Correlations at a fluid surface

A new formalism is developed for the statistical mechanical description of fluid surfaces that enables the interfacial density profile and the density profile in the vicinity of a wall to be treated in a parallel fashion. The work facilitates a direct comparison between interfacial and wall-fluid phenomena and immediately suggests a new approximation procedure for computing the interfacial density. As an illustrative example, the approach is applied to a fluid of sticky spheres, treated in the bulk according to the Percus–Yevick approximation. The results are of sufficient analytic simplicity in our approximation to permit a closed-form representation of the density profile in the vicinity of a smooth hard wall, and an interfacial profile given by a simple quadrature over an analytic function.