Decay of Correlations in Bulk Fluids and at Interfaces: A Density-Functional Perspective

Density functional methods can be used to show that for classical fluids with short-ranged interatomic potentials the length scales which describe the asymptotic decay of the one-body density profile at a fluid interface are the same as those which determine the decay of the two-body correlation function g(r) of the bulk fluid. This general result has striking implications for a variety of interracial properties - the possible occurrence of oscillations in the liquid-vapour density profile, the occurrence of wetting and layering phase transitions at substrate-fluid interfaces and the nature of the decay of the solvation force for a confined fluid. For fluids whose potentials have power-law decay the density profiles and g(r) exhibit power-law decay at longest range. However, for liquid densities the intermediate range damped oscillatory decay is governed by the same leading-order pole structure that describes short-ranged forces. Recent work on the decay of correlations in binary liquid mixtures and in ionic fluids is also described.