  We investigate the behavior of a patchy particle model close to a hard-wall
via Monte Carlo simulation and density functional theory (DFT). Two DFT
approaches, based on the homogeneous and inhomogeneous versions of Wertheim's
first order perturbation theory for the association free energy are used. We
evaluate, by simulation and theory, the equilibrium bulk phase diagram of the
fluid and analyze the surface properties for two isochores, one of which is
close to the liquid side of the gas-liquid coexistence curve. We find that the
density profile near the wall crosses over from a typical high-temperature
adsorption profile to a low-temperature desorption one, for the isochore close
to coexistence. We relate this behavior to the properties of the bulk network
liquid and find that the theoretical descriptions are reasonably accurate in
this regime. At very low temperatures, however, an almost fully bonded network
is formed, and the simulations reveal a second adsorption regime which is not
captured by DFT. We trace this failure to the neglect of orientational
correlations of the particles, which are found to exhibit surface induced
orientational order in this regime.
