An investigation was made of the role that was played, by the preparation of the system, in governing the diffusion of O ions in these superconductors. The asymmetrical next-nearest neighbor Ising model, and standard Monte Carlo simulations, were used. It was noted that, when only 1 sub-lattice was initially populated with O ions, the system was in a 1-domain state and the diffusion coefficient exhibited, at all temperatures, a minimum when the deviation from O stoichiometry was equal to unity (that is: Cu3Ba2YO7). When the O ions were initially present on both sub-lattices, 2 or more domains could form. This led to the appearance of an additional diffusion mechanism, and the tracer diffusivity went through a maximum, at low temperatures, when the composition was Cu3Ba2YO7.

A.Pekalski, K.Skwarek: Physical Review B, 1996, 54[6], 4315-9