Molecular modeling of fluid-phase equilibria using an isotropic multipolar potential
EA Muller and LD Gelb, INDUSTRIAL & ENGINEERING CHEMISTRY RESEARCH, 42, 4123-4131 (2003).
We apply a simplified intermolecular potential function to model the fluid-phase behavior of realistic multicomponent polar systems. The isotropic multipolar potential includes dispersion, repulsion, and spherically averaged multipolar contributions and has a simple isotropic mathematical form with only two adjustable parameters. These energy and size parameters may be fitted to experimental pure-component properties such as liquid densities or critical points. These potentials, coupled with large-scale temperature-quench molecular dynamics simulations, yield thermophysical data such as the temperature-density diagram of benzene and naphthalene, the high-pressure PupsilonT properties of carbon dioxide, the vapor-liquid equilibria of 1,2-dichloroethane/cyclohexane, and the liquid-liquid equilibria of the sulfolane/n-octane/benzene system. Despite the explicit omission of both molecular shape and directionality of multipolar interactions from the potential, the results are in quantitative agreement with experimental results, suggesting that it is the average energetic interactions that dictate the gross details of fluid phase equilibria.
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