Molecular dynamics simulation of diffusion and viscosity of liquid lithium fluoride

LiF is an important component in the mixtures of the coolant, fuel, and carrier for molten salt reactor. The studies of diffusion properties and viscous flowability of liquid LiF provide significant guidance to the development of modern molten salt reactor. In this work, the structural characteristics, diffusion properties and viscous flowability of liquid LiF are investigated by means of molecular dynamics simulations with the Born-Mayer potential. The distribution of coordination numbers of Li+ ions for liquid LiF is statistically calculated, and it is found that the Li+ ions of 3 and 4 coordination numbers are in the majority. The micro-structural analysis indicates that the Li+ ions and their nearest-neighbor coordination F- ions mainly form planar and tetrahedral configuration. The diffusion behaviors of Li+ and F- ions are simulated as the temperature ranged from 900 K to 1400 K. The results show that the diffusion coefficients increase with the increase of the temperature for both Li+ and F- ions, and the diffusion coefficients of Li+ ions are a little higher than F ions'. In addition, the effects of pressure on the diffusion coefficients are discussed. The viscosity of liquid LiF is obtained at a temperature range of 1000-1400 K. The results confirm that the higher temperature, the lower viscosity, which is consistent with the experiential rule. (C) 2015 Elsevier B.V. All rights reserved.