Molecular Dynamics Simulation of Molten NiF2: Structure and Physicochemical Properties

Computer simulation of molten nickel fluoride is performed using classical molecular dynamics in the temperature range from 1750 to 1900 K. The pair potential parameters calculated in the framework of a quantum-chemical approximation are verified using the density of crystalline NiF2 at the relative error lower than 1%. The radial distribution functions and the coordination numbers calculated for the Ni–F pair indicate a distorted octahedral environment of the nickel cation in the melt. In this case, a slight decrease in the nearest cation–anion distance is found as compared that in crystalline nickel fluoride. The curve of the radial distribution function for the fluorine–fluorine pair in the vicinity of the main peak is shown to split into two maxima. The position of the first peak at 2.67 Å is characterized by a coordination number of 5.1 and describes the neighboring anions in the distorted octahedron, whereas the second maximum can be associated with the fluorine anions located along the F–Ni–F line with a peak position at 3.83 Å, which indicates a decrease in the similar distance as compared to that in the crystal. The self-diffusion coefficients of the ions and the viscosity of the NiF2 melt are calculated at different temperatures.