Figure 6.

Two alternative schemes for the separation of all charges in the ICSM into explicit and implicit regions. In scheme (a), only water molecules whose oxygen atom is more than the length of the hydrogen-oxygen bond, d_OH , away from the sphere boundary are included in the explicit part. This choice allows for free rotation of waters near the boundary. In scheme (b), water molecules whose all three atoms, as in example I, are within R_c +τ are included in the explicit part. Example J shows that not all waters in this scheme are allowed to rotate. As a consequence, this scheme will create a nonzero potential at the site of the sodium ion in the orientational disorder limit.⁵⁷ In the terminology of Kastenholz and Hünenberger (Ref. ⁵⁷) such potentials lead to the first C-type correction.