To ascertain whether these hemibonded minima might simply be SIE artifacts, additional cluster optimizations with larger QM regions were performed at the MP2/ 6-31G* level (Fig. ), including all water molecules within 7.2 Å of the radical. In all cases where the starting geometry exhibits a hemibond, the Hartree-Fock spin density fully localizes onto the hydroxyl moiety upon MP2 optimization, suggesting that the spin delocalization is indeed an artifact. Closer examination reveals that the hemibonded water moves slightly farther away from the radical upon MP2 structural relaxation (Fig. ), yet maintains a pseudo-hemibond configuration, by which we mean that an exposed O * • • • O facet persists with no intervening hydrogen bond. The O * • • • O distance in these pseudo-hemibonded structures is larger than what is traditionally associated with a hemibond, and there is no spin delocalization. The latter observation makes sense in view of the decreased orbital overlap at larger distance.