I missed this short communication last year, (thanks to the computational chemistry list CCL for bringing this to our attention!) but it is worth commenting on even a year later as this topic is one that frequently confuses users.

Ho, Klamt, and Coote1 note that popular quantum chemistry codes, including the Gaussian series, present the output of continuum solvent models in a way that can be misleading. What is called the free energy is in fact the sum of the electronic energy in solution and the free energy associated with non-electrostatic contributions. What is missing are corrections to the solute to give its free energy. What is assumed (oftentimes without fully recognizing this assumption) is that the thermal corrections for the solute in the gas and solution phase will cancel – but this does not have to be. Let the QM code user (and reader of the literature) beware!


(1) Ho, J.; Klamt, A.; Coote, M. L., "Comment on the Correct Use of Continuum Solvent Models," J. Phys. Chem. A 2010, 114, 13442-13444, DOI: 10.1021/jp107136j