where ε i = ε(s i ) is a dielectric constant for the surface element s i . For C-PCM, the factor fε (ζ) in eq. 9 could be modified analogously. In the examples considered herein, we use no more than two different values for the quantities ε i , namely, ε solv = 78 for solvent-exposed parts of the cavity surface and something smaller (ε nonp = 2-10) for hydrophobic portions of the surface. These are trivial modifications, in any implementation of C-PCM or IEF-PCM.