MULTICONFIGURATIONAL SELF-CONSISTENT REACTION FIELD-THEORY FOR NONEQUILIBRIUM SOLVATION

We present multiconfigurational self-consistent reaction field theory and implementation for solvent effects on a solute molecular system th at is not in equilibrium with the outer solvent. The approach incorpor ates two different polarization vectors for studying the influence of the solvent. The solute, an atom, a molecule or a supermolecule, is as sumed to be surrounded by a linear, homogeneous medium described by tw o polarization vector fields, the optical polarization vector and the inertial polarization vector fields. The optical polarization vector i s always in equilibrium with the actual electronic structure whereas t he inertial polarization vector is not necessarily in equilibrium with the actual electronic structure. The electronic structure of the comp ound is described by a correlated electronic wave function-a multiconf igurational self-consistent field (MCSCF) wave function. This wave fun ction is fully optimized with respect to all variational parameters in the presence of the surrounding polarizable dielectric medium having two distinct polarization vectors. We develop from a compact and simpl e expression a direct and second-order convergent optimization procedu re for the solvent states influenced by the two types of polarization vectors. The general treatment of the correlation problem through the use of complete and restricted active space methodologies makes the pr esent multiconfigurational self-consistent reaction field approach gen eral in that it can handle any type of state, open-shell, excited, and transition states. We demonstrate the theory by computing solvatochro matic shifts in optical/UV spectra of some small molecules and electro n ionization and electron detachment energies of the benzene molecule. It is shown that the dependency of the solvent induced affinity in be nzene is nonmonotonic with respect the optical dielectric constant if inertial polarization effects also are accounted for. (C) 1995 America n Institute of Physics.