For each combination of dielectric constants, we examine two different Voronoi-based constructions of ε(r) that are called "scheme 1" and "scheme 2" in Tables and. This is a reference to the numbering scheme introduced in Fig. , which shows how three-dimensional space is partitioned into polar and nonpolar regions characterized by ε solv and ε nonp , respectively. Taking NO - 3 as an example, the difference between schemes 1 and 2 lies in whether a single N-O moiety is exposed to the high-dielectric region (scheme 1, Fig. ) or else two N-O moieties are immersed in ε solv (scheme 2, Fig ). One may object that this is not a physically realistic setup for a strongly polar species such as NO - 3 , although it is a well-defined model problem. Considering glycine as another example, the difference between schemes 1 and 2 lies in whether the carboxylate moiety is solvent-exposed (scheme 1, Fig. ) or whether the amino group is instead solvent-exposed (scheme 2, Fig. ). For other solutes, the meaning of scheme 1 versus scheme 2 can be gleaned from Fig. , and in each case amounts to exposing different parts of the vdW cavity surface to ε solv = 78.4 versus a smaller dielectric value, ε nonp . In the Voronoi-PEqS calculations this is done in a smooth way-and Fig. is actually a color map of the permittivity function ε(r) that is constructed-whereas for HetPCM, ε solv and ε nonp are assigned at the atomic level, in a manner that should be obvious from Fig. .