In the generalization from an atomic to a molecular solvent, the choice is made to apply a common value of the scaling factor s (as determined by the position of a specified reference point in the molecule) to all atoms within a given molecule. This choice is considered more appropriate than the use of distinct scaling factors for the different atoms (determined by their own positions) because it is consistent with a linear scaling of the interatomic distances (bonds) that preserves the angular structure (bond angles, dihedral angles) as well as the electroneutrality (zero net charge) of the solvent molecule upon scaling. For simplicity, it is also assumed that the selected FG solvent model is entirely rigid (no intramolecular interactions), and that its specification is complemented by the selection of a reference atom (e.g. oxygen atom for a rigid water model).