高压下稳态六方Ge_2Sb_2Te_5结构、电子和光学性质的第一性原理研究

First-principles investigations on structural,electronic and optical properties of stable hexagonal Ge_2Sb_2Te_5 under pressures

采用基于密度泛函理论的广义梯度近似方法研究了稳态六方petrov原子序列结构Ge2Sb2Te5的结构、电子和光学性质.计算所得的平衡态晶格参数与实验数据和先前的理论结果吻合很好.基态的能带结构和态密度表明了稳态六方petrov原子序列结构的Ge2Sb2Te5持有金属性.从压强影响下体积的变化趋势发现稳态六方Ge2Sb2Te5在17GPa和34GPa出现不稳定,暗示在此压强下的相变发生,这与2009年Krbal等人的实验结果相吻合.同时,还系统地研究了稳态六方petrov原子序列结构的Ge2Sb2Te5高压下的光学性质,得到了高压下介电函数、吸收率、光反射率、折射率、消光系数和电子能量损失谱在20eV内的变化情况.

The structural, electronic and optical properties of stable hexagonal Gez Sb2 Tes with the petrov sequence have been studied by the density functional theory （DFT） method within the generalized gradi- ent approximation （GGA）. The calculated equilibrium lattice parameters are in reasonable agreement with the available experimental data and other theoretical results. Both the band structure and density of states （DOS） show that the stable hexagonal Gez Sbz Tes with the petrov sequence possesses metallic properties. The pressure-induced variations of cell volume indicate that the structure occurs unstable at 17 GPa and 34 GPa, suggesting that the phase transitions may occur at the two pressure points, which are good agreement with experimental results （Krbal. et al. 2009）. In addition, the optical properties of the stable hexagonal GezSbzTe~ with the petrov sequence under pressure are also investigated. The die- lectric function, absorption coefficient, optical reflectivity and refractive index, extinction coefficient, complex dielectric function, as well as electron energy loss are systematically obtained for radiation up to 20 eV.