Mixture Rules for the Mie (n, 6) Intermolecular Pair Potential and the Dymond–Alder Pair Potential

Abstract

Formulas for the unlike-pair parameters in terms of the like-pair parameters for the Mie (n, 6) potential energy model are examined for their abilities to predict cross-term second virial coefficients. Formulas based on the London dispersion formula and an assumption of geometric mean repulsion energies are tested and shown to apply only for special cases. A geometric mean rule for each one of the parameters including the repulsion exponent, n, is shown to have far more general applicability and to give high accuracy in predicting the cross-term second virial coefficient. Potential energy parameters for several molecules are obtained using corresponding states relationships and the Dymond and Alder numerical potential energy function for argon. The geometric mean rule for the energy and distance parameter is shown to perform well for predicting the cross-term second virial coefficient for mixtures of molecules which obey the Dymond and Alder potential energy function.

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