Numerical modelling of dislocations and deformation mechanisms in CaIrO 3 and MgGeO 3 post-perovskites—Comparison with MgSiO 3 post-perovskite

Abstract

In this study, we propose a theoretical approach to test the validity of the isomechanical analogues for post-perovskite structures. Intrinsic plastic properties are evaluated for three materials exhibiting a post-perovskite phase: MgSiO 3, MgGeO 3 and CaIrO 3. Dislocation properties of each structure are determined using the Peierls–Nabarro model based on first-principles calculations of generalised stacking fault and the plastic properties are extended to crystal-preferred orientations using a visco-plastic self-consistent method. This study provides intrinsic parameters of plastic deformation such as dislocation structures and Peierls stresses that can be directly compared between the three materials. It appears that it is very difficult to draw any simple conclusions on polycrystalline deformation simply by comparing single crystal properties. In particular, contrasting single crystal properties of MgSiO 3 and CaIrO 3 lead to similar crystal-preferred orientation of the polycrystal aggregates.