RheoMan: a five-year, ERC-funded (Advanced Grant), project to model the rheology of the Earth's mantle

Jan 21, 2016 Dislocation glide in bridgmanite Results

New publication in Physical Review B describing glide of [100] screw dislocation MgSiO3 perovskite (bridgmanite)

The glide of [100] screw dislocation MgSiO3 perovskite is investigated by coupling atomistic calculations to an elastic interaction model. The Peierls potential, corresponding to the resistance of the crystal lattice opposed to glide, is first computed with nudged elastic band calculation (a brief review of this method can be found in section “More about”). At 0K, the dislocation glides when enough stress is reached to remove the Peierls potential. The figure below corresponds to the energy barrier opposed to the glide of [100] screw dislocation in (010) plane. With the help of stress, the energy barrier opposed to dislocation glide is decreasing. Above a given stress (which corresponds to the Peierls stress), the energy barrier is down, the resistance of the lattice is removed by the stress and the dislocation glide is energetically favorable.

 

Energy barrier of [100](010) screw dislocation

This article presents the Peierls potential of a dislocation in a complex ionic material, with a study of the sensitivity of the Peierls potential to the applied stress. Theses results are then used to determine the thermally activated motion of [100](010) dislocation, via the nucleation and propagation of kink-pairs over the Peierls potential. The kink-pair enthalpy is calculated with an elastic interaction model, using the atomistic calculations to provide the input parameters of the model (Peierls potential, self energy of the dislocation). The critical nucleation enthalpy, providing the key of thermally activated dislocation motion, is finally presented:


 

For more details, see A. Kraych, Ph. Carrez, P. Hirel, E. Clouet, & P. Cordier (2016) Peierls potential and kink-pair mechanism in high-pressure MgSiO3 perovskite: an atomic scale study, Physical Review B, 93, 014103, doi: 10.1103/PhysRevB.93.014103