Grüneisen parameter is one of the most valuable quantities in thermodynamics, which links the material properties of bulk modulus, heat capacity at constant volume, thermal expansion coefficient, and volume toget...Grüneisen parameter is one of the most valuable quantities in thermodynamics, which links the material properties of bulk modulus, heat capacity at constant volume, thermal expansion coefficient, and volume together. A new thermodynamic model of temperature-dependent potential energy is proposed here to investigate the temperature dependent Grüneisen parameter of bulk material. The newly developed thermodynamic model leads to temperature dependent analytical solutions of Grüneisen parameter and other thermo-mechanical properties including the Grüneisen equation of state. Molecular dynamics simulations are conducted on single crystalline Ni, Cu, and Au bulk crystals and the simulation results verify the newly developed thermodynamic model and quantitively evaluate the theoretically derived physical quantities. In addition, the Debye model is also employed in the study of temperature dependent Grüneisen parameter and the results also verify the theoretical approach.展开更多
Ⅰ. INTRODUCTIONAlH<sub>3</sub> is a hydride with higher hydrogen content. Thus, many scientists are very interested in it. In recent years, properties of AlH<sub>3</sub> have been much studied...Ⅰ. INTRODUCTIONAlH<sub>3</sub> is a hydride with higher hydrogen content. Thus, many scientists are very interested in it. In recent years, properties of AlH<sub>3</sub> have been much studied under the atmospheric pressure, but less under high pressure. Our purposes in studying the properties of hydrides under high pressure are as follows:展开更多
We report high-temperature thermodynamics for fcc silver by combining ab initio phonon dynamics to empirical quadratic temperature-dependent term for anharmonic part of Helmholtz free energy. The electronic free energ...We report high-temperature thermodynamics for fcc silver by combining ab initio phonon dynamics to empirical quadratic temperature-dependent term for anharmonic part of Helmholtz free energy. The electronic free energy is added through an interpolation scheme, which connects ambient condition free electron gas model to Thomas-Fermi results.The present study shows good agreement with experimental and reported findings for several thermal properties, and the discrepancy observed in some caloric properties is addressed. The decreases in the product of volume thermal expansion coefficient and isothermal bulk modulus and in the constant volume anharmonic lattice specific heat at high temperature are the clear evidences of proper account of anharmonicity. The present study also reveals that T-2-dependent anharmonic free energy is sufficient for correct evaluation of thermal pressure and conventional Grüneisen parameter. We observe that the intrinsic phonon anharmonicity starts dominating above characteristic temperature, which is attributed to higher order anharmonicity and can be related to higher order potential derivatives. We conclude that the uncorrelated and largeamplitude lattice vibrations at high temperature raise dominating intrinsic thermal stress mechanism, which surpasses the phonon-anharmonism and requires future consideration.展开更多
The temperature dependence of the ultrasonic parameters like ultrasonic velocities and Grüneisen parameters in americium monopnictides AmY (Y: N, P, As, Sb and Bi) have been studied for longitudinal and shear wav...The temperature dependence of the ultrasonic parameters like ultrasonic velocities and Grüneisen parameters in americium monopnictides AmY (Y: N, P, As, Sb and Bi) have been studied for longitudinal and shear waves along , and crystallographic directions in the temperature range 100 K - 500 K. The second- and third- order elastic constants have also been evaluated for these monopnictides using Coulomb and Born-Mayer potential. The values of elastic constants are the highest for AmN. Hence the mechanical properties of AmN are better than other monopnictides AmP, AmAs, AmSb and AmBi. Ultrasonic velocity is found large for AmP. So the ultrasonic wave propagation will be much better than others in AmP. Obtained results are compared with available results of same type of materials.展开更多
基金supported by the National Key R&D Program of China(Grant No.2017YFB0701604)the National Natural Science Foundation of China(Grant Nos.11672168&11802169)
文摘Grüneisen parameter is one of the most valuable quantities in thermodynamics, which links the material properties of bulk modulus, heat capacity at constant volume, thermal expansion coefficient, and volume together. A new thermodynamic model of temperature-dependent potential energy is proposed here to investigate the temperature dependent Grüneisen parameter of bulk material. The newly developed thermodynamic model leads to temperature dependent analytical solutions of Grüneisen parameter and other thermo-mechanical properties including the Grüneisen equation of state. Molecular dynamics simulations are conducted on single crystalline Ni, Cu, and Au bulk crystals and the simulation results verify the newly developed thermodynamic model and quantitively evaluate the theoretically derived physical quantities. In addition, the Debye model is also employed in the study of temperature dependent Grüneisen parameter and the results also verify the theoretical approach.
文摘Ⅰ. INTRODUCTIONAlH<sub>3</sub> is a hydride with higher hydrogen content. Thus, many scientists are very interested in it. In recent years, properties of AlH<sub>3</sub> have been much studied under the atmospheric pressure, but less under high pressure. Our purposes in studying the properties of hydrides under high pressure are as follows:
基金Project supported by the Major Research Project,UGC,New Delhi,India(Grant No.42-771/2013(SR))
文摘We report high-temperature thermodynamics for fcc silver by combining ab initio phonon dynamics to empirical quadratic temperature-dependent term for anharmonic part of Helmholtz free energy. The electronic free energy is added through an interpolation scheme, which connects ambient condition free electron gas model to Thomas-Fermi results.The present study shows good agreement with experimental and reported findings for several thermal properties, and the discrepancy observed in some caloric properties is addressed. The decreases in the product of volume thermal expansion coefficient and isothermal bulk modulus and in the constant volume anharmonic lattice specific heat at high temperature are the clear evidences of proper account of anharmonicity. The present study also reveals that T-2-dependent anharmonic free energy is sufficient for correct evaluation of thermal pressure and conventional Grüneisen parameter. We observe that the intrinsic phonon anharmonicity starts dominating above characteristic temperature, which is attributed to higher order anharmonicity and can be related to higher order potential derivatives. We conclude that the uncorrelated and largeamplitude lattice vibrations at high temperature raise dominating intrinsic thermal stress mechanism, which surpasses the phonon-anharmonism and requires future consideration.
文摘The temperature dependence of the ultrasonic parameters like ultrasonic velocities and Grüneisen parameters in americium monopnictides AmY (Y: N, P, As, Sb and Bi) have been studied for longitudinal and shear waves along , and crystallographic directions in the temperature range 100 K - 500 K. The second- and third- order elastic constants have also been evaluated for these monopnictides using Coulomb and Born-Mayer potential. The values of elastic constants are the highest for AmN. Hence the mechanical properties of AmN are better than other monopnictides AmP, AmAs, AmSb and AmBi. Ultrasonic velocity is found large for AmP. So the ultrasonic wave propagation will be much better than others in AmP. Obtained results are compared with available results of same type of materials.
