Diffusion mechanism of bound Schottky defect in magnesium oxide

Sami Mahmoud, Philippe Carrez, Marie Landeiro Dos Reis, Normand Mousseau, and Patrick Cordier
Phys. Rev. Materials 5, 033609 – Published 25 March 2021

Abstract

In simple ionic crystals, intrinsic point defects must satisfy electrical neutrality and exist as Schottky defects. In magnesium oxide (MgO), a Schottky defect is then a combination of anionic and cationic vacancies. Since vacancies are charged, the stable configuration of the Schottky defect corresponds to a bound pair of vacancies of opposite signs. In this study, we investigate the kinetics of formation and migration of such a bound pair on long timescales reaching in some cases thousands of seconds using the kinetic activation-relaxation technique, an off-lattice kinetic Monte Carlo method with an event catalog built on-the-fly during static molecular simulations. We show that the diffusion of this bound Schottky defect involves the migration of vacancies bounded to the first and third neighbor sites of the crystal structure with an apparent migration energy which cannot be inferred from the migration energies expected from isolated defects. Overall, this study gives insights and constraints on the oxygen diffusion mechanism reported experimentally in high-purity MgO samples.

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  • Received 21 September 2020
  • Accepted 12 March 2021

DOI:https://doi.org/10.1103/PhysRevMaterials.5.033609

©2021 American Physical Society

Physics Subject Headings (PhySH)

Condensed Matter, Materials & Applied PhysicsAtomic, Molecular & Optical

Authors & Affiliations

Sami Mahmoud1,*, Philippe Carrez1, Marie Landeiro Dos Reis1, Normand Mousseau2, and Patrick Cordier1,3

  • 1Université de Lille, CNRS, INRAE, Centrale Lille, UMR 8207 - UMET - Unité Matériaux et Transformations, F-59000 Lille, France
  • 2Département de physique and Regroupement québécois sur les matériaux de pointe, Université de Montréal, CP 6128, Succursale Centre-Ville, Montréal, Québec H3C 3J7, Canada
  • 3Institut Universitaire de France, 1 rue Descartes, F-75005 Paris, France

  • *sami.mahmoud@univ-lille.fr

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Vol. 5, Iss. 3 — March 2021

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