Molecular dynamics simulation of UO2 nanocrystals melting under isolated and periodic boundary conditions

► We perform MD simulation of UO2 nanocrystals melting (in range of 768-49 152 ions). ► T(P) melting curves intersect zero near −20 GPa and saturate near 25 GPa. ► Reciprocal size dependences of nanocrystal melting point decrease nonlinearly. ► Linear and parabolic extrapolations to macroscopic values are considered. ► Melting point and density jump are reproduced, but heat of fusion is underestimated.