Modeling defects and plasticity in MgSiO3 post-perovskite: Part 2-screw and edge 100 dislocations

AM Goryaeva and P Carrez and P Cordier, PHYSICS AND CHEMISTRY OF MINERALS, 42, 793-803 (2015).

DOI: 10.1007/s00269-015-0763-8

In this study, we propose a full atomistic study of 100 dislocations in MgSiO3 post-perovskite based on the pairwise potential parameterized by Oganov et al. (Phys Earth Planet Inter 122:277-288, 2000) for MgSiO3 perovskite. We model screw dislocations to identify planes where they glide easier. We show that despite a small tendency to core spreading in 011, 100 screw dislocations glide very easily (Peierls stress of 1 GPa) in (010) where only Mg-O bonds are to be sheared. Crossing the Si- layers results in a higher lattice friction as shown by the Peierls stress of 100(001): 17.5 GPa. Glide of 100 screw dislocations in 011 appears also to be highly unfavorable. Whatever the planes, (010), (001) or 011, edge dislocations are characterized by a wider core (of the order of 2b). Contrary to screw character, they bear negligible lattice friction (0.1 GPa) for each slip system. The layered structure of post-perovskite results in a drastic reduction in lattice friction opposed to the easiest slip systems compared to perovskite.

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