Molecular dynamics study on defect structure of gadolinia-doped thoria

A molecular dynamics study on the defect structure of Gd-doped thoria was carried out. The partially ionic two-body potential was used with empirically obtained parameters for Th, Gd and O ions in the fluorite structure. Different defect structures were assumed and their effects on the lattice parameter were investigated. Molecular dynamics simulations were carried out with Gd fractions and temperatures ranging from 0 to 45% and from 298 to 1200 K, respectively. Diffusion coefficients of O ions in the Gd-doped thoria having various Gd fractions were also calculated at 1273 K. Comparison of the calculated results with the experimental ones lead to the conclusion that the Gd-oxygen vacancy-Gd type cluster is the most likely defect structure in the Gd-doped thoria. (author)