Optimized Unlike-Pair Interactions for Water-Carbon Dioxide Mixtures Described by the SPC/E and EPM2 Models

The unlike-pair interaction parameters for the SPC/E-EPM2 models have been optimized to reproduce the mutual solubility of water and carbon dioxide at the conditions of liquid-supercritical fluid phase equilibria. An efficient global optimization of the parameters is achieved through an implementation of the coupling parameter approach, adapted to phase equilibria calculations in the Gibbs ensemble, that explicitly corrects for the overpolarization of the SPC/E water molecule in the nonpolar CO2 environments. The resulting H2O-CO2 force field accurately reproduces the available experimental solubilities at the two fluid phases in equilibria as well as the corresponding species tracer diffusion coefficients.