Interatomic potential for sodium and chlorine in both neutral and ionic states

Molten salts could play an important role in energy storage, in the form of liquid batteries, and heat storage for solar and nuclear power. However, their widespread application is hindered by a limited understanding of the mechanisms by which they corrode metallic containers. This knowledge gap necessitates atomic-scale studies on salt-metal interactions. Molecular dynamics simulations are well suited for such research but require interatomic potential capable of accurately modeling both ionic and neutral states of salt and metal elements. Herein, we developed a moment tensor potential (MTP) with this capability, employing a small-cell training approach. The proposed MTP is compact: It is described by 449 parameters fitted on 609 configurations; 30% of these are one- or two-atom configurations. Extensive testing of our MTP points to a high-fidelity description of the structural and transport properties of solid/liquid Na, gaseous Cl, and crystalline/molten NaCl. Furthermore, we applied this MTP to calculate the standard reduction potential and solubility limit of Na in molten NaCl, achieving results that closely align with experimental and ab initio simulation data. This approach offers a robust framework for exploring the electrochemical and physical properties of molten salts across various compositions and solutes.