Analytical expressions of the free energy derivatives for molecules in solution. Application to the geometry optimization

We have developed and implemented analytical expressions of the free energy derivatives for molecules in solution with respect to nuclear coordinates. The solvation is described with the Polarizable Continuum Model, in which the solute molecules are embedded in cavities of realistic shape: no further approximations are introduced for the computation of derivatives. We report some test calculations of analytical derivatives, compared to numerical results. An application to the geometry optimization of acetaldehyde and N-methylformamide in water is presented.