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 g_Ce-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.

Key words: LiCl-KCl-CeCl₃, Structure, Thermodynamics, Molecular dynamics, Diffusion coefficient