COMMON THEORETICAL FRAMEWORK FOR QUANTUM CHEMICAL SOLVENT EFFECT THEORIES

Quantum chemical solvent effect theories deal with the description of the electronic structure of a molecular subsystem embedded in a solvent or other molecular environment. The average reaction field theories, which describe electrostatic and polarization interactions between solute and solvent, can be formulated in terms of a nonlinear reaction potential operator. This operator depends on the one hand on the reaction potential function of the solvent, and on the other hand on the charge density operators, which appear in the solute-solvent interaction. The former quantity is determined by the physical model of the solvent (e.g. dielectric continuum, discrete model, crystal lattice, etc.). The charge density operator can be approximated at different levels, like exact, one-centered and multicentered multipolar forms. These two ingredients of the theory, the reaction potential response function and the specific charge density operator, define unequivocally different solvent effect models. Various versions of average reaction field models are critically reviewed on the basis of this common theoretical framework.