scholarly journals On the Jumps of Volume, Enthalpy and Entropy at the Melting Point, the Thermal Conductivity and Thermal Diffusivity for F.C.C. Au: the Temperature- and Pressure-Dependences

2021 ◽  
Vol 22 (4) ◽  
pp. 511-530
Author(s):  
Nguyen Quang  Hoc ◽  
Bui Duc  Tinh ◽  
Nguyen Duc  Hien ◽  
Le Hong  Viet
Keyword(s):  
Thermal Conductivity ◽  
Thermal Diffusivity ◽  
Melting Point ◽  
Melting Curve ◽  
Debye Model ◽  
High Temperature And Pressure ◽  
Enthalpy And Entropy ◽  
Temperature And Pressure ◽  
Limiting Condition ◽  
Good Agreement

The melting temperature, the jumps of volume, enthalpy and entropy at the melting point, the isothermal compressibility, the thermal expansion coefficient, the heat capacity at constant volume, the Grüneisen parameter, the Debye temperature, the electrical resistivity, the thermal conductivity, and the thermal diffusivity for defective and perfect f.c.c. metals are studied by combining the statistical moment method (SMM), the limiting condition of the absolute stability of the crystalline state, the Clapeyron–Clausius equation, the Debye model, the Grüneisen equation, the Wiedemann–Franz law, and the Mott equation. Numerical calculations are carried out for Au under high temperature and pressure. The calculated melting curve of Au is in good agreement with experiments and other calculations. Obtained results are predictive and orient towards new experiments.

scholarly journals Study on the Melting Temperature, the Jumps of Volume, Enthalpy and Entropy at Melting Point, and the Debye Temperature for the BCC Defective and Perfect Interstitial Alloy WSi under Pressure

2021 ◽  
Vol 5 (6) ◽  
pp. 153
Author(s):  
Hoc Nguyen Quang ◽  
Hien Nguyen Duc ◽  
Dung Nguyen Trong ◽  
Van Cao Long ◽  
Ştefan Ţălu
Keyword(s):  
Melting Point ◽  
Debye Temperature ◽  
Melting Temperature ◽  
Absolute Stability ◽  
Crystalline State ◽  
Nearest Neighbor ◽  
Vacancy Concentration ◽  
Melting Curve ◽  
Debye Model ◽  
Enthalpy And Entropy

The objective of this study is to determine the analytic expressions of the Helmholtz free energy, the equilibrium vacancy concentration, the melting temperature, the jumps of volume, enthalpy the mean nearest neighbor distance and entropy at melting point, the Debye temperature for the BCC defective, the limiting temperature of absolute stability for the crystalline state, and for the perfect binary interstitial alloy. The results obtained from the expressions are combined with the statistical moment method, the limiting condition of the absolute stability at the crystalline state, the Clausius–Clapeyron equation, the Debye model and the Gruneisen equation. Our numerical calculations of obtained theoretical results were carried out for alloy WSi under high temperature and pressure. Our calculated melting curve and relation between the melting temperature and the silicon concentration for WSi are in good agreement with other calculations. Our calculations for the jumps of volume, enthalpy and entropy, and the Debye temperature for WSi predict and orient experimental results in the future.

scholarly journals Electronic Contribution to the Thermal Diffusivity: DyBa2Cu3O7-y and Y0.9Ca0.1Ba2Cu3O7-z

1998 ◽  
Vol 12 (29n31) ◽  
pp. 3087-3090 ◽  
Author(s):  
S. Dorbolo ◽  
H. Bougrine ◽  
M. Ausloos
Keyword(s):  
Thermal Conductivity ◽  
Thermal Diffusivity ◽  
Band Structure ◽  
Order Parameter ◽  
Saddle Points ◽  
Three Dimensional ◽  
Electronic Contribution ◽  
Wave Symmetry ◽  
D Wave ◽  
Good Agreement

The electronic contribution to the specific heat and the thermal conductivity of high-T c superconductors is calculated with a three-dimensional band structure including saddle points and a Lawrence–Doniach coupling between the CuO2 planes. The electronic thermal diffusivity is deduced for s- and d-wave symmetry of the order parameter. Data on DyBa2Cu3O 7-y and Y0.9Ca0.1Ba2Cu3O 7-z and theory are in good agreement on the change of the slope near T c .

scholarly journals First Principles Calculations on Elastic, Thermodynamic and Electronic Properties of Co2Zr and Co2Ti at High Temperature and Pressure

2020 ◽  
Vol 10 (6) ◽  
pp. 2097
Author(s):  
Mi-An Xue ◽  
Xiaoli Yuan ◽  
Cheng Zhong ◽  
Peng Wan
Keyword(s):  
High Temperature ◽  
Electronic Properties ◽  
Debye Temperature ◽  
First Principles ◽  
Density Functional ◽  
Debye Model ◽  
First Principles Calculations ◽  
Generalized Gradient ◽  
High Temperature And Pressure ◽  
Temperature And Pressure

Co2Zr and Co2Ti are both cubic crystals with a Cu2Mg-type structure. The elastic, thermodynamic and electronic properties of the intermetallic compounds Co2Zr and Co2Ti are investigated by using ab initio plane-wave pseudopotential density functional theory (PWPDFT) and generalized gradient approximation (GGA) under high temperature and pressure. The partially calculated results are consistent with the available experimental data. The elastic properties of Co2Zr and Co2Ti under high pressure were first studied by first principles calculations. The results indicate that the elastic constants, elastic modulus and Poisson’s ratio are functions of pressure, indicating that the effect of pressure on the ductility and anisotropy is significant. The thermodynamic properties are also calculated by the quasi-harmonic Debye model. In the range of 0~100 GPa pressure and 0~1500 K temperature, the Debye temperature Θ, the heat capacity CV and the thermal expansion α vary with pressure and temperature. Co2Ti has a higher Debye temperature than Co2Zr under the same pressure. Decreasing temperature and increasing pressure have the same effects on CV and α. The electron density difference and density of states of Co2Zr and Co2Ti are finally investigated. The results show that both Co2Zr and Co2Ti are typically metal crystals but Co2Zr has greater covalence than Co2Ti.

Property and Microstructure of CNTs/AlN Ceramics

2010 ◽  
Vol 434-435 ◽  
pp. 48-49 ◽  
Author(s):  
Hong Lei Wang ◽  
Xin Gui Zhou ◽  
Hai Jiao Yu ◽  
Shuang Zhao ◽  
Zheng Luo
Keyword(s):  
Thermal Conductivity ◽  
High Temperature ◽  
Fracture Surface ◽  
Flexural Strength ◽  
Grain Boundary ◽  
Bulk Density ◽  
Hot Pressing ◽  
Microstructure Observation ◽  
High Temperature And Pressure ◽  
Temperature And Pressure

CNTs/AlN ceramics were fabricated by hot-pressing and their bulk density, flexural strength, thermal conductivity were characterized. The microstructure was also investigated. The fracture surface were analyzed by SEM. TEM was used for analyzing the microstructure. It is found that the density, mechanic and thermal-conductivity properties markedly decreased as the CNTs reinforced AlN ceramic; through microstructure observation, the conglomeration of CNTs mostly exist among the AlN grain boundary, and the CNTs were scathed by the high temperature and pressure of the hot-pressing.

Solubility of Hydrogen and Vacancy Concentration in Nickel from First Principles Calculations

MRS Advances ◽  
2016 ◽  
Vol 1 (24) ◽  
pp. 1785-1790 ◽  
Author(s):  
Arnaud Metsue ◽  
Abdelali Oudriss ◽  
Xavier Feaugas
Keyword(s):  
Experimental Data ◽  
Melting Point ◽  
Single Crystals ◽  
First Principles ◽  
Thermal Equilibrium ◽  
Vacancy Concentration ◽  
First Principles Calculations ◽  
Solution Enthalpy ◽  
Enthalpy And Entropy ◽  
Good Agreement

ABSTRACTThe hydrogen solubility and the vacancy concentration in Ni single crystals at thermal equilibrium with a H2 gas have been determined from a combination of first principles calculations and statistical mechanics up to the melting point. We show that the H solubility increases and the vacancy formation is promoted at high PH2. The apparent solution enthalpy and entropy are extracted from the fit of the solubility with the Sieverts’s law. We show that our results are in good agreement with previous experimental data at PH2=1 bar. The vacancy concentration increases with PH2 whatever the temperature but the effect of H is more significant at low temperature. However, the vacancy concentration and the H solubility in single crystals remain small and a comparison with the experimental data on polycrystals indicates that the grain boundaries may play the most important source of superabundant vacancies and preferential sites for H incorporation.

First Principle Study for the Melting Properties of Face-Centred-Cubic Aluminum

2013 ◽  
Vol 535-536 ◽  
pp. 342-345
Author(s):  
Lin Zhou ◽  
Qing Ming Zhang ◽  
Guang Fu Ji ◽  
Zi Zheng Gong
Keyword(s):  
Diamond Anvil Cell ◽  
Melting Curve ◽  
Structure Optimization ◽  
Debye Model ◽  
First Principle ◽  
Static Calculation ◽  
Different Temperatures ◽  
Diamond Anvil ◽  
Melting Properties ◽  
Good Agreement

Ab initio electronic structure optimization and total energy calculations for fcc aluminum are used to study the equation of state (EOS).Through fitting to quasi-harmonic Debye model, the thermodynamics properties of different temperatures are calculated. The melting curve at different pressures is presented based on Lindemann measures. The results show that the calculated EOS and the revised melting curve both are in a good agreement with the shock compression and the diamond-anvil-cell (DAC) data. The results illustrate that we can use simple static calculation method which takes less time to gain reasonable melting results. It can be used in the qualitative forecast for materials with difficult experiments.

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