[SY-C6] Prediction of mechanical twinning in post-perovskite structure
The plastic properties of MgSiO3 post-perovskite are believed to be one of the key issues for the understanding of the recorded seismic anisotropy at the bottom of the Earth in a thin layer at the boundary between Earth mantle and Earth core. Indeed, the seismic waves velocities are sensitive to the development of crystallographic preferred orientations directly related to the plastic properties of the phases. Experimental results from high pressure deformation experiments, have unfortunately led to several conflicting interpretations regarding slip systems and dislocation activities in the various investigated post-perovskite material. Whereas, plastic slip in post-pervoskite has attracted much more attention, twinning mechanism has not been addressed despite some experimental evidence on low-pressure analogues such as CaIrO3 compounds.
In this work, we present a twin nucleation model in MgSiO3 and CaIrO3 post-perovskite based on a hierarchical mechanical model of the emission of 1/6<110> partial dislocations. Relying on first-principles calculations, we show that {110} twin wall formation resulting from the interaction of multiple twin dislocations occurs at rather low stresses, suggesting that twinning is a strain producing mechanism as competitive as dislocation activities in our understanding of the development of preferred orientations in post-perovskite materials.
In this work, we present a twin nucleation model in MgSiO3 and CaIrO3 post-perovskite based on a hierarchical mechanical model of the emission of 1/6<110> partial dislocations. Relying on first-principles calculations, we show that {110} twin wall formation resulting from the interaction of multiple twin dislocations occurs at rather low stresses, suggesting that twinning is a strain producing mechanism as competitive as dislocation activities in our understanding of the development of preferred orientations in post-perovskite materials.