Atomwise force fields for molten alkali chlorides (LiCl and KCl) and their mixtures: efficient parameterization via genetic algorithms

Over the last few decades, molten salts have gained significant attention in the field of green energy production. One useful method that can accelerate the discovery and optimization of desirable molten salts from a vast range of materials is classical molecular dynamics (CMD). However, because of the absence of CMD force fields that can reasonably reproduce experimental physical properties, the use of CMD to study molten salts remains a significant challenge. Hence, in this study, we report non-polarizable rigid ion models (RIMs) for the widely used LiCl, KCl, and LiCl–KCl molten salts, obtained via genetic algorithms (GAs). Based on the results presented in this study, GAs proved to be very effective in simultaneously optimizing a large number of force field parameters. With GAs, the force field generation process is automated and no manual intervention is required. The RIM force fields developed herein can reasonably reproduce experimental physical properties at different temperatures and various salt compositions, provides microstructural characteristics similar to those obtained using highly accurate and reliable first-principles MD, and an improved overall performance in contrast to previously reported polarizable force fields, all at a lower computational cost. In contrast to previous studies, we developed atomwise RIM force fields that employ mixing rules for interactions between ions of different types. This reduced the total number of optimizable terms, and thus resulted in RIM parameters that are transferrable between different molten salt systems.