Simulation of proton diffusion in In-doped CaZrO 3

Abstract

First principles calculations, based on density functional theory, are exploited to investigate the mechanisms and energetics of proton mobility in In-doped CaZrO 3. Binding sites for protons in the crystal are provided for a range of local In concentrations. A set of proton transfer hops is identified and associated energy barriers for these proton steps are computed. The calculated lowest energy paths that lead to proton propagation in CaZrO 3 exhibit energy barriers in excess of 0.6 eV. Together with previously reported activation energies for proton reorientations and attempt frequencies for proton moves, the present results provide a comprehensive set of data from which the rates of proton migration in In:CaZrO 3 may be determined. The use of the data in kinetic Monte Carlo simulations at 1160 K reveals slightly higher proton mobility in In-doped crystal than in the pure CaZrO 3. This suggests that dopant–proton trapping, expected from larger binding strengths at In octahedra by 0.1–0.2 eV, is relatively weak and short-ranged.