Solvent Effect on the Electronic Structure of Molecules Studied by the Langevin Dipoles/Monte Carlo Approach

A method for calculation of the solvent effect on the molecular electronic ground-state structure of ions and molecules has been presented. In this method, being a modification of the Warshel et al. approach, solvent molecules are represented by a three-dimensional cubic grid of Langevin polarizable point dipoles. The modifications introduced into the original model include (a) the representation of a solute molecule by atomic point charges, dipoles, and quadrupoles, (b) the full (i.e., without dumping) Langevin formula for the polarization, (c) mutual polarization of the solute and the solvent molecules, and (d) the Monte Carlo sampling technique for determination of the optimal position and orientation of the solute molecule. The proposed method has been applied in the calculation of hydration energies for small molecules, ions, α-amino acids, and DNA bases, as well as in calculations of the solvent effect on the electronic spectra of acetone, 4-nitroaniline, and Reichardt's betaine dye.