Evaluation of thermal properties of UO2 and PuO2 by equilibrium molecular dynamics simulations from 300 to 2000Â K

The thermal properties of UO2 and PuO2 have been investigated by the equilibrium molecular dynamics (EMD) simulations between 300 and 2000 K using the Born-Mayer-Huggins interatomic potential with the partially ionic model (PIM). The thermal expansion behaviors of UO2 and PuO2 are well reproduced by assuming that the effective ion valence is 67.5% for PIM. The constant-pressure heat capacities deduced only by the present EMD simulation are a little smaller than experimental data. This result explains that the electronic contribution, Schottky or small polaron contribution, is not small for the heat capacity of the actinide oxide including 5f-electrons. The thermal conductivity estimated by the Green-Kubo formula under the NVE ensemble is comparable with experimental data at temperatures greater than 500 K.