Oxygen diffusion in YBa2Cu3O7-δ at various temperatures and oxygen contents was explored using molecular dynamics simulations. At low temperatures, the diffusivity of oxygen ions in was found to be strongly dependent upon the lattice site. It was shown that oxygen ions in Cu-O chains diffused much faster than those in Ba-O layers and Cu-O planes. When the temperature was increased, the diffusivity became less sensitive to lattice sites. Moreover, a distinct anisotropy was also observed for oxygen diffusion on different lattice sites. By explicitly calculating the directional mean-square displacement, it was shown that the oxygen ions in the Cu-O planes and Ba-O layers were similarly more prone to diffusion along the c-axis direction. In the Cu-O chains, the oxygen ions were more likely to migrate along the ab plane. As temperature increased from 700 to 1100K, the diffusion anisotropies decreased.

Molecular Dynamics Analysis of Lattice Site Dependent Oxygen Ion Diffusion in YBa2Cu3O7-δ: Exposing the Origin of Anisotropic Oxygen Diffusivity. Liu, C., Zhang, J., Wang, L., Shu, Y., Fan, J.: Solid State Ionics, 2013, 232, 123-8