Molecular dynamics simulation of solar salt (NaNO3-KNO3) mixtures

Molten salts have extended applications in concentrated solar power (CSP) installations, both as heat transfer and energy storage materials. In this study, a set of Lennard-Jones interatomic parameters are introduced for simulating NaNO3 and KNO3, as well as their most frequently industrially used mixture the so-called solar-salt (60% NaNO3 - 40% KNO3). Local structures are studied via radial distribution functions. Furthermore, density, thermal conductivity, self-diffusivity, viscosity and surface tension are calculated, from melting to decomposition temperature, and compared with experimental data. The local structures are calculated with both existing and presented interatomic potentials and are found to be in excellent agreement. Additionally, density, viscosity and surface tension present minor differences from literature data. Thermal conductivity, in terms of absolute values is in the proximity of reported data but is questionable in terms of trend. Finally, self-diffusion coefficients declinate from measured values, but are similar in terms of trend. Results are found to be in good agreement. This work represents the first extended validated effort in modelling molten nitrate salts and their mixtures at elevated temperatures using a Lennard-Jones potential, providing new tools that can aid in the fundamental understanding of molten salt structures at the molecular scale.