Monte Carlo Simulation of NaCl–H2O Phase Equilibria: Comparison of Classical Force Fields

Gibbs ensemble Monte Carlo simulations were performed to predict the pressure–composition phase diagrams of binary H 2 O–NaCl mixtures at 573 K and 633 K, pressures of 4500 to 19,000 kPa, and NaCl mole fractions of zero to 0.3. Understanding the high-temperature behavior of aqueous salt solutions is important for geochemical and industrial applications, including supercritical desalination. We employed both the SPC/E and TIP4P/2005 models for water, as well as the Joung-Cheatham (JC), Dang 1995 (D95), and Kirkwood-Buff (KBFF) force fields for NaCl. In addition, we performed simulations using the Madrid 2019 model for NaCl, which uses scaled charges and is parameterized only for use with TIP4P/2005. To compare the effect of scaling the charges, we also included a scaled charge version of the JC model. SPC/E with either the JC or KBFF NaCl force field results in the most accurate predictio…