Abstract

Abstract

Highlights

  • In the Earth’s mantle, with increasing depth, pressure increases rapidly, reaching values as high as 136 GPa at the base of the mantle.[1]. These ultrahigh pressures have profound implications on the rheology of the Earth’s constituents that can be quite different from that observed at ordinary pressure

  • Within a recent elastoplastic framework proposed by Fressengeas et al.[16] and Acharya–Fressengeas,[17] it was shown that dislocation, disclination and generalized-disclination (g-disclination) density fields were appropriate mathematical objects for a consistent continuous description of the atomic defected structures, energetics, and dynamics of grain boundary (GB).[18,19,20]

  • By using an atomistic-to-continuum crossover method, we provide a continuous description of the defect density fields within a MgO {310}/[001] tilt GB at different pressures

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Summary

INTRODUCTION

In the Earth’s mantle, with increasing depth, pressure increases rapidly, reaching values as high as 136 GPa at the base of the mantle.[1]. Within a recent elastoplastic framework proposed by Fressengeas et al.[16] and Acharya–Fressengeas,[17] it was shown that dislocation, disclination and generalized-disclination (g-disclination) density fields were appropriate mathematical objects for a consistent continuous description of the atomic defected structures, energetics, and dynamics of GBs.[18,19,20] For instance, disclinations were found to decorate GBs in minerals and were proposed as good candidates at providing plastic accommodation mechanisms in dislocation slip-deprived rocks in the upper mantle.[19] Here we focus on how pressure influences the dislocation, disclination, and g-disclination structures of a MgO {310}/[001] tilt GB. The dislocation, disclination and g-disclination density fields are calculated to study the influence of pressure on the defected structure of GBs, in terms of discontinuities of elastic displacement, rotation, and strain fields

MgO boundaries from first principles calculations
From atomic to continuous description of GB structures
Elastic fields
Dislocation and disclination density fields
G-disclination density fields
CONCLUSIONS
Displacement gradient
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