Abstract:The structure of molten DyF₃-BaF₂-LiF system has been computer-simulated by Monte Carlo method. The radial distribution functions (RDFs), the local structure as well as the energy distribution have been obtained. The study indicates that F^- ions distribute closely around Dy³⁺ ions and mainly form octahedral complex ions like DyF₆^3-. There exist some “free” Li⁺ ions in the molten system, which have the highest potential energy and are current-carrying ions in the electrolytic process. F-ions may be classified into three types:“terminal fluoride”,“free fluoride”and“bridge fluoride”, which have different behaviours and potentialenergies. Some complex ions like DyF_m^3-m clusters are connected to one another by“fluoride-bridge”, forming more complicated ionic clusters like F_m-Dy-F-Dy-F_n or F_m-Dy < ^F_F>Dy-F_n. As compared with
molten DyF₃-LiF system, the octahedral complex ions like DyF₆^3- seem closer and in better order than the binary system because of the addition of BaF₂.

Key words: rare-earth fluoride　molten salt　computer simulation　Monte Carlo method　local structure