Kinetic Monte Carlo study of protonic diffusion and conduction in Gd-doped BaCeO₃

Protonic diffusion and conduction in Gd-doped BaCeO₃ are studied by Kinetic Monte Carlo simulations using transition rates deduced from previous ab initio calculations. The dopants behave like shallow traps for the protonic defects, but at low doping concentrations, their presence does not reduce the diffusion coefficient, and the activation energy (≈ 0.36 eV) is not significantly affected by the doping rate. We tentatively explain this result by the interplay between the creation of traps consecutive to doping, and the removal of obstacles in the primitive protonic energy landscape, keeping in mind that our model neglects the increase in attraction between protons and dopants when the dopant concentration increases. The protonic mobility is computed, under finite applied electric field, and found at ≈ 5.54 × 10 ^{- 9} m²·s^{- 1}·V^{- 1} at 600 K and at 86.1 × 10^{- 9} m²·s ^{- 1}·V^{- 1} at 1200 K. These first results suggest that protonic conduction in Gd-doped BaCeO₃ is rather isotropic.