Digging a hole: Scaled-particle theory and cavity solvation in organic solvents

A recent extension of scaled-particle theory for cavity solvation in polyatomic solvents developed by Ashbaugh and Pratt [J. Phys. Chem. B 111, 9330 (2007)] is tested against molecular simulations of 13 organic liquids. This molecular scaled-particle theory incorporates the intramolecular structure of the solvent in the calculation of the cavity excluding volume, compared with traditional applications of scaled-particle theory where the solvent is treated as an individual hard sphere with no internal structure. Once the diameters of the constituent carbon interaction sites are specified, molecular scaled-particle theory is able to discriminate between geometrically distinct solvents and provides accurate predictions for cavity solvation free energies and near quantitative predictions of the cavity contact correlation function. The diameters of the solvent interaction sites are argued to be transferable between related groups on different solvents, leading to a truly predictive scaled-particle theory given only information on the solvent pressure, density, and molecular topology.