First-principles calculation of point defects in uranium dioxide

A first-principles calculation for uranium dioxide (UO2) in an antiferromagnetic structure with four types of point defects, uranium vacancy, oxygen vacancy. uranium interstitial, and oxygen interstitial, has been performed by the projector-augmented-wave method with generalized gradient approximation combined with the Hubbard U correction. Defect formation energies are estimated under lattice relaxation for supercells containing 1, 2, and 8 unit cells of UO2. The electronic structure, the atomic displacement and the stability of defected systems are obtained. and the effects of cell sizes on these properties are discussed. The results form a self-consistent dataset of formation energies and atomic distance variations of vafious point defects in UO2 with relatively high precision. We show that a supercell with 8 UO2 unit cells or larger is necessary to investigate the defect behavior with reliable precision, since point defects have a wide-ranging effect, not only on the first nearest neighbor atoms of the defect. but on the second neighbors and on more distant atoms.