Cavity Expulsion and Weak Dewetting of Hydrophobic Solutes in Water

Perturbation theory is used to study the solvation of nonpolar molecules in water, supported by extensive computer simulations. Two contributions to the solvent-mediated solute-water interactions are identified: a cavity potential of mean force that transforms by a simple translation when the solute size changes, and a solute-size-independent cavity-expulsion potential. The latter results in weak dewetting of the solute-water interface that can explain the approximate area dependence of solvation free energies with apparent surface tensions similar to macroscopic values.