Oxygen migration and local structural changes with schottky defects in pure zirconium oxide crystals

By employing the Buckingham potential, we performed classical molecular-dynamics computer simulations at constant pressure and temperature for a pure ZrO₂ crystal without any vacancies and for a pure ZrO₂ crystal containing zirconium vacancies and oxygen vacancies. We examined the positions of atoms and vacancies in the steady state, and we investigated the migration behavior of atoms and the local structure of vacancies of the pure ZrO₂ crystal. We found that Schottky defects (aggregates consisting of one zirconium vacancy with an effective charge of −4 and two oxygen vacancies each with an effective charge of +2 to maintain charge neutrality) are the main defects formed in the steady state in cubic ZrO₂, and that oxygen migration occurs through a mechanism involving vacancies on the oxygen sublattice near such defects. We also found that several oxygen atoms near each defect are displaced far from the sublattice site and induce oxygen migration.