Molecular dynamics simulation evaluation on viscosity of typical alkali metal fluorine salts

The molten salt viscosity of alkali metal fluoride LiF, NaF and KF was calculated by molecular dynamics simulation method, the results of which were evaluated by measured values. The results show that on the basis of the van der Waals potential, as the core-shell model Coulomb potential is introduced, and the polarization energy added as the potential function, the viscosity at different temperature points in the range of 1 100~1 700 K is calculated by Gromacs software according to the principle of energy dissipation, which can accurately express the qualitative relationship between temperature, alkali metal ion radius and viscosity. The calculated results have systematic negative deviation from the measured values. The main reasons and solutions are as follows. ① Newtonian fluid model is applied to LiF, NaF, KF viscosity description model of molten salt system in the calculation process, while the actual LiF, NaF and KF molten salt system is a quasi-Newtonian fluid, so it is necessary to add a correction term to the ion acceleration equation. ② Coulomb constant β, polarizability α and nuclear charge q_core are the key parameters to determine the calculation accuracy. The basic value of the Coulomb constant β, as well as the matching relationship between reasonable nuclear charge quantity q_core and polarizability α have a significant impact on the calculated results.