Ab initiosimulations of cation ordering in oxides: application to spinel

Abstract

At high temperature, MgAl₂ O₄ spinel is stabilized by disorder of Mg and Al between octahedral and tetrahedral sites. Recent neutron experiments cover only a limited temperature range and are not sufficient to discriminate between analytic models. Electronic structure calculations have been used to parametrize on-site and short-ranged cluster potentials from a small number of disordered configuations. These potentials were then used in Monte Carlo simulations at finite temperatures to predict disordering thermodynamics beyond the range of experimental measurements. Within the temperature range of the experiment, good agreement is obtained for the degree of order.