Molecular dynamics study of the effect of doping and disorder on diffusion in gadolinium zirconate

Abstract

We present the results of molecular dynamics (MD) simulations of gadolinium zirconate (Gd 2Zr 2O 7), an oxide fast ion conductor with the pyrochlore structure. Calculations of mean temperature dependent diffusion coefficients are used to obtain activation energies for diffusion which are compared with values obtained from static lattice calculations and from conductivity measurements. Simulations of yttrium and gadolinium doped zirconia were performed as a test of the potential parameters and the results compare well with experiment. The gadolinium zirconate simulations show no diffusion for the ordered material which is consistent with static lattice calculations. But appreciable diffusion is predicted for the simulations which incorporate cation disorder or doping with calcium where the present results agree well with those from static lattice simulations and from experimental observations. We find that diffusion occurs only by the 48 f sites, in line with previous computational and experimental studies. An increase in the activation energy for diffusion with doping level suggests that dopant/vacancy and defect–defect interactions become significant at the higher level of doping.