Solvent distortion energy

In order to clarify the role played by the solvent in the stabilization of the different structures it is useful to split the AGint term into two terms A int and AGsoiv. The last term, AGsoiv, provides the solvent distortion energy, i.e., the energy spent in changing the solvent structure from the initial to the final state. The term A nt accounts for the difference in the solute-solvent interaction energy between the final and initial states. For a non-polarizable solvent this term reads... 

Here, q refers to the permanent charges of solvent molecules, p to the solvent induced dipoles, and p is the solute charge density. The last term in Equation (4.152) is the distortion energy of the solute, i.e., the energy spent in polarizing it. 

Fig. 6 Optimized transition states for the hydrolysis reaction. The selected NBO charges for Q, Cb and Cc are given in the box. The selected bond lengths (bold) are in angstroms, and the relative free energies including solvent effect AGsoi (bold) and the relative distortion energies (DE, italic underlined) are in kcal/mol. Calculated at the B3LYP/6-311+G A-anl2DZ level...

These studies discuss vertical and adiabatic excitation energies but the photophysical behavior requires calculations along the PES and at highly distorted geometries, which are more difficult to carry out in the presence of solvent. Some theoretical work has been done in this area, but it is quite limited. 

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