Determination of excess Gibbs free energy from computer simulation by the single charging-integral approach. I. Theory

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Abstract
A recently proposed procedure for the determination of excess Gibbs free energy by computer simulation, due to Chialvo and Haile, and based on Kirkwood’s coupling parameter interpretation of the chemical potential, is revised and improved. New theoretical expressions for excess Gibbs free energy, excess enthalpy and excess volume, are derived in this paper. The new equations allow the simultaneous determination of these quantities via isobaric–isothermal (NPT) simulations involving coupling-parameter charging from only one ideal solution (i.e., pure component), irrespective of either the number of components in the mixture or the number of potential parameters involved. Theoretical expressions are derived which allow the determination of infinite dilution activity coefficients, pure component fugacity ratios, and Henry’s constant ratios without resorting to infinite dilution simulations.