FIG. 1.

(Color online) Radial dependence of (a) the dielectric constant ε(r/a) and (b) ε′(r/a)/[4πε(r/a)] for a monotonic step [red broken line, Eq. (69)] and for a nonmonotonic step simulating a hydration layer (blue solid line). The dielectric constant changes smoothly from ε₁ =4 inside the sphere to ε_o =80 outside. The effective radii r₀ =1.13a and r₀ =1.17a, respectively, are chosen so that the Born solvation energy in each case is equal to that in the case of a sharp boundary at radius a (shown with dotted line). The half width of the steps δr=0.2a.