Temperature Dependent Dislocation Mobility in MgSiO3 Perovskite: An Atomic Scale Study
Abstract:Heat transfer through the mantle is carried by convection, which involves plastic flow of the mantle constituents. Among these constituents, (Mg,Fe,Al)(Si,Al)O3 perovskite is known to be the most abundant. This material is deformed at very low strain rate (from 10-12 to 10-16 s-1), and under extreme pressure and temperature conditions (from 30 to 140GPa, 1500 to 4000°C). Its plastic behaviour is challenging to reproduce experimentally, but crucial for a better understanding of the Earth's dynamic.
The recent progress in modelling the behaviours of materials, which until now have been mostly used on metals, are applied here on MgSiO3 perovskite (Mg-Pv). We characterize dislocations at the atomic scale, as the first step of a multi-scale modelling approach on Mg-Pv plastic deformation.
We model dislocations with  and  Burgers vectors (described within the Pbnm space group), which are the shortest lattice parameters in the orthorhombic structure. Dislocation cores are determined to be described at various pressures. The resistance to glide of the dislocations is quantified indicating that (010) and (100) are the easiest slip systems in Mg-Pv over the full pressure range of the lower mantle.