【摘要】 后钙钛矿MgSiO3对于重新认识地球的基本结构和成分具有重大意义.采用基于密度泛函理论的第一性原理计算对后钙钛矿MgSiO3在静水压力和单轴压力下的弹性性质和地震波速特征进行了研究.首先通过总能比较和力学稳定性判据验证了后钙钛矿MgSiO3在高压下的稳定性,并且计算得到的晶格常数与前人结果符合很好.计算表明在高压下(D层),后钙钛矿具有比钙钛矿大的体变模量、剪切模量及密度,并且具有大的地震波速,这与地震观测D层中地震波速的不连续性一致.在静水压力作用下,计算结果显示压缩波各向异性基本保持不变,而剪切波各向异性增强.有单轴应力作用时,后钙钛矿地震波各向异性差异非常明显,当压力作用在a轴或c轴上时,能够得到比对应静水压力下后钙钛矿更强的各向异性,而恰好相反的是,压缩b轴时,各向异性有减小的趋势.本研究能为解释地幔底部地震波不连续性和横向差异提供一定的参考.更多还原

【Abstract】 The elastic property and seismic velocity of Post-Perovsikt(PPv)MgSiO3 have been studied using first-principles calculations based on density of functional theory(DFT).Firstly,the stability of PPv-MgSiO3 under high pressure is validated through total energy calculations and the criterion of mechanical stability.The obtained lattice constants are in accordance well with the previous calculated and experimental results.The calculations indicate that the bulk modulus,shear modulus,density and seismic velocity of PPv-MgSiO3 are larger than those of Pv-MgSiO3,which are in agreement with seismic observations.Under hydrostatic pressure,the anisotropy of compressed wave has little change,while that of shear wave is enhanced.For the uniaxial pressure,both compressed and shear anisotropies are increased with strain along the a or c axis,while are decreased with strain along the b axis with respect to that of hydrostatic pressure.This study is useful for explaining the seismic velocity discontinuity and lateral heterogeneity in the D’’ layer.更多还原