Atomistic investigation of the structure and transport properties of tilt grain boundaries of UO2

We apply atomistic simulation techniques to address whether oxygen shows higher diffusivity at the grain boundary region compared to that in bulk UO2, and whether the relative diffusivity is affected by the choice of the grain boundary. We consider coincident site lattice grain boundaries, Σ3, Σ5, Σ9, Σ11 and Σ19, expressing the {n n 1}, {n 1 1}, and {n 1 0} surfaces, and evaluate the extent that the grain boundary structures affect the diffusion of oxygen. We found that oxygen diffusion is enhanced at all boundaries and in the adjacent regions, with strong dependence on the temperature and local structure.