Molecular dynamics study of the hydrophobic interaction in an aqueous solution of krypton

Molecular dynamics calculations have been performed for systems of two and several atomic solutes dissolved in a model for liquid water to study the hydrophobic association of nonpolar solutes in aqueous solutions. The parameters of the potentials were chosen to be appropriate for an aqueous solution of Kr. In accordance with previous work, it is found that at infinite dilution a pair of atoms has two preferred configurations, one in which they are near neighbors and another in which they are separated by a water molecule, and that the latter is more stable. In the simulations of systems containing several atomic solutes, the atoms were found to form clusters in which the atom-atom distances corresponded to the formation of near-neighbor and solvent-separated pairs. On the average, the effect of the solvent is to tend to keep the solutes apart rather than to cause them to associate. This result contradicts the conventional wisdom on hydrophobic interaction, and a new analysis of experimental solubility data gives support to the result.