MOLECULAR DYNAMICS SIMULATION OF MOLTEN NiF₂: STRUCTURE AND TRANSPORT PROPERTIES

Abstract

Computer modeling of molten nickel fluoride was carried out using classical molecular dynamics in the temperature range 1750–1900 K. The density of crystalline NiF2 with a relative error of less than 1% verified the parameters of the pair potential obtained in the framework of the quantum-chemical approximation. The calculated radial distribution functions and coordination numbers 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 was found in comparison with solid nickel fluoride. It is shown that the curve of the radial distribution function for the fluorine-fluorine pair near the main peak splits into two maxima. The position of the first peak at 2.67 Å is characterized by a coordination number of 5.1 and describes neighboring anions in a distorted octahedron. Whereas, the second maximum can be associated with fluorine anions located along the F–Ni–F line with a peak position at 3.83 Å, which indicates a decrease in a similar distance compared to the crystal. The coefficients of self-diffusion of ions and the viscosity of the NiF2 melt at different temperatures were calculated.