高温高压下(Mg,Fe)SiO_3钙钛矿的相稳定性

Phase stability of pervoskite at high temperature and pressure

在冲击波物理实验测量高温高压下（Mg，Fe）SiO3钙钛矿的声速结果的基础之上，发现了在70～85GPa压力范围内发生了声速的“软化”现象．利用沃尔什热力学-冲击压缩线方法和Mie-Grüneisen物态方程等熵线方法计算了声速测量实验中的冲击温度，并计算了冲击压缩下70～85OPa压力范围内的相变边界，然后用电子自旋相变的自由能变化估算了这个压力范围内的相变边界，发现两种方法计算得到的相变边界相同，从而证实这种声速“软化”现象是由（Mg，Fe）SiO3钙钛矿的晶格畸变引起的，没有发生（Mg，Fe）SiO3钙钛矿向氧化物（Mg，h）O＋SiO2的分解相变、

On the basis of the sound velocities of （Mg, Fe）SiO3 measured by shock wave experiments, the softening phenomena at 70- 85 GPa has been found. By the line methods of Walsh thermodynamics-shocked compressed and Mie-Griineisen equation of state-isoentropy, the shocked temperature and the phase boundary at 70- 85 GPa have been calculated. The phase boundary has also been obtained by the free energy change of electronic spin. The two results are same. The fact proves that the softening phenomena arise by means of the crystal lattice distortion. There is no possibility for the chemical decomposition reaction of （Mg, Fe）SiO3 to oxides SiO2 and （Mg, Fe） O occurring under shocked compression.