Oxygen ion diffusion in cation ordered/disordered GdBaCo₂O _5+δ

We use molecular dynamics in conjunction with an established set of Born model potentials to examine the oxygen ion diffusion mechanism in the double perovskite GdBaCo₂O_5+δ. We predict that the mechanism of oxygen diffusion is highly anisotropic diffusion occurring only in the Gd-O and adjacent Co-O layers. For GdBaCo₂O_5.5 the activation energy of oxygen diffusion is 0.5 eV. We investigate the effect that cation disorder of the Gd-Ba sublattice has upon the diffusivity, the anisotropy and the diffusion mechanism in GdBaCo₂O_5+δ, which is a model system for double perovskites and other layered compounds. Cation disorder results in a reduction of the oxygen diffusivity and the appearance of diffusion along the c-axis of the material. Oxygen diffusion becomes effectively isotropic when the cation sublattice is disordered.