  Three dimensional implementations of liquid state theories offer an efficient
alternative to computer simulations for the atomic-level description of aqueous
solutions in complex environments. In this context, we present a (classical)
molecular density functional theory (MDFT) of water that is derived from first
principles and is based on two classical density fields, a scalar one, the
particle density, and a vectorial one, the multipolar polarization density. Its
implementation requires as input the partial charge distribution of a water
molecule and three measurable bulk properties, namely the structure factor and
the k-dependent longitudinal and transverse dielectric constants. It has to be
complemented by a solute-solvent three-body term that reinforces tetrahedral
order at short range. The approach is shown to provide the correct
three-dimensional microscopic solvation profile around various molecular
solutes, possibly possessing H-bonding sites, at a computer cost two-three
orders of magnitude lower than with explicit simulations.
