Diffusion in lattice arrays reducible to cubic symmetry could be simulated by Monte Carlo procedures. Tracer correlation factors could be derived for diffusion mechanisms in such arrays which included simple solids with point defects and non-stoichiometric materials with complex defect structures subject to defect-defect interactions. It was shown that such interactions could substantially reduce the correlation factor. A cooperative diffusion mechanism involving Willis 2:2:2 defect clusters in UO2+x was shown to have a correlation factor greater than unity.

Diffusion Correlation Effects in Non-Stoichiometric Solids. H.J.De Bruin, G.E.Murch: Philosophical Magazine, 1973, 27[6], 1475-88