高压相变晶体化学Ⅱ. 高压下镁硅酸盐和氧化物中硅氧离子的半径变化和迁移行为

High-Pressure Phase Transition Crystal Chemistry Ⅱ. Changes of Ionic Radius and Ionic Migration Behaviors of Oxygen and Silicon in Magnesium Silicates and Silicon-Magnesium Oxides Under High Pressures

考查了高压下镁硅酸盐和硅镁氧化物(橄榄石、硅镁尖晶石、钙钛矿及后钙钛矿)中氧、硅的离子半径,发现在压力增加的条件下,不论相变是否发生,氧离子半径总是随压力增加而逐渐缩小的,但对于阳离子硅来说,相变导致它从配位数低的多面体向配位数高的多面体迁移时,其离子半径是逐渐增大的。这种现象与SiO2在高压相变时硅离子增大的趋势完全一致。这种现象可能是在高压下离子化合物逐渐向金属相化合物转变引起的。

In this paper the study on crystal chemical behavior of silicon and oxygen ions in Mg2SiO4 and MgSiO3 under high pressures were continued.Ionic radii of oxygen and silicon in magnesium silicate and magnesium-silicon oxides,i.e.olivine,ringwoodite,and the phases of Mg2SiO4,MgSiO3（perovskite and post perovskite）under high pressures were investigated.The result indicated that ionic radius of oxygen decreased gradually with increasing pressure,but cation radius of silicon increased with increasing pressure and the occurrence of phase transition.Radii of silicon cation of SiO2 polymorphs also increased with phase transition under high pressures.This variation may be result of a transition from ionic compounds to metallic compounds under high pressures.