We have developed a self-consistent description of an interface between a metal and a molecular liquid by combination of the density functional theory in the Kohn–Sham formulation (KS DFT) for the electronic structure, and the three-dimensional generalization of the reference interaction site model (3D RISM) for the classical site distribution profiles of liquid. The electron and classical subsystems are coupled in the mean field approximation. The procedure takes account of many-body effects of dense fluid on the metal–liquid interactions by averaging the pseudopotentials of liquid molecules over the classical distributions of the liquid. The proposed approach is substantially less time-consuming as compared to a Car–Parrinello-type simulation since it replaces molecular dynamics with the integral equation theory of molecular liquids. The calculation has been performed for pure water at normal conditions in contact with the (100) face cubic centered (fcc) surface of a metal roughly modeled after copper. The results are in good agreement with the Car–Parrinello simulation for the same metal model. The shift of the Fermi level due to the presence of water conforms with experiment. The electron distribution near an adsorbed water molecule is affected by dense water, and so the metal–water attraction follows the shapes of the metal effective electrostatic potential. For the metal model employed, it is strongest at the hollow site adsorption positions, and water molecules are adsorbed mainly at the hollow and bridge site positions rather than over metal atoms. Layering of water molecules near the metal surface is found. In the first hydration layer, adsorbed water molecules are oriented in parallel to the surface or tilted with hydrogens mainly outwards the metal. This orientation at the potential of zero charge agrees with experiment.

A generalization of the RISM integral equation for site–site pair correlation functions previously proposed by us is discussed and applied to model liquids composed of strongly polar diatomic molecules. The nonuniform molecular charge distribution is represented by the introduction of charged interaction sites. The generalization consists of applying closure conditions analogous to those which are known to be reasonable for the description of atomic ionic fluids, and the corresponding renormalization of the contributions arising from long range forces. We discuss both the symmetry properties of the pair correlation functions in special cases and the dielectric properties implied by theory. Applications are presented for three two‐site models which differ substantially in the degree of asymmetry of the non‐Coulombic potential between the two sites, and for three three‐site models for Br₂. The two sites models are compared to computer simulation results, and those for Br₂ to experimental results. The analysis shows that the integral equation is well balanced in that in every case the qualitative features of the liquids structure which are introduced by polarity are well represented, even in cases where the site–site potentials are individually much larger than k_BT. In cases where the molecular shape and polar forces are in competition, the results are of comparable accuracy to the corresponding theory for nonpolar systems. In the extreme case where changes in orientational structure can occur without interfering with packing requirements, the results appear quantitatively less reliable.

In the previous study, Chem. Phys. Lett. 214, 391 (1993), we developed a new computational procedure for the solvation effect on the electronic structure of solute based upon the reference interaction site model (RISM) integral equation and the Hartree–Fock equation. The method enables us to calculate the solvent distribution and solute electronic wave functions simultaneously, which is free from such empirical parametrizations as appeared in the usual models based on the dielectric continuum picture. In the present article, we have applied the method to several carbonyl compounds in aqueous solution. The SPC model was used to describe the liquid water. The vertical n→π*, π→π*, and σ→π* transitions of formaldehyde are examined by the RISM‐self‐consistent field formalism coupled with the restricted Hartree–Fock approximation, and then the free energy calculation was performed for the excited state in order to estimate the contributions for the optical fluorescence spectra. The intramolecular energy turned out to give significant contribution to the bathochromic shift of fluorescence relative to the absorption in the liquid phase. Furthermore the importance of the structural effect of the functional group was discussed by the calculations of three more carbonyl compounds, acetaldehyde, acetone, and acrolein.