标题： 地球D"层的各向异性以及MgSiO3后钙钛矿相中的堆垛层错 显示英文标题

标题： Anisotropy of Earth's D" layer and stacking faults in the MgSiO3 post-perovskite phase

摘要： (Mg,Fe)SiO3的后钙钛矿相被认为是地球最下部地幔（D"层）的主要矿物相。 其特性解释了与该层相关的众多地球物理观测结果——例如，D"不连续性、该层的地形以及地震各向异性。 在这里，我们使用一种新颖的模拟技术——第一性原理元动力学，来识别一系列低能的多型堆垛层错结构，这些结构介于钙钛矿相和后钙钛矿相之间。 元动力学轨迹表明，涉及堆垛层错形成的平面滑动是相变的最有利途径，并且是钙钛矿和后钙钛矿塑性变形的可能机制。 特别是，预测的滑移面对于钙钛矿是(010)（与实验一致），而对于后钙钛矿是(110)（与之前预期的(010)滑移面相反）。 主要滑移面定义了晶格优选取向和纹理的弹性各向异性。 后钙钛矿中的(110)滑移面需要更小程度的晶格优选取向来解释D"层中剪切波各向异性的地球物理观测结果。 显示英文摘要

摘要： The post-perovskite phase of (Mg,Fe)SiO3 is believed to be the main mineral phase of the Earth's lowermost mantle (the D" layer). Its properties explain numerous geophysical observations associated with this layer - for example, the D'' discontinuity, its topography and seismic anisotropy within the layer. Here we use a novel simulation technique, first-principles metadynamics, to identify a family of low-energy polytypic stacking-fault structures intermediate between the perovskite and post-perovskite phases. Metadynamics trajectories identify plane sliding involving the formation of stacking faults as the most favourable pathway for the phase transition, and as a likely mechanism for plastic deformation of perovskite and postperovskite. In particular, the predicted slip planes are (010) for perovskite (consistent with experiment) and (110) for postperovskite (in contrast to the previously expected (010) slip planes). Dominant slip planes define the lattice preferred orientation and elastic anisotropy of the texture. The (110) slip planes in post-perovskite require a much smaller degree of lattice preferred orientation to explain geophysical observations of shear-wave anisotropy in the D" layer.