scholarly journals Verification of ab-initio mixing enthalpy using thermodynamic simulation of phase equilibrium and the temperature dependences of the heat capacity of the bcc Fe- Cr alloys

2016 ◽  
Vol 130 ◽  
pp. 012065
Author(s):  
A L Udovsky ◽  
D A Vasilyev
Keyword(s):  
Heat Capacity ◽  
Phase Equilibrium ◽  
Ab Initio ◽  
Thermodynamic Simulation ◽  
Mixing Enthalpy ◽  
Temperature Dependences

EXAMINATION OF THERMOPHYSICAL CHARACTERISTICS OF A HEAT-PROTECTIVE MATERIAL BASED ON FIBERGLASS DURING DESTRUCTION

2021 ◽  
pp. 91-97
Author(s):  
D.Ya. Barinov ◽  
◽  
S.Yu. Shorstov ◽  
M.G. Razmahov ◽  
A.I. Gulyaev ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Heat Capacity ◽  
Thermophysical Properties ◽  
Thermal Effects ◽  
Space Technology ◽  
Muffle Furnace ◽  
Thermophysical Characteristics ◽  
Initial State ◽  
Protective Material ◽  
Temperature Dependences

When designing advanced samples of aviation and rocket and space technology, during the operation of which the temperature on the surface of the material can exceed the temperature of destruction, it is important to have an understanding of the values of thermophysical properties. The work investigates the thermophysical properties of fiberglass in the initial state and after the binder is burned out in a muffle furnace. The temperature dependences of thermal effects, heat capacity, thermal diffusivity and thermal conductivity were determined, density was measured, and thermogravimetric analysis was carried out. Using a stereomicroscope, the microstructure of the lateral cut of the samples was examined and its evolution was determined during the burning of the binder.

scholarly journals Study of High-Temperature Behaviour of ZnO by Ab Initio Molecular Dynamics Simulations and X-ray Absorption Spectroscopy

Materials ◽  
2021 ◽  
Vol 14 (18) ◽  
pp. 5206
Author(s):  
Dmitry Bocharov ◽  
Inga Pudza ◽  
Konstantin Klementiev ◽  
Matthias Krack ◽  
Alexei Kuzmin
Keyword(s):  
Molecular Dynamics ◽  
High Temperature ◽  
Ab Initio ◽  
Ab Initio Molecular Dynamics ◽  
Mean Square ◽  
Structural Anisotropy ◽  
X Ray ◽  
Temperature Dependences ◽  
Dynamics Simulations ◽  
X Ray Absorption

Wurtzite-type zinc oxide (w-ZnO) is a widely used material with a pronounced structural anisotropy along the c axis, which affects its lattice dynamics and represents a difficulty for its accurate description using classical models of interatomic interactions. In this study, ab initio molecular dynamics (AIMD) was employed to simulate a bulk w-ZnO phase in the NpT ensemble in the high-temperature range from 300 K to 1200 K. The results of the simulations were validated by comparison with the experimental Zn K-edge extended X-ray absorption fine structure (EXAFS) spectra and known diffraction data. AIMD NpT simulations reproduced well the thermal expansion of the lattice, and the pronounced anharmonicity of Zn–O bonding was observed above 600 K. The values of mean-square relative displacements and mean-square displacements for Zn–O and Zn–Zn atom pairs were obtained as a function of interatomic distance and temperature. They were used to calculate the characteristic Einstein temperatures. The temperature dependences of the O–Zn–O and Zn–O–Zn bond angle distributions were also determined.

Ab initio study of the gas-phase equilibrium between (H2O)4 and (H2O)8

1993 ◽  
Vol 212 (6) ◽  
pp. 644-648 ◽  
Author(s):  
A.M. Ferrari ◽  
E. Garrone ◽  
P. Ugliengo
Keyword(s):  
Phase Equilibrium ◽  
Ab Initio ◽  
Gas Phase ◽  
Ab Initio Study

Thermodynamic Functions of Zirconolite and their Uses in Computer Simulation

2002 ◽  
Vol 713 ◽  
Author(s):  
George A. Bergman ◽  
Alexandra Navrotsky ◽  
Michael I. Ojovan ◽  
Vsevolod L. Klimov ◽  
Olga K. Karlina ◽  
...  
Keyword(s):  
Computer Simulation ◽  
Heat Capacity ◽  
Thermodynamic Functions ◽  
Thermodynamic Simulation ◽  
Exothermic Reaction ◽  
The Self ◽  
Enthalpy Of Melting ◽  
Computational Thermodynamic ◽  
Bearing Materials ◽  
Thermochemical Synthesis

ABSTRACTThe enthalpy of melting and the heat capacity of liquid zirconolite (CaZrTi2O7) are estimated as equal to 200 ± 20 kJ·dmol−1 and 350 ± 50 J·mol−1·K−1, respectively. Thermodynamic functions of solid and liquid zirconolite are calculated based on these estimated data and the results of Navrotsky et al. On the basis of these thermodynamic functions, computational thermodynamic simulation is performed on the thermochemical synthesis of zirconolite-bearing materials. Demonstration indicates that synthesis of zirconolite-like matrix materials is possible using the self-sustaining exothermic reaction.

scholarly journals Iron and sulfur isotope factors for pyrite from experimental gamma-resonant studies and heat capacity

2019 ◽  
Vol 64 (4) ◽  
pp. 372-386
Author(s):  
V. B. Polyakov ◽  
E. G. Osadchii ◽  
M. V. Voronin ◽  
V. O. Osadchii ◽  
L. V. Sipavina ◽  
...  
Keyword(s):  
Heat Capacity ◽  
Kinetic Energy ◽  
Ab Initio Calculations ◽  
Ab Initio ◽  
Temperature Dependence ◽  
Isotope Exchange ◽  
Resonant Scattering ◽  
Debye Model ◽  
Crystalline Lattice ◽  
Thermal Vibrations

Pyrite Moessbauer spectra (FeS2) is measured in the temperature range from 90 to 295 K. The temperature dependence of the isomer shift is described by the Debye model with Moessbauer temperature θM=551.4 K. Using these results, we calculated the kinetic energy of thermal vibrations of the iron sublattice of pyrite and the iron β-factor for pyrite: 103lnβ57Fe/54Fe=(1.2665±0.0391)x–(0.4584±0.0283) × 10-2x2+(0.2581±0.0239) × 10-4x3; x=106/T 2 (K-2) The Moessbauer-derived iron β-factor for pyrite agrees well with results of ab initio calculations, 57Fe nuclear inelastic γ-resonant scattering synchrotron experiments and direct isotope exchange experiments between pyrite and Fe2+ dissolved in water. Heat capacity of pyrite is measured at temperatures from 79 to 300 K. Its temperature dependence are described using the Thirring expansion. Based on this expansion, the kinetic energy of thermal vibrations of total crystalline lattice of pyrite is calculated. The kinetic energy of the thermal vibrations of the sulfur sublattice in pyrite is found by subtracting the iron sublattice kinetic energy from the total kinetic energy of pyrite crystalline lattice. Temperature dependence of 34S/32S β-factor for pyrite calculated from the kinetic energy of the sulfur sublattice is following: 103lnβ34Fe/32Fe=(1.7532±0.0623) x–(1.0470±0.0752) × 10-2 x2+(1.0424±0.1126) × 10-4 x3; x=106/T 2 (K-2) This 34S/32S β-factor values exhibit a good agreement with of ab initio calculations and isotope-exchange experimental results in the pyrite-sphalerite-galenite system.

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