Thermal Properties of UO2 by Molecular Dynamics Simulation

Abstract

Molecular dynamics (MD) simulation was performed to investigate thermal expansion, specific heat and thermal conductivity of UO 2 . For thermal expansion, experimental measurements were made and compared with MD simulation results. These thermal expansion values and other reported data were in good agreement with the MD thermal expansion value. Effects of Schottky defects on thermal properties were evaluated. For thermal expansion, the effect was negligible. For specific heat, the constant volume term of specific heat increased with increasing Schottky defect concentration. But the dilation term of specific heat was nearly-unchanged. Thermal conductivity decreased with increasing Schottky defect concentration. It was considered that the increasing constant volume term was caused by increasing internal energy which was attributed to the Schottky defects. Calculated thermal conductivity values corresponded to experimental data when the supercell contained Schottky defects. It was thought that a perfect crystalline supercell caused high thermal conductivity and the defect structure scattered phonon vibrations and decreased the thermal conductivity.