Point defects in uranium dioxide: Ab initio pseudopotential approach in the generalized gradient approximation

The stability of point defects in uranium dioxide is studied using an ab initio plane wave pseudopotential method in the generalized gradient approximation of the density functional theory. Uranium pseudopotentials are first tested in both the generalized gradient approximation and the local density approximation on metallic phases of uranium and on uranium dioxide. It is found that the generalized gradient approximation gives the best description of these materials. The energies of formation of point defects (single vacancies and interstitials, Frenkel pairs and Schottky defects) in UO2 are calculated. The values obtained lead to a reliable set of numerical data that are analyzed in the framework of the point defect model commonly used to assess defect concentrations in uranium dioxide as a function of the stoichiometry. The ability of the point defect model to accurately reproduce defect concentrations in uranium dioxide is discussed.