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

被引:169
作者
Oganov, AR
Martonák, R
Laio, A
Raiteri, P
Parrinello, M
机构
[1] ETH, Dept Mat, Crystallog Lab, CH-8093 Zurich, Switzerland
[2] ETH, Dept Chem & Appl Sci, CH-6900 Lugano, Switzerland
关键词
D O I
10.1038/nature04439
中图分类号
O [数理科学和化学]; P [天文学、地球科学]; Q [生物科学]; N [自然科学总论];
学科分类号
07 ; 0710 ; 09 ;
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(1-6) numerous geophysical observations associated with this layer - for example, the D '' discontinuity(7), its topography(8) and seismic anisotropy within the layer(9). 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 post-perovskite. In particular, the predicted slip planes are {010} for perovskite ( consistent with experiment(10,11)) and {110} for postperovskite ( in contrast to the previously expected {010} slip planes(1-4)). 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.
引用
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页码:1142 / 1144
页数:3
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