高压下B_(12)As_2晶体结构及晶格振动的第一性原理研究

First-Pprinciples Study on the Crystalline Structure and Lattice Vibration of B_(12)As_2 Crystal Under High Pressure

利用基于密度泛函理论的第一性原理计算,本文研究了二十面体硼化砷(B12As2)在外部静水压强0～30GPa范围内的晶格结构变化。计算结果表明:二中心B-B键在高压下压缩率最大,硼二十面体基团相对比较稳定,外界压力对其影响较小。利用基于密度泛函微扰理论的计算,本文给出了在0～30GPa范围内B12As2晶体所有12个拉曼活性振动模的频率随外部静水压的变化,并给出了零压附近的压强系数和Grüneisen系数。计算结果表明,低频区有关As原子振动的模和频率为502.7cm-1的Eg模对于压力较为不敏感;高频区有关二中心B-B键振动的模对于压力最为敏感。

In this paper,the crystalline structure of icosahedral boron arsenide（B12As2） is studied under hydrostatic pressure in the range of 0~30 GPa using first-principles calculations based on the density functional theory.The results show that the two-center B-B bonds are mostly compressed under pressure,and the icosahedra are relatively stable,which are least compressed by the external pressure.Using the density functional perturbation theory,frequencies of all the 12 Raman-active vibrational modes in B12As2 crystal are calculated in the pressure range of 0~30 GPa,the pressure coefficients at 0 GPa and the Grüneisen parameters are also given.The results indicate that the modes in the low frequency part that are related to the vibrations of As and the 502.7 cm-1 Eg mode are comparatively insensitive to pressure,and the high frequency modes that are related to the vibrations of the two-center B-B bonds are relatively most sensitive to pressure.