ZnSe高压相变和声子谱的第一性原理研究

摘要

Using the plane wave pseudo-potential (PWP) and the general gradient approximation (GGA) methods based on the density functional theory,we performed an ab initio investigation of thermal dynamics of ZnSe in zinc-blende (ZB),rock-salt (RS) and wurtzite (WZ) phases.The lattice parameters,equation of state and phase transition properties of ZnSe in different phases were obtained from the calculated energy-volume curves.The results show that the RS structure is a stable phase at high pressure,and the transition pressure from ZB to RS phase is 14.95 GPa,which is well consistent with the experimental and theoretical results.In addition,the phonon spectra of ZnSe in ZB and RS phases were obtained through the quasi harmonic model,and the temperature dependence of their heat capacities,entropies,and free energies were also calculated.%采用基于第一性原理的平面波赝势和广义梯度近似方法,对闪锌矿(ZB)、纤锌矿(WZ)和岩盐(RS)结构的ZnSe在0～40 GPa压力下的热力学性质及相变特性进行了研究.通过数值计算得出3种结构ZnSe的能量随体积变化的曲线,在此基础上,研究了不同结构ZnSe的晶格常数、高温高压物态方程、结构相变及弹性性质,解释了高压下结构相变的机理,并通过焓相等原理得到ZB结构到RS结构的相变压力为14.95 GPa.最后,利用VASP软件结合Phonopy计算了ZB结构和RS结构ZnSe的声子谱,并将温度效应引入,得到亥姆霍兹自由能、熵和等容热容随温度的变化关系.