Density functional description of water condensation in proximity of nanoscale asperity

Abstract

We apply non-local density functional formalism to describe an equilibrium distribution of the water-like fluid in the asymmetric nanoscale junction presenting an atomic force microscope (AFM) tip dwelling above an arbitrary surface. The hydrogen bonding dominating in intermolecular attraction is modeled as a square well potential with two adjustable parameters (energy and length) characterizing well's depth and width. A water meniscus formed inside nanoscale junction is explicitly described for different humidity. Furthermore, we suggest a simple approach using polymolecular adsorption isotherms for the evaluation of an energetic parameter characterizing fluid (water) attraction to substrate. This model can be easily generalized for more complex geometries and effective intermolecular potentials. Our study establishes a framework for the density functional description of fluid with orientational anisotropy induced by non-uniform external electric field.