A New Ionic Pair Potential for Evaluation the Thermal Properties of Uranium Dioxide by Molecular Dynamics

Abstract

Inter-atomic potential parameters of uranium dioxide, for a new partially ionic model (PIM), were found out by fitting method using experimental lattice parameter data in an improvised way. Thermodynamics properties of solid uranium dioxide that have been assessed in a wide temperature range from 300 K up to 3000 K include enthalpy, isobaric heat capacity, melt point, density variation with temperature, mean square displacement and diffusion coefficients of oxygen ion. Measurements were performed with 1 K accuracy in a wide temperature range from 300 K up to melting points. The results were compared with the literature data and suggested that the new rigid ionic potential provided perfect results in wide spectrum of experimental data. The model also successfully predicts Bredig transition. The thermodynamics properties data became unacceptable when the temperature is very high. Compared with previous five different empirical potentials sets for uranium and oxygen (potentials Bssak-03, Morelon-03, Arima-05, Nekrasov-08, Goel-08), the new pair potential improves the agreement of these data with the experimental data recommended by IAEA-06.