Stress-induced phase transformation in nanocrystalline UO2

 We report a stress-induced phase transformation in stoichiometric UO2 from fluorite to α-PbO2 structure using molecular dynamics (MD) simulations and density functional theory (DFT) calculations. MD simulations, performed on nanocrystalline microstructure under constant-stress tensile loading conditions, reveal a heterogeneous nucleation of α-PbO2 phase at the grain boundaries followed by the growth of this phase towards the interior of the grain. The DFT calculations confirm the existence of the α-PbO2 structure, showing that it is energetically favored under tensile loading conditions.