Several of the variations in the H = 6.70 Å slit coordination number give insight into the unique features of this system's PMF. For example, states in which ions are separated by two water molecules (the third minimum of the PMF and structure "e" in Fig. ) coincide with a local maximum in coordination number of the chloride ions. This relative over-coordination, which is not observed in any of the other systems, may stabilize the state.