Towards the calculations of redox potentials in molten LiCl-KCl eutectic by ensemble averages based on first principles molecular dynamics

Abstract

A calculation approach for redox potentials of metallic cations in molten salt is proposed by ensemble averages based on first principles molecular dynamics (FPMD) and is applied to the calculation of the redox potentials of a series of metallic cations Mn+ (=Cu+, Tl+, Au+, La3+, Ce3+, U3+, and Pu3+) in molten LiCl-KCl eutectic versus reference electrode of Ag+|AgCl(s)|Ag(s) with satisfactory results. Special thermodynamic cycle is designed by using Ag+|AgCl(s)|Ag(s) as reference electrode and by enclosing the reduced metallic atoms in the molten salts, and thus the energies related to the chloride anions, as well as the absolute energies related metallic atoms or cations, are cancelled. In addition, self-diffusion coefficients of the cations, as well as ionic conductivities and viscosities of the molten salt mixtures are evaluated from FPMD. The significance and prospects of this approach and FPMD in the prediction of physicochemical properties of molten salt mixtures for the pyroprocessing of spent nuclear fuels are discussed.