Nonlinear theory of metal-solvent interface using the density functional approach

A nonlinear theory for the calculation of spatial and orientational structure of a dipolar solvent near a metal surface is developed by using the density functional approach. The theory is based on a weighted density approximation for the isotropic part of the density and the anisotropic part is calculated by using a perturbative approach. The theory, however, retains the full nonlinear dependence of the inhomogeneous solvent structure on the field produced by the metal surface and also on solvent-solvent interactions. Explicit numerical results are obtained for the number density and polarization of a dipolar solvent near a metal surface. The number density of the solvent near the surface is found to increase with increase of the electrostatic field of the metal, which is a nonlinear effect. The polarization is also found to increase nonlinearly with the metal field and exhibits the presence of pronounced orientational order near the metal surface.