A STUDY OF SOLUTE-SOLVENT INTERACTIONS AT INFINITE DILUTION VIA THE COUPLING PARAMETER APPROACH

The dependence of chemical potential at infinite dilution on size and energy parameters as well as on arbitrary combining rules is studied using a novel version of Kirkwood's coupling parameter method. This method enjoys several advantages over the test particle approach (it does not fail at high density or increasing size ratio) and the literal interpretation of Kirkwood's coupling parameter approach (the simulation quantities are well-behaved, and the simulation requirement is at least an order of magnitude smaller). The simulations predict a monotonic size-ratio dependence for the chemical potential of Lennard-Jones mixtures at infinite dilution, for which earlier calculations showed a minimum about a size ratio of unity. A simulation method is also proposed to calculate the isochoric rate of change of pressure upon solute addition at infinite dilution. This quantity plays a key role in the thermodynamics of dilute supercritical mixtures and determines their classification into attractive or repulsive.