Statistical Mechanical Study of Hydrophobic Interaction. IV. The Behavior of the Function y(R) at Short Distances

The function [A. Ben-Naim, J. Chem. Phys. 54, 1387, 3696 (1971)] y(R) = exp[−δAHI(R)], playing a central role in the theory of solute-solute interaction, is shown to be a monotonous decreasing function of R at short distances. A formal proof is given for two hard cube solutes approaching along a particular line. Further evidence, based on the Percus-Yevick equations for a two-dimensional system of spherical solutes, is provided.