Abstract: Instead of continuous medium theory, quantum mechanics/molecular dynamics method was adopted to deal with the electrostatic effect on the spectrum of the solute molecule by considering the concrete structure of solvent molecules. By constructing the external electric field felt with solute molecule and introducing the molecular polarizability of the solvent molecule, the mutual polarization between the solute and the solvent was taken into account and reasonable charge distributions of the solute and the solvent molecule were obtained. With a detailed deduction, we found that the spring energy of the permanent dipole of the solvent molecule was ignored unreasonably in the expressions of the solvation energy for equilibrium and nonequilibrium states. Including the energy contribution of this part, the new expression for the solvation energy and formulas for the spectral shifts of light absorption and emission were established. With the modified averaged solvent electrostatic potential/molecular dynamics program, the calculated spectral shift of the n→π* transition of acetone molecule in water is very close to the experimental value and the rationality of our new formula is testified.

Key words: Solvation energy, Spring energy of the permanent dipole, Spectral shift, Molecular dynamics, Radial distribution function