ACCURATE FIRST PRINCIPLES CALCULATION OF MOLECULAR CHARGE-DISTRIBUTIONS AND SOLVATION ENERGIES FROM AB-INITIO QUANTUM-MECHANICS AND CONTINUUM DIELECTRIC THEORY

In this paper, we combine high-level ab initio quantum chemical calcul ations with a continuum description of the solvent to obtain accurate solvation free energies of organic solutes in water. By using correlat ed wave functions at the generalized valence bond/perfect pairing (GVB -PP) level, we are able to efficiently produce accurate gas-phase char ge distributions. These are then used to obtain solvation energies in a self-consistent formalism which cycles through quantum chemical calc ulations in the solvent reaction field and continuum electrostatic cal culations utilizing polarized solute charges. An average error of 0.6 kcal/mol for solvation energies is obtained for 29 molecules. A system atic discrepancy between theory and experiment is obtained for the dif ference in solvation foe energy between several methylated and unmethy lated primary amines and amides. This poses a major puzzle in theoreti cal modeling of solvation effects.