MgSiO_3后钙钛矿在三轴应力场中的第一原理模拟及地球物理学应用  

First principle simulation of MgSiO_3 post-perovskite in triaxial stress field and geophysical application

作　　者：张虎[1] 刘斌[1] 杨莉[2] 祖小涛[2] 戴志阳[1] 杨凤琴[1] 吕彦[1] 

机构地区：[1]中国科学技术大学地球和空间科学学院,安徽合肥230026 [2]电子科技大学应用物理系,四川成都610054

出　　处：《中国科学技术大学学报》2007年第8期922-926,共5页JUSTC

基　　金：国家自然科学基金(40474016)资助

摘　　要：MgSiO3后钙钛矿具有明显的弹性各向异性,可以解释地球核幔边界D″层中地震波的不连续性等现象,但目前的研究对晶格优选方位的机理一直没有好的解释.针对复杂的D″层应力环境中晶体特性与应力场和晶轴取向的密切关联,引入三轴应力场对矿物性质进行约束,模拟应力场状态下后钙钛矿相弹性性质,通过最小能量原理获得稳定的晶体空间取向类型.对具有最小能量类型的晶体弹性常数和地震波速研究发现,晶体a轴取向平行于最大压缩方向;以b轴为垂直对称轴的剪切波横向各向异性(横向各向同性平均)大于静水力场中的剪切波横向各向异性.结果支持以(010)为主滑移面的观点,为D″层各向异性和晶体取向研究提供新的数据和证据.MgSiO3 post-perovskite which is remarkably elastic anisotropic can explain the core-mantle boundary discontinuity（D＂ discontinuity）, but the mechanism for lattice preferred orientation still defies satisfactory explanation. Considering the complex stress environment of D＂ and properties of minerals associated with the stress field and the orientation of crystallographic axes, single-crystal energy in triaxial stress field was calculated to study elastic constants, single crystal and aggregated acoustic velocities. The conditions were found under which energy is a minimum. The calculation results show that the a-axes tend to align paralleling to the maximal compression direction, and transversely anisotropism in shear wave velocities with the b-axis as vertical symmetry axis becomes greater than that under the condition in hydrostatic stress field. The results also support （010） plane as the dominant slip plane and do supply new evidence of LPO and anisotropic properties of D＂ layer.

关 键 词：MgSiO3后钙钛矿 三轴应力场 弹性常数 晶格优选方位 各向异性 

分 类 号：P578.491[天文地球—矿物学] P315.2[天文地球—地质学]