Atomistic simulations were used to predict the lowest-energy defect-cluster geometries for M3+ dopant cations which were adjacent to a Co vacancy. Simple dimers (1 dopant-ion and 1 vacancy) and trimers (2 dopant-ions and 1 vacancy) were considered. The results suggested that small-radius dopant ions preferred a cluster geometry in which they were in a second-nearest neighbour cation position with respect to a vacant Co site. Meanwhile, large-radius ions preferred a first-nearest neighbour cation position. As a result of this changing geometrical preference, the binding energies which were associated with small and large dopant cations (such as Al and La) were larger than those which were associated with intermediate-sized ions (such as Fe and Sc).

The Influence of Ion Size on the Binding of a Charge Compensating Cobalt Vacancy to M3+ Dopant Ions in CoO. R.W.Grimes, S.P.Chen: Journal of the Physics and Chemistry of Solids, 2000, 61[8], 1263-8