(Mg, Fe)SiO3钙钛矿在高压下光学性质的第一性原理研究
First-principles studies of optical properties of (Mg, Fe)SiO3 perovskite under high pressure

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并结合局域密度近似(LDA)，计算了(Mg0.875, Fe0.125)SiO3钙钛矿在高压下的光吸收和折射率性质.结果表明：(1)计算得到的二价铁吸收带的波数位置以及其吸收带随压力增大出现的蓝移现象与实验观测结果基本一致.(2)压力是导致二价铁吸收带强度降低的一个重要因素，而二价铁自旋态的转变对其吸收带强度的降低没有贡献.因此，实验中观测到的二价铁吸收带强度的降低或许与其自旋态的转变关.(3)在近红外和可见光区，折射率随着压力增大而降低，随波数增加而缓慢上升.
The optical absorption coefficients and refraction indexes of (Mg0.875, Fe0.125)SiO3 perovskite at high pressure have been calculated by the first-principles ultra-soft pseudopotential approach of the plane wave based upon the density functional theory. The results show that: (1) The wavenumber of the absorption band of the ferrous iron and its blue-shift with pressure are basically consistent with the experimental observation. (2) The pressure is an important factor to cause a decrease in intensity of the absorption band, but its spin transition could not contribute to that. Therefore, the experimentally observed decrease in intensity of optical absorption band of the ferrous iron would not be relative with the spin transition. (3) The refractive index is reduced with increasing pressure and slightly increased with wavenumber in the near-infrared and visible spectral ranges.