第一性原理研究TiH_2的结构和热力学性质

Structural and thermodynamic properties of TiH_2 from first-principles calculations

采用基于密度泛函理论的第一性原理平面波超软赝势方法,计算了TiH2原胞体系的晶体结构、电子结构和总能,获得了体系的稳定晶格常数、总体能量与体积的函数关系.并利用准谐德拜模型研究了在不同温度(T=0～1800K)和压力(P=0～140GPa)下TiH2的热力学性质,如弹性模量与压强,热熔与温度,热膨胀系数与温度或压力的变化关系.结果表明:TiH2的晶格常数与实验值符合较好;在一定温度下,相对体积、热熔随着压强的增加而减少,德拜温度、弹性模量随着压强的增加而增加;而定容热容CV随温度升高而升高,高压下温度对TiH2热膨胀系数的影响小于压强对热膨胀系数的影响.

The crystal and electronic structure of TiH2 was calculated by the first-principle plane-wave density function theory pseudopotential method. Through the quasi-harmonic Debye model,the thermodynamic properties of TiH2 was successfully obtained in the whole temperature range from 0 to 1800 K and pressure range from 0 to 140 GPa. The thermodynamic properties including the relationship of elastic bulk modulus and pressure,heat capacities and temperature,thermal expansion and temperature and pressure. The calculated results indicated the lattice parameters are consistent with the experimental data,and when the temperature is constant,the relative volumes and heat capacities decreases with increasing pressure,Debye temperature and elastic bulk increase with increasing pressure,and temperature effect is smaller than pressure under high temperature and pressure.