Development of a Polarizable Interatomic Potential for Molten Lithium, Sodium, and Potassium Nitrate

Abstract

A polarizable interatomic potential is developed for atomistic simulations of molten MNO3 (M = Li;Na;K) salts. The potential is parameterized using a force match- ing method relying on the adjustment of parameters such that Density Functional Theory-generated forces, stress tensors and dipole moments are reproduced. Simu- lations conducted using the new potential are used to estimate physical parameters of the melt, which are then compared with available experimental results. The av- erage calculated densities of NaNO3 and KNO3 are within 2% of the experimental value within the temperature range studied, while that of LiNO3 is within 3%. Ther- mal conductivities and viscosities are estimated using equilibrium calculations and the Green-Kubo method. The thermal conductivity values of NaNO3 and KNO3 are found to match well to experimental data, while that of LiNO3 is approximately 20% larger than experimentally determined values throughout the temperature ranges simulated. The calculated viscosities are also in good agreement with experimentally determined values. The (NaxK1x)NO3 mixture is also investigated, with densities, 1 thermal conductivities, and viscosities determined and compared with experimentally determined values where available. Additionally, radial and angular distribution func- tion data is presented for all salts, revealing details of the atom-level structures present in the melts. We have found that the new interatomic potential is eective for atom scale modeling of the physical properties of molten nitrate salts.