Evaluation of thermal properties of uranium dioxide by molecular dynamics

The molar specific heat and the thermal conductivity of UO2 were studied by a molecular dynamics (MD) technique. The partially ionic model was used. It was confirmed that the temperature dependence of the calculated lattice parameters well agreed with the reported values for UO2. The calculated compressibility agreed with the experimental values up to 1600 K, and markedly increased at T>2000 K similar to the real material. The MD cell reproduced the Bredig transition at high temperature. The calculated molar specific heat of UO2 at the constant pressure well agreed with the experimental data. At 2200 K, the calculated specific heat revealed a peak which is associated with the onset of superionic conduction. At low temperatures, the calculation without the quantum correction for the kinetic energy provided too high values of the specific heat. The variation of the calculated thermal conductivity with temperature, obtained by the Green-Kubo technique, agreed well with the experimental data. (C) 2000 Elsevier Science S.A. All rights reserved.