Wetting and drying of an inert wall by a fluid in a molecular-dynamics simulation

The contact angle in a wall-fluid system can be obtained directly from a visual inspection of the liquid-vapor meniscus or it can be calculated from the solid-liquid, solid-vapor and liquid-vapor surface tensions. These routes were exploited in two previous simulations in which the wetting of a wall was studied. Both simulations showed the existence of a wetting and a drying transition with changing wall-fluid interaction, but the location of especially the drying transition was not consistent. It was suggested that the discrepancy was due to the use of a ``live'' wall, i.e., a wall in which the particles are not fixed at their lattice positions, in the measurements of the surface tensions. We have replaced the live wall by an inert wall and measured the surface tensions again, treating the wall as an external field now. The contact angles that are calculated from these measurements agree with the visual observations.