Viscosity of molten MgF2-LiF-MgO system and structure investigation using classical molecular dynamics simulations

Abstract The effect of temperature and fluoride structure on the viscosity of a molten 32.8MgF2-67.2LiF system with varying MgO concentration was investigated for the environmentally sound electrolytic reduction process of magnesium extraction. Whereas the temperature dependence of the viscosity was not significant, increasing viscosity was observed with the increase in the MgO concentration. Using classical molecular dynamics simulation, the molten fluoride structure in the 32.8MgF2-67.2LiF with varying MgO concentration was investigated at 1123 K. From the result of the radial distribution function and coordination numbers, the formation of a characteristic bonding structure between the Mg-F and O-Mg was verified. The F-Mg-F bond-angle distribution results indicated the formation of a marginally distorted octahedral structure of MgF6 in the present MgF2-LiF-MgO system. Moreover, the Mg-F-Mg bond angle distribution revealed the formation of a three-dimensional MgF6 network structure by sharing one or two fluorine atoms. Owing to the increasing edge-sharing MgF6 structure unit and formation of a larger three-dimensional network associated by the oxygen atoms, the viscosity increased by the addition of MgO in the 32.8MgF2-67.2LiF system.