Metadynamics simulations of strontium-vacancy diffusion in SrTiO3

HJ Heelweg and RA De Souza, PHYSICAL REVIEW MATERIALS, 5, 013804 (2021).

DOI: 10.1103/PhysRevMaterials.5.013804

The sluggish diffusion of strontium vacancies in the perovskite-oxide SrTiO3 was studied by means of classical metadynamics simulations. Two different mechanisms were examined: the migration of an isolated strontium vacancy and the migration of a strontium vacancy in a defect associate with an oxygen vacancy. Combining activation Gibbs energies of migration with the appropriate temperature-dependent pre-exponential terms, we obtained diffusivities of strontium vacancies by the two mechanisms for the temperature range 1000 <= T/K <= 2000. Comparisons with experimental data (where available) yield excellent agreement, both in terms of the effective activation enthalpy of migration as well as the absolute rate of diffusion. In this way we demonstrate the ability of classical metadynamics simulations to predict diffusion coefficients quantitatively for extremely slow-moving defects in oxides, and we highlight the complexity of cation diffusion in perovskite materials.

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