A molecular theory of solvation force oscillations in nonpolar liquids

A molecular theory based on the nonlocal density functional theory is used to calculate the solvation-force oscillations in nonpolar liquids observed with an atomic-force microscope (AFM) and a surface-force apparatus (SFA) operated within liquid. The fluid-fluid as well as wall-fluid interactions are represented by a Lennard-Jones type potential, whose parameters are related to the Hamaker constant, The density functional calculation shows that a stronger wall-fluid than fluid-fluid interaction is necessary to observe this solvation-force oscillation. The magnitude of the Hamaker constants of various nonpolar organic liquids and various substrates shows that this criterion for the observation of oscillation is normally satisfied. (C) 1998 Academic Press.