Molecular dynamics simulations of water on a hydrophilic silica surface at high air pressures

Abstract

We present a force field for Molecular Dynamics (MD) simulations of water and air in contact with an amorphous silica surface. We calibrate the interactions of each species present in the system using dedicated criteria such as the contact angle of a water droplet on a silica surface, and the solubility of air in water at different pressures. Using the calibrated force field, we conduct MD simulations to study the interface between a hydrophilic silica substrate and water surrounded by air at different pressures. We find that the static water contact angle is independent of the air pressure imposed on the system. Our simulations reveal the presence of a nanometer thick layer of gas at the water–silica interface. We believe that this gas layer could promote nucleation and stabilization of surface nanobubbles at amorphous silica surfaces.