The mapping from the solvent accessible volume fraction to the solvation state . In panel A, the naïve choice is shown along with corrections introduced by the natural bounds of (see text). In panel B, the generalized, sigmoidal interpolation is shown. At τd=0.25 and χd=0.5, the curve is very similar to the linear case using the same bounds. Shifting χd to 0.1 and 0.9, respectively, shifts the mid-point of the transition accordingly, but leaves the overall curvature largely unaffected. Conversely, values of χd=0.5 and τd=0.1 increase curvature and yield a more step-like transition. See Equation 4 for details.