A pair sum approximation for predicting defect cluster binding energies in fluorites

Atomic scale computer simulations have been used to investigate clustering of those defects that result from the accommodation of Gd2O3 in a CeO2 host lattice. It has been found that binding energies of the defect clusters can be accurately described by a model in which the total binding energy is deconvoluted into its constituent pair terms (though a three body correction is necessary for a specific cluster type). At short defect-defect distances, these interaction energies must be calculated explicitly because of the complexity of the lattice relaxation. At longer distances, binding energies can be approximated by calculating the coulomb interactions between the effective charges of the defects divided by the relative permittivity of the host lattice. This scheme provides a framework within which the total of defect-defect interactions can be determined for a large ensemble of defects disordered throughout this lattice.