YbB6晶体结构、物态方程、弹性和热学性质的第一性原理计算

Structure, equation of states, elastic and thermal properties of YbB6 crystal: First-principles calculations

摘要:

基于第一性原理的密度泛函理论及准谐德拜模型, 研究了YbB6的晶体结构、状态方程(EOS)、弹性性质和热学性质. 计算得到的YbB6晶体晶格常数、体弹模量、弹性常数和实验符合得很好. 状态方程的研究结果显示, 压强和温度对YbB6晶体体积的影响都非常显著, 在高温和低压下, 压强对YbB6晶体体积的影响比在低温和低压大. 在讨论的压强和温度范围内, 压强对YbB6晶体的体弹模量的影响要比温度的影响大. 弹性常数及与弹性相关量的计算结果显示, 在零温零压下, YbB6晶体结构是稳定的, 具有延展性, 是中心力场固体. 计算的定压、定体热容及热膨胀系数的结果表明, 压强对YbB6晶体的热容和热膨胀系数的影响比温度的影响小.

Abstract:

Based on the first-principles density functional theory calculations combined with the quasi-harmonic Debye model, the ground state structure, equation of state (EOS), elastic and thermal properties of YbB6 crystal are studied. The calculated results of the lattice constant, bulk modulus and elastic constants in YbB6 crystal are in good agreement with the experimental results. The research results of EOS show that the effects of pressure and temperature on the volume of YbB6 crystal are very significant, and the pressure has more influence on the volume of the YbB6 crystal under higher temperatures and lower pressures than that of case under the lower temperatures and lower pressures. Furthermore, the bulk modulus is greatly affected by the pressure compared with the temperature in the whole pressure and temperature ranges. The results of elastic constants and elasticity-relevant properties show that the YbB6 crystal is mechanically stable with a ductile manner and is solid with a central force field under zero temperature and 0 GPa pressure. The calculated values of the heat capacity and thermal expansion coefficient indicate that the influence of pressure on the heat capacity and expansion coefficient of YbB6 crystal is less than that of temperature.