Interstitial and vacancy mediated transport mechanisms in perovskites: A comparison of chemistry and potentials

• Defect migration mechanisms in perovskites examined via long-time simulation methods.
• Some cation defects are unstable, transforming into antisite complexes.
• Some interstitial species exhibit one- and two-dimensional migration mechanisms.
• Migration pathways are independent of perovskite chemistry, but the energetics vary.
• Long-time simulations can discover migration mechanisms in complex materials.

Perovskites are important materials for fast-ion conduction applications and have been used extensively as model systems for irradiation studies, two situations where understanding defect mobility is critical for predicting performance. Using long-time scale simulation methods, we examine point defect mobility in perovskites as a function of the chemistry of the perovskite and the empirical potential used. We find that, while the basic mechanisms are the same regardless of these factors, the energies associated with the mechanisms vary significantly. We identify diffusion pathways for each type of interstitial, finding relatively complex behavior for A cation interstitials, which can diffuse one-dimensionally, and oxygen interstitials, which exhibit a two-dimensional diffusion mechanism. We further find that several cation defects are immobile with a preference to transform into antisite complexes rather than migrate. These results provide new insight into the migration behavior of point defects in perovskites and complex oxides more generally.