It was recalled that recent research had suggested that diffusion via vacancy-pairs could make an important contribution to cation diffusion in fluorite-related oxides, such as yttria-stabilized zirconia. A combination of analytical developments and Monte Carlo simulations was used here in order to analyze various diffusion correlation effects for cation and O ion diffusion via tightly bound vacancy-pairs in the fluorite structure. It was shown that the application of sum-rule relationships furnished exact expressions for the collective correlation functions. It was also shown that a formalism which was inspired by the diffusion kinetics formalism of Manning led to accurate expressions for tracer correlation factors, when tested against Monte Carlo simulation results. It was also shown that the tracer correlation factors were of impurity-form; thus simplifying interpretation of the diffusion isotope effect.

Correlation Effects for Cation Diffusion via Vacancy-Pairs in Fluorite-Related Oxides. I.V.Belova, D.Samuelis, M.Martin, G.E.Murch: Philosophical Magazine, 2006, 86[23], 3559-67