Dynamic Fluctuation of U3+ Coordination Structure in the Molten LiCl-KCl Eutectic via First Principles Molecular Dynamics Simulations

The dynamic fluctuation of the U3+ coordination structure in a molten LiCl-KCl mixture was studied using first principles molecular dynamics (FPMD) simulations. The radial distribution function, probability distribution of coordination numbers, fluctuation of coordination number and cage volume, self-diffusion coefficient and solvodynamic mean radius of U3+, dynamies of the nearest U-Cl distances, and van Hove function were evaluated. It was revealed that fast exchange of CI- occurred between the first and second coordination shells of U3+ accompanied with fast fluctuation of coordination number and rearrangement of coordination structure. It was concluded that 6-fold coordination structure dominated the coordination structure of U3+ in the molten LiCl-KCl UCl3 mixture and a high temperature was conducive to the formation of low coordinated structure.