrams evaluated in the undressed fermion propagator, leads to unphysical results like negative entropy and/or specific heat. We propose a phenomenological pair susceptibility that avoids these problems and calculate the entropy and specific heat for different values of the parameters.

Sofo, J. O.; Balseiro, C. A.

1992-04-01

104

Nonlinear thermodynamic quantum master equation: Properties and examples

The quantum master equation obtained from two different thermodynamic arguments is seriously nonlinear. We argue that, for quantum systems, nonlinearity occurs naturally in the step from reversible to irreversible equations and we analyze the nature and consequences of the nonlinear contribution. The thermodynamic nonlinearity naturally leads to canonical equilibrium solutions and extends the range of validity to lower temperatures. We discuss the Markovian character of the thermodynamic quantum master equation and introduce a solution strategy based on coupled evolution equations for the eigenstates and eigenvalues of the density matrix. The general ideas are illustrated for the two-level system and for the damped harmonic oscillator. Several conceptual implications of the nonlinearity of the thermodynamic quantum master equation are pointed out, including the absence of a Heisenberg picture and the resulting difficulties with defining multitime correlations.

Oettinger, Hans Christian [ETH Zuerich, Department of Materials, Polymer Physics, HCI H 543, CH-8093 Zuerich (Switzerland)

2010-11-15

105

Experimental verification of the thermodynamic properties for a jet-A fuel

NASA Technical Reports Server (NTRS)

Thermodynamic properties for a Jet-A fuel were determined by Shell Development Company in 1970 under a contract for NASA Lewis Research Center. The polynomial fit necessary to include Jet-A fuel (liquid and gaseous phases) in the library of thermodynamic properties of the NASA Lewis Chemical Equilibrium Program is calculated. To verify the thermodynamic data, the temperatures of mixtures of liquid Jet-A injected into a hot nitrogen stream were experimentally measured and compared to those calculated by the program. Iso-octane, a fuel for which the thermodynamic properties are well known, was used as a standard to calibrate the apparatus. The measured temperatures for the iso-octane/nitrogen mixtures reproduced the calculated temperatures except for a small loss due to the non-adiabatic behavior of the apparatus. The measurements for Jet-A were corrected for this heat loss and showed excellent agreement with the calculated temperatures. These experiments show that this process can be adequately described by the thermodynamic properties fitted for the Chemical Equilibrium Program.

Graciasalcedo, Carmen M.; Brabbs, Theodore A.; Mcbride, Bonnie J.

1988-01-01

106

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

107

Temperature and pressure dependent thermodynamical properties of uranium dinitrides: UN2

NASA Astrophysics Data System (ADS)

The high temperature and high pressure thermodynamic properties of UN2 are evaluated by developing an effective interionic interaction potential with long range Coulomb, charge transfer, covalency, van der Waals interaction and the short-range repulsive interaction upto second-neighbor ions within the Hafemeister and Flygare approach. The second order elastic constants are used to estimate the Debye temperature which in turn computes the heat capacity and elastic wave velocities propagating in the UN2. Deduced results on pressure (temperature) dependence of thermodynamical properties are consistent with the available experimental data and theoretical results.

Shriya, Swarna; Chaudhary, S.; Varshney, M.; Varshney, Dinesh

2013-02-01

108

Numerical prediction of the thermodynamic properties of ternary Al-Ni-Hf alloys

NASA Astrophysics Data System (ADS)

Thermodynamic properties of ternary Al-Hf-Ni system, such as exG, ?Al, ?Ni and ?Zr at 1373K were predicted on the basis of thermodynamic properties of binary systems included in the investigated ternary system. The idea of predicting exG values was regarded as the calculation of excess Gibbs energy values inside a certain area (a Gibbs triangle) unless all boundary conditions, that is values of exG on all legs of the triangle are known. exG and Lijk ternary interaction parameters in the Muggianu extension of the Redlich-Kister formalism are calculated numerically using Wolfram Mathematica 9 software.

Romanowska, Jolanta; Kotowski, S?awomir; Zagula-Yavorska, Maryana

2014-10-01

109

The extended thermodynamic properties of Taub-NUT/Bolt-AdS spaces

NASA Astrophysics Data System (ADS)

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

Lee, Chong Oh

2014-11-01

110

Thermodynamic properties of arbitrary perfect gas mixtures at low pressures and high temperatures

Atmospheric entry flights, combusting flows, experiments in high-enthalpy wind tunnels, CFD simulation of high-velocity, high-temperature flow fields, are a number of areas in which the thermodynamic properties of gases at high temperatures must be correctly computed because of their important influence on the flow field. For low-density applications (up to about 10 times the normal density), the gas properties can

2000-01-01

111

Quantum and thermodynamic properties of spontaneous and low-energy induced fission of nuclei

It is shown that A. Bohr’s concept of transition fission states can be matched with the properties of Coriolis interaction\\u000a if an axisymmetric fissile nucleus near the scission point remains cold despite a nonadiabatic character of nuclear collective\\u000a deformation motion. The quantum and thermodynamic properties of various stages of binary and ternary fission after the descent\\u000a of a fissile nucleus

S. G. Kadmensky

2005-01-01

112

Symmetry, Optical Properties and Thermodynamics of Neptunium(V) Complexes

Recent results on the optical absorption and symmetry of the Np(V) complexes with dicarboxylate and diamide ligands are reviewed. The importance of recognizing the 'silent' feature of centrosymmetric Np(V) species in analyzing the absorption spectra and calculating the thermodynamic constants of Np(V) complexes is emphasized.

Rao, Linfeng; Tian, Guoxin

2009-12-21

113

Thermodynamic Properties for A Drop-in Refrigerant R-SP34E

NASA Astrophysics Data System (ADS)

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

Kayukawa, Yohei; Hondo, Takashi; Watanabe, Koichi

114

NASA Astrophysics Data System (ADS)

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

Satoh, Katsuhiko

2013-08-01

115

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

116

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

NSDL National Science Digital Library

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

117

Thermodynamic Properties of the Kinesin Neck-Region Docking to the Catalytic Core

Kinesin motors move on microtubules by a mechanism that involves a large, ATP-triggered conformational change in which a mechanical element called the neck linker docks onto the catalytic core, making contacts with the core throughout its length. Here, we investigate the thermodynamic properties of this conformational change using electron paramagnetic resonance (EPR) spectroscopy. We placed spin probes at several locations

S. Rice; Y. Cui; C. Sindelar; N. Naber; M. Matuska; R. Vale; R. Cooke

2003-01-01

118

Hypothetical Thermodynamic Properties: The Boiling and Critical Temperatures of Polyethylene. Louis, Missouri 63121 The normal (p ) 101.325 kPa) boiling-temperature behavior of a homologous series and approximately TB() ) 915 K for those related to polytetrafluoroethylene. Normal boiling temperatures have been

Chickos, James S.

119

In the present study, a simultaneous chemical kinetics and heat transfer model is used to predict the effects of the most important thermal and thermodynamic properties (thermal conductivity, heat transfer coefficient, emissivity and heat of reaction number) of the feedstock on the convective-radiant pyrolysis of biomass fuels. A finite difference pure implicit scheme utilizing the tri-diagonal matrix algorithm is employed

B. V. Babu; A. S. Chaurasia

2004-01-01

120

Thermodynamic properties for humid gases from 298 to 573 K and up to 200 bar

For the needs of process design, the model proposed in our previous papers was extended to calculate the thermodynamic properties of humidity, heat capacity, molar volume, partial pressure of water vapour, enthalpy and entropy for humid gases (nitrogen, oxygen, air or a nitrogen–oxygen mixture). The comparison with other models from 300 to 473K and 1 to 100bar shows that the

Xiaoyan Ji; Jinyue Yan

2006-01-01

121

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

122

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

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

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

2011-01-01

123

Thermodynamic properties of uranium in Ga-In based alloys

NASA Astrophysics Data System (ADS)

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

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

2013-07-01

124

Physicochemical and thermodynamic properties of monomeric Concanavalin a

An alkylated monomer of Concanavalin A was prepared photochemically according to the method of Tanaka et al. (1981). Its affinities for methyl-a-d-gluco, methyl-a-d-manno and p-nitro-phenyl-a-d-manno pryranoside were calculated. The enthalpies of these binding reactions were measured calorimetrically and the thermodynamic parameters were calculated. The values obatined suggest that the structure of the monomer differs from that of the dimeric and

E. Battistel; G. Lazzarini; F. Manca; G. Rialdi I

1985-01-01

125

Thermodynamic properties of an evaporation process in self-gravitating N -body systems.

By means of N -body simulations, we consider self-gravitating open systems enclosed in a spherical container with semipermeable reflecting walls, in order to investigate the thermodynamics of the evaporation process in self-gravitating N -body systems (such as the escape of stars from globular clusters). To simulate the evaporation process, when the energy of a particle exceeds a certain threshold value, the particle passes through the semipermeable reflecting wall freely. We show that the thermodynamic properties of the evaporation process, such as the dependence of the temperature on energy, agree well with those of stellar polytropes, if the system is in an approximate virial equilibrium state. However, in a lower-energy region or for a rapid evaporation process, the thermodynamic properties deviate from those for the stellar polytrope. Nevertheless, we found that a negative specific heat occurs even in the lower-energy region or for a rapid evaporation process. PMID:20866786

Komatsu, Nobuyoshi; Kiwata, Takahiro; Kimura, Shigeo

2010-08-01

126

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

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

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

1990-02-01

127

Transport and thermodynamic properties of mesoscopic quantum systems

NASA Astrophysics Data System (ADS)

The transport properties of three-dimensional quantum microconstrictions in field-free conditions and under the influence of magnetic fields of arbitrary strengths and directions are studied via a generalized Buttiker model. It is shown that conductance quantization is influenced by the geometry of the microconstriction (that is, its length and the shape of its transverse cross-section). In a weak longitudinal magnetic field, when rsb{c}? d, where rsb{c} is the cyclotron radius and d the effective transverse size of the narrowing of the microconstriction, the conductance exhibits Aharonov-Bohm type behavior. This behavior transforms in the strong field limit, rsb{c}? d, into Shubnikov-de Haas oscillations with a superimposed Aharonov-Bohm fine-structure. The dependence of the Aharonov-Bohm type features on the length of the microconstriction and on temperature are demonstrated. Effects of the shapes of the cross sections of three-dimensional nanowires on electronic conductance quantization are studied for both hard- and soft-wall potentials. In both models the quantum conductance is determined by both the area and shape of the narrowmost part of the nanowire. For the hard-wall potential the semiclassical (Weyl) correction to the Sharvin formula provides an adequate approximation to the average quantized conductance. For nanowires modeled by soft-wall potentials the average quantum conductance may be well estimated using a classical approximation. Magnetic field switching and blockade of quantum transport through three-dimensional metallic and semimetallic nanowires with a small number of conducting channels are proposed. Temperature enhancement of magnetotransport in such wires is predicted. Thermoelectric properties of nanowires in a magnetic field are studied. Magnetic splitting of thermopower peaks associated with electronic energy levels which are degenerate at zero field, leading to the development of separate thermopower peaks at larger fields, are predicted. A method for numerical calculation of the conductance through microconstrictions based on the time-dependent Schrodinger equation is developed, allowing investigations of electronic transport in complex situations. An algorithm for conductance calculations via propagation of wave packets is presented, and results for electronic transport through various constrictions are given, including model calculations of the conductance of a one-atom contact in the scanning tunneling microscope.

Scherbakov, Andrew Germanovich

128

Standard thermodynamic properties of nitrobenzene in the ideal gas state

The standard enthalpy of formation of gaseous nitrobenzene was calculated by the G3X nonempirical quantum-mechanical method.\\u000a The value obtained (56 kJ\\/mol) was noticeably lower than the experimental enthalpy, which casts doubt on the accuracy of measurements.\\u000a The thermodynamic functions (C°\\u000a p\\u000a , S°, ?[G° ? H°(0)]\\/T, H° ? H°(0), ?f\\u000a H°, and ?f\\u000a G°) of nitrobenzene in the ideal gas

O. V. Dorofeeva; N. F. Moiseeva

2008-01-01

129

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

130

Evaluation of phosphate thermodynamic properties for spent electrolyte recycle

NASA Astrophysics Data System (ADS)

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

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

2009-06-01

131

Thermodynamic and fluid properties of cells, tissues and membranes

NASA Astrophysics Data System (ADS)

This dissertation studies cellular rearrangements in tissues and attempts to establish the role of physical properties of cells, tissues and membranes in several biological phenomena. Using experiments and statistical mechanical modeling, we study cell sorting, tissue engulfment, single cell motion and membrane fluctuations. When cells of two different types are mixed together, they sort out, with the less cohesive tissue surrounding the more cohesive one. This sorting out resembles the phase separation of a mixture of immiscible liquids. We have measured the rate of sorting in tissues and compared it with a cellular automaton based model of cell aggregates. We have also established that cell sorting agrees well with the theory for phase separating fluids. Engulfment is the spreading of one type of tissue over the surface of another tissue placed adjacent to it. Differences in adhesion cause an imbalance of surface tension forces which drives tissue spreading. We have quantitatively studied engulfment between different tissue types and compared the experimental rate with results from computer simulations and a liquid model. Our results suggest that simple physical principles can model tissue motion. Studying the motion of single cells in aggregates is important to understanding the overall pattern formation in tissues. We characterized cell motion in different types of adhesive aggregates to elucidate the role of adhesion in cell motion. We also observed that the cells exhibited a novel type of statistics including correlations and collective motion. Membrane deformations of cells played a negligible role in large scale cell motion. Our results indicate the importance of correlated motion for cells to move long distances in tissues. At the single cell level, tension of the cell membrane and intracellular membrane can play an important role in cell shape changes, regulation of cell motility and membrane dynamics. We used optical tweezers to measure the membrane tension of tubulo-vesicular networks obtained from Golgi and Endoplasmic Reticulum (ER) membranes within cells. As expected on the basis of some previous experiments, the ER has a higher membrane tension than the Golgi.

Upadhyaya, Arpita

2000-10-01

132

National Technical Information Service (NTIS)

The objectives of this research project are to: develop a thermodynamic properties correlation framework for pure coal fluids; extend the framework to prediction of thermodynamic properties of defined binary mixtures; develop correlations for the correlat...

K. E. Starling, L. L. Lee, S. Watanasiri, K. H. Kumar, M. R. Brule

1983-01-01

133

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

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. PMID:24737253

Perkgöz, Nihan Kosku; Sevik, Cem

2014-05-01

134

Thermodynamics properties of copper-oxide superconductors described by an Ising frustrated model

NASA Astrophysics Data System (ADS)

In this work we will study the thermodynamics properties of the quenched decorated Ising model with competitive interactions through the effective field theory (EFT) of a one-spin cluster. This model is used here to describe the thermodynamics properties of the cooper-based oxide superconductors compounds in its insulating phase (antiferromagnetic). The model consists of planes in which the nodal spins interact antiferromagnetically (JA<0) with their nearest-neighbors and ferromagnetically (JF>0) with the spins that decorated the bonds, which are quenched randomly distributed over the two-dimensional lattice. The planes interact antiferromagnetically with weak exchange interaction (i.e., JA?=?JA, ?=10-5). By using the framework of an effective-field theory, based on the differential operator technique, we discuss beyond thermodynamics properties the antiferromagnetic-phase stability limit in the temperature-decorated bond concentration space (T×p), for ?=10-5 and various values of frustration parameter (?=JA/JF), magnetic field (H) and concentration parameter (p). For certain range of the parameter ? we observe a reentrant behavior in low-temperature that it reflects in the properties behavior itself.

Padilha, Igor T.; de Sousa, J. Ricardo; Neto, Minos A.; Salmon, Octavio R.; Viana, J. R.

2013-10-01

135

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

136

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

137

LDA+ U calculation of structural and thermodynamic properties of Ce2O3

NASA Astrophysics Data System (ADS)

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

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

2014-08-01

138

NASA Astrophysics Data System (ADS)

A theoretical investigation on the structural and thermodynamic properties of CdO under high pressure is performed by employing the pseudopotential plane-wave method in the framework of the density functional theory. Some structural parameters of CdO in both B1 and B2 phases are reported. According to the third-order Birch-Murnaghan equation of states, the transition pressure Pt of CdO from the B1 structure to the B2 structure is determined. The calculated results are found to be in good agreement with the available experimental data and theoretical values. Based on the quasi-harmonic Debye model, the Debye temperature of CdO under high pressure is derived from the average sound velocity. This is a quantitative theoretical prediction of the elastic and thermodynamic properties of CdO and it still awaits experimental confirmation.

Lu, Cheng; Kuang, Xiao-Yu; Wang, Su-Juan; Zhao, Ya-Ru; Tan, Xiao-Ming

2010-07-01

139

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

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

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

2011-01-01

140

Structural, vibrational and thermodynamic properties of Mg2 FeH6 complex hydride

NASA Astrophysics Data System (ADS)

Mg2FeH6, which has one of the highest hydrogen storage capacities among Mg based 3d-transitional metal hydrides, is considered as an attractive material for hydrogen storage. Within density-functional perturbation theory (DFPT), we have investigated the structural, vibrational and thermodynamic properties of Mg2FeH6. The band structure calculation shows that this compound is a semiconductor with a direct X-X energy gap of 1.96 eV. The calculated phonon frequencies for the Raman-active and the infrared-active modes are assigned. The phonon dispersion curves together with the corresponding phonon density of states and longitudinal-transverse optical (LO-TO) splitting are also calculated. Findings are also presented for the temperature-dependent behaviors of some thermodynamic properties such as free energy, internal energy, entropy and heat capacity within the quasi-harmonic approximation based on the calculated phonon density of states.

Zhou, H. L.; Yu, Y.; Zhang, H. F.; Gao, T.

2011-02-01

141

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

142

Interpolymer complexes (IPCs) formed between complimentary polymers in solution have shown a wide range of applications from drug delivery to biosensors. This work describes the combined use of isothermal titration calorimetry and surface plasmon resonance to investigate the thermodynamic and kinetic processes during hydrogen-bonded interpolymer complexation. Varied polymers that are commonly used in layer-by-layer coatings and pharmaceutical preparations were selected to span a range of chemical functionalities including some known IPCs previously characterized by other techniques, and other polymer combinations with unknown outcomes. This work is the first to comprehensively detail the thermodynamic and kinetic data of hydrogen bonded IPCs, aiding understanding and detailed characterization of the complexes. The applicability of the two techniques in determining thermodynamic, gravimetric and kinetic properties of IPCs is considered. PMID:25186562

Bizley, Samuel C; Williams, Adrian C; Khutoryanskiy, Vitaliy V

2014-11-01

143

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

144

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

145

Thermodynamic properties of ammonia–water mixtures for power-cycle applications

Ammonia–water mixtures have been used as working fluids in absorption–refrigeration cycles for several decades. Their use as multi-component working fluids for power cycles has been investigated recently. The thermodynamic properties required are known or may be calculated at elevated temperatures and pressures. We present a new method for these computations using Gibbs free energies and empirical equations for bubble and

Feng Xu; D. Yogi Goswami

1999-01-01

146

Thermodynamic properties for rare earths and americium in pyropartitioning process solvents

The design of a molten metal-molten salt based chemical and electrochemical process for separation of actinides from plutonium-uranium extraction waste requires a consistent set of thermodynamic properties for the actinides and rare earths present in nuclear waste. Standard potential data for Y, La, Ce, Pr, and Gd in molten LiCl-KCl were obtained. Americium data obtained were standard potentials in molten

S. P. Fusselman; J. J. Roy; D. L. Grimmett

1999-01-01

147

Vibrational and thermodynamic properties of GeSe in the quasiharmonic approximation

NASA Astrophysics Data System (ADS)

Finite-temperature properties such as thermodynamic state functions can be obtained for a range of crystalline materials by combining density functional theory (DFT) with lattice-dynamics approaches. Despite the usefulness of such first-principles predictions, their results must be carefully checked for accuracy, especially in cases where the DFT description of the material itself is nontrivial. Here, we investigate a prototypical layered semiconductor, namely, germanium selenide (GeSe) by dispersion-corrected DFT, lattice-dynamics computations, and a thermodynamic framework that relies on the quasiharmonic approximation (QHA). We study phonon band structures, their evolution under pressure, and finite-temperature thermodynamic state functions. Besides the layered orthorhombic structure, this analysis includes the high-temperature cubic (rocksalt-type) polymorph of GeSe, which is shown to exhibit imaginary vibrational modes but emerging dynamic stability under increasing external pressure. The effect of these imaginary vibrational modes on the QHA and hence on computed thermochemical properties is critically evaluated. First-principles thermodynamics correctly predict a high-temperature transition from the orthorhombic to the cubic structure, albeit the transition temperature is severely underestimated. This simple compound allows us to address important methodological questions regarding the QHA treatment of crystalline solids.

Deringer, Volker L.; Stoffel, Ralf P.; Dronskowski, Richard

2014-03-01

148

Thermodynamic consistency of liquid-gas lattice Boltzmann methods: interfacial property issues.

In the present study we examine the thermodynamic consistency of lattice Boltzmann equation (LBE) models that are based on the forcing method by comparing different numerical treatments of the LBE for van der Waals fluids. The different models are applied for the calculation of bulk and interfacial thermodynamic properties at various temperatures. The effect of the interface density gradient parameter, kappa , that controls surface tension, is related explicitly with the fluid characteristics, including temperature, molecular diameter, and lattice spacing, through the employment of a proper intermolecular interaction potential. A comprehensive analysis of the interfacial properties reveals some important shortcomings of the LBE methods when central finite difference schemes are employed in the directional derivative calculations and proposes a proper treatment that ensures thermodynamically consistent interfacial properties in accord with the van der Waals theory. The results are found to be in excellent quantitative agreement with exact results of the van der Waals theory preserving all the major features of the interfacial characteristics of vapor-liquid systems of different shapes and sizes. PMID:18851184

Kikkinides, E S; Yiotis, A G; Kainourgiakis, M E; Stubos, A K

2008-09-01

149

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

150

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

NASA Technical Reports Server (NTRS)

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

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

1979-01-01

151

Thermodynamic properties of reaction mixture of air and copper up to 4000 K for 0.05 to 2 MPa

NASA Astrophysics Data System (ADS)

This paper deals with the thermodynamic properties of a system of products of the reaction of air with copper. Unlike the results that have been published up to now, this system is assumed to contain species in the condensed state. The system is supposed to be in thermodynamic equilibrium for temperatures ranging from ambient temperature to 4000 K. The thermodynamic properties are obtained directly from the equilibrium composition and the thermochemical properties of the species. The occurrence of condensed species and their phase transformations considerably affect the composition and thermodynamic properties of the system. The calculated data are in agreement with the published data, which are the results of measurement and observation, but the calculated data cover an incomparably wider region of pressures, temperatures and amounts of copper in the system.

Coufal, O.

2014-06-01

152

Computer programs for thermodynamic and transport properties of hydrogen (tabcode-II)

NASA Technical Reports Server (NTRS)

The thermodynamic and transport properties of para and equilibrium hydrogen have been programmed into a series of computer routines. Input variables are the pair's pressure-temperature and pressure-enthalpy. The programs cover the range from 1 to 5000 psia with temperatures from the triple point to 6000 R or enthalpies from minus 130 BTU/lb to 25,000 BTU/lb. Output variables are enthalpy or temperature, density, entropy, thermal conductivity, viscosity, at constant volume, the heat capacity ratio, and a heat transfer parameter. Property values on the liquid and vapor boundaries are conveniently obtained through two small routines. The programs achieve high speed by using linear interpolation in a grid of precomputed points which define the surface of the property returned.

Roder, H. M.; Mccarty, R. D.; Hall, W. J.

1972-01-01

153

NASA Astrophysics Data System (ADS)

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

Kaplun, Alexander; Meshalkin, Arkadiy

2014-08-01

154

We present the results of a molecular dynamics simulation study of thermodynamic and structural properties upon supercooling of a low concentration sodium chloride solution in TIP4P water and the comparison with the corresponding bulk quantities. We study the isotherms and the isochores for both the aqueous solution and bulk water. The comparison of the phase diagrams shows that thermodynamic properties of the solution are not merely shifted with respect to the bulk. Moreover, from the analysis of the thermodynamic curves, both the spinodal line and the temperatures of maximum density curve can be calculated. The spinodal line appears not to be influenced by the presence of ions at the chosen concentration, while the temperatures of maximum density curve displays both a mild shift in temperature and a shape modification with respect to bulk. Signatures of the presence of a liquid-liquid critical point are found in the aqueous solution. By analysing the water-ion radial distribution functions of the aqueous solution we observe that upon changing density, structural modifications appear close to the spinodal. For low temperatures additional modifications appear also for densities close to that corresponding to a low density configurational energy minimum.

D. Corradini; P. Gallo; M. Rovere

2008-05-16

155

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

156

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

NASA Astrophysics Data System (ADS)

The ability of intermolecular potentials to correctly predict the thermodynamic properties of liquid water at a density of 0.998 g/cm3 for a wide range of temperatures (298-650 K) and pressures (0.1-700 MPa) is investigated. Molecular dynamics simulations are reported for the pressure, thermal pressure coefficient, thermal expansion coefficient, isothermal and adiabatic compressibilities, isobaric and isochoric heat capacities, and Joule-Thomson coefficient of liquid water using the non-polarizable SPC/E and TIP4P/2005 potentials. The results are compared with both experiment data and results obtained from the ab initio-based Matsuoka-Clementi-Yoshimine non-additive (MCYna) [J. Li, Z. Zhou, and R. J. Sadus, J. Chem. Phys. 127, 154509 (2007)] potential, which includes polarization contributions. The data clearly indicate that both the SPC/E and TIP4P/2005 potentials are only in qualitative agreement with experiment, whereas the polarizable MCYna potential predicts some properties within experimental uncertainty. This highlights the importance of polarizability for the accurate prediction of the thermodynamic properties of water, particularly at temperatures beyond 298 K.

Shvab, I.; Sadus, Richard J.

2013-11-01

157

NASA Astrophysics Data System (ADS)

The ground states of the actinides have been matters of considerable controversies, theory often contradicting experiment specifically in regards to the magnetic nature. To resolve this discrepancy, we present here hybrid density functional theory (HYB-DFT) based studies of the structural, magnetic, electronic, and thermodynamic properties of Americium-II. Three configurations of non-magnetic (NM), anti-ferromagnetic (AFM), and ferromagnetic (FM) with and without spin-orbit coupling (SOC) have been considered to determine the ground state of Am-II. We find that the experimental NM ground state configuration is indeed obtained for Am-II at a level of 40% Hartree-Fock (HF) exchange with SOC and the computed structural properties and the electronic density of states are in good agreement with experimental observations. We also find that HBY-DFT with NSOC fails to predict the correct magnetic and electronic structures for Am-II, indicating the importance of the inclusion of SOC for studies of strongly correlated materials. The phonon related thermodynamic properties of Am-II are presented for the NM ground state configuration and the computed heat capacity and entropy are found to be in good agreement with the experimental measurements. The lattice constant, bulk modulus, heat capacity, and entropy of AM-II are predicted to be 9.44 a.u., 21.7 GPa, 24.3 J K mol, and 55.7 J K mol, respectively.

Wang, Jianguang; Ma, Li; Ray, Asok K.

2010-10-01

158

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

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

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

1987-04-01

159

Modeling of Thermodynamic Properties and Phase Equilibria for the Al-Sm Binary System

The thermodynamic properties and associated phase equilibria for the Al-Sm binary system are examined, and experimental results regarding the stability of the Al{sub 3}Sm, Al{sub 11}Sm{sub 3}, and Al{sub 4}Sm intermetallics are incorporated. In the analysis presented, the liquid phase is described using a three-species association model, the intermediate phases are treated as stoichiometric compounds, and the terminal phases are treated as solid solutions with a single sublattice model. In addition to the stable phases, thermodynamic descriptions of the metastable Al{sub 11}Sm{sub 3}-{alpha} and Al{sub 4}Sm-{gamma} phases are employed, and both stable and metastable phase equilibria are presented over the full composition range, providing a general model, which is consistent with available experimental data. Metastable liquidus curves are examined with respect to the observed crystallization behavior of amorphous Al-Sm alloys.

Zhou, S.H.; Napolitano, R.E.

2008-01-25

160

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

161

Critical evaluation and optimization of the thermodynamic properties of liquid tin solutions

NASA Astrophysics Data System (ADS)

Thermodynamic and phase equilibrium data for the following 18 elements in molten Sn were collected and critically evaluated: Al, Ca, Ce, Co, Cr, Cu, Fe, H, Mg, Mo, Na, Ni, O, P, S, Se, Si, and Ti. Binary and ternary data were optimized to give polynomial expressions for the excess Gibbs energies as functions of temperature and composition. For some solutes, the optimized expressions are valid over the entire composition range 0 ? XSn ? 1. In other cases, the expressions apply to Snrich solutions. Solute-solute interaction terms were estimated where data were not available. The optimized Gibbs energy expressions are also presented in the form of interaction parameters, and the equivalence between the polynomial and interaction parameter formalisms is discussed. Through the Kohler equation, or the modified interaction parameter formalism, the thermodynamic properties of the multicomponent solution of 18 elements in Sn can be calculated. The database is suitable for computer storage and manipulation.

Heuzey, Marie-Claude; Pelton, Arthur D.

1996-10-01

162

The instability of some industrially important synthetic azo colorants, including sunset yellow, azorubine, and allura red, toward gum arabic in aqueous solution has been a long-standing problem for the beverage and confectionery industries. Precipitation of these colorants causes the deterioration of product appearance and properties. This work examines the origin and nature of the problem by analysis of the precipitate and thermodynamic studies of gum arabic-colorant interactions using isothermal titration calorimetry (ITC). The presence of divalent alkaline earth metals in gum arabic samples, that is, calcium and magnesium, is shown to be responsible for the precipitation of the azo colorants. There is no direct interaction between gum arabic and the colorant molecules, and the precipitate is formed likely due to the mediation/bridging by the divalent cations. The thermodynamic knowledge gained from the ITC studies, for example, binding affinity, stoichiometry, and enthalpy, enables interpretation of many industrial observations. PMID:17910512

Fang, Yapeng; Al-Assaf, Saphwan; Sakata, Makoto; Phillips, Glyn O; Schultz, Matthias; Monnier, Vivianne

2007-10-31

163

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

164

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

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

1990-12-01

165

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

166

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

167

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

168

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

169

Thermodynamics and Structural Properties of the High Density Gaussian Core Model

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

Atsushi Ikeda; Kunimasa Miyazaki

2011-04-18

170

NASA Astrophysics Data System (ADS)

The formation thermodynamics and migration properties of self-interstitials in aluminum and nickel are investigated as a function of temperature using atomistic simulation techniques and embedded-atom-type interatomic potentials. Molecular dynamics and nonequilibrium free-energy techniques are employed to investigate anharmonic effects on the HO ?100? dumbbell formation properties. The equilibrium concentration of this defect is compared to those of vacancies and divacancies. The results are then analyzed in the framework of the interstitialcy model, according to which very high vibrational formation entropies should be expected for self-interstitials at high temperatures. The kinetics of self-interstitial migration is also investigated using different atomistic techniques, revealing the simultaneous activity of more than one distinct interstitial configuration as the temperature increases.

Ramos de Debiaggi, Susana; de Koning, Maurice; Monti, Ana María

2006-03-01

171

Investigations on uranium carbonitrides. III. Nitrogen vapour pressures and thermodynamic properties

NASA Astrophysics Data System (ADS)

Nitrogen pressures of UN and UC-UN solid solutions have been measured between 1900 and 2300 K by mass spectrometry with the Knudsen effusion technique. For the reaction UN(s) ? U(1) + 0.5 N 2 (g) it has been found by third-law calculations that ?H°(298 K) = 280.7 ±1.3 kJ/mol (67.1 ± 0.3 kcal/mol) . Reliable uranium vapour pressure data could not be obtained. The thermodynamic properties of UN and the UC-UN solid solution will be discussed in relationship with previous investigations in the literature. These properties cannot be described by the regular solution model.

Prins, G.; Cordfunke, E. H. P.; Depaus, R.

1980-04-01

172

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

NASA Astrophysics Data System (ADS)

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

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

1992-02-01

173

[Age-related thermodynamic and mechanical properties of the rat collagen].

The age peculiarities of cross-linking degree, thermodynamic and mechanic properties of rat tail tendon collagen fibres were investigated. It is shown that during the period from 1 to 3 months the melting temperature decreases and the enthalpy difference increases, from 3 to 24 months the melting temperature increases and the enthalpy difference decreases. The strength of fibres increases during the whole life. The maximal relative extension increases during the first 12 months and tends to decrease in after-life. The Young's module in the elastic deformation region decreases during the period from 1 to 3 months, then increases. It is shown tht those changes in fibre properties may be connected with the age dynamics of collagen cross-linking degree observed here: its decreasing during the period from 1 to 3 months and its following continuous increasing in after-life. PMID:3224105

Gasan, A I; Perski?, E E; Maleev, V Ia; Utevskaia, L A

1988-01-01

174

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

175

We study bulk structural and thermodynamic properties of methanol-water solutions via molecular dynamics simulations using novel interaction potentials based on the charge equilibration (fluctuating charge) formalism to explicitly account for molecular polarization at the atomic level. The study uses the TIP4P-FQ potential for water-water interactions, and the CHARMM-based (Chemistry at HARvard Molecular Mechanics) fluctuating charge potential for methanol-methanol and methanol-water interactions. In terms of bulk solution properties, we discuss liquid densities, enthalpies of mixing, dielectric constants, self-diffusion constants, as well as structural properties related to local hydrogen bonding structure as manifested in radial distribution functions and cluster analysis. We further explore the electronic response of water and methanol in the differing local environments established by the interaction of each species predominantly with molecules of the other species. The current force field for the alcohol-water interaction performs reasonably well for most properties, with the greatest deviation from experiment observed for the excess mixing enthalpies, which are predicted to be too favorable. This is qualitatively consistent with the overestimation of the methanol-water gas-phase interaction energy for the lowest-energy conformer (methanol as proton donor). Hydration free energies for methanol in TIP4P-FQ water are predicted to be ?5.6±0.2 kcal/mole, in respectable agreement with the experimental value of ?5.1 kcal/mole. With respect to solution micro-structure, the present cluster analysis suggests that the micro-scale environment for concentrations where select thermodynamic quantities reach extremal values is described by a bi-percolating network structure. PMID:18074339

Zhong, Yang; Warren, G. Lee; Patel, Sandeep

2014-01-01

176

Thermodynamic Properties of the NaNO3 + H2O System

NASA Astrophysics Data System (ADS)

New equations that describe the thermodynamic properties of the NaNO3+H2O system were obtained from previously published measurements for this system. The measured values included in the fitted equations spanned the range of temperatures of approximately 236-425 K for NaNO3(aq) and 16-548 K for NaNO3(cr). New equations and/or values for the following properties are given in the present work: (1) thermal properties of NaNO3(cr) from 0 K to near the lambda transition, 548.6 K, (2) the change in chemical potential for both NaNO3 and H2O in NaNO3(aq) as a function of temperature, and molality, valid from 236 to 425 K, and the molality range of 0 mol?kg-1 to the lesser of the saturation molality or 25 mol?kg-1, and (3) standard-state properties for the aqueous solution process.

Archer, Donald G.

2000-09-01

177

As hydrogen, deuterium and tritium storage materials, a series of investigations of mechanical and thermal properties of titanium hydrides, deuterides and tritides have been performed, however, very limited theoretical studies of thermodynamic properties for them can be found. Based on density-functional theory (DFT) and density-functional perturbation theory (DFPT) we have discussed systematically the hydrogen isotope effects on the thermodynamic properties

C. H. Hu; D. M. Chen; Y. M. Wang; K. Yang

2008-01-01

178

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

179

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

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

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

1993-08-01

180

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

181

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

182

Structural and thermodynamic properties of the model solution containing charged oligomers and the equivalent number of counterions were studied by means of the canonical Monte Carlo simulation technique. The oligomers are represented as (flexible) freely jointed chains or as a linear (rigid) array of charged hard spheres. In accordance with the primitive model of electrolyte solutions, the counterions are modeled as charged hard spheres and the solvent as dielectric continuum. Significant differences in the pair distribution functions, obtained for the rigid (rod-like) and flexible model are found but the differences in thermodynamic properties, such as, enthalpy of dilution and excess chemical potential, are less significant. The results are discussed in light of the experimental data an aqueous polyelectrolyte solutions. The simulations suggest that deviations from the fully extended (rod-like) conformation yield slightly stronger binding of counterions. On the other hand, the flexibility of polyions, even when coupled with the ion-size effects, cannot be blamed for qualitative differences between the theoretical results and experimental data for enthalpy of dilution.

T. Sajevic; J. Rescic; V. Vlachy

2012-02-20

183

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

184

The metastable T-P phase diagram and anomalous thermodynamic properties of supercooled water

NASA Astrophysics Data System (ADS)

The metastable T-P phase diagram and the anomalies of the thermodynamic properties of supercooled water are calculated on the basis of a two-level thermodynamic model. Water is considered as a mixture of two components which differ in atomic configurations and correspond to low-density amorphous (lda) and high-density amorphous (hda) ice. The expression for the Gibbs potential of water is written in the form which is analogous to that of usual regular binary solutions. But this model considers the concentration, c, of the components, as a pressure and temperature-dependent internal parameter. There are only four constants in the expression for the Gibbs potential: the differences in the specific volumes, entropies, and energies of the two components and the mixing energy of the components whose values are ?V0=-3.8 cm3/mol, ?S0=4.225 J/mol, ?E0=1037 J/mol, and U=3824 J/mol, respectively. The lda-hda phase equilibrium line terminates at the critical point, Tcr=230 K and Pcr=0.173 kbar, the second critical point in the phase diagram of water. The anomalous thermal dependence of the specific volume, the heat expansion coefficient, and the specific heat of water calculated for the atmospheric pressure is in a good quantitative agreement with the available experimental data. Thus anomalous properties of supercooled water are well explained by the occurrence of the second critical point close to the atmospheric pressure. The absolute value of parameter c is not crucial for the thermal behavior of properties, instead, the anomalies in water are due to the dependence on pressure and temperature. The parameter c behavior is analyzed in various pressure and temperature ranges around the second critical point. The thermal dependence of parameter c is very weak in the temperature range of 290-350 K at atmospheric pressure. As a consequence, the thermodynamic properties of water behave in this range like those of a normal liquid though water stays a mixture of two components, lda-like and hda-like, in an approximate proportion 2:3.

Ponyatovsky, E. G.; Sinitsyn, V. V.; Pozdnyakova, T. A.

1998-08-01

185

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

NASA Astrophysics Data System (ADS)

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

Wang, Jianguang; Ma, Li; Ray, Asok

2011-03-01

186

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

Donohue, M.D.

1990-09-01

187

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

188

Elastic, Electronic and Thermodynamic Properties of Rh3X(X = Zr, Nb and Ta) Intermetallic Compounds

NASA Astrophysics Data System (ADS)

Structural, electronic, elastic and thermodynamic properties of Rh3X(X = Zr, Nb, Ta) intermetallic compounds are investigated in the framework of density functional theory (DFT). The exchange-correlation (XC) potential is treated with the generalized gradient approximation (GGA) and local density approximation (LDA). The computed ground state properties agree well with the available theoretical and experimental values. The elastic constants are obtained by calculating the total energy versus volume conserving strains using Mehl model. The electronic and bonding properties are discussed from the calculations of band structures (BSs), densities of states and electron charge densities. The volume and bulk modulus at high pressure and temperature are investigated. Additionally, thermodynamic properties such as the heat capacity, thermal expansion and Debye temperature at high pressures and temperatures are also analyzed.

Ould Kada, M.; Seddik, T.; Sayede, A.; Khenata, R.; Bouhemadou, A.; Deligoz, E.; Alahmed, Z. A.; Bin Omran, S.; Rached, D.

2014-11-01

189

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

190

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

191

Thermodynamic properties of non-conformal soft-sphere fluids with effective hard-sphere diameters.

In this work we study a set of soft-sphere systems characterised by a well-defined variation of their softness. These systems represent an extension of the repulsive Lennard-Jones potential widely used in statistical mechanics of fluids. This type of soft spheres is of interest because they represent quite accurately the effective intermolecular repulsion in fluid substances and also because they exhibit interesting properties. The thermodynamics of the soft-sphere fluids is obtained via an effective hard-sphere diameter approach that leads to a compact and accurate equation of state. The virial coefficients of soft spheres are shown to follow quite simple relationships that are incorporated into the equation of state. The approach followed exhibits the rescaling of the density that produces a unique equation for all systems and temperatures. The scaling is carried through to the level of the structure of the fluids. PMID:22158949

Rodríguez-López, Tonalli; del Río, Fernando

2012-01-28

192

We present the bulk thermodynamic properties and phase diagram of strongly interacting matter in an extension of the 3-flavor NJL and PNJL models of QCD. Using a three momentum cut-off scheme, we have extended the multiquark interaction terms up to eight order so that the stability of the vacuum is ensured in these models. We explore the effects of various combinations of the two eight-quark couplings $g_1$ and $g_2$ and present a comparative study between the NJL and PNJL models as well as Lattice QCD data. The main effect of the eight-quark interaction term is to shift the critical end point in the $T-\\mu$ phase diagram to a lower value of $\\mu$ and higher value of $T$, thus bringing them closer to Lattice QCD results.

Abhijit Bhattacharyya; Paramita Deb; Sanjay K. Ghosh; Rajarshi Ray

2010-03-17

193

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

194

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

195

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, polymer-nanoparticle and nanoparticle-nanoparticle interactions strengths have been performed. In this paper, however, we focus the discussion on the results for varying polymer-nanoparticle interactions strengths at different temperatures. By examining the structure and dynamics, we show 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.

Sumpter, Bobby G [ORNL; Goswami, Monojoy [ORNL

2009-01-01

196

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

197

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

198

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

199

NASA Technical Reports Server (NTRS)

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

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

1976-01-01

200

The High Pressure Superconductivity of CaLi2 Compound: The Thermodynamic Properties

NASA Astrophysics Data System (ADS)

The thermodynamic properties of the superconducting state in CaLi2 at 60 GPa have been described in the paper. The numerical analysis has been carried out in the framework of the Eliashberg formalism. It has been shown that: (i) the critical value of the Coulomb pseudopotential is equal to 0.20, which corresponds to the value of 1795 meV for the Coulomb potential; (ii) the critical temperature ( T C ) cannot be correctly calculated by using the Allen-Dynes (AD) formula; (iii) the dimensionless ratios: TCCN (TC )/H2C (0 ), ( C S ( T C )- C N ( T C ))/ C N ( T C ) and 2?(0)/ k B T C take the non-BCS values: 0.157, 1.78 and 3.85, respectively. The symbol C N represents the specific heat in the normal state, C S denotes the specific heat in the superconducting state, H C (0) is the thermodynamic critical field near the temperature of zero Kelvin, and ?(0) is the order parameter; (iv) the ratio of the electron effective mass (m^{star}e) to the electron band mass ( m e ) assumes a high value, in the whole range of the temperature, where the superconducting state exists. The maximum of m^{star}e/me is equal to 2.15 for T= T C .

Szcz??niak, R.; Durajski, A. P.; Pach, P. W.

2013-06-01

201

Thermodynamic properties and phase equilibria in the MnO-SiO{sub 2} system

The Knudsen effusion technique with mass-spectrometric analysis of evaporated products has been applied for determination of thermodynamic properties of solid and liquid phases in the MnO-SiO{sub 2} system. To bring about volatile substances with measurable pressures, reduction reactions of MnO-SiO{sub 2} with molybdenum or niobium were conducted in effusion cells. Activities of the components have been calculated by several methods. The results coincided within the experimental error limits (2--3%). The following equations have been found for Gibbs energies of formation of the compounds MS and M{sub 2}S (M = MnO, S = SiO{sub 2}): {Delta}{sub f}G(MS) = {minus}(10,090 {+-} 616) {minus} (0.81 {+-} 0.42)T, J/mol (1,369 < T < 1,525 K) and {Delta}{sub f}G(M{sub 2}S) = {minus}(11,560 {+-} 588) {minus} (1.30 {+-} 0.38)T, J/mol (1,388 < T < 1,585 K). Temperature and concentration dependencies of {alpha}{sub MnO} and {alpha}{sub SiO{sub 2}} in liquid solutions have been described by the associated-solution model. Formation of associative complexes MnO-SiO{sub 2} and 2MnO-SiO{sub 2} as well as polymer SiO{sub 2} networks was taken into account. Thermodynamic computation of the phase diagram was carried out.

Zaitsev, A.I.; Litvina, A.D.; Tsaplin, A.A.; Mogutnov, B.M. [Inst. of Physical Metallurgy, Moscow (Russian Federation). Lab. of Thermodynamic Investigations

1995-08-01

202

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

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

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

2013-12-28

203

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

204

NASA Astrophysics Data System (ADS)

A calculational approach for the design of new complex materials for hydrogen storage with favorable thermodynamic stability and enhanced diffusion kinetics is presented. By combining density functional theory (DFT) calculations on stable crystal structures and local coordination models with database methods, we perform large-scale screening studies to determine a number of potential alloys/mixtures with favorable thermodynamic stabilities and identify simple descriptors for subsequent materials prediction. Predictors for the kinetic properties of the materials are derived from combining materials screening with path techniques and harmonic transition state theory (TST) to indentify materials parameters, e.g. the hydrogen binding energy, which correlate with the macroscopic diffusion rates. These predictors are then used to design new alloy/mixture compositions and ratios to favor structures with optimal diffusion kinetics. We present results from binary and ternary alkali-transition metal borohydrides and Perovskite based hydrogen permeable membranes, as well as results from studies of binary and mixed metal ammines. Results from the modeling of pathways and rates of dynamical processes involved in the ab-/desorption mechanisms will also be presented and compared to quasi elastic neutron scattering data.

Hummelshoej, Jens

2011-03-01

205

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

NASA Astrophysics Data System (ADS)

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

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

2011-01-01

206

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

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

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

1991-04-01

207

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

Mittal, Shruti; Singh, Laishram Rajendrakumar

2013-01-01

208

High-precision thermodynamic and critical properties from tensor renormalization-group flows.

The recently developed tensor renormalization-group (TRG) method provides a highly precise technique for deriving thermodynamic and critical properties of lattice Hamiltonians. The TRG is a local coarse-graining transformation, with the elements of the tensor at each lattice site playing the part of the interactions that undergo the renormalization-group flows. These tensor flows are directly related to the phase diagram structure of the infinite system, with each phase flowing to a distinct surface of fixed points. Fixed-point analysis and summation along the flows give the critical exponents, as well as thermodynamic functions along the entire temperature range. Thus, for the ferromagnetic triangular lattice Ising model, the free energy is calculated to better than 10(-5) along the entire temperature range. Unlike previous position-space renormalization-group methods, the truncation (of the tensor index range D) in this general method converges under straightforward and systematic improvements. Our best results are easily obtained with D=24, corresponding to 4624-dimensional renormalization-group flows. PMID:18351815

Hinczewski, Michael; Berker, A Nihat

2008-01-01

209

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

210

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

211

NASA Astrophysics Data System (ADS)

First principles calculations are performed to investigate the structural, electronic, elastic, and thermodynamic properties of the less known PrN compound for various space groups: NaCl(Fm3m(2 2 5)), CsCl(Pm3m (2 2 1)), ZB(F43m(2 1 6)), Wc(P6m2(1 8 7)), and CuAu (P4/mmm (1 2 3)). Our calculation indicates that the NaCl type structure is energetically more stable than the other phases. The calculated lattice parameters are consisted with available theoretical and experimental results. Our band structure calculations show that PrN possessess a semi-metallic character for both with and without spin polarized (SP) cases. The calculated elastic constants satisfy the mechanical stability conditions at all considered pressures and the present values are significantly higher than those of the previous results. The related mechanical properties such as Zener anisotropy factor ( A), Poisson’s ratio ( ?), Young’s modulus ( E), and shear modulus ( C) are also computed for NaCl structure. The temperature/pressure-dependent behaviours of bulk modulus, Debye temperature, heat capacity, thermal expansion coeffient, and V/ V0 ratio estimated within the quasi-harmonic Debye model.

Kocak, B.; Ciftci, Y. O.; Colakoglu, K.; Deligoz, E.

2010-10-01

212

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

213

Ab initio studies of thermodynamic and electronic properties of phosphorene nanoribbons

NASA Astrophysics Data System (ADS)

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

Ramasubramaniam, Ashwin; Muniz, Andre R.

2014-08-01

214

Structural and thermodynamic properties of Fe1.12Te with multiple phase transitions

NASA Astrophysics Data System (ADS)

The parent compound of iron chalcogenide superconductors, Fe1+yTe, with a range of excess Fe concentrations exhibits intriguing structural and magnetic properties. Here, the interplay of magnetic and structural properties of Fe1.12Te single crystals have been probed by low-temperature synchrotron X-ray powder diffraction, magnetization, and specific heat measurements. Thermodynamic measurements reveal two distinct phase transitions, considered unique to samples possessing excess Fe content in the range of 0.11?y?0.13. On cooling, an antiferromagnetic transition, TN?57 K is observed. A closer examination of powder diffraction data suggests that the transition at TN is not purely magnetic, but accompanied by the commencement of a structural phase transition from tetragonal to orthorhombic symmetry. This is followed by a second prominent first-order structural transition at TS with TS

Cherian, Dona; Rößler, S.; Koz, C.; Tsirlin, A. A.; Schwarz, U.; Wirth, S.; Elizabeth, Suja

2014-03-01

215

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

216

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

217

ThermoML is an Extensible Markup Language (XML)-based new\\u000d\\u000aIUPAC standard for storage and exchange of experimental, predicted, and critically\\u000d\\u000aevaluated thermophysical and thermochemical property data. The basic principles,\\u000d\\u000ascope, and description of all structural elements of ThermoML are discussed.\\u000d\\u000aThermoML covers essentially all thermodynamic and transport property\\u000d\\u000adata (more than 120 properties) for pure compounds, multicomponent mixtures,\\u000d\\u000aand chemical reactions

MICHAEL FRENKEL; ROBERT D. CHIRICO; VLADIMIR DIKY; QIAN DONG; KENNETH N. MARSH; JOHN H. DYMOND; WILLIAM A. WAKEHAM; STEPHEN E. STEIN; ERICH KÖNIGSBERGER; ANTHONY R. H. GOODWIN

2006-01-01

218

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

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

2009-10-01

219

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

220

Thermodynamic and mechanical properties of EPON 862 with curing agent DETDA by molecular simulation

Fully atomistic molecular dynamics (MD) simulations were used to predict the properties of EPON 862 cross-linked with curing agent DETDA, a potentially useful epoxy resin for future applications of nanocomposites. The properties of interest were...

Tack, Jeremy Lee

2009-05-15

221

Interfacial, thermodynamic, and performance properties of aqueous binary mixtures of ?-sulfonato palmitic acid methyl ester,\\u000a C14H29CH(SO3Na)COOCH3(PES), and hexaoxyethylene monododecyl ether, CH3(CH2)11(OCH2CH2)6OH (C12E6), were investigated with tensiometric, conductometric, fluorimetric, and viscometric techniques. The critical micelle concentration\\u000a (CMC), maximum surface excess, minimum area per molecule of surfactant at the air\\/water interface, and the thermodynamics\\u000a of micellization and adsorption were determined. The CMC

Sandeep R. Patil; Tsuneharu Mukaiyama; Animesh Kumar Rakshit

2004-01-01

222

NASA Astrophysics Data System (ADS)

Basing on the Schiff effective interionic potential that has an oscillatory character and the correlative method of unsymmetrized self-consistent field (CUSF) that enables one to take into account the strong anharmonicity of the crystal lattice vibrations, we have calculated a complete set of equilibrium thermodynamic properties of solid sodium as functions of pressure and temperature: the lattice parameter, the elastic moduli, the thermal expansion coefficient, the Grüneisen parameter and the isochoric and isobaric heat capacities. Our results are compared with available experimental data. We also discuss the thermodynamic stability of the BCC lattice, the mechanism of its loss and its change under pressure.

Zubov, V. I.; Caparica, A. A.

223

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

2014-08-14

224

JavaScript Programs To Calculate Thermodynamic Properties Using Cubic Equations of State

NASA Astrophysics Data System (ADS)

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

Barrie, Patrick J.

2005-06-01

225

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

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

2002-07-18

226

Structural and Thermodynamic Properties of TiAl intermetallics under High Pressure

NASA Astrophysics Data System (ADS)

The structural and thermodynamic properties of TiAl intermetallics under high pressure have been investigated by ab initio plane-wave pseudopotential density functional theory method. It is found that the ratio of lattice parameter c to a keeps almost constant with a value of 1.02 under the pressure from 0 to 20 GPa, which agrees well with the experimental results. With the pressure increasing from 20 to 45 GPa the values of c/a decrease almost linearly from 1.02 to 0.99. These calculated results indicate under low pressure the variation rate for a-axis is almost the same to that for c-axis, but under higher pressure the variation for a-axis is smaller than along c-axis. Through the quasi-harmonic Debye model, the equation of state (EOS) of TiAl intermetallics, as well as the thermal expansion and heat capacity at various pressures and temperatures are also studied.

Li, Xu-Sheng; Wang, Hai-Yan; Li, Chang-Yun; Mi, Guo-Fa; Hu, Qian-Ku

2012-01-01

227

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

228

Thermodynamic Properties of Supported and Embedded Metallic Nanocrystals: Gold on/in SiO2

We report on the calculations of the cohesive energy, melting temperature and vacancy formation energy for Au nanocrystals with different size supported on and embedded in SiO2. The calculations are performed crossing our previous data on the surface free energy of the supported and embedded nanocrystals with the theoretical surface-area-difference model developed by W. H. Qi for the description of the size-dependent thermodynamics properties of low-dimensional solid-state systems. Such calculations are employed as a function of the nanocrystals size and surface energy. For nanocrystals supported on SiO2, as results of the calculations, we obtain, for a fixed nanocrystal size, an almost constant cohesive energy, melting temperature and vacancy formation energy as a function of their surface energy; instead, for those embedded in SiO2, they decreases when the nanocrystal surface free energy increases. Furthermore, the cohesive energy, melting temperature and vacancy formation energy increase when the nanocrystal size increases: for the nanocrystals on SiO2, they tend to the values of the bulk Au; for the nanocrystals in SiO2 in correspondence to sufficiently small values of their surface energy, they are greater than the bulk values. In the case of the melting temperature, this phenomenon corresponds to the experimentally well-known superheating process. PMID:21752308

2008-01-01

229

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

230

NASA Astrophysics Data System (ADS)

The thermodynamic properties and the phase transition of ThO2 from the cubic structure to the orthorhombic structure are investigated using the first-principles projector-augmented wave method. The vibrational contribution to Helmholtz free energy is evaluated from the first-principles phonon calculations. The anharmonic contribution to quasi-harmonic free energy is accounted for by using an effective method (2010 Phys. Rev. B 81 172301). The results reveal that at ambient temperature, the phase transition from the cubic phase to the orthorhombic phase occurs at 26.45 GPa, which is consistent with the experimental and theoretical data. With increasing temperature, the transition pressure decreases almost linearly. By comparing the experimental results with the calculation results, it is shown that the thermodynamic properties of ThO2 at high temperature improve substantially after including the anharmonic correction to quasi-harmonic free energy.

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

2014-01-01

231

We analyze thermodynamics of water samples confined in nanopores and prove that although the freezing temperature can be dramatically lower, the suppression of the ice nucleation leading to the freezing temperature depression is a truly macroscopic effect rather than a consequence of microscopic interactions. The freezing transition itself is a truly collective phenomenon described by a macroscopic order parameter (the nearly homogeneous density of the liquid within the pore away from the pores wall) exactly in the same way as in the bulk liquid. The thermodynamics properties of the confined and the bulk liquid can be described by macroscopic thermodynamics and be readily related to each other simply by proper inclusion of the additional Laplace pressure exerted by the solid-liquid boundary.

P. O. Fedichev; L. I. Menshikov

2012-06-15

232

A brief review is presented for the pre-history and discovery of fullerenes. Single-site potentials with parameters proposed by Girifalco was used to describe the interactions of the fullerene molecules C70 and C96. We present theoretical model for calculating the thermodynamic properties of liquid for both C70 and C96 by means of an improved equation of state (EOS), in which the

M. Bahaa Khedr; S. M. Osman

2011-01-01

233

Using first-principles calculations, the elastic constants, thermodynamic properties and structural phase transition of NbN under high pressure are investigated by means of the pseudopotential plane-waves method, in addition to the effect of metallic bonding on its hardness. Three candidate structures are chosen to investigate NbN, namely, rocksalt (NaCl), NiAs and WC types. On the basis of the third-order Birch-Murnaghan equation

Zhen-Hua Wang; Xiao-Yu Kuang; Xiao-Fen Huang; Peng Lu; Ai-Jie Mao

2010-01-01

234

NASA Astrophysics Data System (ADS)

The scarcity and sustainability of energy sources have always been a concern while seeking for alternative fuels. Biofuels have drawn the attention of various researchers due to their abundancy and renewability. Understanding the physical and chemical properties of these molecules is essential to determining their potential as alternative fuels or fuel additives. In this work, the properties of these molecules are predicted through methods developed from quantum mechanics and statistical mechanics theories. The heats of formations are calculated with the Gaussian program and combined with the Benson group contribution method to predict the Benson parameters of unknown functional groups in a molecule. The methods developed are used to expand the Benson database and improve the practicability of the group contribution method. The heats of formations are also used to predict and correlate heat capacities across a range of temperatures and energy densities in this study.

Chai, Weisin

235

NASA Astrophysics Data System (ADS)

The high-pressure (temperature) elastic and thermodynamic properties of UO2 and UN2 is presented. For cubic UO2 and UN2, 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 UO2 and UN2 is mechanically stiffened, thermally softened, and ductile (brittle) in nature as inferred from the pressure (temperature) dependent elastic constants behavior. To our knowledge this is the first quantitative theoretical prediction of the pressure and temperature dependence of elastic, thermal and thermodynamical properties of UO2 and UN2 and still awaits experimental confirmation.

Varshney, Dinesh; Shriya, Swarna

2013-09-01

236

NASA Astrophysics Data System (ADS)

The structural, magnetic, and thermodynamic properties of the Au(001)/Fe(001) interface are investigated as a function of the in-plane strain using density functional theory calculations for two different Au slab thicknesses: 2 and 8 monolayers. The structural and magnetic properties are analyzed by studying the interlayer distance in the direction perpendicular to the interface and the atomic magnetic moments of Fe atoms, as a function of the in-plane strain. The structural study evidences both the bulk elastic and surface and interface contributions. The atomic magnetic moments of Fe atoms are essentially dependent on their local environment (number and distance of the Fe first neighbors). Thermodynamic properties of the interface are investigated through the calculation of the interface energy and interface stress. These thermodynamic quantities are subsequently used in a simple model to evaluate the strain state of an ideal spherical symmetric Fe@Au core-shell nanoparticle. The surface elastic effects are found to be significant for nanoparticles of diameter smaller than ˜20 nm and predominant for diameters smaller than ˜2.3 nm. Interface elastic effects are weaker than surface elastic effects but can not be neglected for very small nanoparticles (?1.9 nm) or for thin shells.

Benoit, Magali; Combe, Nicolas; Ponchet, Anne; Morillo, Joseph; Casanove, Marie-José

2014-10-01

237

EFFECT OF HEATING RATE ON THE THERMODYNAMIC PROPERTIES OF PULVERIZED COAL

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

Ramanathan Sampath

2000-01-01

238

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

239

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

240

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

NASA Astrophysics Data System (ADS)

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

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

2014-10-01

241

NASA Astrophysics Data System (ADS)

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

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

2014-10-01

242

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

243

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

244

NASA Astrophysics Data System (ADS)

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

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

2011-12-01

245

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

246

Cationic gemini surfactant homologues alkanediyl-?,?-bis(dodecyldiethylammonium bromide), [C(12)H(25)(CH(3)CH(2))(2)N(CH(2))(S)N(CH(2)CH(3))(2)C(12)H(25)]Br(2) (where S=2, 4, 6, 8, 10, 12, 16, 20), referred to as C(12)C(S)C(12)(Et) were synthesized systematically. This paper focused on various properties of the above gemini surfactants in order to give a full understanding of this series of surfactants. The following points are covered: (1) surface properties, which include (i) effect of the spacer carbon number on the general properties and (ii) the effect of added NaBr on the general surface properties; (2) aggregation behavior in bulk solution, including (i) morphologies of above gemini surfactants classed as having short spacers, middle-length spacers and long spacers and (ii) superior vesicle stability against high NaBr concentration for the long spacer gemini surfactants; (3) thermodynamic properties during micellization and the effect of spacer carbon number on them; and (4) perspectives for the further use and application of these compounds. PMID:22513166

Lu, Ting; Lan, Yuru; Liu, Chenjiang; Huang, Jianbin; Wang, Yilin

2012-07-01

247

Thermodynamic phase diagram and electronic properties of Co2VAl<001> film: A first-principles study

NASA Astrophysics Data System (ADS)

The structural, magnetic and electronic properties of Co2VAl in both states of bulk and <001> thin film are studied as well as the Curie temperature of the first and thermodynamic phase diagram of the second form. According to the results from generalized gradient approximation+U (GGA+U) approximation, the ferromagnetic (FM) in bulk phase is of more stability than anti-ferromagnetic (AFM) and nonmagnetic (NM) ones and appear with a relatively high Curie temperature and a 100% spin polarization at the Fermi level. In the case of the thin film, the Co-Co and V-Al terminations are both thermodynamically stable with a half-metallic performance at surface and a spin-polarization at Fermi level as well. Notably, the V-Al termination is a 100% spin-polarization half-metal.

Khosravi, Heidar; Boochani, Arash; Khodadadi, Jabbar; Solaymani, Shahram; Sartipi, Elmira

2014-06-01

248

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

249

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

250

On thermodynamic and dielectric properties of PbHPO4 and PbHAsO4 crystals

NASA Astrophysics Data System (ADS)

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

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

2014-11-01

251

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

252

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

253

Thermodynamic Properties of o-Xylene, m-Xylene, p-Xylene, and Ethylbenzene

NASA Astrophysics Data System (ADS)

Equations of state for the xylene isomers (o-xylene, m-xylene, and p-xylene) and ethylbenzene have been developed with the use of the Helmholtz energy as the fundamental property with independent variables of density and temperature. The general uncertainties of the equations of state are 0.5% in vapor pressure above the normal boiling point, and increase as the temperature decreases due to a lack of experimental data. The uncertainties in density range from 0.1% in the liquid region to 1.0% elsewhere (the critical and vapor-phase regions). The uncertainties in properties related to energy (such as heat capacity and sound speed) are estimated to be 1.0%. In the critical region, the uncertainties are higher for all properties. The behavior of the equations of state is reasonable within the region of validity and at higher and lower temperatures and pressures. Detailed analyses between the equations and experimental data are reported.

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

2012-06-01

254

Structure and thermodynamic properties of liquid transition metals: An embedded-atom-method approach

We have obtained the volume term and effective pair potentials for liquid transition metals using the embedded-atom method (EAM). The EAM embedding functions are fitted to bulk solid-state properties: the experimental Voigt average bulk and shear moduli and sublimation energies. The same fitting procedure is used for all the transition metals. This potential is used in conjunction with the variational

G. M. Bhuiyan; M. Silbert; M. J. Stott

1996-01-01

255

NASA Astrophysics Data System (ADS)

We calculated the phase diagram of {AlPO}4 up to 15 GPa and 2,000 K and investigated the thermodynamic properties of the high-pressure phases. The investigated phases include the berlinite, moganite-like, {AlVO}4, P2_1/c , and {CrVO}4 phases . The computational methods used include density functional theory, density functional perturbation theory, and the quasiharmonic approximation. The investigated thermodynamic properties include the thermal equation of state, isothermal bulk modulus, thermal expansivity, and heat capacity. With increasing pressure, the ambient phase berlinite transforms to the moganite-like phase, and then to the {AlVO}4 and P2_1/c phases, and further to the {CrVO}4 phase. The stability fields of the {AlVO}4 and P2_1/c phases are similar in pressure but different in temperature, as the {AlVO}4 phase is stable at low temperatures, whereas the P2_1/c phase is stable at high temperatures. All of the phase relationships agree well with those obtained by quench experiments, and they support the stabilities of the moganite-like, {AlVO}4 , and P2_1/c phases, which were not observed in room-temperature compression experiments.

Wang, Riping; Kanzaki, Masami

2014-07-01

256

NASA Astrophysics Data System (ADS)

Fundamental investigations were carried out to find out the admixing influence of CF3I to CO2. Firstly, thermodynamic properties at 0.1MPa were derived in a temperature range of 300-30,000K for various CF3I-concentrations XCF3I. Secondly, from the thermodynamic properties, a temperature-reduction factor was determined as a function of the temperature for different XCF3I. This determination led to the suggestion that admixture of CF3I to CO2 at XCF3I above 0.9 can produce a rapid effect on decay in the temperature of an extinguishing arc. Finally, the principal particles present after an arc extinction were obtained in consideration of the phase transformation of iodine molecules at 0.1MPa. For instance, the principal particles proved to be CO2, CF4 and CO in the gaseous phase and I2 in the solid phase for XCF3I of 0.01-0.94.

Yokomizu, Yasunobu; Ochiai, Ryusuke; Matsumura, Toshiro

257

NASA Astrophysics Data System (ADS)

The lattice dynamic, elastic, superconducting, and thermodynamic properties of the high-pressure cubic metallic phase AlH3 are studied within density function theory. The calculated elastic modulus and phonon dispersion curves at various pressures indicate that the cubic phase is both mechanically and dynamically stable above 73 GPa. The superconducting transition temperature was calculated using Allen-Dynes modification of the McMillan formula based on the Bardeen-Cooper-Schrieffer theory. It is found that Tc approaches a linear decrease in the low pressure range at the rate dTC/dP ?-0.22 K/GPa but gradually decreases exponentially at higher pressure, and then it becomes 0 K upon further compression. The calculations indicate that Tc is about 2.042 K at 110 GPa, in agreement with experimental results. The soft phonon modes, especially the lowest acoustic mode, contribute almost 79% to the total electron-phonon coupling parameter s? for cubic AlH3 at 73 GPa. However, they disappear gradually with increasing pressure, showing a responsibility for the variation of Tc. The thermodynamic properties of cubic AlH3, such as the dependence of thermal expansion coefficient ?V on pressure and temperature, the specific heat capacity CP, as well as the electronic specific heat coefficient Cel, were also investigated by the quasi-harmonic approximation theory.

Wei, Yong-Kai; Ge, Ni-Na; Ji, Guang-Fu; Chen, Xiang-Rong; Cai, Ling-Cang; Zhou, Su-Qin; Wei, Dong-Qing

2013-09-01

258

NASA Astrophysics Data System (ADS)

Using first-principles calculations, the elastic constants, thermodynamic properties and structural phase transition of NbN under high pressure are investigated by means of the pseudopotential plane-waves method, in addition to the effect of metallic bonding on its hardness. Three candidate structures are chosen to investigate NbN, namely, rocksalt (NaCl), NiAs and WC types. On the basis of the third-order Birch-Murnaghan equation of states, the transition pressure Pt (Pt=200.64 GPa) between the WC phase and the NaCl phase of NbN is predicted for the first time. Elastic constants, formation enthalpies, shear modulus, Young's modulus, and Poisson's ratio of NbN are derived. The calculated results are found to be in good agreement with the available experimental data and theoretical values. According to the quasi-harmonic Debye model, the Debye temperature under high pressure is derived from the average sound velocity. Moreover, the effect of metallic bonding on the hardness of NbN is investigated and the hardness shows a gradual decrease rather than increase under compression. This is a quantitative investigation on the structural and thermodynamic properties of NbN, and it still awaits experimental confirmation.

Wang, Zhen-Hua; Kuang, Xiao-Yu; Huang, Xiao-Fen; Lu, Peng; Mao, Ai-Jie

2010-12-01

259

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

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

Hindler, Michael; Guo, Zhongnan; Mikula, Adolf

2012-01-01

260

The electronic structure, absorption spectra, and thermodynamic properties of crystalline styphnic acid and its metal salts (potassium, barium, and lead styphnates) have been studied using density functional theory within the local density approximation. The results show that the metal states affect the electronic structure of styphnic acid by modifying the density of states of the O atoms of hydroxyls. The C-O bond fission may be favorable in the decomposition of styphnic acid and its metal salts. The absorption spectra of the four crystals display a few strong bands in the fundamental absorption region. Compared with styphnic acid, potassium, barium, and lead styphnates decrease its enthalpy, entropy, free energy, and heat capacity as the temperature increases. However, the differences of the thermodynamic functions between each metal salt are very small. As the temperature increases, the decomposition reactions of the four crystals are more and more favorable thermodynamically. It is also found that there is a relationship between the band gap and impact sensitivity for the four crystals. PMID:19572665

Zhu, Weihua; Xiao, Heming

2009-07-30

261

NASA Astrophysics Data System (ADS)

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

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

2014-12-01

262

The adsorption of water on porous silica surfaces at 300 K, has been qualitatively reproduced by Grand Canonical Monte Carlo simulations (GCMC) without any adjustment of adsorbate/substrate potential parameter. The simulated adsorption isotherm and isosteric differential enthalpy of adsorption compare well to experimental data for Vycor, showing the ability of the model in describing hydrophilic properties of silica surfaces. The analysis of fluid structure in the mesoporous glass gives detailed insights into confinement and disorder effects on water adsorbed on the hydrophilic surface of a porous glass. It is shown that hydrophilic properties are not simply related to surface hydroxyl density but are also related to local structure of the silica surface. PMID:15011019

Puibasset, J; Pellenq, R J-M

2003-11-01

263

Ab initio calculation of lattice dynamics and thermodynamic properties of beryllium

NASA Astrophysics Data System (ADS)

We investigate the phase transition, elastic constants, phonon dispersion curves, and thermal properties of beryllium (Be) at high pressures and high temperatures using density functional theory. By comparing the Gibbs free energy, in the quasiharmonic approximation (QHA), of hexagonal-closed-packed (hcp) with those of the face-centered cubic (fcc) and body-centered-cubic (bcc) we find that the hcp Be is stable up to 390 GPa, and then transforms to the bcc Be. The calculated phonon dispersion curves are in excellent agreement with experiments. Under compression, the phonon dispersion curves of hcp Be do not show any anomaly or instability. At low pressure the phonon dispersion of bcc Be display imaginary along ?-N in the T1 branches. Within the quasiharmonic approximation, we predict the thermal equation of state and other properties including the thermal expansion coefficient, Hugoniot curves, heat capacity, Grüneisen parameter, and Debye temperature.

Luo, Fen; Cai, Ling-Cang; Chen, Xiang-Rong; Jing, Fu-Qian; Alfè, Dario

2012-03-01

264

THE ELASTIC AND THERMODYNAMIC PROPERTIES OF Lu DOPED ScVO3

NASA Astrophysics Data System (ADS)

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

Parveen, Atahar; Gaur, N. K.

2012-12-01

265

Universal Thermodynamic and Spin Transport Properties of Strongly Interacting Fermi Gases

NASA Astrophysics Data System (ADS)

We perform a high-precision measurement of the equation of state of a Fermi gas with unitarity limited interactions by in- situ imaging of ultracold ^6Li at a Feshbach resonance. We observe the superfluid phase transition in the chemical potential, entropy, compressibility and heat capacity, and provide a new value of the Bertsch parameter ?S. In a separate set of measurements, we determine the spin transport properties of strongly interacting Fermi gases by spatially separating the two spin components and allowing the system to relax to equilibrium (arXiv:1101.0780v1). We find that the spin diffusivity approaches a universal minimum value set by the ratio of Planck's constant to the atomic mass, and determine the spin susceptibility from spin transport properties.

Sommer, Ariel; Ku, Mark; Cheuk, Lawrence; Zwierlein, Martin W.

2011-06-01

266

Based on relevant material property data and previous model formulations, a magnetothermodynamic property map for gadolinium gallium garnet (Gd{sub 3}Ga{sub 5}O{sub 12}) was adapted for refrigeration cycle analysis in the temperature range 4-40 K and the magnetic field range 0-6 T. Employing methods similar to those previously developed for other materials and temperature ranges, assessments of limitations and relative performance were made for Carnot, ideal regenerative, and pseudo-constant field regenerative cycles. It was found that although Carnot cycle limitations on available temperature lift for gadolinium gallium garnet are not as severe as the limitations for materials previously examined, considerable improvement in cooling capacity and temperature lift combinations can be achieved by using regenerative cycles if serious loss mechanisms are avoided.

Murphy, R.W.

1994-12-01

267

Atomistic molecular dynamics simulations were performed on a low-molecular-weight nitroplasticized Estane® mixture representative of the binder used in PBX-9501. Pressure-volume-temperature (PVT) behavior over a wide range of pressures and temperatures above the order-disorder temperature (ODT) of Estane was determined and represented with the empirical Tait and Sun equations of state. The effect of temperature, pressure, and plasticization on transport properties

H. Davande; D. Bedrov; G. D. Smith

2008-01-01

268

NASA Astrophysics Data System (ADS)

The correlative unsymmetrized self-consistent field method is used to study surface properties of the two-dimensional model of an anharmonic crystal with square lattice having various Miller indices. The lattice relaxation, the amplitudes of atomic vibrations and the thermodynamic surface functions are calculated. The typical nonsingular and vicinal surfaces are considered. The dependence of thermodynamic surface functions on the surface orientation is obtained.

Zubov, V. I.; Banyeretse, F.

269

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

NASA Astrophysics Data System (ADS)

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

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

2014-09-01

270

The Helmholtz function for pure isobutane from a recent correlation has been converted to a dimensionless form and a pressure-enthalpy chart based on this function has been generated by computer. A Helmholtz function for mixtures of isobutane and isopentane has been formed based upon the dimensionless isobutane Helmholtz function as the reference fluid by means of an extended corresponding-states principle. Scarce literature data for saturation properties of isopentane, and new data for its vapor pressure and for the critical line of the mixture were used. The accuracy of the surface was checked by comparing with literature enthalpy data and with new VLE data for the mixture. Tables of thermodynamic properties have been generated from this Helmholtz function for the 0.1 mole fraction isopentane-in-isobutane mixture in the single-phase region and on the dew- and bubble-point curves, together with properties of the coexisting phase. A pressure-enthalpy chart for this mixture has also been generated.

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

1984-07-01

271

We study the applicability of the semiclassical Feynman and Hibbs (FH) (second-order or fourth-order) effective potentials to the description of the thermodynamic properties of quantum fluids at finite temperatures. First, we use path integral Monte Carlo (PIMC) simulations to estimate the thermodynamic/static properties of our model quantum fluid, i.e. low-density 4He at 10 K. With PIMC we obtain the experimental equation of state, the single-particle mean kinetic energy, the single-particle density matrix and the single-particle momentum distribution of this system at low densities. We show that our PIMC results are in full agreement with experimental data obtained with deep inelastic neutron scattering at high momentum transfers (D. Colognesi, C. Andreani, R. Senesi, Europhys. Lett., 2000, 50, 202). As expected, in this region of the 4He phase diagram, quantum effects modify the width of the single-particle momentum distribution but do not alter its Gaussian shape. Knowing the exact values of density, pressure and single-particle mean kinetic energy for our model quantum fluid, we investigate the limitations of the semiclassical FH effective potentials. We show that commonly used 'short-time' approximations to the high-temperature density matrix due to Feynman and Hibbs can only be applied in a very limited range of the 4He phase diagram. We found that FH effective potentials reproduce the experimental densities of 4He at 10 K for Lambda/a < 0.45 (Lambda = 2.73 A denotes the thermal de Broglie wavelength, a = rho(-1/3) is the mean nearest-neighbor distance in the fluid and rho denotes fluid density). Moreover, semiclassical FH effective potentials are able to correctly predict the single-particle mean kinetic energy of 4He at 10 K in a very limited range of fluid densities, i.e.Lambda/a < 0.17. We show that the ad hoc application of the semiclassical FH effective potentials for the calculation of the thermodynamic properties of dense liquid-like para-hydrogen (para-H2) adsorbed in nanoporous materials below 72 K is questionable. PMID:19812839

Kowalczyk, Piotr; Brualla, Lorenzo; Gauden, Piotr A; Terzyk, Artur P

2009-10-28

272

The present project is on a new software environment for thermodynamic considerations based on object-oriented programming styles. At its heart is a graphical modeling language for interactive definition of thermodynamic problems. The modeling language is based on seven modeling elements that are linked to express cause-and-effect relationships. The language can generate problem definitions (“models”) graphically (i) that capture the user's

Jens Uhlemann

1995-01-01

273

Thermodynamic properties of charged ideal spin-1 bosons in a trap under a magnetic field

NASA Astrophysics Data System (ADS)

Thermodynamics of trapped charged ideal spin-1 bosons confined in a magnetic field are investigated within semi-classical approximation and truncated-summation approach. It is shown that the critical temperature increases slightly at the first, and then decreases slowly with increasing external magnetic field. Charged spin-1 Bose gases present a crossover from diamagnetism to paramagnetism as the spin factor increases. Charged spin-1 Bose gases exhibit distinct thermodynamic behaviors from the spinless case.

Li, Yushan

2014-10-01

274

The structure of dehydrated schoepite, ?-UO2(OH)2, was investigated using computational approaches that go beyond standard density functional theory and include van der Waals dispersion corrections (DFT-D). Thermal properties of ?-UO2(OH)2, were also obtained from phonon frequencies calculated with density functional perturbation theory (DFPT) including van der Waals dispersion corrections. While the isobaric heat capacity computed from first-principles reproduces available calorimetric data to within 5% up to 500 K, some entropy estimates based on calorimetric measurements for UO3·0.85H2O were found to overestimate by up to 23% the values computed in this study. PMID:25318965

Weck, Philippe F; Kim, Eunja

2014-10-28

275

Prediction of thermodynamic properties of natural gases using Monte Carlo simulations

NASA Astrophysics Data System (ADS)

In this paper an applications of Monte-Carlo simulation in natural gas production is presented. We have investigated model of natural gas of the Bavlinskoye deposit located in the southeast of the Republic of Tatarstan. For this natural gas and for pure methane and ethane gases we have obtained thermal expansivity, isothermal compressibility, compressibility factor, heat capacity, Joule-Thompson coefficient and density at pressures up to 110 MPa at deposit temperature (463 K). Also we have obtained vapor pressures and liquid-vapor phase diagrams. Simulated properties for methane are in a good agreement with available experimental data.

Piyanzina, I.; Lysogorskiy, Yu; Nedopekin, O.

2012-11-01

276

NASA Astrophysics Data System (ADS)

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

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

2014-10-01

277

NASA Technical Reports Server (NTRS)

Procedures for calculating the mass flow rate of methane and natural gas through nozzles are given, along with the FORTRAN 4 subroutines used to make these calculations. Three sets of independent variables are permitted in these routines. In addition to the plenum pressure and temperature, the third independent variable is either nozzle exit pressure, Mach number, or temperature. A critical-flow factor that becomes a convenient means for determining the mass flow rate of methane through critical-flow nozzles is tabulated. Other tables are included for nozzle throat velocity and critical pressure, density, and temperature ratios, along with some thermodynamic properties of methane, including compressibility factor, enthalpy, entropy, specific heat, specific-heat ratio, and speed of sound. These tabulations cover a temperature range from 120 to 600 K and pressures to 3 million N/sq m.

Johnson, R. C.

1972-01-01

278

Electronic structure and thermodynamic properties of CeRh(2)Sn(4) and LaRh(2)Sn(4).

The electronic structure and thermodynamic properties of CeRh(2)Sn(4) and LaRh(2)Sn(4) are reported. The crystal structure of CeRh(2)Sn(4) has been determined from single-crystal diffraction experiments. The Ce core-level x-ray photoemission spectra and Ce L(III) x-ray absorption data unanimously indicate a stable trivalent state of the Ce ions in CeRh(2)Sn(4), consistent with static magnetic susceptibility. Thermodynamic measurements for CeRh(2)Sn(4) show a noncollinear antiferromagnetic ordering with a ferromagnetic component at T(N)?3.2 K. There is evidence for spin fluctuations in both CeRh(2)Sn(4) and LaRh(2)Sn(4). A Fermi surface analysis reveals sections, which could generate 'nesting' instabilities and be responsible for the spin fluctuation effects. Both CeRh(2)Sn(4) and LaRh(2)Sn(4) exhibit slight homogeneity ranges and can be described by RE(1+x)Rh(2)Sn(4-x), where [Formula: see text] for Ce and [Formula: see text] in the case of La. Implantation of additional Ce atoms into the CeRh(2)Sn(4) structure leads to a distinct lowering of T(N) and the weakening of the ferromagnetic component of the magnetic ground state, whereas for the La-based systems the alloying reduces the strong diamagnetism. PMID:21693970

Gam?a, M; Schnelle, W; Gumeniuk, R; Prots, Yu; Slebarski, A; Rosner, H; Grin, Yu

2009-08-12

279

The thermodynamic properties of poly(2,2,2-trifluoroethyl methacrylate) (PTFEMA) were determined by the aid of the inverse gas chromatography technique (IGC), at infinite dilution. The interactions between the polymer and 15 solvents were examined in the temperature range of 120-150 °C via the estimation of the thermodynamic sorption parameters, the parameters of mixing at infinite dilution, the weight fraction activity coefficients and the Flory-Huggins interaction parameters. Additionally, the total and the partial solubility parameters of PTFEMA were estimated. The findings of this work indicate that the type and strength of the intermolecular interactions between the polymer and the solvents are strongly depended on the functional groups of the polymer and the solvents. The proton acceptor character of the polymer is responsible for the preferential solubility of PTFEMA in chloroform which acts as a proton donor solvent. The results also reveal that the polymer is insoluble in alkanes and alcohols whereas it presents good miscibility with polar solvents, especially with 2-butanone, 2-pentanone and 1,4-dioxane. Furthermore, the total and dispersive solubility parameters appear diminishing upon temperature rise, whereas the opposite behavior is noticed for the polar and hydrogen bonding solubility parameters. The latter increase with temperature, probably, due to conformational changes of the polymer on the solid support. Finally, comparison of the solubilization profiles of fluorinated methacrylic polymers studied by IGC, leads to the conclusion that PTFEMA is more soluble compared to polymers with higher fluorine content. PMID:24332349

Papadopoulou, Stella K; Panayiotou, Costas

2014-01-10

280

The thermodynamical properties of charged dilaton-axion black hole and its quasi-localized energy

NASA Astrophysics Data System (ADS)

We calculate the heat transfer passing through two horizons of charged dilaton-axion black hole and the quasi-localized energy in the patch ? between two horizons. The result EEinstein|? = E Møller|?-???TS is a Legendre transformation. So that the quasi-localized energy EEinstein and EMøller in the patch ? could be considered as thermodynamic potentials.

Yang, I.-Ching; Huang, Wen-Kuei

2014-07-01

281

This study investigates the radiative, cloud, and thermodynamic characteristics of the atmosphere separated into objectively defined cloud regimes in the tropical western Pacific (TWP). A cluster analysis is applied to 2 yr of daytime-only data from the International Satellite Cloud Climatology Project (ISCCP) to identify four major cloud regimes in the TWP region. A variety of data collected at the

Christian Jakob; George Tselioudis; Timothy Hume

2005-01-01

282

Thermodynamic Properties of Pentanol Deduced from Ultrasonic Velocity Data of its Aqueous Solutions

The thermodynamic method of Eyring and Hirschfelder has been employed to evaluate intermolecular free length Lf whereas free length theory FLT of Jacobson was used to compute the theoretical data of ultrasonic sound velocity CFLT. A maximum variation of 0.06% is observed between experimental velocity and the velocity deduced from free length theory (Cexp > CFLT), while uncertainty for Cexp

Anil Kumar

1991-01-01

283

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

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

Andrew C. Victor; Thomas B. Douglas

1963-01-01

284

NASA Technical Reports Server (NTRS)

A high molecular weight synthetic polypeptide has been designed which exhibits favorable interactions with single wall carbon nanotubes (SWCNTs). The enthalpic and entropic penalties of mixing between these two molecules are reduced due to the polypeptide's aromatic sidechains and helical secondary structure, respectively. These enhanced interactions result in a well dispersed SWCNT/Poly (L-Leucine-ran-L-Phenylalanine) nanocomposite with enhanced mechanical and electrical properties using only shear mixing and sonication. At 0.5 wt% loading of SWCNT filler, the nanocomposite exhibits simultaneous increases in the Young's modulus, failure strain, and toughness of 8%, 120%, and 144%, respectively. At one kHz, the same nanotube loading level also enhances the dielectric constant from 2.95 to 22.81, while increasing the conductivity by four orders of magnitude.

Lovell, Conrad S.; Wise, Kristopher E.; Kim, Jae-Woo; Lillehei, Peter T.; Harrison, Joycelyn S.; Park, Cheol

2009-01-01

285

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

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

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

2014-04-14

286

NASA Astrophysics Data System (ADS)

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

Almasi, Mohammad

2014-11-01

287

Correlation corrections to the thermodynamic properties of spin asymmetric QGP matter

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

Kausik Pal

2014-05-29

288

Correlation corrections to the thermodynamic properties of spin asymmetric QGP matter

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

Pal, Kausik

2014-01-01

289

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

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

Qi, Yan

2013-01-01

290

NASA Astrophysics Data System (ADS)

We propose a method for estimating the radius of the maximum r max and significant r sign for the manifestation of the size effect in nanomaterials. Our method is based on the size dependence of the melting temperature and the concept of limit values for the effect at points where properties vary by factors of e 2 and e. It was established that an empirical dependence based on the vibrational approach is most advantageous for determining r max and r sign. The Kelvin equation allows to estimate the r value and to predict its periodic dependence on the atomic number of individual elements. The range of variation of r for transition metals is ˜1 nm within the limits of 0.62-1.69 nm.

Apostolova, E. S.; Tikhonov, A. P.

2011-10-01

291

The solid phase FT-IR and FT-Raman spectra of 1-methyl-2-phenyl benzimidazole (MPBZ) have been recorded in the condensed state. In this work, experimental and theoretical study on the molecular structure, quantum chemical calculations of energies and vibrational wavenumbers of MPBZ is presented. The vibrational frequencies of the title compound were obtained theoretically by DFT/B3LYP calculations employing the standard 6-311+G(d,p) and 6-311++G(d,p) basis set for optimized geometry and were compared with Fourier transform infrared spectrum (FTIR) in the region of 4000-400 cm(-1) and with Fourier transform Raman spectrum in the region of 4000-100 cm(-1). Complete vibrational assignments, analysis and correlation of the fundamental modes for the title compound were carried out. The vibrational harmonic frequencies were scaled using scale factor, yielding a good agreement between the experimentally recorded and the theoretically calculated values. The study is extended to calculate the HOMO-LUMO energy gap, NBO, mapped molecular electrostatic potential (MEP) surfaces, polarizability, Mulliken charges and thermodynamic properties of the title compound. PMID:24785089

Karnan, M; Balachandran, V; Murugan, M; Murali, M K

2014-09-15

292

NASA Technical Reports Server (NTRS)

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

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

1992-01-01

293

The thermodynamic, kinetic, and magnetic properties of the hydrogen monomer on doped graphene layers were studied by ab initio simulations. Electron doping heightens the diffusion potential barrier, while hole doping lowers it. However, both kinds of dopings heighten the desorption potential barrier. The underlying mechanism was revealed by investigating the effect of charge doping on the bond strength of graphene and on the electron transfer and the coulomb interaction between the hydrogen monomer and graphene. The kinetic properties of H and D monomers on doped graphene layers during both the annealing process (annealing time t(0) = 300 s) and the constant-rate heating process (heating rate ? = 1.0 K/s) were simulated. Macroscopic diffusion of hydrogen monomers on graphene can be achieved when the doping-hole density reaches 5.0 × 10(13) cm(-2). Both electron and hole dopings linearly reduce the total magnetic moment and exchange splitting, which was explained by a simple exchange model. The laws found in this work had been generalized to explain many phenomena reported in literature. This study can further enhance the understanding of the interaction between hydrogen and graphene and was expected to be helpful in the design of hydrogenated-graphene-based devices. PMID:21842947

Huang, Liang Feng; Ni, Mei Yan; Zhang, Guo Ren; Zhou, Wang Huai; Li, Yong Gang; Zheng, Xiao Hong; Zeng, Zhi

2011-08-14

294

NASA Astrophysics Data System (ADS)

Fragments of the phase diagram of the H2O-2-C4H9OH-NaCl system were studied experimentally at 298 and 313 K. The thermodynamic properties of sodium chloride in three-component solutions with ionic strengths up to 1.9 mol/kg and alcohol content in the solvent 4.97 and 10 wt % were measured at 298 and 323 K by the electromotive force method with ion-selective electrodes. The eNRTL (electrolyte Non-Random Two-Liquids) model parameters correctly describing the results of electrochemical measurements of the partial properties of NaCl and phase equilibria in the water-2-butanol-sodium chloride ternary system and binary subsystems constituting it were determined. The isothermal sections of the phase diagram of the H2O-2-C4H9OH-NaCl system were calculated using the method of convex hulls implemented in the TernAPI package.

Veryaeva, E. S.; Bogachev, A. G.; Shishin, D. I.; Voskov, A. L.; Igumnov, S. N.; Mamontov, M. N.; Uspenskaya, I. A.

2012-06-01

295

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

NASA Astrophysics Data System (ADS)

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 N 2 pressure up to 20 kbar. It is shown that the best conditions for crystal growth at available pressure and temperature conditions can be achieved for GaN. High quality 6-10 mm single crystals of GaN have been grown at high N 2 pressure in 60-150 h processes. The mechanisms of nucleation and growth of GaN crystals are discussed on the basis of the experimental results. The crystallization of AlN is less efficient due to relatively low solubility of AlN in liquid Al. Possibility for the growth of InN crystals is strongly limited since this compound loses its stability at T > 600°C, even at 2 GPa N 2 pressure. The crystals of GaN grown at high pressure are the first crystals of this material used for homoepitaxial layer deposition. Both MOCVD and MBE methods have been successfully applied. Structural, electrical and optical properties of both GaN single crystals and homoepitaxial layers are reviewed.

Porowski, S.; Grzegory, I.

1997-06-01

296

Normal spinel zinc ferrite (ZnFe2O4) nanoparticles (NPs) with zero net magnetization were synthesized by a facile coprecipitation method in which two kinds of organic alkali, namely, 1-amino-2-propanol (MIPA) and bis(2-hydroxypropyl)-amine (DIPA), were used. The diameters of the ZnFe2O4 NPs were determined to be about 7 and 9 nm for samples prepared with MIPA and DIPA, respectively, and the normal spinel structure was confirmed by the magnetic property measurement at room temperature and the temperature dependence of the direct current magnetization. These results are different from those reported in the literature, where ZnFe2O4 NPs show a nonzero net magnetization. The heat capacity of the ZnFe2O4 NPs synthesized using DIPA was measured using a physical property measurement system in the temperature range from 2 to 300 K, and the thermodynamic functions were calculated based on the curve fitting of the experimental heat capacity data. The heat capacity of the ZnFe2O4 NPs was compared with that of a nanosized (Zn0.795Fe0.205)[Zn0.205Fe1.795]O4 material studied in the literature, indicating that the Debye temperature of the present sample is more comparable with that of the bulk ZnFe2O4 reported by Westrum et al. PMID:25192353

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

2014-10-01

297

Thermodynamic properties of a condensed 39K Bose gas in a harmonic trap

NASA Astrophysics Data System (ADS)

In this paper, the thermodynamic behavior of a 39K Bose gas with a finite number of atoms confined in a harmonic potential is investigated. By taking into account the conservation of the total number of particles N and using a modified semiclassical approximation, we derive analytically the simple explicit expression for the thermal atoms number in the excited state. This modification assures to include, finite size and indirectly the interatomic interaction effects simultaneously. Various experimental, the critical atoms number and its corresponding temperature are predicted via the graphical representation. The calculated results show that the thermodynamical parameters depend critically on the size, shape, and harmonic nature of the potential. The calculated critical atoms number are coincide with the measured experimental results for 39K, as reported in Tammuz et al. [3] and Smith et al. [4].

El-Badry, Azza M.; Hassan, Ahmed S.; Soliman, Shemi S. M.

2013-02-01

298

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

Daniel, Davis George

2014-01-01

299

The rare earth element complexes have never been analyzed in the gaseous state due to experimental concerns. The thermodynamic properties of rare earth element complexes are important for various applications, from high-intensity discharge lamps to recovery of rare earth metals. 46 refs., 4 figs., 1 tab.

Zhi-Chang Wang; Lin-Shan Wang [Northeastern Univ., Liaoning (China)

1997-04-09

300

Standard partial molal thermodynamic properties including association constants for 246 inorganic aqueous rare earth element (REE) complexes with chloride, fluoride, hydroxide, carbonate, sulfate, bicarbonate, nitrate, and orthophosphate can be calculated at pressures from 1 to 5000 bars and temperatures from 0 to 1000°C, using experimental data from the literature and correlation algorithms. Predicted association constants for REE complexes are used

Johnson R. Haas; Everett L. Shock; David C. Sassani

1995-01-01

301

Experimental solubilities of gibbsite and corundum in aqueous KOH solutions at elevated temperatures and pressures reported by Fricke and Jucaitis (1930), Wesolowski (1992), and Pascal and Anderson (1989) were used together with the Hückel (1925) and Setchénow (1892) equations for activity coefficients of aqueous species and the thermodynamic properties of the aluminate ion AlO2? to retrieve dissociation constants for the

Vitalii A. Pokrovskii; Harold C. Helgeson

1997-01-01

302

.1063/1.4821287 Pressure induced structural phase transition in solid oxidizer KClO3: A first-principles study J. ChemAnharmonicity, mechanical instability, and thermodynamic properties of the Cr-Re - phase Mauro of the cubic metallic phase of AlH3 via first-principles calculations J. Appl. Phys. 114, 114905 (2013); 10

AlfÃ¨, Dario

303

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

Chickos, James S.

304

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

Chickos, James S.

305

Precision measurement of the speed of sound and thermodynamic properties of gases

Conclusions The main significance of this paper is to evidence that the speedu of an acoustic wave propagating through a fluid provides nearly exhaustive information about its thermodynamic state.\\u000a \\u000a In recent years a substantial improvement of the experimental techniques and the associated theoretical models have made it\\u000a possible to measureu with outstanding precision and accuracy (some parts in 106). Thus, even

G. Benedetto; R. M. Gavioso; R. Spagnolo

1999-01-01

306

Study of Thermodynamic Properties of AuCu Superlattice by the Statistical Moment Method

NASA Astrophysics Data System (ADS)

We have investigated the thermodynamic quantities of AuCu superlattice using the statistical moment method in the statistical physics. The free energy, thermal lattice expansion coefficients, mean-square atomic displacements, and specific heats at the constant volume and those at the constant pressure, Cv and Cp, are derived in closed analytic forms in terms of the power moments of the atomic displacements. The present analytic formulas including the anharmonic effects of the lattice vibration give the predicted values of these quantities.

Van Hung, Vu; Phuong, Cao Huy; Thi Hoa, Nguyen

2014-09-01

307

NASA Astrophysics Data System (ADS)

The thermoelectric and thermodynamic properties of polycrystalline InxCo4Sb12 (0.0 ? x ? 0.26) skutterudites were investigated and analysed between 2 and 800 K by means of electrical resistivity, thermopower, thermal conductivity and specific heat measurements. Hall effect, sound velocity and thermal expansion measurements were also made in order to gain insights into the transport and elastic properties of these compounds. The impact of the In filling on the crystal structure as well as the thermal dynamics of the In atoms were tracked down to 4 K using powder neutron diffraction experiments. Analyses of the transport data were compared with the evolution of the electronic band structure with x determined theoretically within the Korringa-Kohn-Rostoker method with the coherent potential approximation. These calculations indicate that In gives rise to a remarkably large p-like density of states located at the conduction band edge. The electrical properties show typical trends of heavily doped semiconductors regardless of the In content. The thermal transport in CoSb3 is strongly influenced by the presence of In in the voids of the crystal structure resulting in a drop in the lattice thermal conductivity values in the whole temperature range. The low value of the Grüneisen parameter suggests that this decrease mainly originates from enhanced mass-fluctuations and point-defect scattering mechanisms. The highest thermoelectric figure of merit ZT ˜ 1.0 at 750 K was achieved at the maximum In filling fraction, i.e. for x = 0.26.

Leszczynski, J.; Da Ros, V.; Lenoir, B.; Dauscher, A.; Candolfi, C.; Masschelein, P.; Hejtmanek, J.; Kutorasinski, K.; Tobola, J.; Smith, R. I.; Stiewe, C.; Müller, E.

2013-12-01

308

NASA Astrophysics Data System (ADS)

Based on the quasiparticle model of the quark-gluon plasma (QGP), a color quantum path-integral Monte-Carlo (PIMC) method for the calculation of thermodynamic properties and—closely related to the latter—a Wigner dynamics method for calculation of transport properties of the QGP are formulated. The QGP partition function is presented in the form of a color path integral with a new relativistic measure instead of the Gaussian one traditionally used in the Feynman-Wiener path integral. A procedure of sampling color variables according to the SU(3) group Haar measure is developed for integration over the color variable. It is shown that the PIMC method is able to reproduce the lattice QCD equation of state at zero baryon chemical potential at realistic model parameters (i.e., quasiparticle masses and coupling constant) and also yields valuable insight into the internal structure of the QGP. Our results indicate that the QGP reveals quantum liquidlike(rather than gaslike) properties up to the highest considered temperature of 525 MeV. The pair distribution functions clearly reflect the existence of gluon-gluon bound states, i.e., glueballs, at temperatures just above the phase transition, while mesonlike qq¯ bound states are not found. The calculated self-diffusion coefficient agrees well with some estimates of the heavy-quark diffusion constant available from recent lattice data and also with an analysis of heavy-quark quenching in experiments on ultrarelativistic heavy-ion collisions, however, appreciably exceeds other estimates. The lattice and heavy-quark-quenching results on the heavy-quark diffusion are still rather diverse. The obtained results for the shear viscosity are in the range of those deduced from an analysis of the experimental elliptic flow in ultrarelativistic heavy-ions collisions, i.e., in terms the viscosity-to-entropy ratio, 1/4???/S<2.5/4?, in the temperature range from 170 to 440 MeV.

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

2013-03-01

309

NASA Astrophysics Data System (ADS)

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

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

2014-01-01

310

The special properties of supercritical fluids include high density, high diffusivity, low viscosity, and high compressibility. The liquid-like density gives it a large capacity for solutes. The solubility of heavy organic solutes in SCF's is frequently many orders of magnitude greater than the solubility in an ideal gas. The ratio of these two solubilities is defined as the enhancement factor and values of 10W to 10Z are quite common. The high diffusivity and low viscosity make it an efficient medium for mass transfer. Finally, the high compressibility permits extradordinary selectivity since small pressure changes yield large density changes and, consequently, large solubility changes. We have measured the solubilities of several representative coal compounds in supercritical ammonia at 142 C and 162 C. We conducted a comparison of the ability of four equations of state to predict solubilities of the compounds in SC CO2, butane, and ammonia, and found that the PR2 and AVDW4 equations performed the best for these fluids. In addition, we conducted a search for new representative coal compounds that are better suited to higher temperature investigation. 7 figs., 3 tabs.

Eckert, C.A.

1987-01-01

311

Melting and thermodynamic properties of pyrope (Mg3Al2Si3O12)

The heat capacity of Mg3Al2Si3O12 glass has been measured from 10 to 1000 K by adiabatic and differential scanning calorimetry. The heat capacity of crystalline pyrope has been determined from drop-calorimetry measurements between 820 and 1300 K. From these and previously published results a consistent set of thermodynamic data is presented for pyrope and Mg3Al2Si3O12 glass and liquid for the interval 0-2000 K. The enthalpy of fusion at 1570 ?? 30 K, the metastable congruent 1-bar melting point, is 241 ?? 12 kJ/mol. ?? 1991.

Tequi, C.; Robie, R.A.; Hemingway, B.S.; Neuville, D.R.; Richet, P.

1991-01-01

312

Microscopic study of nuclear level densities and thermodynamical properties in 170,171,172Yb

NASA Astrophysics Data System (ADS)

The nuclear level density and entropy were extracted for 170,171,172Yb isotopes within microscopic theory, which includes nuclear pairing interaction. The calculations were based on the modified harmonic oscillator according the Nilsson potential for deformed nuclei. From the level densities, thermodynamical quantities such as temperature and entropy have been deduced. The entropies of the neutron hole and particle are estimated from the entropy difference between the odd-mass and even-even nuclei. The critical temperature of the pair-breaking process is found to be Tc ˜ 0.4-0.5 MeV. The results were compared with experimental data obtained by the Oslo group.

Razavi, Rohallah; Behkami, Aziz N.; Mohammadi, Saeed

2012-10-01

313

Effects of Calcium Ions on Thermodynamic Properties of Mixed Bilirubin/Cholesterol Monolayers

NASA Astrophysics Data System (ADS)

The mixed monolayer behavior of bilirubin/cholesterol was studied through surface pressure-area (?-A) isotherms on aqueous solutions containing various concentrations of calcium ions. Based on the data of ?-A isotherms, the mean area per molecule, collapse pressure, surface compressibility modulus, excess molecular areas, free energy of mixing, and excess free energy of mixing of the monolayers on different subphases were calculated. The results show an expansion in the structure of the mixed monolayer with Ca2+ in subphase, and non-ideal mixing of the components at the air/water interface is observed with positive deviation from the additivity rule in the excess molecular areas. The miscibility between the components is weakened with the increase of concentration of Ca2+ in subphase. The facts indicate the presence of coordination between Ca2+ and the two components. The mixed monolayer, in which the molar ratio of bilirubin to cholesterol is 3:2, is more stable from a thermodynamic point of view on pure water. But the stable 3:2 stoichiometry complex is destroyed with the increase of the concentration of Ca2+ in subphase. Otherwise, the mixed monolayers have more thermodynamic stability at lower surface pressure on Ca2+ subphase.

Wu, Qiong; Tang, Yu-feng; Li, Ye-min; Xie, An-jian; Shen, Yu-hua; Zhu, Jin-miao; Li, Chuan-hao

2008-04-01

314

Ab Initio Study of Thermodynamic Properties of Lithium, Sodium, and Potassium Sulfates

NASA Astrophysics Data System (ADS)

The thermodynamic parameters of lithium, sodium, and potassium single and double sulfate crystals are determined by the method of ab initio calculation of a linear combination of atomic orbitals in the gradient approximation of density functional theory using the software package CRYSTAL09 within the framework of the quasi-harmonic approximation of the Debye theory. It is demonstrated that the standard entropies and heat capacities as well as the temperature dependences are in satisfactory agreement with the available experimental data. The average frequency, Debye temperature, and thermal conductivity coefficient increase with external pressure, whereas the Gruneisen parameter decreases. The dependences of the potentials of free and internal energies on the temperature and volume are expressed through the Birch-Murnaghan equation of state and a square-law dependence on these parameters of their vibrational components. The thermodynamic parameters of lithium-potassium sulfate appear closer to potassium sulfate, whereas for sodium-potassium, they lie between the corresponding parameters for single compounds.

Zhuravlev, Yu. N.; Bugaeva, I. A.; Zhuravleva, L. V.

2013-11-01

315

NASA Astrophysics Data System (ADS)

This paper proposes a procedure on the thermodynamically consistent determination of virial coefficients from speed-of-sound measurements. Using the speed-of-sound values for gaseous Difluoromethane (R-32) +Pentafluoroethane (R-125), R -32+ 1, 1, 1, 2 - tetrafluoroethane (R-134a), R125/134a and R-32/125/134a which have already been reported in the previous paper, the second virial coefficients of R-32/125, R -32/134a, R-125/134a and R-32/125/134a were determined by means of thermodynamic relation among the virial coefficients of two different virial equations of state with respect to pressure and density. The present virial equation of state regarding density expansion can represent not only the speed-of-sound values but also the P?T-data for R-32/125, R -32/134a, R -125/134a and R-32/125/134a. The deviation of the speed-of-sound data from the virial equation of state is about±100ppm.And the deviation of the P?T-measurements by Kleemiss and Tillner-Roth (1997) from the virial equation of state against density is about ±0.l%. The behavior of the second virial coefficient is shown at the available compositions.

Hozumi, Tsutomu; Sato, Haruki; Watanabe, Koichi

316

Thermodynamic Properties Of Alkali Species In Coal Based Combined Cycle Power Systems

The aim of this project is to support the development of a concept for a successful alkali removal. Two strategies are possible: optimizing the alkali retention potential of the coal ash slag in the combustion chamber and the liquid slag separators and separate alkali removal with solid sorbents (getters) at temperatures below 1450 C. Therefore in a first step the alkali partial pressure over coal ash slag should be determined in order to get information about the retention potential of the slag. The influence of additives on the retention potential of the slag should be investigated. The measurements should show if the alkali partial pressure over the slag is generally low enough in case of thermodynamic equilibrium. In case of too high alkali partial pressures a separate alkali removal is needed. Therefore in a second step commercial sorbent materials should be investigated concerning their sorption potential for alkalis. To get information about the influence of getter components on the sorption potential some mixtures of pure components, predicted by thermodynamic modeling to be most effective, should be investigated.

Willenborg, W.; Wolf, K.J.; Fricke, C.; Moeller, M.; Prikhodovsky, A.; Hilpert, K.; Singheiser, L.

2002-09-20

317

Objective: To compare surface cooling and deep cooling produced by 3 common forms of cryotherapy. Design and Setting: We used a 3 × 4 × 4 factorial with repeated measures on measurement depth and treatment. Independent variables were measurement depth (surface, fat + 1 cm, and fat + 2 cm), treatment (ice bag, Wet-Ice, Flex-i-Cold, and control), and treatment order (first, second, third, and fourth). The lowest temperature recorded was the dependent variable. The treatment order was counterbalanced using a Latin square. Data were analyzed with a repeated-measures analysis of variance. Subjects: Fifteen collegiate volunteers who were free of lower extremity abnormalities. Measurements: Thigh skin and thigh intramuscular temperatures (1- and 2-cm subadipose) were measured at 30-second intervals both before and during the 30-minute treatments using fine-wire implantable and surface thermocouples. The coldest recorded temperatures were analyzed. Results: Statistical differences were observed for the depth-by-treatment interaction as well as for the depth and treatment main effects. During cold treatments, superficial depths were colder than deeper depths, and all cold treatments were colder than controls at all depths. For the interaction effect at both the skin surface and at 1-cm subadipose, the ice-bag and Wet-Ice treatments were colder than the Flex-i-Cold treatment. For the interaction at 2-cm subadipose, the cold treatments did not differ from each other. Order of treatments did not produce a significant effect. Conclusions: During a 30-minute cryotherapy treatment, modalities that undergo a phase change caused lower skin and 1-cm intramuscular temperatures than cold modalities that do not possess these properties. These differences were not seen at 2-cm subadipose but may become apparent with longer treatments. PMID:12937469

Jutte, Lisa S.; Smith, Michael E.

2003-01-01

318

Effects of Vacancy Cluster Defects on Electrical and Thermodynamic Properties of Silicon Crystals

A first-principle plane-wave pseudopotential method based on the density function theory (DFT) was employed to investigate the effects of vacancy cluster (VC) defects on the band structure and thermoelectric properties of silicon (Si) crystals. Simulation results showed that various VC defects changed the energy band and localized electron density distribution of Si crystals and caused the band gap to decrease with increasing VC size. The results can be ascribed to the formation of a defect level produced by the dangling bonds, floating bonds, or high-strain atoms surrounding the VC defects. The appearance of imaginary frequencies in the phonon spectrum of defective Si crystals indicates that the defect-region structure is dynamically unstable and demonstrates phase changes. The phonon dispersion relation and phonon density of state were also investigated using density functional perturbation theory. The obtained Debye temperature (?D) for a perfect Si crystal had a minimum value of 448?K at T = 42?K and a maximum value of 671?K at the high-temperature limit, which is consistent with the experimental results reported by Flubacher. Moreover, the Debye temperature decreased with increases in the VC size. VC defects had minimal effects on the heat capacity (Cv) value when temperatures were below 150?K. As the temperature was higher than 150?K, the heat capacity gradually increased with increasing temperature until it achieved a constant value of 11.8?cal/cell·K. The heat capacity significantly decreased as the VC size increased. For a 2 × 2 × 2 superlattice Si crystal containing a hexagonal ring VC (HRVC10), the heat capacity decreased by approximately 17%. PMID:24526923

Huang, Pei-Hsing; Lu, Chi-Ming

2014-01-01

319

The present study is focused on the evaluation of the interfacial composition, thermodynamic properties, and structural parameters of water-in-oil mixed surfactant microemulsions [(cetylpyridinium chloride, CPC+polyoxyethylene (20) cetyl ether, Brij-58 or polyoxyethylene (20) stearyl ether, Brij-78)/1-pentanol/n-heptane, or n-decane] under various physicochemical environments by the Schulman method of cosurfactant titration of the oil/water interface. The estimation of the number of moles of 1-pentanol at the interface (n(a)(i)) and bulk oil (n(a)(o)) and its distribution between these two domains at the threshold level of stability have been emphasized. The thermodynamics of transfer of 1-pentanol from the continuous oil phase to the interface have been evaluated. n(a)(i),n(a)(i), standard Gibbs free energy (?G(t)(0)), standard enthalpy (?H(t)(0)), and standard entropy (?G(t)(0)) of transfer process have been found to be dependent on the molar ratio of water to surfactant (?), type of nonionic surfactant and its content (X(Brij-58 or Brij-78)), oil and temperature. A correlation between (?H(t)(0)) and (?S(t)(0)) is examined at different experimental temperatures. Bulk surfactant composition dependent temperature insensitive microemulsions have been reported. Associated structural parameters, such as droplet dimensions and aggregation number of surfactant and cosurfactant at the droplet interface have been evaluated using a mathematical model after suitable modifications for mixed surfactant systems. In light of these parameters, the prospect of using these microemulsion systems for the synthesis of nanoparticles and the modulation of enzyme activity has been discussed. Correlations of the results in terms of the evaluated physicochemical parameters have been attempted. PMID:22884225

Kundu, Kaushik; Guin, Gourhari; Paul, Bidyut K

2012-11-01

320

Heat capacities and thermodynamic properties of one manganese-based MOFs

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

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

2010-01-01

321

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

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

2011-01-01

322

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

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

2012-01-01

323

Thermodynamic properties of melts of the binary Ag(Au)-Sm systems

NASA Astrophysics Data System (ADS)

The enthalpies of mixing for liquid alloys of the Ag-Sm system are determined by isoperibolic calorimetry at 1450-1506 K in the 0.46 < x Sm < 1 range of concentrations. The partial and integral enthalpies of mixing for melts of the Ag-Sm system are obtained over the whole range of concentrations. The activities of components and the entropy of mixing in melts of the Ag-Sm system at 1506 K are calculated using a model of ideal associated solutions (IAS). The partial and integral enthalpies of mixing for melts of the Ag-Sm system, the activities of the components, and the molar fractions of associates in them are calculated using the IAS model. It is concluded that the thermodynamic activities of components in melts of the Ag (Au)-Sm system at 1506 K exhibit great negative deviation from the ideal behavior, and the enthalpies of mixing indicate there are considerable exothermal effects.

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

2014-02-01

324

NASA Astrophysics Data System (ADS)

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

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

2014-04-01

325

NASA Astrophysics Data System (ADS)

Enthalpies of K-Na mixing for the analbite - sanidine feldspar series were investigated by Hovis (1988, J. Petrology) in the early 80's. That work was based on data at a limited number of compositions, owing to the large sample sizes required for HF solution calorimetric measurements at the time. Thermodynamic mixing properties for mineral series, especially those exhibiting compositionally asymmetric mixing quantities, are best defined when samples at a large number of compositions are utilized. Enabled by the small sample sizes now possible for HF solution calorimetric dissolutions (Hovis et al., 1998, Amer. Mineral.), we revisit feldspar thermodynamic properties, having synthesized an analbite - sanidine series consisting of samples at 20 compositions. Solution calorimetric experiments on these samples at 50 °C in 20.1 wt% HF under isoperibolic conditions have resulted in highly precise calorimetric data (standard deviation per sample averaging 0.06 % of the heat of solution). Although enthalpies of K-Na mixing based on the new data display some degree of compositional asymmetry, with a maximum value of 4.8 kJ/mol at a mole fraction potassium of 0.47, the distribution of enthalpy-of-mixing values remains nearly symmetric with respect to K content. This contrasts significantly with data for Al-Si ordered low albite - microcline crystalline solutions, reinvestigated via synthesis of a 21-member series, which show significantly higher mixing magnitudes and considerably greater asymmetry with respect to composition. The maximization of enthalpies of K-Na mixing at sodic compositions correlates well with the sodic critical compositions for both solvi. The lower mixing magnitudes for analbite - sanidine are consistent with the comparatively lower critical temperature of the analbite - sanidine solvus (e.g., Smith & Parsons, 1974, Mineral. Mag.) relative to that for low albite - microcline (Bachinski & Müller, 1971, J. Petrology). Entropies of K-Na mixing for analbite - sanidine have been calculated by combining present enthalpy data with Gibbs free energies of mixing derived from the earlier phase equilibrium study of Hovis et al. (1991, Amer. Mineral.). These may be compared with directly measured entropy data for analbite - sanidine based on the heat capacity measurements of Haselton et al. (1983, Amer. Mineral.). Thanks to the National Science Foundation for funding this research.

Hovis, G. L.

2013-12-01

326

EFFECT OF HEATING RATE ON THE THERMODYNAMIC PROPERTIES OF PULVERIZED COAL

This semi-annual technical progress report describes work performed under DOE Grant No. DE-FG22-96PC96224 during the period September 24, 1998 to March 23, 1999 which covers the fifth six months of the project. Devolatilization is an important initial step in virtually all commercial fossil fuel applications such as combustion, gasification, and liquefaction. Characterization of the temperature history of pulverized coal particles under high heating rates, representative of coal combustors, is critical to the understanding of devolatilization. During this reporting period, characterization experiments were continued from the previous reporting period and completed to a total of 28 single coal particles. These particles were caught in the electrodynamic balance and their volume, external surface area, mass, and density were measured. The same single particles were then heated bidirectionally with a pulsed (10 ms pulse width) Nd:YAG laser beams of equal intensity with heating rates (10{sup 4} - 10{sup 7} K/s) representative of coal combustors. The temporal power variation in the laser pulse was monitored for use in the heat transfer analysis by an ultra-fast fiber optic uv light transmitter included in the beam path and coupled to a silicon photodiode. Transient surface temperatures of the particles were measured using a single-color pyrometer. Dynamics of volatile evolution and particle swelling were recorded using well established time-resolved high-speed cinematography. Presently, extraction of devolatilization time-scales and temperature data at these time-scales running the high-speed films taken during the experiments employing a 16mm movie projector are in progress. Heat transfer analyses for the devolatilization time-scales, and temperature measurements (and hence an understanding of the effect of heating rates on coal thermal properties) are also in progress. Shipment of the donated heated grid system components from our industrial partner, United Technologies Research Center (UTRC), CT to CAU was complete during the previous reporting period. Testing of the heated grid system components at CAU and sensitivity analyses of the heated grid heat transfer calculations are also in progress.

Ramanathan Sampath

1999-04-29

327

NASA Astrophysics Data System (ADS)

A new global approach for calculating thermodynamic properties of fluids with equations of state is proposed. This method uses an object-oriented library, written in C + +, and containing a number of routines that facilitate thermodynamic calculations. It is applicable to any equation of state formulated by an analytical expression of the Helmholtz free energy. The programming work of the user is limited to the building of a parse representation of the Helmholtz free energy. This parse graph is then processed by the program for analytically calculating the required derivatives and thermodynamic properties of fluids. A demonstration of this library is made with the Anderko and Pitzer equation of state for H 2O-NaCl-KCl fluids. The Helmholtz free energy has been differentiated analytically up to the fourth order with respect to the temperature, molar volume, and composition. Calculated derivatives are used to calculate the critical line of H 2O-NaCl mixtures and other thermodynamic properties, which otherwise would be difficult to obtain.

Thiéry, Régis

1996-08-01

328

NASA Astrophysics Data System (ADS)

We present first-principles calculations of the structural, elastic, vibrational and thermodynamic properties of SnSi, SnGe, SnC and GeC. We employ the density-functional perturbation theory (DFPT) within the local density approximation in conjunction with the quasi-harmonic approximation. The calculated lattice parameters, which are obtained by minimizing the total energy, are in the range of those reported in the literature for the binary compounds and in good agreement with the measured ones for the elemental components. Our results for the elastic properties show that c44 softens as pressure increases for SnSi and SnGe. The phonon spectra, the density of states and the Born effective charge at zero pressure are calculated and the phonon frequencies are positive. A pressure induced soft transverse acoustic phonon mode is identified at the zone boundary X point of the Brillouin zone at pressure of 12.95 and 12.45 GPa for SnSi and SnGe respectively. The linear expansion coefficient for the elemental components is calculated and compared to experiment. The temperature and pressure dependence of the thermal expansion, the overall Grüneisen parameter, the bulk modulus and the heat capacity is predicted. The thermal expansion coefficient decreases with increasing pressure and does not show any negative behavior for GeC and this is due to the positive transverse acoustic mode Grüneisen parameters. Our results for SnxGe alloys using the supercell method indicate that the variation of the Grüneisen parameter and the thermal expansion with concentration has the same trend and the bulk modulus softens.

Souadkia, M.; Bennecer, B.; Kalarasse, F.

2013-11-01

329

Thermodynamic mixing properties and behavior of almandine-spessartine solid solutions

NASA Astrophysics Data System (ADS)

The heat capacity, Cp, of five solid-solution members of the almandine(Alm)-spessartine(Sps) binary, consisting of three synthetic polycrystalline and two natural single-crystal samples, was measured in the temperature range between 2 and 300 K using relaxation calorimetry and between 282 and 764 K using DSC methods. All garnets exhibit a ?-type heat-capacity anomaly at low temperatures resulting from a paramagnetic to antiferromagnetic phase transition. The temperature of the magnetic transition in Fe-rich garnets occurs between those of the two end-members (i.e. 9.2 K for almandine and 6.2 K for spessartine), but lies at lower values between 3.5 and 4.5 K for more Sps-rich compositions with XMngrt>0.5. The calorimetric entropy at 298 K shows mechanical-mixture behavior for Sps-rich garnets and a slight possible negative deviation from such behavior for Alm-rich compositions. At the 2? level all data are, however, consistent with ideal mixing behavior and the Margules entropy interaction parameter, WS,FeMngrt, is zero for the Alm-Sps binary. Thermodynamic analysis of published high P and T phase-equilibrium Fe-Mn exchange experiments between garnet and ilmenite shows that the excess Gibbs free energy of mixing, ?Gex, for Fe-Mn in garnet is positive and asymmetric towards spessartine. Margules enthalpy interaction parameters of WH,FeMngrt=4170±518 J/cation?mol and WH,MnFe=1221±588 J/cation?mol are derived giving a maximum of ?Gex?0.7 kJ/cation?mol at XMngrt?0.6. ?Hex obtained using autocorrelation analysis of published IR spectra of Alm-Sps solid solutions is in reasonable agreement with that derived from phase-equilibrium and calorimetry data. Previous diffraction and spectroscopic results on Alm-Sps garnets and quantum mechanical calculations made on almandine are used to interpret the macroscopic thermodynamic behavior from a microscopic basis. The relevance of the new garnet Fe-Mn mixing model for petrological calculations is demonstrated by incorporating it into the quaternary garnet mixing model of Berman (1990). Thus, better agreement for temperatures calculated using Fe-Mn garnet-ilmenite and Fe-Mg garnet-biotite geothermometry could be achieved. Temperatures calculated for Mn-poor and Mn-rich garnet-bearing assemblages, applying garnet-biotite thermometry, are in better agreement taking Fe-Mn mixing into account.

Dachs, Edgar; Geiger, Charles A.; Benisek, Artur; Grodzicki, Michael

2014-01-01

330

Thermodynamic properties of a symmetrical binary mixture in the coexistence region

A three-dimensional symmetric binary fluid is studied, as a function of temperature, in the two-phase (liquid-liquid) coexistence region via Monte Carlo simulations. Particular focus has been in the understanding of curvature-dependent interfacial tension, which is observed to vary as {sigma}(R)={sigma}({infinity})/[1+2((l/R)){sup 2}], implying that a Tolman length is zero in the limit R{yields}{infinity}. The length l is found to have a critical divergence the same as the correlation length, but its amplitude is significantly larger (l{approx_equal}4{xi}). Our findings hence imply that the barrier against homogeneous nucleation is significantly reduced (in comparison with the classical nucleation theory) in the critical region. We also report results for the critical behavior of the flat interfacial tension {sigma}({infinity}) and the concentration susceptibility, as well as the amplitude ratios involving these thermodynamic quantities. Noting that the interatomic potential in our model is described by the Lennard-Jones form that decays faster that 1/r{sup 3}, all of our results for critical phenomena are expectedly consistent with the Ising universality class of three spatial dimensions.

Das, Subir K. [Theoretical Sciences Unit, Jawaharlal Nehru Centre for Advanced Scientific Research, Jakkur P.O., Bangalore 560064 (India); Institut fuer Physik, Johannes Gutenberg-Universitaet, Staudinger Weg 7, D-55099 Mainz (Germany); Binder, Kurt [Institut fuer Physik, Johannes Gutenberg-Universitaet, Staudinger Weg 7, D-55099 Mainz (Germany)

2011-12-15

331

Infrared spectra and thermodynamic properties of CH4/H2O ices

NASA Astrophysics Data System (ADS)

The coexistence of solid methane and water ice has been observed in outer Solar System objects, in comets, and in interstellar ice mantles (1-3). CH4 is proposed to be the starting point of rich organic chemistry in the astrophysical media. This work presents an investigation on ice mixtures of methane and water. The samples were analysed by infrared spectroscopy. In the range of temperatures spanned in this study our investigations provide evidence of the existence of a distorted CH4 structure, characterized by an absorption band at 2900 cm-1, corresponding to the symmetric stretch motion of the molecule, forbidden by symmetry in the pure solid. A quantification of the amount of distorted CH4 trapped in the water ice structure, and its dependence on the ice generation procedure has been conducted. The CH4:H2O desorption energy has been determined. These and other findings will be discussed in the presentation. Boogert, A.C.A. "Interstellar Ices". Astrophysics of Dust, ASP Conference Series, Vol. 309, p. 547, 2004. A.N. Witt, G.C. Clayton. Voss, L.F. et al., "Methane thermodynamics in nanoporous ice: A new methane reservoir on Titan." J. Geophys. Res., 112, E05002, doi: 10.1029/2006JE002768, 2007.

Galvez, O.; Mate, B.; Herrero, V. J.; Escribano, R. M.

2009-04-01

332

We have developed new equations of state for pure-component chain molecules. The excellent performance of complicated theories, such as the Generalized Flory Dimer (GFD) theory can be mimicked by simpler equations, if assumptions for the shape parameters are made. We developed engineering correlations based on GFD theory, using local composition theory to take into account attractive forces. During this period, we compared methods for calculating repulsive and attractive contributions to equation of state against computer simulation data for hard and square-well chains, and against experimental data from the literature. We also have studied microstructure and local order in fluids that contain asymmetric molecules. We developed a thermodynamic model for polar compounds based on a site-site interaction approach. We have shown the equivalence of various classes of theories for hydrogen bonding, and used this equivalence to derive a multiple site model for water. In addition, simple cubic equations of state have been applied to calculate physical and chemical-reaction equilibria in nonideal systems. We measured infinite dilution activity coefficients using HPLC. We also measured high pressure vapor liquid equilibria of ternary and quaternary systems containing supercritical solvents. We used FT-IR spectroscopy to examine self-association of aliphatic alcohols due to hydrogen bonding, and to investigate the hydrogen bonding in polymer-solvent mixtures.

Donohue, M.D.

1993-09-01

333

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

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

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

2014-10-01

334

NASA Technical Reports Server (NTRS)

A survey is presented of representative equations for various thermophysical properties of fluids in the critical region. Representative equations for the transport properties are included. Semi-empirical modifications of the theoretically predicted asymtotic critical behavior that yield simple and practical representations of the fluid properties in the critical region are emphasized.

Sengers, J. V.; Basu, R. S.; Sengers, J. M. H. L.

1981-01-01

335

The thermodynamic properties of coherent interphase boundaries (IPBs) between the Al-rich-matrix and Guinier-Preston-zone (GP-zone) precipitate phases in Ag-Al are studied from first principles. The cluster-variation-method (CVM), with effective-cluster-interaction (ECI) parameters derived from the results of ab initio total energy calculations, is used to compute the interfacial free energies ({gamma}) and composition profiles of flat {l_brace}111{r_brace} and {l_brace}100{r_brace} IPBs as a function of temperature (T). The calculated values of {gamma} increase monotonically from zero to 35 (37)mJ/M{sup 2} for {l_brace}111{r_brace}({l_brace}100{r_brace}) IPBs as T is lowered from the critical temperature (calculated to be 760 K) to 450 K. Monte-Carlo simulations, based on the same set of ECIs used in the CVM work, have been performed to compute GP-zone morphologies at 450 K. Simulated precipitate shapes are found to be anisotropic, consistent with experimental observations. The CVM is used also to compute the gradient coefficient ({kappa}) in the Cahn-Hilliard coarse-grained free energy. Calculated values of {kappa} are found to display non-negligible concentration and temperature dependencies, in contrast to the predictions of regular-solution theory.

Asta, M.; Hoyt, J.J.

2000-03-14

336

NASA Astrophysics Data System (ADS)

The phonon spectra of ? , ? , and ? Ti were studied using the supercell approach. The lattice vibrational energy was calculated in the quasiharmonic approximation using both first-principles phonon density of state and Debye model. The thermal electronic contribution to the free energy was evaluated from the integration over the electronic density of states. The Helmholtz energy was thus obtained by combining them with the 0 K total energy calculated within the framework of all-electron projector-augmented-wave method. The thermodynamic properties of ? and ? Ti calculated by phonon and Debye model are very close to each other. The predicted enthalpy, entropy, bulk modulus, thermal expansion coefficient and heat capacity of ? are in good agreement with experiments. By comparing with the experimental enthalpy of ? , we found that the 0 K total energy calculated from bcc Ti is incorrect. This problem can be solved by shifting the total energy of ? down by 8kJmol-1 to match the experimental value. With the Gibbs energy calculated from the Debye model as a function of pressure and temperature, the phase transformation conditions of ??? , ??? , and ??? were identified. The predicted transition temperature between ? and ? at ambient pressure and the triple point are close to experiments. It was found that the entropy plays an important role in the ??? and ??? transitions, and the thermal electronic contribution to the Gibbs energy cannot be neglected for studying the ??? transition. Our calculations also showed that zero-point energy is crucial to predict the transition pressure of Ti at low temperatures.

Mei, Zhi-Gang; Shang, Shun-Li; Wang, Yi; Liu, Zi-Kui

2009-09-01

337

NASA Astrophysics Data System (ADS)

The thermodynamic mixing properties for isometric ThxCe1-xO2, CexZr1-xO2, and ThxZr1-xO2 were determined using quantum-mechanical calculations and subsequent Monte-Carlo simulations. Although the ThxCe1-xO2 binary indicates exsolution below 600 K, the energy gain due to exsolution is small (Eexsoln=1.5 kJ/(mol cations) at 200 K). The energy gain for exsolution is significant for the binaries containing Zr; at 1000 K, Eexsoln=6 kJ/(mol cations) for the CexZr1-xO2 binary, and Eexsoln=17 kJ/(mol cations) for the ThxZr1-xO2 binary. The binaries containing Zr have limited miscibility and cation ordering (at 200 K for x=0.5). At 1673 K, only 4.0 and 0.25 mol% ZrO2 can be incorporated into CeO2 and ThO2, respectively. Solid-solution calculations for the tetragonal ThxZr1-xO2 binary show decreased mixing enthalpy due to the increased end-member stability of tetragonal ZrO2. Inclusion of the monoclinic ZrO2 is predicted to further reduce the mixing enthalpy for binaries containing Zr.

Shuller-Nickles, L. C.; Ewing, R. C.; Becker, U.

2013-01-01

338

CH4/H2O ices: infrared spectra and thermodynamic properties

NASA Astrophysics Data System (ADS)

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

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

2009-12-01

339

NASA Astrophysics Data System (ADS)

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

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

2012-12-01

340

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

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

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

1996-01-01

341

The thermodynamic and spectral properties of a two-dimensional electron gas with an antidot in a strong magnetic field, rc<=r0, where rc is the cyclotron radius and r0 is the antidot effective radius, are studied via a solvable model with the antidot confinement potential U~1\\/r2. The edge states localized at the antidot boundary result in an Aharonov-Bohm-type oscillatory dependence of the

E. N. Bogachek; Uzi Landman

1995-01-01

342

New values of the dissociation constants of HCl° referring to low density supercritical solutions and near-critical temperatures of water (350–500°C and 500–2500 bars) have been obtained based on comparison of AgCl(s) solubility in NaCl or KCl solutions with Ag(s) solubility in HCl + NaCl or KCl solutions at controlled hydrogen fugacities. During the course of this study the thermodynamic properties

B. R. Tagirov; A. V. Zotov; N. N. Akinfiev

1997-01-01

343

To examine the potential role of methanobactin (mb) as the extracellular component of a copper acquisition system in Methylosinus trichosporium OB3b, the metal binding properties of mb were examined. Spectral (UV-visible, fluorescence, and circular dichroism), kinetic, and thermodynamic data suggested copper coordination changes at different Cu(II):mb ratios. Mb appeared to initially bind Cu(II) as a homodimer with a comparatively high

Dong W. Choi; Corbin J. Zea; Young S. Do; Jeremy D. Semrau; William E. Antholine; Mark S. Hargrove; Nicola L. Pohl; Eric S. Boyd; G. G. Geesey; Scott C. Hartsel; Peter H. Shafe; Marcus T. McEllistrem; Clint J. Kisting; Damon Campbell; Vinay Rao; Arlene M. de la Mora; Alan A. DiSpirito

2006-01-01

344

Air quality models that generate the concentrations of semi-volatile and other condensable organic compounds using an explicit reaction mechanism require estimates of the physical and thermodynamic properties of the compounds that affect gas\\/aerosol partitioning: vapour pressure (as a subcooled liquid), and activity coefficients in the aerosol phase. The model of Griffin, Kleeman and co-workers (e.g., Griffin et al., 1999; Kleeman

S. L. Clegg; M. J. Kleeman; R. J. Griffin; J. H. Seinfeld

2007-01-01

345

Air quality models that generate the concentrations of semi-volatile and other condensable organic compounds using an explicit reaction mechanism require estimates of the physical and thermodynamic properties of the compounds that affect gas\\/aerosol partitioning: vapour pressure (as a subcooled liquid), and activity coefficients in the aerosol phase. The model of Griffin, Kleeman and co-workers (e.g., Griffin et al., 2003; Kleeman

S. L. Clegg; M. J. Kleeman; R. J. Griffin; J. H. Seinfeld

2008-01-01

346

Air quality models that generate the concentra- tions of semi-volatile and other condensable organic com- pounds using an explicit reaction mechanism require esti- mates of the physical and thermodynamic properties of the compounds that affect gas\\/aerosol partitioning: vapour pres- sure (as a subcooled liquid), and activity coefficients in the aerosol phase. The model of Griffin, Kleeman and co- workers (e.g.,

S. L. Clegg; M. J. Kleeman; R. J. Griffin; J. H. Seinfeld

2008-01-01

347

Although there have been many experimental investigations of the Diels-Alder dimerization of 1,3-cyclopentadiene, there remains considerable uncertainty in such thermodynamic properties as {Delta}H{degree}, {Delta}S{degree}, {Delta}G{degree}, and K{sub p} for the reaction at various temperatures. Despite this uncertainty, the reaction is a good subject for computational models, because it is one of the few Diels-Alder reactions which has been studied extensively in the laboratory both in the gas and liquid phase over a wide range of temperatures. This paper describes application of a force-field model to calculate thermodynamic properties of the monomer and both endo and exo isomers of the dimer for temperatures ranging from 273 to 500 K. The Boyd MOLBD3 force-field program modified to include (1) -ene and -diene parameters introduced by Anet and Yavari and (2) five-member and methylene bridge parameters suggested by the present authors was used for the calculations. Calculated equilibrium constants for both the gas and liquid phase, and other thermodynamic properties, agreed satisfactorily with what appear to be somewhat inconsistent existing experimental data. This work thus indicates that force-field methods hold promise as a useful alternative to experimental methods for the study of equilibrium of chemically reactive systems involving nontrivial molecules.

Lenz, T.G.; Vaughan, J.D. (Colorado State Univ., Fort Collins (USA))

1989-02-23

348

NASA Technical Reports Server (NTRS)

Simple relations for determining the enthalpy and temperature of hydrogen-helium gas mixtures were developed for hydrogen volumetric compositions from 1.0 to 0.7. These relations are expressed as a function of pressure and density and are valid for a range of temperatures from 7,000 to 35,000 K and pressures from 0.10 to 3.14 MPa. The proportionality constant and exponents in the correlation equations were determined for each gas composition by applying a linear least squares curve fit to a large number of thermodynamic calculations obtained from a detailed computer code. Although these simple relations yielded thermodynamic properties suitable for many engineering applications, their accuracy was improved significantly by evaluating the proportionality constants at postshock conditions and correlating these values as a function of the gas composition and the product of freestream velocity and shock angle. The resulting equations for the proportionality constants in terms of velocity and gas composition and the corresponding simple realtions for enthalpy and temperature were incorporated into a flow field computational scheme. Comparison was good between the thermodynamic properties determined from these relations and those obtained by using a detailed computer code to determine the properties. Thus, an appreciable savings in computer time was realized with no significant loss in accuracy.

Zoby, E. V.; Gnoffo, P. A.; Graves, R. A., Jr.

1976-01-01

349

NASA Astrophysics Data System (ADS)

Estimates of standard molal Gibbs energy (?Gf°) and enthalpy (?Hf°) of formation, entropy (S°), heat capacity (CP°) and volume (V°) at 25 °C and 1 bar of aqueous phenanthrene (P) and 1-, 2-, 3-, 4- and 9-methylphenanthrene (1-MP, 2-MP, 3-MP, 4-MP, 9-MP) were made by combining reported standard-state properties of the crystalline compounds, solubilities and enthalpies of phenanthrene and 1-MP, and relative Gibbs energies, enthalpies and entropies of aqueous MP isomers from published quantum chemical simulations. The calculated properties are consistent with greater stabilities of the ? isomers (2-MP and 3-MP) relative to the ? isomers (1-MP and 9-MP) at 25 °C. However, the metastable equilibrium values of the abundance ratios 2-MP/1-MP (MPR) and (2-MP + 3-MP)/(1-MP + 9-MP) (MPI-3) decrease with temperature, becoming <1 at ?375-455 °C. The thermodynamic model is consistent with observations of reversals of these organic maturity parameters at high temperature in hydrothermal and metamorphic settings. Application of the model to data reported for the Paleoproterozoic Here’s Your Chance (HYC) Pb-Zn-Ag ore deposit (McArthur River, Northern Territory, Australia) indicates a likely effect of high-temperature equilibration on reported values of MPR and MPI-3, but this finding is contingent on the location within the deposit. If metastable equilibrium holds, a third aromatic maturity ratio, 1.5 × (2-MP + 3-MP)/(P + 1-MP + 9-MP) (MPI-1), can be used as a proxy for oxidation potential. Values of logaH2aq determined from data reported for HYC and for a sequence of deeply buried source rocks are indicative of more reducing conditions at a given temperature than those inferred from data reported for two sets of samples exposed to contact or regional metamorphism. These results are limiting-case scenarios for the modeled systems that do not account for effects of non-ideal mixing or kinetics, or external sources or transport of the organic matter. Nevertheless, quantifying the temperature dependence of equilibrium constants of organic reactions enables the utilization of organic maturity parameters as relative geothermometers at temperatures higher than the nominal limits of the oil window.

Dick, Jeffrey M.; Evans, Katy A.; Holman, Alex I.; Jaraula, Caroline M. B.; Grice, Kliti

2013-12-01

350

ERIC Educational Resources Information Center

Intellectual property is a term that covers a number of different rights. Considers issues such as what are the basic forms of intellectual property; who owns the intellectual property created by a teacher; who owns intellectual property created by students; and use of downloaded materials from the internet. (Author/LM)

Swinson, John V.

2000-01-01

351

NSDL National Science Digital Library

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

Wood, Mr.

2010-11-14

352

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

353

NASA Astrophysics Data System (ADS)

Whereas the structures of multi-component silicate melts at ambient and high pressure provide insight into the macroscopic properties of natural magmas and has implication for magmatic processes in the Earth’s interior, the structure of most multi-components melts has not been fully described. This is primarily because of a usual increase in inhomogeneous broadening of the spectra with increasing number of components and with pressure. Advent of high-resolution NMR techniques and synchrotron inelastic scattering allow us to yield previously unknown details of pressure-induced structural changes in divers oxide melts (e.g. Lee SK et al. Phys. Rev. Lett. 2009, 103, 095501; J. Phys. Chem. B. 2009, 113, 5162; Proc. Nat. Aca. Sci. 2008, 105, 7925), shedding light on microscopic origins of their thermodynamic properties. Multi-nuclear high-resolution NMR spectra for quaternary, Ca-Mg and Ca-Na aluminosilicate glasses, a model system for primary basaltic magmas, show the presence of a substantial fraction of five coordinated Al and Al-O-Al at 1 atm. The NMR results also suggest a considerable extent of mixing between network modifying cations around non-bridging oxygen, and increases in the topological entropy with the Ca content in those quaternary silicates. The non-linear variation of O-17 NMR parameters for diverse oxygen clusters implies that Na plays a preferential role as a charge-balancing cation, while Ca can act as a network-modifying. With increasing pressure up to 8 GPa, the degree of polymerization (NBO/T) in multi-component glasses decreases with pressure while high-coordinately aluminum are dominant at 8 GPa. Na-O bond length also decreases with pressure. Through-bond and space correlation NMR spectroscopy reveals differential proximity among framework cations and anions in oxide glasses at high pressure. The Al-O-Al cluster is apparently stable up to 8 GPa, suggesting a moderate degree of chemical disorder in the multi-components melts. The core and valence electron excitation spectroscopy for oxide glasses using non-resonant inelastic x-ray scattering also reveal the pressure-induced structural changes around Ca, Fe, O, and B in complex oxide glasses and reports the changes in cation-oxygen bond length and confirms the formation of tri-coordinated oxygens with pressure. While the total entropy of melt is expected to decrease with pressure, the current spectroscopic results rather suggest an increase in the extent of diverse aspects of chemical and topological disorder in the melts with pressure. A decrease in Si-O-Si fraction at high pressure also implies a decrease in activity coefficient of silica. The formation of silica-rich melts is, thus, expected in the multi-component melts formed at elevated pressure ranges. Because the fraction of small-ring clusters and oxygen tricluster increase with pressure, the crystal-melt partitioning coefficient is likely to decrease with pressure.

Lee, S.

2009-12-01

354

Very little data is available on the thermodynamic properties of coal model compounds in liquid phase at high pressures. The authors present preliminary compilations of available data. It is anticipated that they will require vapor pressure and saturated liquid density data for coal model compounds in their high pressure liquid equation of state development. These data sets have also been compiled and are presented. They have at this time completed a review of techniques for high pressure density measurements. Some thought is being given to the possibility of building an apparatus to carry out density measurements for selected model compounds. Finally, they reproduce the Thomson et al equation and describe their preliminary procedure to test this equation with available high pressure thermodynamic data. They acknowledge the possibility that a number of modifications of the Thomson equation will be necessary before a reasonably accurate liquid state equation of state for coal model compound emerges.

Kabadi, V.N.; Ilias, S.

1993-12-31

355

The electronic, structural and phonon properties of LiMZrO{sub 3} (M=Na, K) were investigated by the density functional theory and lattice phonon dynamics. Their thermodynamic properties for CO{sub 2} absorption/desorption were analyzed in comparison with the corresponding M{sub 2}ZrO{sub 3}. Two substituted configurations of LiMZrO{sub 3} were created from Li{sub 2}ZrO{sub 3}. Both types of LiNaZrO3 have direct band gaps with values of 3.84 eV and 3.49 eV respectively. While in the case of LiKZrO{sub 3}, one type has an indirect band gap of 3.79 eV between ? and M high symmetric points while another has a direct band gap of 3.12 eV. The phonon dispersions and phonon density of states of LiMZrO{sub 3} were calculated with the direct method. From the calculated thermodynamic properties of LiMZrO{sub 3} reacting with CO{sub 2}, our results showed that by doping Na into Li{sub 2}ZrO{sub 3}, the obtained new solid LiNaZrO{sub 3} has better performance as a CO{sub 2} sorbent applying to post-combustion capture technology. For K doping into Li{sub 2}ZrO{sub 3}, our calculated thermodynamic results showed that the new solid LiKZrO{sub 3} does not gain improvement on its CO{sub 2} capture performance because its regeneration temperature is much higher than Li{sub 2}ZrO{sub 3}.

Duan, Yuhua

2014-01-01

356

NASA Astrophysics Data System (ADS)

Using first-principles calculation, we investigate systematically the properties of ZrNi2Ga with fcc L 21 Heusler structure, including the electronic structure, phonon dispersion, electron-phonon interaction and thermodynamics. The calculated electron-phonon coupling constant ? and the logarithmically averaged frequency \\langle \\omega \\rangle_{\\mathrm {log}} are 0.747 and 68.48 cm-1, respectively, giving the superconducting transition temperature Tc = 3.15 K according to the Allen-Dynes formula. It is in good agreement with the corresponding experimental Tc and ZrNi2Ga therefore can be explained as a conventional phonon-mediated superconductor.

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

2009-02-01

357

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

Dalla-Betta, Peter; Schulte, Mitchell

2009-01-01

358

NASA Technical Reports Server (NTRS)

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 (or enthalpy), molecular weight, viscosity, specific heat at constant pressure, thermal conductivity, isentropic exponent (equal to the specific heat ratio at conditions where gases do not react), Prandtl number, and entropy for air and a combustion gas mixture of ASTM-A-1 fuel and air over fuel-air ratios from zero to stoichiometric, pressures from 1 to 40 atm, and temperatures from 250 to 2800 K.

Hippensteele, S. A.; Colladay, R. S.

1978-01-01

359

NASA Astrophysics Data System (ADS)

The hysteresis loops and the thermodynamic properties of a ferroelectric or ferrielectric double walled nanotubes (A and B) are studied within the Ising model with mixed spins (SA=3/2 and SB=1/2 >) in the presence of the crystal and the external longitudinal electric fields. We use the Monte Carlo method to investigate the effects of the external electric field, the crystal field and the exchange interactions on the total polarization, susceptibility, specific heat and the internal energy of a double walled nanotubes (DWNTs).

Benhouria, Y.; Essaoudi, I.; Ainane, A.; Ahuja, R.; Dujardin, F.

2014-11-01

360

NASA Astrophysics Data System (ADS)

Mathematical modeling of the non-equilibrium condensing transonic steam flow in the complex 3D geometry of a steam turbine is a demanding problem both concerning the physical concepts and the required computational power. Available accurate formulations of steam properties IAPWS-95 and IAPWS-IF97 require much computation time. For this reason, the modelers often accept the unrealistic ideal-gas behavior. Here we present a computation scheme based on a piecewise, thermodynamically consistent representation of the IAPWS-95 formulation. Density and internal energy are chosen as independent variables to avoid variable transformations and iterations. On the contrary to the previous Tabular Taylor Series Expansion Method, the pressure and temperature are continuous functions of the independent variables, which is a desirable property for the solution of the differential equations of the mass, energy, and momentum conservation for both phases.

Hrubý, Jan

2012-04-01

361

Thermophysical properties of argon

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

Jaques, A.

1988-02-01

362

March 2012 Available online 23 March 2012 Keywords: Gemini surfactants Ethyl ammonium headgroups Enhanced aggregation capability Full understanding a b s t r a c t Cationic gemini surfactant homologues properties; (2) aggregation behavior in bulk solution, including (i) morphologies of above gemini surfactants

Huang, Jianbin

363

We present an experimental study of the pore formation processes of small amphipathic peptides in model phosphocholine lipid membranes. We used atomic force microscopy to characterize the spatial organization and structure of alamethicin- and melittin-induced defects in lipid bilayer membranes and the influence of the peptide on local membrane properties. Alamethicin induced holes in gel DPPC membranes were directly visualized

Vitaliy Oliynyk; Udo Kaatze; Thomas Heimburg

2007-01-01

364

NSDL National Science Digital Library

Standard 1 Objective 2: Students will recognize and use the identity properties of addition and multiplication, the multiplicative property of zero, the commutative and associative properties of addition and multiplication, and the distributive property of multiplication over addition. This lesson is self-paced so here are some guidelines to insure that you have learned everything you need to know by the end of the lesson: 1. What does it mean to distribute? 2. How to simplify an expression. 3. How to combine like terms once you distribute. Today you will be learning about ...

Lhalls

2009-09-22

365

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

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

2008-11-01

366

NASA Astrophysics Data System (ADS)

A first principles quantum mechanical approach is used to investigate the structural, elastic, vibrational and thermodynamic properties of the hexagonal boron nitride ( h-BN) in the framework of the pseudopotential plane wave density-functional perturbation theory for the two popular exchange-correlation functionals: local density approximation and the revised Perdew-Burke-Ernzerhof generalized gradient approximation [Y. Zhang, W. Yang, Phys. Rev. Lett, 80 (1998), 890]. The LDA calculations of the structural parameters are in good agreement with experimental results, whereas GGA largely overestimated them. The computed elastic constants are improved by performing the calculations at room temperature and using the experimental lattice parameters. A good agreement with the experimental data is obtained for the phonon frequencies using both functionals. The thermodynamic properties such as the thermal equation of state, the in-plane and out-of-plane thermal expansion coefficients (LTEC), the bulk modulus and the heat capacity are calculated at the experimental lattice parameters using the quasiharmonic approximation (+ an empirical anharmonic term) for the Helmholtz free energy. Anharmonic corrections are important at high temperature. A good agreement with the experimental data for the LTEC has been obtained with the GGA functional, especially for the out-of-plane LTEC. In contrast with recent experimental findings, our calculated bulk modulus decreases with temperature for both functionals. This (decreasing) behavior is in a good agreement with other experimental data. The constant pressure heat capacity calculated with LDA and GGA is in very good agreement with experimental results.

Hamdi, Ilyes; Meskini, Noureddine

2010-07-01

367

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

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

2014-01-01

368

NASA Astrophysics Data System (ADS)

Th xU 1-xO 2+y binary compositions occur in nature, uranothorianite, and as a mixed oxide nuclear fuel. As a nuclear fuel, important properties, such as the melting point, thermal conductivity, and the thermal expansion coefficient change as a function of composition. Additionally, for direct disposal of Th xU 1-xO 2, the chemical durability changes as a function of composition, with the dissolution rate decreasing with increasing thoria content. UO 2 and ThO 2 have the same isometric structure, and the ionic radii of 8-fold coordinated U 4+ and Th 4+ are similar (1.14 nm and 1.19 nm, respectively). Thus, this binary is expected to form a complete solid solution. However, atomic-scale measurements or simulations of cation ordering and the associated thermodynamic properties of the Th xU 1-xO 2 system have yet to be determined. A combination of density-functional theory, Monte-Carlo methods, and thermodynamic integration are used to calculate thermodynamic properties of the Th xU 1-xO 2 binary (? H mix, ? G mix, ? S mix, phase diagram). The Gibbs free energy of mixing (? G mix) shows a miscibility gap at equilibration temperatures below 1000 K (e.g., E exsoln = 0.13 kJ/(mol cations) at 750 K). Such a miscibility gap may indicate possible exsolution (i.e., phase separation upon cooling). A unique approach to evaluate the likelihood and kinetics of forming interfaces between U-rich and Th-rich has been chosen that compares the energy gain of forming separate phases with estimated energy losses of forming necessary interfaces. The result of such an approach is that the thermodynamic gain of phase separation does not overcome the increase in interface energy between exsolution lamellae for thin exsolution lamellae (10 Å). Lamella formation becomes energetically favorable with a reduction of the interface area and, thus, an increase in lamella thickness to >45 Å. However, this increase in lamellae thickness may be diffusion limited. Monte-Carlo simulations converge to an exsolved structure [lamellae || (2 1 1¯)] only for very low equilibration temperatures (below room temperature). In addition to the weak tendency to exsolve, there is an ordered arrangement of Th and U in the solid solution [alternating U and Th layers || {1 0 0}] that is energetically favored for the homogeneously mixed 50% Th configurations. Still, this tendency to order is so weak that ordering is seldom reached due to kinetic hindrances. The configurational entropy of mixing (? S mix) is approximately equal to the point entropy at all temperatures, indicating that the system is not ordered.

Shuller, Lindsay C.; Ewing, Rodney C.; Becker, Udo

2011-05-01

369

The objective of this research was to combine new experimental measurements on heat capacities, volumes, and association constants of key compounds with theoretical equations of state and with first principles quantum mechanical calculations to generate predictions of thermodynamic data. The resulting thermodynamic data allow quantitative models of geochemical processes at high temperatures and pressures. Research funded by a DOE grant to Prof. Robert Wood at the University of Delaware involved the development of new theoretical equations of state for aqueous solutions of electrolytes and non-electrolytes, methods to estimate thermodynamic data not available from experiments, collection of data on model compounds through experiments and predictions of properties using ab initio quantum mechanics. During the last three and a half years, with support from our DOE grant, 16 papers have been accepted or published, and 3 more are in preparation. Results of this research have been reported in numerous invited and contributed presentations at national and international meetings. For this report, we will briefly comment on the highlights of the last 3 and a half years and give a complete list of papers published, accepted, or submitted during these years.

Wood, Robert H.

2005-10-11

370

to Estimates of Enthalpies of Sublimation and Aqueous Solubilities Swati Puri, James S. Chickos, and William J estimations of vaporization and sublimation enthalpies, were used to construct a thermodynamic cycleHm(298.15 K))8 and sublimation enthalpies (subHm- (298.15 K))9 of PCBs. The aim of the presen

Chickos, James S.

371

NSDL National Science Digital Library

This site from the Mineralogical Society of America describes the physical properties of minerals in terms that kids will understand. The site also includes the definition of a mineral, an identification chart, and links to descriptions of the physical properties used to identify minerals.

Mineralogy 4 Kids; America, Mineralogical S.

372

Modifications to an automated low-T, adiabatic calorimeter are described. Thermodynamic data obtained with this instrument are reported for minerals from metamorphic terrains. (U.S. Bureau of Mines Report of Investigations 8451)-J.A.Z.

Hemingway, B.S.; Robie, R.A.; Kittrick, J.A.; Grew, E.S.; Nelen, J.A.; London, D.

1984-01-01

373

We have carried out self-consistent Monte–Carlo simulations for a model fluid of monovalent atoms which interact via hard-sphere repulsions and an attraction arising from the free energy of its valence electrons. This attractive energy is derived from a tight-binding model with an electronic hopping which decays exponentially with distance. The liquid–vapor phase diagram and the structural properties are obtained in

E. Chacon; P. Tarazona; J. A. Vergés; M. Reinaldofalagan; E. Velasco; J. P. Hernandez

2007-01-01

374

NASA Astrophysics Data System (ADS)

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

Osadchii, Evgeniy; Voronin, Mikhail; Osadchii, Valentin

2014-05-01

375

Atmospheric aerosols: Their Optical Properties and Effects

NASA Technical Reports Server (NTRS)

Measured properties of atmospheric aerosol particles are presented. These include aerosol size frequency distribution and complex retractive index. The optical properties of aerosols are computed based on the presuppositions of thermodynamic equilibrium and of Mie-theory.

1976-01-01

376

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

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

2014-11-01

377

NASA Astrophysics Data System (ADS)

We present the thermodynamic properties in the clathrate-type silver- and copper-oxides Ag6O8MX and Cu6O8MX (M = cation, X = anion) compounds, having Ag6O8 (or Cu6O8)-cage in their crystal structure. Ag6O8MX and Cu6O8MX are crystallized in a cubic structure with a space group of Fm3¯m. We synthesized high quality samples of Ag6O8MX and Cu6O8MX and examined the electrical resistivity, magnetic susceptibility, and specific heat measurements. The superconductivity in Ag6O8AgX (X = NO3- and HF2- have an isotropic gap symmetry by means of the specific heat data. In Cu6O8MCl, the ground sata of Cu6O8MCl compounds changed metallic to semiconducting by changing the valence state of M site ion.

Kawashima, K.; Tozawa, H.; Maruyama, M.; Ichinokawa, R.; Sugiyama, T.; Akimitsu, J.

2010-12-01

378

NASA Astrophysics Data System (ADS)

We present the thermodynamic properties in the clathrate-type silver- and copper-oxides Ag 6O 8MX and Cu 6O 8MX (M = cation, X = anion) compounds, having Ag 6O 8 (or Cu 6O 8)-cage in their crystal structure. Ag 6O 8MX and Cu 6O 8MX are crystallized in a cubic structure with a space group of Fm3barm. We synthesized high quality samples of Ag 6O 8MX and Cu 6O 8MX and examined the electrical resistivity, magnetic susceptibility, and specific heat measurements. The superconductivity in Ag 6O 8AgX (X = NO3- and HF2- have an isotropic gap symmetry by means of the specific heat data. In Cu 6O 8MCl, the ground sata of Cu 6O 8MCl compounds changed metallic to semiconducting by changing the valence state of M site ion.

Kawashima, K.; Tozawa, H.; Maruyama, M.; Ichinokawa, R.; Sugiyama, T.; Akimitsu, J.

379

This report covers the development work on the R123a/ETFE (ethyltetrahydro furfuryl ether) pair and an economic analysis of the system. Extensive thermodynamic and physical properties of the R123a/ETFE system were developed. Theoretical analysis of the data was made and showed very good performance. Subsequent testings on equipment not fully developed for R123a/ETFE confirmed this very good performance. The economic analysis showed the system competitive in most areas of the US if improved performance goals (COP = 1.5) can be met. The most important factors in determining the competitiveness are heating to cooling ratios and the relative cost of gas and electric.

Murphy, K.; Simon, R.; Phillips, B.; Marsala, J.; Whitlow, E.

1985-08-01

380

Thermodynamic properties of aqueous-alcoholic solutions of sodium chloride. H2O-2-C3H7OH-NaCl

NASA Astrophysics Data System (ADS)

The temperature-concentration dependences of the NaCl activity coefficient in aqueous solutions of isopropanol (propanol-2) at temperatures of 298.15 and 323.15 K (solution ionic force, 0.01 to 3 m; alcohol content, 10-60 wt %) were determined through the electromotive force method with an ion-selective electrode. A Pitzer model was used to mathematically describe the thermodynamic properties. The integral Gibbs energy of the solution formation of the H2O-2-C3H7OH-NaCl ternary system was performed according to Darken's method. The dissociation degree of salt in the investigated solutions was estimated using the literature data on the association constant of NaCl in aqueous-isopropanol solution.

Veryaeva, E. S.; Konstantinova, N. M.; Mamontov, M. N.; Uspenskaya, I. A.

2010-11-01

381

NASA Astrophysics Data System (ADS)

The temperature dependences of the heat capacities of 5-vinyltetrazole and poly-5-vinyltetrazole were measured by adiabatic vacuum calorimetry over the temperature range 6-(350-370) K with errors of ˜0.2%. The results were used to calculate the thermodynamic functions of the compounds, C {/p ?}, H ?( T) - H ?(0), S ?( T), and G ?( T) - H ?(0), over the temperature range from T ? 0 to 350-370 K. The energy of combustion of 5-vinyltetrazole and poly-5-vinyltetrazole was measured in an isothermic-shell static bomb calorimeter. The standard enthalpies of combustion ? c H ? and thermodynamic characteristics of formation ?f H ?, ?f S ?, and ?f G ? at 298.15 K and p = 0.1 MPa were calculated. The results were used to determine the thermodynamic characteristics of polymerization of 5-vinyltetrazole over the temperature range from T ? 0 to 350 K.

Smirnova, N. N.; Kulagina, T. G.; Bykova, T. A.; Kizhnyaev, V. N.; Petrova, T. L.

2009-01-01

382

The structural and thermodynamic properties of Cu-Ni, Cu-Ag, and Au-Ni solid solutions have been studied using a computational approach which combines an embedded-atom-method (EAM) description of alloy energetics with a second-order-expansion (SOE) treatment of compositional and displacive disorder. It is discussed in detail how the SOE approach allows the EAM expression for the energy of a substitutional alloy to be cast in the form of a generalized lattice-gas Hamiltonian containing effective pair interactions with arbitrary range. Furthermore, we show how the SOE-EAM method can be combined with either mean-field or Monte Carlo statistical mechanics techniques in order to calculate short-range-order (SRO) parameters, average nearest-neighbor bond lengths, and alloy thermodynamic properties which include contributions from static displacive relaxations and dynamic atomic vibrations. We demonstrate that the contributions to alloy heats of mixing arising from displacive relaxations can be sizeable, and that the neglect of these terms can lead to large overestimations of calculated phase-transition temperatures. The effects of vibrational free-energy contributions on the results of composition-temperature phase diagram calculations are estimated to be relatively small for the phase-separating alloy systems considered in this study. It is shown that within the SOE approach displacive effects can act only to displace the peak in the Fourier-transformed SRO parameter away from Brillouin-zone-boundary special points and towards the origin. Consistent with this result, we show that the unusual SRO observed in diffuse scattering experiments for Au-Ni solid solutions can be understood as arising from a competition between chemical and displacive driving forces which favor ordering and clustering, respectively. {copyright} {ital 1996 The American Physical Society.}

Asta, M.; Foiles, S.M. [Computational Materials Science Department, Sandia National Laboratories, P.O. Box 939, MS 9163, Livermore, California 94551-0939 (United States)] [Computational Materials Science Department, Sandia National Laboratories, P.O. Box 939, MS 9163, Livermore, California 94551-0939 (United States)

1996-02-01

383

NASA Astrophysics Data System (ADS)

The structural and thermodynamic properties of Cu-Ni, Cu-Ag, and Au-Ni solid solutions have been studied using a computational approach which combines an embedded-atom-method (EAM) description of alloy energetics with a second-order-expansion (SOE) treatment of compositional and displacive disorder. It is discussed in detail how the SOE approach allows the EAM expression for the energy of a substitutional alloy to be cast in the form of a generalized lattice-gas Hamiltonian containing effective pair interactions with arbitrary range. Furthermore, we show how the SOE-EAM method can be combined with either mean-field or Monte Carlo statistical mechanics techniques in order to calculate short-range-order (SRO) parameters, average nearest-neighbor bond lengths, and alloy thermodynamic properties which include contributions from static displacive relaxations and dynamic atomic vibrations. We demonstrate that the contributions to alloy heats of mixing arising from displacive relaxations can be sizeable, and that the neglect of these terms can lead to large overestimations of calculated phase-transition temperatures. The effects of vibrational free-energy contributions on the results of composition-temperature phase diagram calculations are estimated to be relatively small for the phase-separating alloy systems considered in this study. It is shown that within the SOE approach displacive effects can act only to displace the peak in the Fourier-transformed SRO parameter away from Brillouin-zone-boundary special points and towards the origin. Consistent with this result, we show that the unusual SRO observed in diffuse scattering experiments for Au-Ni solid solutions can be understood as arising from a competition between chemical and displacive driving forces which favor ordering and clustering, respectively.

Asta, Mark; Foiles, Stephen M.

1996-02-01

384

Sedimentary minerals are generally metastable phases that, given time and changing environmental conditions, recrystallize to more stable phases. The actual pathway of stabilization is governed by a host of kinetic factors. Unfortunately, much of the theoretical and experimental work on thermodynamic and kinetic behavior of sedimentary minerals either has not reached field practitioners in sedimentary petrology, or has been conducted

Jane S. Tribble; Rolf S. Arvidson; Fred T. Mackenzie

1995-01-01

385

"Intellectual property" (IP) is a generic legal term for patents, copyrights, and trademarks, all of which provide legal rights to protect ideas, the expression of ideas, and the inventors of such ideas (1). Intellectual property has many of the characteristics of real property (houses, buildings, and so forth); intellectual property can be bought, sold, assigned, and licensed. Additionally, the owner of IP can prevent "trespass" on his property by others, though in IP this is referred to as infringement. A patent provides legal protection for a new invention, that is, an application of a new idea, discovery, or concept that is useful. Copyright provides legal protection from copying for any creative work (e.g., works of art, literature [fiction ornonfiction], music, lyrics, photographs), as well as business and scientific publications, computer software, and compilations of information. A trademark provides rights to use symbols, particular words, logos, or other markings that indicate the source of a product or service. A further method of benefitting from an invention is simply to keep it secret, rather than to disclose it; the most famous trade secret of all time is the formula for Coca-Cola, still a closely guarded secret to this day (2,3). Trade secrets have the advantage that they never expire, but special measures are required to ensure the continued secrecy, and should it be violated, there is little legal protection for the owner (2,3). PMID:21337093

Brown, W M

2000-01-01

386

NASA Astrophysics Data System (ADS)

The dielectric properties of (Nb, Y)-doped BaTiO3 in a multilayer ceramic capacitor (MLCC) under combined external uniaxial compressive stress and dc bias field were investigated at room temperature by using a modified Ginsburg-Landau-Devonshire thermodynamic theory and the dielectric measurement. It is found that although dc bias decreases the dielectric properties dominantly, the influence of the external uniaixial compressive stress should not be neglected. When applied along a direction perpendicular to the internal electrode layer in the MLCC, the external uniaixal compressive stress will strengthen the negative effect of dc bias. In contrast, the external uniaxial compressive stress along a direction parallel to the internal electrode layer in the MLCC will increase the dielectric permittivity under dc bias field, i.e. improve the ?-V response of the MLCC. Furthermore, although there is a difference between the calculated permittivity and the measured permittivity, the effects of the combined external uniaxial compressive stress and dc bias field on the dielectric permittivity described through two approaches are in good agreement.

Yang, Gang; Yue, Zhenxing; Sun, Tieyu; Gou, Huanlin; Li, Longtu

2008-02-01

387

NASA Astrophysics Data System (ADS)

First-principles (FP) calculations of total energies for 32 different configurations of Re-W ? phase were used to fit a compound energy formalism (CEF) Hamiltonian that was used in phenomenological Calphad method calculations to model finite-temperatures thermodynamic properties. A comparison with Connolly-Williams method-cluster variation method (CWM-CVM) calculations indicates that the first-principles CEF (FP-CEF) describes temperature-dependent site occupancies as well as the CWM-CVM approximation within the temperature range of interest for applications. This result seems to indicate that the Bragg-Williams approximation (BWA) is sufficient to describe the Re-W ? phase. A complete Re-W phase diagram is calculated using the FP-CEF Hamiltonian for the ? phase. Differences between the phase diagrams, and single phase properties calculated both with, and without, the first-principles results are striking. It is expected that using the FP-CEF ?-phase description that takes into account the first-principles energetics will yield more reliable extrapolations into higher-order system.

Fries, Suzana G.; Sundman, Bo

2002-06-01

388

Molecular dynamics simulations of ionic liquids (IL) comprised of 1-butyl-3-methylimidazolium [bmim] cation and nitrate [NO(3)], azide [N(3)], or dicyanamide [N(CN)(2)] anions were conducted using the polarizable APPLE&P force field. Comparison of thermodynamic properties such as densities, enthalpies of vaporization, and ion binding energies as well as structural correlations obtained from simulations at atmospheric pressure and temperature range 298-393 K showed that IL with the N(CN)(2) anion shows significantly different characteristics as compared to ILs with the N(3) and NO(3) anions. [bmim][N(CN)(2)] IL was found to have the lowest enthalpy of vaporization and the weakest ion-ion structural correlation as compared to ILs with the other two ions. This trend was further manifested in dynamical properties characterized by self-diffusion coefficients and molecular rotational relaxation times, where IL with the N(CN)(2) anion showed the fastest dynamics as compared to other ILs. We also examine the dynamic correlations between the ions' translational and rotational motions as well as discuss the anisotropy of the latter. PMID:20849137

Bedrov, Dmitry; Borodin, Oleg

2010-10-14

389

NASA Astrophysics Data System (ADS)

The FT-IR (4000-400 cm-1) and FT-Raman spectra (3500-100 cm-1) of 2,3,4,5,6-pentafluorophenylacetic acid (PAA) have been recorded. Density functional theory calculation with LSDA/6-31+G(d,p) and B3LYP/6-31+G(d,p) basis sets have been used to determine ground state molecular geometries (bond lengths and bond angles), harmonic vibrational frequencies, infrared intensities, Raman intensities and bonding features of the title compound. The assignments of the vibrational spectra have been carried out with the help of normal coordinate analysis (NCA) following the scaled quantum mechanical force field (SQMFF) methodology. The first order hyperpolarizability (?0) and related properties (?, ?0 and ??) of PAA are calculated using B3LYP/6-31+G(d,p) method on the finite-field approach. The calculated first hyperpolarizability shows that the molecule is an attractive molecule for future applications in non-linear optics. The stability of molecule has been analyzed by using NBO analysis. The calculated HOMO and LUMO energies show that charge transfer occurs within this molecule. Mulliken population analysis on atomic charges is also calculated. Thermodynamic properties (heat capacity, enthalpy, Gibb's free energy and entropy) of the title compound at different temperatures were calculated.

Balachandran, V.; Karunakaran, V.

2014-06-01

390

In this work, we will report a combined experimental and theoretical study on molecular and vibrational structure of N,N'-di(p-thiazole)formamidine (DpTF). DpTF has been synthesized and characterized by elemental analysis, FT-IR, FT-Raman, 1H NMR, 13C NMR spectroscopy and X-ray single crystal diffraction. The FT-IR and FT-Raman spectra of DpTF were recorded in the solid phase. The optimized geometry was calculated by HF and B3LYP methods using 6-31G(d) basis set. The FT-IR and FT-Raman spectra of DpTF was calculated at the HF/B3LYP/6-31G(d) level and were interpreted in terms of potential energy distribution (PED) analysis. The scaled theoretical wavenumber showed very good agreement with the experimental values. A detailed interpretation of the infrared and Raman spectra of DpTF was reported. On the basis of vibrational analyses, the thermodynamic properties of the title compound at different temperatures have been calculated, revealing the correlations between Cp,m°, Sm°, Hm° and temperatures. Furthermore, molecular electrostatic potential maps (MESP) and total dipole moment properties of the compound have been calculated. PMID:20943433

Rofouei, M K; Fereyduni, E; Sohrabi, N; Shamsipur, M; Attar Gharamaleki, J; Sundaraganesan, N

2011-01-01

391

The B3LYP/6-31G (d) method of density functional theory (DFT) was used to study molecular geometry, electronic structure, infrared spectrum (IR) and thermodynamic properties. The heat of formation (HOF) and calculated density were estimated to evaluate the detonation properties using Kamlet-Jacobs equations. Thermal stability of 3,5,7,10,12,14,15,16-octanitro- 3,5,7,10,12,14,15,16-octaaza-heptacyclo[7.5.1.1(2,8).0(1,11).0(2,6).0(4,13).0(6,11)]hexadecane (cage-tetranitrotetraazabicyclooctane) was investigated by calculating the bond dissociation energy (BDE) at unrestricted B3LYP/6-31G (d) level. The calculated results show that the N-NO2 bond is a trigger bond during thermolysis initiation process. The crystal structure obtained by molecular mechanics (MM) methods belongs to Pna2(1) space group, with cell parameters a=12.840 Å, b=9.129 Å, c=14.346 Å, Z=6 and ?=2.292 g·cm(-3). Both the detonation velocity of 9.96 km·s(-1) and the detonation pressure of 47.47 GPa are better than those of CL-20. According to the quantitative standard of energetics and stability, as a high energy density compound (HEDC), cage-tetranitrotetraazabicyclooctane essentially satisfies this requirement. PMID:22790340

Zhao, Guo-zheng; Lu, Ming

2013-01-01

392

Bulk modulus and thermodynamic properties of electron-doped calcium manganate—Ca 1-xRE xMnO 3

NASA Astrophysics Data System (ADS)

We have investigated the thermodynamic properties of electron-doped perovskite manganite CaMnO 3 by incorporating the effect of lattice distortions. In this paper the functional relation between the MnO 6 distortions, charge and size mismatch and the thermal properties is determined. In the insulating state, distortions of the Mn-O environment are linear with calcium concentration. In the low-temperature spin-ordered ferromagnetic/anti-ferromagnetic state, at least 50% of the distortion is removed. The lattice contributions to the specific heat at constant volume ( C v(lattice)) of Ca 1-xRE xMnO 3 ( x=0.05, 0.1, 0.15, 0.20) with rare earth cation doping at the A-site has been studied as a function of temperature (10 K? T?500 K) by means of a Modified Rigid Ion Model (MRIM). In addition, the results on the bulk modulus ( B), cohesive energy ( ?), molecular force constant ( f), Reststrahlen frequency ( ?0) and Gruneisen parameter ( ?) are also presented. Findings indicate an anomalous behavior of some highly Jahn-Teller (JT) distorted Ca 1-xRE xMnO 3.

Srivastava, Archana; Gaur, N. K.

2009-12-01

393

The thermodynamic properties of 2-ethylhexyl acrylate over the temperature range from T ? 0 to 350 K

NASA Astrophysics Data System (ADS)

The temperature dependence of the heat capacity C {/p o}= f( T) 2 of 2-ethylhexyl acrylate was studied in an adiabatic vacuum calorimeter over the temperature range 6-350 K. Measurement errors were mainly of 0.2%. Glass formation and vitreous state parameters were determined. An isothermic shell calorimeter with a static bomb was used to measure the energy of combustion of 2-ethylhexyl acrylate. The experimental data were used to calculate the standard thermodynamic functions C {/p o}( T), H o( T)- H o(0), S o( T)- S o(0), and G o( T)- H o(0) of the compound in the vitreous and liquid states over the temperature range from T ? 0 to 350 K, the standard enthalpies of combustion ?c H o, and the thermodynamic characteristics of formation ?f H o, ?f S o, and ?f G o at 298.15 K and p = 0.1 MPa.

Kulagina, T. G.; Samosudova, Ya. S.; Letyanina, I. A.; Sevast'yanov, E. V.; Smirnova, N. N.; Smirnova, L. A.; Mochalova, A. E.

2012-05-01

394

Thermodynamic properties where determined (differential enthalpy, of differential entropy, integral enthalpy, and integral entropy) of the starch of rhizomes of swamp lily through water adsorption isotherms. The isotherms were determined in water activities in the range of 0.11 to 0.84, in temperatures ranging from 30 to 50 °C. The GAB equation which fits well to the experimental isotherms was used

Diego Palmiro; Ramirez ASCHERI; Wellington de Souza MOURA; José Luis; Edson Alves; Freitas JUNIOR

2009-01-01

395

NASA Astrophysics Data System (ADS)

To supplement the relatively sparse set of calorimetric data available for the multitude of high molecular weight organic compounds of biogeochemical interest, group additivity algorithms have been developed to estimate heat capacity power function coefficients and the standard molal thermodynamic properties at 25°C and 1 bar of high molecular weight compounds in hydrocarbon source rocks and reservoirs, including crystalline and liquid isoprenoids, steroids, tricyclic diterpenoids, hopanoids, and polynuclear aromatic hydrocarbons. A total of ninety-six group contributions for each coefficient and property were generated from the thermodynamic properties of lower molecular weight reference species for which calorimetric data are available in the literature. These group contributions were then used to compute corresponding coefficients and properties for ˜360 representative solid and liquid high molecular weight compounds in kerogen, bitumen, and petroleum for which few or no experimental data are available. The coefficients and properties of these high molecular weight compounds are summarized in tables, together with those of the groups and reference species from which they were generated. The tabulated heat capacity power function coefficients and standard molal thermodynamic properties at 25°C and 1 bar include selected crystalline and liquid regular, irregular and highly branched isoprenoids, tricyclic diterpanes, 17?(H)- and 17?(H)-hopanes, 5?(H),14?(H)-, 5?(H),14?(H)-, 5?(H),14?(H)-, and 5?(H),14?(H)-steranes, double ether- and ester-bonded n-alkanes, and various polynuclear aromatic hydrocarbons, including methylated biphenyls, naphthalenes, phenanthrenes, anthracenes, pyrenes, and chrysenes. However, corresponding coefficients and properties for many more saturated and unsaturated high molecular weight hydrocarbons can be estimated from the equations of state group additivity algorithms. Calculations of this kind permit comprehensive thermodynamic description of the chemical evolution of organic matter with increasing depth in sedimentary basins.

Richard, Laurent; Helgeson, Harold C.

1998-12-01

396

Inelastic neutron scattering (INS) data for SnO2 nanoparticles of three different sizes and varying hydration levels are presented. Data were recorded on five nanoparticle samples that had the following compositions: 2 nm SnO2*0.82H2O, 6 nm SnO2*0.055H2O, 6 nm SnO2*0.095H2O, 20 nm SnO2*0.072H2O, and 20 nm SnO2*0.092H2O. The isochoric heat capacity and vibrational entropy values at 298 K for the water confined on the surface of these nanoparticles were calculated from the vibrational density of states that were extracted from the INS data. This study has shown that the hydration level of the SnO2 nanoparticles influences the thermodynamic properties of the water layers and, most importantly, that there appears to be a critical size limit for SnO2 between 2 and 6 nm below which the particle size also affects these properties and above which it does not. These results have been compared with those for isostructural rutile-TiO2 nanoparticles [TiO2*0.22H2O and TiO2*0.37H2O], which indicated that water on the surface of TiO2 nanoparticles is more tightly bound and experiences a greater degree of restricted motion with respect to water on the surface of SnO2 nanoparticles. This is believed to be a consequence of the difference in chemical composition, and hence surface properties, of these metal oxide nanoparticles.

Spencer, Elinor [Virginia Polytechnic Institute and State University (Virginia Tech); Ross, Dr. Nancy [Virginia Polytechnic Institute and State University (Virginia Tech); Parker, Stewart F. [ISIS Facility, Rutherford Appleton Laboratory; Kolesnikov, Alexander I [ORNL; Woodfield, Brian [Brigham Young University; Woodfield, K [Brigham Young University; Rytting, M [Brigham Young University; Boerio-Goates, Juliana [Brigham Young University; Navrotsky, Alexandra [University of California, Davis

2011-01-01

397

NASA Astrophysics Data System (ADS)

We present magnetization, specific heat, resistivity, and Hall effect measurements on the cubic B20 phase of MnGe and CoGe and compare to measurements of isostructural FeGe and electronic-structure calculations. In MnGe, we observe a transition to a magnetic state at Tc=275K as identified by a sharp peak in the ac magnetic susceptibility, as well as second phase transition at lower temperature that becomes apparent only at finite magnetic field. We discover two phase transitions in the specific heat at temperatures much below the Curie temperature, one of which we associate with changes to the magnetic structure. A magnetic field reduces the temperature of this transition which corresponds closely to the sharp peak observed in the ac susceptibility at fields above 5 kOe. The second of these transitions is not affected by the application of field and has no signature in the magnetic properties or our crystal-structure parameters. Transport measurements indicate that MnGe is metallic with a negative magnetoresistance similar to that seen in isostructural FeGe and MnSi. Hall effect measurements reveal a carrier concentration of about 0.5 carriers per formula unit, also similar to that found in FeGe and MnSi. CoGe is shown to be a low carrier density metal with a very small, nearly temperature-independent diamagnetic susceptibility.

DiTusa, J. F.; Zhang, S. B.; Yamaura, K.; Xiong, Y.; Prestigiacomo, J. C.; Fulfer, B. W.; Adams, P. W.; Brickson, M. I.; Browne, D. A.; Capan, C.; Fisk, Z.; Chan, Julia Y.

2014-10-01

398

Naproxen (NPX)-loaded poly-(D,L-lactic-co-glycolic acid) (PLGA) microparticles were prepared by the emulsion-solvent evaporation method. The different organic solvents used significantly affects the properties of the microparticles obtained. These microparticles exhibited a controlled release profile that extends up to 15 days depending on the organic solvent used. The formulations did not exhibit zero- or first-order release kinetics and no agreement with Higuchi or Korsmeyer-Peppas models was obtained. In all cases, the dissolution profiles were fitted to the model proposed by Gallagher and Corrigan for PLGA systems. It was found that this model fully describes the dissolution processes. An interesting relationship between the NPX solubility in the organic solvents studied and some parameters obtained for the dissolution model of the microparticles prepared with the same solvents is thus obtained. Accordingly, it can be proposed that the drug solubility in organic solvents is relevant to estimate the physical characteristics of microparticles other than its dissolution profiles. PMID:23369165

Aragón, Diana Marcela; Rosas, Jaiver Eduardo; Martínez, Fleming

2013-01-01

399

Structures, vibrational frequencies, atomization energies at 0 K, and heats of formation at 0 and 298 K are predicted for the compounds As(2), AsH, AsH(2), AsH(3), AsF, AsF(2), and AsF(3) from frozen core coupled cluster theory calculations performed with large correlation consistent basis sets, up through augmented sextuple zeta quality. The coupled cluster calculations involved up through quadruple excitations. For As(2) and the hydrides, it was also possible to examine the impact of full configuration interaction on some of the properties. In addition, adjustments were incorporated to account for extrapolation to the frozen core complete basis set limit, core/valence correlation, scalar relativistic effects, the diagonal Born-Oppenheimer correction, and atomic spin orbit corrections. Based on our best theoretical D(0)(As(2)) and the experimental heat of formation of As(2), we propose a revised 0 K arsenic atomic heat of formation of 68.86 ± 0.8 kcal/mol. While generally good agreement was found between theory and experiment, the heat of formation of AsF(3) was an exception. Our best estimate is more than 7 kcal/mol more negative than the single available experimental value, which argues for a re-examination of that measurement. PMID:22091635

Feller, David; Vasiliu, Monica; Grant, Daniel J; Dixon, David A

2011-12-29

400

Local dynamics and solute-solvent exchange properties of rusticyanin (Rc) from Thiobacillus ferrooxidans have been studied by applying heteronuclear ((1)H, (15)N) NMR spectroscopy. (15)N relaxation parameters have been determined for the reduced protein, and a model-free analysis has been applied. The high average value of the generalized order parameter, S(2) (0.93), indicates that Rc is very rigid. The analysis of cross correlation rates recorded in both the reduced and the oxidized forms conclusively proves that Rc possesses the same dynamic features in both oxidation states. The accessibility of backbone amide protons to the solvent at different time scales has also been studied by applying specific heteronuclear pulse sequences and by H(2)O/D(2)O exchange experiments. These experiments reveal that rusticyanin is extremely hydrophobic. The first N-35 amino acids, not present in the other BCPs, protect the beta-barrel core from its interaction with the solvent, and thus, this is one of the main factors contributing to the hydrophobicity. Both characteristics (high rigidity and hydrophobicity) are maintained in the metal ion surroundings. PMID:12950166

Jiménez, Beatriz; Piccioli, Mario; Moratal, José-María; Donaire, Antonio

2003-09-01

401

ERIC Educational Resources Information Center

Discusses issues of copyright and the transfer or use of intellectual property as they relate to librarians. Topics addressed include the purpose of copyright laws, financial losses to publishers from pirating, cultural views of pirating, the fair use doctrine, concerns of authors of scholarly materials, impact of increasing library automation and…

St. Clair, Gloriana

1992-01-01

402

NSDL National Science Digital Library

Astronomy notes is an educational resource for introductory astronomy classes for undergraduates. This section discusses the properties of stars. such as apparent magnitude, absolute magnitude, luminosity, color, temperature, stellar velocities, compositions, and sizes. Other topics included are descriptions of parallax, redshift, blueshift, center of mass, and the HR diagram.

Strobel, Nick

2004-07-16

403

NSDL National Science Digital Library

Pump gas molecules to a box and see what happens as you change the volume, add or remove heat, change gravity, and more. Measure the temperature and pressure, and discover how the properties of the gas vary in relation to each other.

Simulations, Phet I.; Barbera, Jack; Dubson, Michael; Koch, Linda; Lemaster, Ron; Perkins, Kathy

2005-07-01

404

The team will examine how the incorporation of actinide species important for mixed oxide (MOX) and other advanced fuel designs impacts thermodynamic quantities of the host UO2 nuclear fuel and how Pu, Np, Cm and Am influence oxygen mobility. In many cases, the experimental data is either insufficient or missing. For example, in the case of pure NpO2, there is essentially no experimental data on the hyperstoichiometric form it is not even known if hyperstoichiometry NpO2+x is stable. The team will employ atomistic modeling tools to calculate these quantities

Chaitanya Deo; Davis Adnersson; Corbett Battaile; Blas uberuaga

2012-10-30

405

Thermodynamic and transport properties of single crystalline RCo2Ge2 (R=Y, La-Nd, Sm-Tm)

NASA Astrophysics Data System (ADS)

Single crystals of RCo2Ge2 (R=Y, La-Nd, Sm-Tm) were grown using a self-flux method and were characterized by room-temperature powder X-ray diffraction; anisotropic, temperature and field dependent magnetization; temperature and field dependent, in-plane resistivity; and specific heat measurements. In this series, the majority of the moment-bearing members order antiferromagnetically; YCo2Ge2 and LaCo2Ge2 are non-moment-bearing. Ce is trivalent in CeCo2Ge2 at high temperatures, and exhibits an enhanced electronic specific heat coefficient due to the Kondo effect at low temperatures. In addition, CeCo2Ge2 shows two low-temperature anomalies in temperature-dependent magnetization and specific heat measurements. Three members (R=Tb-Ho) have multiple phase transitions above 1.8 K. Eu appears to be divalent with total angular momentum L=0. Both EuCo2Ge2 and GdCo2Ge2 manifest essentially isotropic paramagnetic properties consistent with J=S=7/2. Clear magnetic anisotropy for rare-earth members with finite L was observed, with ErCo2Ge2 and TmCo2Ge2 manifesting planar anisotropy and the rest members manifesting axial anisotropy. The experimentally estimated crystal electric field (CEF) parameters B20 were calculated from the anisotropic paramagnetic ?ab and ?c values and follow a trend that agrees well with theoretical predictions. The ordering temperatures, TN, as well as the polycrystalline averaged paramagnetic Curie-Weiss temperature, ?avg, for the heavy rare-earth members deviate from the de Gennes scaling, as the magnitude of both is the highest for Tb, which is sometimes seen for extremely axial systems. Except for SmCo2Ge2, metamagnetic transitions were observed at 1.8 K for all members that ordered antiferromagnetically.

Kong, Tai; Cunningham, Charles E.; Taufour, Valentin; Bud'ko, Sergey L.; Buffon, Malinda L. C.; Lin, Xiao; Emmons, Heather; Canfield, Paul C.

2014-05-01

406

NASA Astrophysics Data System (ADS)

A new equation of state for the thermodynamic properties of the fluid phase of sulfur hexafluoride (SF6) in the form of a fundamental equation explicit in the Helmholtz energy is presented. The functional form consists of a part describing the ideal-gas state and the residual part as the difference between the real-fluid and the ideal-gas behavior. The residual part was developed using state-of-the-art linear and nonlinear optimization algorithms. It contains 36 coefficients, which were fitted to selected data for the thermal and caloric properties of sulfur hexafluoride in the single-phase region and on the vapor-liquid phase boundary. Especially for the thermal properties in the critical region, a very extensive and high-precision data set was available. In this work, information on the experimental data for the thermodynamic properties and all details of the new equation are presented. The new equation of state describes the p?T surface of sulfur hexafluoride with an uncertainty in density of less than 0.02%-0.03% from the melting line up to temperatures of 500K and pressures of 30MPa. In the critical region, including the immediate vicinity of the critical point, the uncertainty in pressure is less than 0.01%. Reliable data sets of other thermodynamic properties are reproduced within their experimental uncertainties. The primary data, to which the equation was fitted, cover the fluid region from the melting line to temperatures of 625K and pressures up to 150MPa. Beyond this range, the equation can be extrapolated with a physically reasonable behavior up to very high temperatures and pressures. In addition to the equation of state, independent equations for the vapor pressure, the saturated-liquid and saturated-vapor densities, the melting pressure, and the sublimation pressure are given. Tables of thermodynamic properties calculated from the new equation of state are listed in the Appendix.

Guder, C.; Wagner, W.

2009-03-01

407

A comparison between frozen, reactive, and total specific heats calculated by using energy levels derived from Coulomb and Debye-Hueckel potentials is reported. Results for hydrogen plasmas in local thermodynamic equilibrium show that the use of Debye-Hueckel energy levels increases the frozen specific heat of the mixture up to 40% as compared with the corresponding quantities obtained by using Coulomb energy levels, having an opposite effect on the reactive specific heat. The total specific heat of the plasma (the sum of frozen and reactive contributions) is less affected due to compensation effects. Results for the isentropic coefficient {gamma}=c{sub p}/c{sub v} show a similar trend and warn on neglecting the electronic excitation in this coefficient.

Capitelli, M. [Dipartimento di Chimica, Universita di Bari, Bari (Italy); Giordano, D. [ESA-ESTEC, Nordwijk (Netherlands); Colonna, G. [CNR-IMIP, Bari Section, 70125 Bari (Italy)

2008-08-15

408

Simple hydrides of compounds containing N, S, and O are of significant interest due to the role that they play in atmospheric chemistry and in biological pathways. There is a lack of quantitative thermodynamic data on these compounds. We have used a reliable computational chemistry approach based on valence CCSD(T) calculations extrapolated to the complete basis set limit with additional corrections to predict the heats of formation and bond dissociation energies of such compounds. The results show that compounds with the ability of the central S atom to effectively expand its valency leads to more stable isomers and, as a consequence, that those with the NSO structural motif are thermochemically more stable than those with the SNO motif. In addition, S?O bonds are preferred over N?O bonds. PMID:25043524

Méndez, Mariano; Francisco, Joseph S; Dixon, David A

2014-08-11

409

NASA Astrophysics Data System (ADS)

In order to strengthen the comprehensive understanding on the mechanism of the extraction of f-elements in a pyrometallurgical bi-phase extraction system, which is usable for dry-reprocessing of spent nuclear fuels, some thermodynamic quantities related to their affinity to the solvent materials were studied. A reductive extraction system consisting of molten alkaline chloride and liquid Bi and Zn was selected for this purpose, and the excess free energy of tri-chlorides of lanthanides associated with their solution into alkaline chloride molten salt was estimated. The standard Gibbs energy change of formation of diluted liquid alloy of lanthanides with Bi and Zn was discussed with the aid of a semi-empirical model for alloy formation. Their systematic variations along the f-series were studied to elucidate the distribution behaviors.

Yamana, Hajimu; Wakayama, Norihira; Souda, Naohiko; Moriyama, Hirotake

2000-01-01

410

NASA Technical Reports Server (NTRS)

Aldehydes are common in a variety of geologic environments and are derived from a number of sources, both natural and anthropogenic. Experimental data for aqueous aldehydes were taken from the literature and used, along with parameters for the revised Helgeson-Kirkham-Flowers (HKF) equations of state, to estimate standard partial molal thermodynamic data for aqueous straight-chain alkyl aldehydes at high temperatures and pressures. Examples of calculations involving aldehydes in geological environments are given, and the stability of aldehydes relative to carboxylic acids is evaluated. These calculations indicate that aldehydes may be intermediates in the formation of carboxylic acids from hydrocarbons in sedimentary basin brines and hydrothermal systems like they are in the atmosphere. The data and parameters summarized here allow evaluation of the role of aldehydes in the formation of prebiotic precursors, such as amino acids and hydroxy acids on the early Earth and in carbonaceous chondrite parent bodies.

Schulte, Mitchell D.; Shock, Everett L.

1993-01-01

411

NSDL National Science Digital Library

In several of the previous chapters we have talked about the strength of polymers and pointed out some of the unusual properties that make them both interesting and extremely useful materials. Now it is time to understand some of the fundamental reasons for this behavior. We will examine the structure of polymers a bit more carefully so that we can better understand their physical and mechanical properties and discover why plastics such as HDPE (high-density polyethylene), PS (polystyrene), and Kevlar are so different from each other. In this case, the "structure" on which we will focus is the morphology of the sample. We will see that polymers characteristically have amorphous and/or crystalline morphologies.

Teegarden, David

2004-01-01

412

NSDL National Science Digital Library

Students learn about the basic properties of light and how light interacts with objects. They are introduced to the additive and subtractive color systems, and the phenomena of refraction. Students further explore the differences between the additive and subtractive color systems via predictions, observations and analysis during three demonstrations. These topics help students gain a better understanding of how light is connected to color, bringing them closer to answering an overarching engineering challenge question.

Research Experience for Teachers (RET) Program, Center of Advancement of Engineering Fibers and Films,

413

NASA Astrophysics Data System (ADS)

At present, optical measurement methods are the most powerful tools for basic and applied research and inspection of the characteristic properties of a variety of materials, especially following the development of lasers and computers. Optical measurement methods are widely used for optical spectroscopy including linear and nonlinear optics and magneto-optics, conventional and unconventional optical microscopy, fiber optics for passive and active devices, optical recording for CD/DVD and MO disks, and various kinds of optical sensing.

Itoh, Tadashi; Araki, Tsutomu; Ashida, Masaaki; Iwata, Tetsuo; Muro, Kiyofumi; Yamada, Noboru

414

Synthesis, microstructures and properties of ?-aluminum oxynitride

This paper deals with the synthesis, microstructures and properties of ?-aluminum oxynitride (AlON). The thermodynamic properties of AlON were analyzed and the Gibbs energy of AlON with different compositions and temperatures were evaluated. Based on thermodynamic studies, AlON has been synthesized. The microstructures, mechanical properties and oxidation resistance of the synthetic AlON have been examined and discussed.

Wang Xidong; Wang Fuming; Li Wenchao

2003-01-01

415

Thermal equation of state and thermodynamic properties of iron carbide Fe3C to 31 GPa and 1473 K

NASA Astrophysics Data System (ADS)

experimental and theoretical studies suggested preferential stability of Fe3C over Fe7C3 at the condition of the Earth's inner core. Previous studies showed that Fe3C remains in an orthorhombic structure with the space group Pnma to 250 GPa, but it undergoes ferromagnetic (FM) to paramagnetic (PM) and PM to nonmagnetic (NM) phase transitions at 6-8 and 55-60 GPa, respectively. These transitions cause uncertainties in the calculation of the thermoelastic and thermodynamic parameters of Fe3C at core conditions. In this work we determined P-V-T equation of state of Fe3C using the multianvil technique and synchrotron radiation at pressures up to 31 GPa and temperatures up to 1473 K. A fit of our P-V-T data to a Mie-Gruneisen-Debye equation of state produce the following thermoelastic parameters for the PM-phase of Fe3C: V0 = 154.6 (1) Å3, KT0 = 192 (3) GPa, KT' = 4.5 (1), ?0 = 2.09 (4), ?0 = 490 (120) ?, and q = -0.1 (3). Optimization of the P-V-T data for the PM phase along with existing reference data for thermal expansion and heat capacity using a Kunc-Einstein equation of state yielded the following parameters: V0 = 2.327 cm3/mol (154.56 Å3), KT0 = 190.8 GPa, KT' = 4.68, ?E10 = 305 K (which corresponds to ?0 = 407 K), ?0 = 2.10, e0 = 9.2 × 10-5 K-1, m = 4.3, and g = 0.66 with fixed parameters mE1 = 3n = 12, ?? = 0, ? = 0.3, and a0 = 0. This formulation allows for calculations of any thermodynamic functions of Fe3C versus T and V or versus T and P. Assuming carbon as the sole light element in the inner core, extrapolation of our equation of state of the NM phase of Fe3C suggests that 3.3 ± 0.9 wt % ? at 5000 ? and 2.3 ± 0.8 wt % ? at 7000 ? matches the density at the inner core boundary.

Litasov, Konstantin D.; Sharygin, Igor S.; Dorogokupets, Peter I.; Shatskiy, Anton; Gavryushkin, Pavel N.; Sokolova, Tatiana S.; Ohtani, Eiji; Li, Jie; Funakoshi, Kenichi

2013-10-01

416

NASA Astrophysics Data System (ADS)

Over the last decade, a significant research effort has focused on determining the feasibility of sequestering large amounts of CO 2 in deep, permeable geologic formations to reduce carbon dioxide emissions to the atmosphere. Most models indicate that injection of CO 2 into deep sedimentary formations will lead to the formation of various carbonate minerals, including the common phases calcite (CaCO 3), dolomite (CaMg(CO 3) 2), magnesite (MgCO 3), siderite (FeCO 3), as well as the far less common mineral, dawsonite (NaAlCO 3(OH) 2). Nevertheless, the equilibrium and kinetics that control the precipitation of stable carbonate minerals are poorly understood and few experiments have been performed to validate computer codes that model CO 2 sequestration. In order to reduce this uncertainty we measured the solubility of synthetic dawsonite according to the equilibrium: NaAlCO(OH)+2HO?Al(OH)4-+HCO3-+Na+H, from under- and oversaturated solutions at 50-200 °C in basic media at 1.0 mol · kg -1 NaCl. The solubility products ( Qs) obtained were extrapolated to infinite dilution to obtain the solubility constants ( Kso). Combining the fit of these logKso values and fixing ?Cp,roat-185.5J·mol·K-1 at 25 °C, which was derived from the calorimetric data of Ferrante et al. [Ferrante, M.J., Stuve, J.M., and Richardson, D.W., 1976. Thermodynamic data for synthetic dawsonite. U.S. Bureau of Mines Report Investigation, 8129, Washington, D.C., 13p.], the following thermodynamic parameters for the dissolution of dawsonite were calculated at 25 °C: ?Gro=102.1kJ·mol, ?Hro=97.0kJ·mol and ?Sro=-17.1J·mol·K-1. Subsequently, we were able to derive values for the Gibbs energy of formation ( ?fG298.15o=-1782±2kJ·mol), enthalpy of formation ( ?fH298.15o=-1960±7kJ·mol) and entropy ( S298.15o=131±2J·mol·K-1) of dawsonite. These results are within the combined experimental uncertainties of the values reported by Ferrante et al. (1976). Predominance diagrams are presented for the dawsonite/boehmite and dawsonite/bayerite equilibria at 100 °C in the presence of a saline solution with and without silica-containing minerals.

Bénézeth, Pascale; Palmer, Donald A.; Anovitz, Lawrence M.; Horita, Juske

2007-09-01

417

Due to its fundamental importance to molecular biology, great interest has continued to persist in developing novel techniques to efficiently characterize the thermodynamic and structural features of liquid water. A particularly fruitful approach, first applied to liquid water by Lazaridis and Karplus, is to use molecular dynamics or Monte Carlo simulations to collect the required statistics to integrate the inhomogeneous solvation theory equations for the solvation enthalpy and entropy. We here suggest several technical improvements to this approach, which may facilitate faster convergence and greater accuracy. In particular, we devise a nonparametric k’th nearest neighbors (NN) based approach to estimate the water-water correlation entropy, and suggest an alternative factorization of the water-water correlation function that appears to more robustly describe the correlation entropy of the neat fluid. It appears that the NN method offers several advantages over the more common histogram based approaches, including much faster convergence for a given amount of simulation data; an intuitive error bound that may be readily formulated without resorting to block averaging or bootstrapping; and the absence of empirically tuned parameters, which may bias the results in an uncontrolled fashion. PMID:19851475

Wang, Lingle; Abel, Robert; Friesner, Richard A.

2009-01-01

418

NASA Astrophysics Data System (ADS)

We present a study of the thermodynamic and physical properties of Ti2FeGe and Ti2FeSn based on the density-functional theory first-principles calculations. Both compounds are found to be half-metallic ferromagnets with a total spin magnetic moment per formula unit of 2.00 ?B. The stability is evaluated from the physical, chemical and mechanical points of view. The Curie temperature is estimated to be 354 K for Ti2FeGe and 475 K for Ti2FeSn, respectively, which is well-above the room temperature. In addition, the half-metallicity of Ti2FeGe and Ti2FeSn is retained when the lattice constants are changed by -2.6% to 9.7% and -7.1% to 6.9%, respectively. Finally, by using a quasiharmonic Debye model, the Debye temperature, the heat capacity, the coefficient of thermal expansion, and the Grüneisen parameter have also been obtained in the present work. The present calculations show that Ti2FeGe and Ti2FeSn have a great application potential in the spin valve and magnetic tunnel junction.

Wei, Xiao-Ping; Mao, Ge-Yong; Chu, Shi-Bin; Deng, Hong; Deng, Jian-Bo; Hu, Xian-Ru

2013-09-01

419

NASA Astrophysics Data System (ADS)

A one-dimensional hydro-kinetic model is developed to study arc extinction in a low-voltage breaking device. In part 1 of this double paper, the data necessary for the implementation of the hydro-kinetic model are presented. The equilibrium composition of the plasma is derived from the law of mass action. Mixtures of air and materials ablated from the thermoplastic wall (PA66, monomer C12H22O2N2) and from the contacts (copper) are considered. Thermodynamic properties such as mass density, enthalpy and specific heat at constant pressure are then calculated. Transport coefficients (viscosity, electrical conductivity and thermal conductivity) are determined with the Chapman-Enskog theory. Concerning radiation, the net emission coefficient, corresponding to the power radiated per unit volume and per unit solid angle, is calculated. Finally, for chemical kinetics, a reliable set of reaction rate coefficients linking the chemical species of the plasma is compiled. Particular attention is paid to ionization and recombination of atomic species which are obtained with the 'bottleneck' method.

Teulet, Ph; Gonzalez, J. J.; Mercado-Cabrera, A.; Cressault, Y.; Gleizes, A.

2009-09-01

420

NASA Astrophysics Data System (ADS)

The structural, single-crystal and polycrystalline elastic and thermodynamic properties of cubic perovskite BaHfO3 under pressure were investigated using the first-principles total energy calculations in the frame of the generalized gradient approximation (GGA) combined with the quasi-harmonic Debye model in which the phonon effects are considered. The calculated ground-state quantities, such as the lattice constant, Young’s modulus, shear modulus, shear and longitudinal sound velocities and Debye temperature, were in reasonable agreement with previous theoretical and experimental data. Based on the elastic constants, bulk modulus, shear modulus and Young’s modulus, the structural stability, hardness, stiffness and the brittle and ductile behaviors, along with the binding characteristic of BaHfO3 under pressure effects, have been discussed. More importantly, the temperature and pressure dependencies of the lattice constant, bulk modulus, the Debye temperature, heat capacities, volume expansion coefficient and lattice thermal conductivity are predicted successfully in the wide temperature and pressure ranges. It was found that the effects of pressure and temperature are inversely proportional. The obtained specific heat capacities at constant pressure, at the thermal expansion coefficient and at the thermal conductivity match well with the experimental data available in the range of 300–1300 K.

Gu, Fang; Chen, Yun-Yun; Zhang, Xian-Ling; Zhang, Jia-Hong; Liu, Qing-Quan

2014-10-01

421

NASA Astrophysics Data System (ADS)

Density functional theory (DFT) is used to calculate the thermodynamic and kinetic properties of transmutant Mg in 3C-SiC due to high-energy neutron irradiation associated with the fusion nuclear environment. The formation and binding energies of intrinsic defects, Mg-related defects, and clusters in 3C-SiC are systematically calculated. The minimum energy paths and activation energies during point defect migration and small cluster evolution are studied using a generalized solid-state nudged elastic band (G-SSNEB) method with DFT energy calculations. Stable defect structures and possible defect migration mechanisms are identified. The evolution of binding energies during Mg2Si formation demonstrates that the formation of Mg2Si needs to overcome a critical nucleus size and nucleation barrier. It is found that C vacancies promote the formation of the Mg2Si nucleus, and formation of which results in a compressive stress field around the nucleus. These data are important inputs in meso- and macro-scale modeling and experiments to understand and predict the impact of Mg on phase stability, microstructure evolution, and performance of SiC and SiC-based materials during long-term neutron exposures.

Hu, Shenyang; Setyawan, Wahyu; Van Ginhoven, Renee M.; Jiang, Weilin; Henager, Charles H.; Kurtz, Richard J.

2014-05-01

422

NSDL National Science Digital Library

In order to introduce soil properties, students will determine the texture and color of a variety of local soils brought in by their classmates. Each student will describe their soil to the class, indicating where the soil came from and any interesting features regarding the site. Students will group the soils based on this little bit of knowledge and then re-evaluate their groupings after texture and color have been determined. This activity concludes with a discussion of regional soils and variations in soils.

Todd, Carrie D.

423

NASA Astrophysics Data System (ADS)

Electronic materials - conductors, insulators, semiconductors - play an important role in today's technology. They constitute "electrical and electronic devices", such as radio, television, telephone, electric light, electromotors, computers, etc. From a materials science point of view, the electrical properties of materials characterize two basic processes: electrical energy conduction (and dissipation) and electrical energy storage. Electrical conductivity describes the ability of a material to transport charge through the process of conduction, normalized by geometry. Electrical dissipation comes as the result of charge transport or conduction. Dissipation or energy loss results from the conversion of electrical energy to thermal energy (Joule heating) through momentum transfer during collisions as the charges move.

Schumacher, Bernd; Bach, Heinz-Gunter; Spitzer, Petra; Obrzut, Jan

424

Safety-relevant properties of Nanoparticles

In this paper physically measurable properties of Nanoparticles are discussed which are known or supposed to be relevant for toxicological endpoints. First a review of well-known safety-relevant facts about Nanoparticles is given. After discussing some thermodynamic properties a list of features is derived, specifying those objective parameters of Nanoparticles which are responsible for possibly hazardous properties. These can in our

Gerhard Klein

425

The properties of gases and liquids

The fourth edition of this reference volume gives the property values for more than six hundred pure chemicals and also provides a critical survey of the most reliable estimating methods. The book further demonstrates how to estimate physical and thermodynamic properties when experimental data are not available. Physical properties include critical constants, vapor pressures, viscosities, diffusion coefficients, and surface tension,

R. C. Reid; J. M. Prausnitz; B. E. Poling

1987-01-01

426

NASA Astrophysics Data System (ADS)

In this chapter, we first review the fundamental theoretical concepts of mesoscopic transport for low-dimensional systems and disordered materials. Emphasis is put on the Landauer formulation of electronic transmission, weak localization and Aharonov-Bohm phenomena, as well as Coulomb interactions through screening effects and Luttinger liquid model. A pedagogical effort is made to present the currently established physics of quantum conduction in some analytical detail, enabling the reader to further deepen the understanding of more specialized literature. In a subsequent part, the main theoretical features of quantum transport in carbon nanotubes are elaborated, mostly within the non-interacting electron regime, that is to date less controversial. The experimental part starts with a discussion of the commonly employed measurement techniques. Several transport experiments are then analyzed, with a particular focus on device-oriented aspects (field effect, Schottky barriers, etc). Finally, the main physical properties of nanotube-based composites are outlined, followed by a presentation of our current understanding of thermal properties of carbon tubules.

Roche, S.; Akkermans, E.; Chauvet, O.; Hekking, F.; Martel, R.; Issi, J.-P.; Montambaux, G.; Poncharal, Ph.

427

NASA Technical Reports Server (NTRS)

Van is used by Land Inventory Systems to measure and map property for tax assessment purposes. It is adapted from navigation system of the Lunar Rover wheeled vehicle in which moon-exploring astronauts traveled as much as 20 miles from their Lunar Module base. Astronauts had to know their precise position so that in case of emergency they could take the shortest route back. Computerized navigational system kept a highly accurate record of the directional path providing continuous position report. Distance measuring subsystem was a more accurate counterpart of automobile odometer system counts revolutions of wheels and encoders generate electrical pulses for each fractional revolution and the computer analyzed the pulses to determine the distance traveled in a given direction.

1980-01-01

428

The thermodynamic and spectral properties of a two-dimensional electron gas with an antidot in a strong magnetic field, {ital r}{sub {ital c}}{le}{ital r}{sub 0}, where {ital r}{sub {ital c}} is the cyclotron radius and {ital r}{sub 0} is the antidot effective radius, are studied via a solvable model with the antidot confinement potential {ital U}{similar_to}1/{ital r}{sup 2}. The edge states localized at the antidot boundary result in an Aharonov-Bohm-type oscillatory dependence of the magnetization as a function of the magnetic field flux through the antidot. These oscillations are superimposed on the de Haas--van Alphen oscillations. In the strong-field limit, {h_bar}{omega}{sub {ital c}}{similar_to}{epsilon}{sub {ital F}}, where {omega}{sub {ital c}} is the cyclotron frequency and {epsilon}{sub {ital F}} is the Fermi energy, the amplitude of the Aharonov-Bohm-type oscillations of the magnetization due to the contribution of the lowest edge state is {similar_to}{mu}{sub {ital B}}{ital k}{sub {ital F}}{ital r}{sub {ital c}} ({mu}{sub {ital B}} is the Bohr magneton and {ital k}{sub {ital F}} is the Fermi wave vector). When the magnetic field is decreased, higher edge states can contribute to the magnetization, leading to the appearance of a beating pattern in the Aharonov-Bohm oscillations. The role of temperature in suppressing the oscillatory contribution due to higher edge states is analyzed. Rapid oscillations of the magnetization as a function of the Aharonov-Bohm flux, occurring on a scale of a small fraction of the flux quantum {ital hc}/{ital e}, are demonstrated. The appearance of a manifold of non- equidistant frequencies in the magneto-optical-absorption spectrum, due to transitions between electronic edge states localized near the antidot boundary, is predicted.

Bogachek, E.N.; Landman, U. [School of Physics, Georgia Institute of Technology, Atlanta, Georgia 30332 (United States)] [School of Physics, Georgia Institute of Technology, Atlanta, Georgia 30332 (United States)

1995-11-15

429

Thermodynamic properties of saturated methane

0 m -ZO 0 p 04 ~ p p 0 0 0 0 p 4 0 dd 4 0 0 LEGEND 4 Gr igor 0 Armstrong Morrison Vennix -40 0 -80 d 0 -100 4 (-24. 7) 0 (-102) ~ (-273) 26 Figure 6 ~ Pressure Residual vs ~ Temperature (5) 0 CI 20 I 0 -20 -40 0 0 ISO... I20 CI CI CI D Cl CI Cl I30 I40 I 50 I60 Temperature ? K 0 I70 ISO I90 0 g -002 -003 -004 LEGEND ~ Bloomer 0 Vennix 4 Rowlinson Cl Staveley 0 0 40 4 4 30 lower than the rest, and that Keyes ' data are badly scattered. Thus...

Holt, James Louis

2012-06-07

430

Liquid tellurides: Structure and properties

In this paper a review of the thermodynamic, electrical and structural properties of liquid alkali-tellurium alloys is presented with a special emphasis on the interplay between these properties. The thermodynamic properties indicate ordering of the solutions at compositions corresponding to about 12, 50, and 67 atom% of alkali atoms. The electrical conductivity and thermopower data confirm that these liquids are true semiconductors. The neutron diffraction patterns coupled with the above information indicate that in the case of liquid K{sub 0.12}Te{sub 0.88} the measured structure is dominated by the Te-Te contribution, and is remarkably similar to that of pure liquid tellurium, while the equiatomic alloy K{sub 0.50}Te{sub 0.50} is shown to contain mostly Te pairs which are identified with Zintl ions, Te{sub 2}{sup 2{minus}}.

Saboungi, M.L.; Fortner, J.; Richardson, J.W. [Argonne National Lab., IL (United States); Petric, A. [McMaster Univ., Hamilton, ON (Canada); Doyle, M. [Northwestern Univ., Evanston, IL (United States). Div. of Educational Programs; Enderby, J.E. [Bristol Univ. (United Kingdom). H.H. Wills Physics Lab.

1992-10-01

431

Liquid tellurides: Structure and properties

In this paper a review of the thermodynamic, electrical and structural properties of liquid alkali-tellurium alloys is presented with a special emphasis on the interplay between these properties. The thermodynamic properties indicate ordering of the solutions at compositions corresponding to about 12, 50, and 67 atom% of alkali atoms. The electrical conductivity and thermopower data confirm that these liquids are true semiconductors. The neutron diffraction patterns coupled with the above information indicate that in the case of liquid K[sub 0.12]Te[sub 0.88] the measured structure is dominated by the Te-Te contribution, and is remarkably similar to that of pure liquid tellurium, while the equiatomic alloy K[sub 0.50]Te[sub 0.50] is shown to contain mostly Te pairs which are identified with Zintl ions, Te[sub 2][sup 2[minus

Saboungi, M.L.; Fortner, J.; Richardson, J.W. (Argonne National Lab., IL (United States)); Petric, A. (McMaster Univ., Hamilton, ON (Canada)); Doyle, M. (Northwestern Univ., Evanston, IL (United States). Div. of Educational Programs); Enderby, J.E. (Bristol Univ. (United Kingdom). H.H. Wills Physics Lab.)

1992-10-01

432

Static and dynamic properties of stretched water

We present the results of molecular dynamics simulations of the extended simple point charge model of water to investigate the thermodynamic and dynamic properties of stretched and supercooled water. We locate the liquid–gas spinodal, and confirm that the spinodal pressure increases monotonically with T, supporting thermodynamic scenarios for the phase behavior of supercooled water involving a “non-reentrant” spinodal. The dynamics

Paulo A. Netz; Francis W. Starr; H. Eugene Stanley; Marcia C. Barbosa

2001-01-01

433

The thermodynamic mixing properties for isometric Th{sub x}Ce{sub 1-x}O{sub 2}, Ce{sub x}Zr{sub 1-x}O{sub 2}, and Th{sub x}Zr{sub 1-x}O{sub 2} were determined using quantum-mechanical calculations and subsequent Monte-Carlo simulations. Although the Th{sub x}Ce{sub 1-x}O{sub 2} binary indicates exsolution below 600 K, the energy gain due to exsolution is small (E{sub exsoln}=1.5 kJ/(mol cations) at 200 K). The energy gain for exsolution is significant for the binaries containing Zr; at 1000 K, E{sub exsoln}=6 kJ/(mol cations) for the Ce{sub x}Zr{sub 1-x}O{sub 2} binary, and E{sub exsoln}=17 kJ/(mol cations) for the Th{sub x}Zr{sub 1-x}O{sub 2} binary. The binaries containing Zr have limited miscibility and cation ordering (at 200 K for x=0.5). At 1673 K, only 4.0 and 0.25 mol% ZrO{sub 2} can be incorporated into CeO{sub 2} and ThO{sub 2}, respectively. Solid-solution calculations for the tetragonal Th{sub x}Zr{sub 1-x}O{sub 2} binary show decreased mixing enthalpy due to the increased end-member stability of tetragonal ZrO{sub 2}. Inclusion of the monoclinic ZrO{sub 2} is predicted to further reduce the mixing enthalpy for binaries containing Zr. - Graphical abstract: Temperature-composition phase diagram showing miscibility gaps for the isometric Th{sub x}Ce{sub 1-x}O{sub 2}, isometric Ce{sub x}Zr{sub 1-x}O{sub 2}, isometric Th{sub x}Zr{sub 1-x}O{sub 2}, and tetragonal Th{sub x}Zr{sub 1-x}O{sub 2} binaries at low composition (0

Shuller-Nickles, L.C., E-mail: lshulle@clemson.edu [Environmental Engineering and Earth Science, Clemson University, 342 Computer Court, Anderson, SC 29625 (United States); Ewing, R.C., E-mail: rodewing@umich.edu [Earth and Environmental Sciences, University of Michigan, 1100 N. University Avenue, Ann Arbor, MI 48109 (United States); Becker, U., E-mail: ubecker@umich.edu [Earth and Environmental Sciences, University of Michigan, 1100 N. University Avenue, Ann Arbor, MI 48109 (United States)

2013-01-15

434

NASA Astrophysics Data System (ADS)

The phase transition, thermoelastic, lattice dynamic, and thermodynamic properties of the cubic metallic phase AlH3 were obtained within the density-function perturbation theory. The calculated elastic modulus and phonon dispersion curves under various pressures at 0 K indicate the cubic phase is both mechanically and dynamically stable above 73 GPa. The superconducting transition temperature Tc was calculated using the Allen-Dynes modification of the McMillan formula based on BCS theory. The calculations show that Tc for the cubic phase AlH3 is 8.5 K (?*=0.1) at the onset of this phase (73 GPa), while decreases to 5.7 K at 80 GPa and almost disappears at 110 GPa, consisting with experimental phenomenon that there was no superconducting transition observed down to 4 K over a wide pressure range 110-164 GPa. It is found that the soft phonon mode for branch 1, namely, the lowest acoustic mode, plays a crucial role in elevating the total EPC parameter ? of cubic AlH3. And the evolution of Tc with pressure follows the corresponding change of this soft mode, i.e. this mode is responsible for the disappearance of Tc in experiments. Meanwhile, the softening of this lowest acoustic mode originates from the electronic momentum transfer from M to R point. This phenomenon provides an important insight into why drastic changes in the diffraction pattern were observed in the pressure range of 63-73 GPa in Goncharenko's experiments. Specifically, once finite electronic temperature effects are included, we find that dynamical instabilities can be removed in the phonon dispersion for P ?63 GPa, rendering the metastability of this phase in the range of 63-73 GPa, and Tc (15.4 K) becomes remarkably high under the lowest possible pressure (63 GPa) compared with that of under 73 GPa (8.5 K). Our calculations open the possibility that finite temperature may allow cubic AlH3 to be dynamically stabilized even for pressures below 73 GPa. It is reasonable to deduced that if special techniques, such as rapid decompression, quenching, and annealing, are implemented in experiments, higher Tc can be observed in hydrides or hydrogen-rich compounds under much lower pressure than ever before.

Wei, Yong-Kai; Ge, Ni-Na; Chen, Xiang-Rong; Ji, Guang-Fu; Cai, Ling-Cang; Gu, Zhuo-Wei

2014-03-01