First Principles Molecular Dynamics Studies of Oxygen Sub-lattice Melting in Thoria

Abstract

We apply first principles molecular dynamics to investigate the order-disorder transition in the oxygen sub lattice, observed experimentally in thoria. The mean-square displacements were calculated at temperatures of 3000 K, 3300 K and 3600 K and we demonstrated that oxygen atoms become mobile, while they stay confined at 2700 K. The rate of diffusion of oxygen atoms was calculated while, for thorium, the mean-square amplitudes of vibrations were evaluated.