The electric charge and climb of edge dislocations in perovskite oxides: The case of high-pressure MgSiO3 bridgmanite
Résumé
Dislocation climb is expected to play a major role in high-temperature creep of complex ionic oxides, however the fundamental mechanisms for climb are poorly understood in this class of materials. In this work we investigate the interaction of vacancies with an edge dislocation by means of atomic-scale simulations in high-pressure MgSiO3 bridgmanite, a mineral whose natural conditions of deformation are favorable to climb. The evaluation of the interaction with oxygen vacancies reveals that the dislocation favors a non-stoichiometric, oxygen-poor configuration, associated with a positive electric charge of maximum value + 9.17 10−11 C m−1. This result is in qualitative agreement with experimental observations in related perovskite oxides. Subsequently, the interactions between dislocations and vacancies are dominated by electrostatics, with binding enthalpies of several eV in the vicinity of the dislocation core, superseding elastic effects. These results shed a new light on dislocation-vacancy interactions and dislocation climb in this class of materials.