A molecular dynamics study of the heat capacity of uranium mononitride

The heat capacity of uranium mononitride (UN) was estimated by molecular dynamics (MD) calculation with the Morse-type potential function added to the Busing-lda type potential in the temperature range 300-2500 K. The parameters of the interatomic potential were determined by fitting the changes in the lattice parameters with temperature and pressure to those in the literature. The thermal expansion coefficient (alpha) and the compressibility (beta) were calculated. The heat capacity at constant volume (C-V) was evaluated from the variation of the internal energy of the system by the fixed volume MD calculation. The lattice dilational contribution (C-d) was calculated from alpha and beta. The conduction electronic contribution (C-el) was also evaluated from the difference between the MD calculation results (C-V and C-d) and the reported heat capacity at constant pressure (C-p). The conduction electronic contribution coefficient (gamma) was found to be 6.32x10(-3) (J mol(-1) K-2). (C) 2000 Elsevier Science S.A. All rights reserved.