Evaluation of thermophysical properties of (Np,Pu)O2 using molecular dynamics simulations

Molecular dynamics simulations were performed in order to obtain thermophysical properties of the solid solution of (NpxPu1-x)O-2 MOX for the concentrations x = 0.0, 0.2, 0.5, 0.8 and 1.0. Lattice parameter, linear thermal expansion coefficient, enthalpy increment and specific heat at constant pressure were evaluated in the temperature range from 300 K to 3400 K using the NPT ensemble. Elastic constants C-11, C-12 and C-44 were obtained at T = 0 K whereas the bulk modulus was studied in the whole temperature range from 0 K to 3400 K. It was found that most of the evaluated magnitudes closely follow a Vegard's-like law for temperatures below 2000 K. At that point the superionic transition was observed. The results obtained in this work show a good agreement with the available reference data. (C) 2016 Elsevier B.V. All rights reserved.