Effects of atomic-force-microscope tip characteristics on measurement of solvation-force oscillations

We have previously used molecular dynamics to simulate the force oscillations experienced by a model atomic-force-microscope tip brought near a surface under a Lennard-Jones liquid. Here we perform these simulations for additional tip radii. We also apply an Ornstein-Zernicke-type integral equation theory to this system, and obtain force-distance curves for several different state points, tip radii, and surface-liquid potentials. We find this theory to be in good agreement with simulation results for tip-wall separations greater than one molecular diameter. We conclude that the magnitude of the force oscillations experienced by an atomic-force-microscope tip is a linear function of the effective tip radius (at constant temperature) and that measurement of these force curves with a standard solvent could provide a method of estimating the relative radii of different tips.