Molecular dynamics simulations of grain boundary thermal resistance in UO₂

By means of molecular dynamics (MD) simulations, we have calculated Kaptiza resistance of UO₂ with or without radiation damage. For coincident site lattice boundaries of different configurations, the boundary thermal resistance of unirradiated UO₂ can be well described by a parameter-reduced formula by using boundary energies as variables. We extended the study to defect-loaded UO₂ by introducing damage cascades in close vicinity to the boundaries. Following cascade annealing and defect migrations toward grain boundaries, the boundary energy increases and so does Kaptiza resistance. The correlations between these two still follow the same formula extracted from the unirradiated UO₂. The finding will benefit multi-scale modeling of UO₂ thermal properties under extreme radiation conditions by combining effects from boundary configurations and damage levels