MORPHOLOGY AND LINE TENSION OF LIQUID-FILMS ADSORBED ON CHEMICALLY STRUCTURED SUBSTRATES

On the basis of a microscopic density-functional theory for inhomogeneous fluids we investigate the structure of liquidlike films adsorbed on laterally inhomogeneous, flat substrates that consist of two adjacent halves occupied by different chemical species. All atomic interactions are taken to be long ranged. The corresponding integral equations for the equilibrium density profile are solved numerically. The mean position of the interface between the liquidlike adsorbed film and the bulk vapor phase displays van der Waals tails; their amplitudes are calculated analytically for complete and critical wetting. As an approximation we recover the standard phenomenological approach for the profile of the mean interface position whose quantitative behavior turns out to fail drastically as compared with that obtained from the appropriate nonlocal theory. The shape of the interface profile gives rise to a line tension that diverges logarithmically for complete wetting transitions and exhibits a cusplike singularity close to critical wetting transitions. © 1995 The American Physical Society.