Figure 6.

A: The charge-asymmetric 2-point (2P) and the symmetric simple point dipole (SPD) hard sphere water models. Both models have identical dipole moments $\mid \overrightarrow{p}\mid =\mid R_{OH}^z{q}_O\mid$. B: The two orientation states, σ = ±1, of the water dipole in the ion first hydration shell used in Eq. (6). The dipole energy of any other ion-water orientation can be decomposed as a linear combination of these two states.