  In this paper we formulate a nonlocal density functional theory of
inhomogeneous water. We model a water molecule as a couple of oppositely
charged sites. The negatively charged sites interact with each other through
the Lennard-Jones potential (steric and dispersion interactions), square-well
potential (short-range specific interactions due to electron charge transfer),
and Coulomb potential, whereas the positively charged sites interact with all
types of sites by applying the Coulomb potential only. Taking into account the
nonlocal packing effects via the fundamental measure theory (FMT), dispersion
and specific interactions in the mean-field approximation, and electrostatic
interactions at the many-body level through the random phase approximation, we
describe the liquid-vapour interface. We demonstrate that our model without
explicit account of the association of water molecules due to hydrogen bonding
and with explicit account of the many-body electrostatic interactions at the
many-body level is able to describe the liquid-vapour coexistence curve and the
surface tension at the ambient pressures and temperatures. We obtain very good
agreement with available in the literature MD simulation results for density
profile of liquid-vapour interface at ambient state parameters. The formulated
theory can be used as a theoretical background for describing of the capillary
phenomena, occurring in micro- and mesoporous materials.
