Abstract
The motion of [100](010) screw dislocations via a kink-pair mechanism is investigated in high-pressure ${\mathrm{MgSiO}}_{3}$ perovskite by means of atomistic calculations and an elastic interaction model for kink nucleation. Atomistic calculations based on the nudged elastic band method provide the Peierls potential, which is shown to be dynamically asymmetric and stress dependent. The elastic interaction model adjusted to match kink width computed atomistically, is used to evaluate the critical nucleation enthalpy. We demonstrate that the kink-pair mechanism in ${\mathrm{MgSiO}}_{3}$ perovskite is controlled by the nucleation of kinks along the [100] screw dislocation.
Highlights
Convective flow in the deep Earth is responsible for heat transport toward the surface and controls the global dynamics of our planet
A better understanding of the deformation mechanism of magnesium silicate perovskite (Mg-Pv) at pressure and temperature conditions of the Earth’s mantle remains, mandatory to evaluate the role of plastic deformation in the development of convective flow
As Mg-Pv crystallizes in a low symmetry orthorhombic structure, it is not surprising to find an asymmetric Peierls potential
Summary
Convective flow in the deep Earth is responsible for heat transport toward the surface and controls the global dynamics of our planet. Convective flow and seismic properties in the deep mantle are strongly linked to the physical properties of bridgmanite under very high-pressure conditions (30–120 GPa). With the recent progress in high-pressure techniques, deformation experiments of magnesium silicate perovskite (Mg-Pv) have been successfully undertaken in lower mantle pressure and temperature conditions [3,4,5,6,7]. At conditions of the uppermost lower mantle (P = 30 GPa, close to 670 km depth), some of these studies highlighted the presence of dislocations and the development of crystal preferred orientations in the deformed samples [6,7]. A better understanding of the deformation mechanism of Mg-Pv at pressure and temperature conditions of the Earth’s mantle remains, mandatory to evaluate the role of plastic deformation in the development of convective flow
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