Shearing mechanisms of MgSiO 3 at conditions of the Earth's D″ layer

It is shown that the mechanic properties of MgSiO 3 at temperature and pressure conditions of the Earth's D″ layer are strongly affected by perovskite/post‐perovskite stacking faults and, more generally, perovskite → post‐perovskite → perovskite phase transitions. We employ molecular dynamics simulations to explore different shearing routes for {010} layers in the perovskite structure. While the yield strength was found as about 1 GPa for layer displacement along [100], [101] and [001], the underlying mechanisms differ considerably. Shear along [101] induces the formation of a perovskite/post‐perovskite stacking fault. Once such a stacking fault arrangement is formed, further shearing is facilitated and the yield strength is reduced to 0.25 GPa. Thus, perovskite/post‐perovskite stacking faults and/or perovskite/post‐perovskite phase interfaces are suggested as the preferential slip layers of MgSiO 3 in the Earth's D″ layer.