Molecular dynamics simulations of Mg-doped beta″-alumina with potential models fitted for accurate structural response to thermal vibrations

• A set of new interatomic potentials was developed for Mg-doped beta”-alumina.
• Na diffusion simulated with large supercells and nanosecond trajectories.
• Simulations reveal complicated thermal expansion behavior.

A new interatomic potential model has been developed for Mg-doped beta″-alumina, using free energy optimization. By including the thermal expansion during potential fitting, the new potentials allow for an improved description of the structural behavior at different temperatures in molecular dynamics (MD) simulations. The new model was applied to study the detailed structural responses to temperature and transport properties of Mg-doped beta″-alumina. Results suggest that the sodium diffusion in beta″-alumina is highly correlated, and reliable electrical conductivity of beta″-alumina can only be extracted from molecular dynamics with substantial simulation duration and resolution, which may be best provided by long time scale classical simulations with accurate potentials.