  A classical density functional theory is applied to study solvation of
solutes in water. An approx- imate form of the excess functional is proposed
for water. This functional requires the knowledge of pure solvent direct
correlation functions. Those functions can be computed by using molecular
simulations such as molecular dynamic or Monte Carlo. It is also possible to
use functions that have been determined experimentally. The functional
minimization gives access to the solvation free energy and to the equilibrium
solvent density. Some correction to the functional are also proposed to get the
proper tetrahedral order of solvent molecules around a charged solute and to
reproduce the correct long range hydrophobic behavior of big apolar solutes. To
proceed the numerical minimization of the functional, the theory has been
discretized on two tridimensional grids, one for the space coordinates, the
other for the angular coordinates, in a functional minimization code written in
modern Fortran, mdft. This program is used to study the solvation in water of
small solutes of several kind, atomic and molecular, charged or neutral. More
complex solutes, a neutral clay and a small protein have also been studied by
functional minimization. In each case the classical density functional theory
is able to reproduce the exact results predicted by MD. The computational cost
is at least three order of magnitude less than in explicit methods.
