Abstract(s)
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.