The core structure of screw dislocations with [001] Burgers vector in Mg 2 SiO 4 olivine

Abstract

In this study, we report atomistic calculations of the core structure of screw dislocations with [001] Burgers vector in Mg 2 SiO 4 olivine. Computations based on the THB1 empirical potential set for olivine show that the stable core configurations of the screw dislocations correspond to a dissociation in {110} planes involving collinear partial dislocations. As a consequence, glide appears to be favorable in {110} planes at low temperature. This study also highlights the difference between dislocation glide mechanism in {110} versus (010) or (100) for which glide is expected to occur through a locking-unlocking mechanism. Résumé. Dans cette étude, nous présentons les résultats de calculs atomiques de la structure de coeur de la dislocation vis de vecteur de Burgers [001] dans l'olivine (Mg,Fe) 2 SiO 4. Nos simulations, reposant sur l'utilisation du potentiel semi-empirique THB1, montrent que la configuration stable de la dislocation vis correspond à une structure de coeur dissociée dans les plans {110}. A basse température, le glissement des dislocations de vecteur de Burgers [001] dans les plans {110} de l'olivine est donc favorisé.

Foreword: Plasticity and Solid State Physics

“…The conference-debate session of the Académie des Sciences on 25 February 2020 1 highlighted the importance of the interactions between physics and mechanics of solids for a better understanding of the plasticity of materials. The idea then arose to prepare a special issue of the Comptes Rendus Physique de l'Académie des Sciences to deepen these fruitful relationships between a physical understanding of the mechanisms of plasticity and the continuum modelling of these phenomena in view of the use of constitutive laws adapted to the calculation of engineering structures.…”

“…In crystals, these processes involve the motion of defects, that are of different nature depending on the material and the deformation conditions. Plastic deformation may be due to the motion of dislocations, which involves their core region that can only be modeled using atomistic methods, as illustrated in olivine by Mahendran et al [1]. Plasticity may also result from the motion of grain boundaries, that offer complex deformation routes, as discussed by Gautier et al based on in situ microscopy and atomistic calculations [2].…”