Collective ionic motion in oxide fast-ion-conductors

Abstract

Structural correlations and dynamic disorder in the oxide fast-ion-conductor Ba₂In₂O₅ are deduced from a systematic study of the energy-hypersurface using periodic density-functional theory examining 2 × 10⁴ local energy minima. The structure observed experimentally is interpreted as a time and spatial average of those minima which are energetically-accessible. The nature of these has extensive implications for the ionic conductivity. Transition paths connecting minima, characterized using the nudge-elastic-band method, indicate that low-energy collective ion movements must play important rôles in oxide fast-ion conductors such as Ba₂In₂O₅. Saddle-points energies for collective transport are lower in energy than those for conventional single-jump mechanisms.