Figure 4.

Schematic representation of the two contributions to the asymmetric solvent response with respect to the solute charge. (a) Average water orientation at the surface of an uncharged solute gives rise to a non-zero static potential. It can be interpreted as a continuum density of oriented solvent dipoles at the surface. (b) Steric asymmetry in water hydrogen (smaller) and oxygen (larger) drives asymmetric response with water molecules being able to approach a negative charge more closely than a positive charge. This applies even to situations in which the charge is not directly solvent exposed.