First-Principles Study of the Influence of Zirconium on the Diffusion of Uranium Defects in Uranium Dioxide

Abstract

The migration properties of uranium vacancies and interstitials in zirconium-doped uranium dioxide are studied by using density functional theory (DFT) and the climbing-image nudge elastic band (CI-NEB) method. The strong correlations among uranium 5f electrons were described by using a spherically averaged Hubbard parameter. In the model, the zirconium atoms are introduced by replacing the uranium atoms at the nearest and the next nearest neighbor sites along the diffusion path of uranium defects. The doping with zirconium obviously reduces the migration barriers for defects in uranium dioxide. The effect of doping with zirconium on the diffusion of uranium defects decreases with increasing distance between the zirconium dopant and the uranium defects. Further, we investigated the lattice distortion and the electron transfer associated with the migration of uranium defects, and we analyzed the physical origin of the reduction in the migration barriers caused by zirconium doping.