Interface profiles in a dimerizing system

The gas-liquid density profile and surface tension are calculated for a flu id possessing hard sphere repulsion, van der Waals-like dispersion, and sti cky-spot attraction. The sticky spot allows monomers to dimerize and the co nsequences of which are investigated. Association is treated with Wertheim' s thermodynamic perturbation theory and the direct correlation functions ar e derived by means of the Ornstein-Zernike equations for associating system s. The primary effect of association is to shift the critical temperatures and densities from those of a nonassociating fluid. While there are small, nonmonotonic shifts in the correlation length and surface tension, accompan ied by an interface composition change, these effects on the density profil e seem to be subsumed in the use of the proper T/T-c. (C) 2001 American Ins titute of Physics.