Molecular dynamics simulations and thermodynamic modeling of NaCl-KCl-ZnCl₂ ternary system

The NaCl-KCl-ZnCl₂ ternary system is examined and modeled using the CALPHAD methodology in conjunction with molecular dynamics (MD) simulations. In particular, MD simulations are used for calculating liquid enthalpies of mixing as a function of composition for the ternary and its binary sub-systems. In addition, key structural features are obtained from MD that is then used for informing the employed two-sublattice ionic liquid model (Na⁺¹, K⁺¹: Cl^-1, ZnCl₂), which describes the ternary liquid phase. The structure of the simulated liquid systems show that Zn ⁺² cations primarily exhibit 4-fold coordination in addition to a smaller percentage of 5-fold followed by 3-fold coordination; in contrast, the coordination of both Na+ and K+ cations are distributed between 2- and 4-fold states. The optimized self-consistent thermodynamic model parameters show good agreement with MD data obtained in this work and available experimental literature data.