Cavity contact correlation function of water from scaled particle theory

The ratio of the number density of solvent molecules just outside a cavity of radius R-c to that in the bulk represents the cavity contact correlation function G(R-c). Experimental determination of G(R-c) for water by means of computer simulations has led to the claim that the shape of this function is a basic manifestation of the structural features of the H-bonded network of water [H.S. Ashbaugh, L.R. Pratt, Rev. Mod. Phys. 78 (2006) 159]. In this Letter, I would like to show that classic scaled particle theory is able to reproduce in a satisfactory manner the experimental G(R-c) values by taking into account two things: (a) the size of a water molecule depends on the interactions in which it is involved, so that the effective diameter of H-bonded molecules is 2.8 angstrom, whereas the van der Waals diameter of a water molecule is 3.2 angstrom; (b) at any time, liquid water contains both H-bonded molecules and molecules interacting by means of van der Waals forces. (c) 2006 Elsevier B.V. All rights reserved.