Molecular dynamics simulation on the structure and thermodynamics of molten LiCl-KCl-CeCl3

Abstract

The structure and thermodynamics of CeCl3 in molten LiCl-KCl-CeCl3 mixtures were studied by molecular dynamics simulation. The relationship formulas of temperature and density, and composition and density were obtained. The first peak for the gCe-Cl(r) radial distribution function was located at 0.259 nm and the corresponding first coordination number of Ce3+ was ~6.9. This inconsistency between molecular dynamics and experimental data could be attributed to the fact that our values were obtained for molten LiCl-KCl-CeCl3 mixtures, in which the interaction between Ce3+ and Cl- was more powerful than that in pure molten CeCl3. Regarding self-diffusion coefficients, the activation energy of Ce3+ was 22.5 kJ·mol-1, which is smaller than that of U3+ (25.8 kJ·mol-1). Furthermore, the pre-exponential factors for Ce3+ decreased from 31.9×10-5 to 21.8×10-5 cm2·s-1 as the molar fraction of Ce3+ increased from 0.005 to 0.05. This means that in the unit volume (ignoring the change of total volume), the diffusion resistance of Ce3+ increased, and the self-diffusion ability decreased, which resulted in a decrease of pre-exponential factors.