下地幔硅酸盐矿物的结构和电子相变对其高压下光学性质的影响
The effects of structural and electronic transitions on high-pressure optical properties of the lower-mantle silicate minerals

基于第一性原理平面波超软赝势法并结合局域密度近似，计算了(Mg0.875, Fe0.125)SiO3钙钛矿和(Mg0.9, Fe0.1)SiO3后钙钛矿晶体在高压下的光学性质.计算数据表明：(1)钙钛矿的结构相变将导致其吸收性增强，证实了基于实验数据的推断.(2)后钙钛矿二价铁吸收带的波数位置与实验观测结果相近.(3)在后钙钛矿相区，压力将导致吸收带的强度缓慢增加，但二价铁自旋态的转变对其吸收谱的影响却非常微弱.(4)钙钛矿的结构相变将导致其折射率升高；在后钙钛矿相区，压力及自旋态转变对折射率的影响不明显.(5)波数大约在12500 cm-1以下，后钙钛矿折射率随波数的增加而降低，钙钛矿的折射率则变化不大；波数大约在12500 cm-1以上，钙钛矿折射率随波数的增加而增大，后钙钛矿的折射率则显著上升.
The optical properties of (Mg0.875, Fe0.125)SiO3 perovskite and (Mg0.9, Fe0.1)SiO3 post-perovskite at high pressure have been calculated by the first-principles ultra-soft pseudopotential approach of the plane wave. The calculated data show that: (1) The structural transition in perovskite causes an increase in the absorption, confirming the inference from experimental data. (2) The wavenumber peak of the ferrous-iron absorption band in post-perovskite is close to the experimental observations. (3) In the post-perovskite region, the absorption-band intensity is slightly enhanced with increasing pressure, but the spin transition in ferrous-iron could have little influence on the absorption spectrum. (4) The perovskite-post perovskite structural transition results in a refractive-index increase; in the post-perovskite region, the effects of the pressure and spin transition are not obvious. (5) Below the wavenumbers of ~12500cm-1, the post-perovskite refractive index is reduced with increasing wavenumber, but the perovskite refractive index has been changed slightly; over ~12500cm-1, the perovskite refractive index is enhanced with increasing wavenumber, but the post-perovskite refractive index increases more significantly.