Going from ESP embedding to EHF embedding in G 4 only slightly modifies the excitation energies of the site states, leaving their energy ordering and characters untouched. The reason can be seen in Figure , which shows that the embedding charges of the guanines in G 4 do not significantly change between ESP and EHF (compare EHF cycle = 1 and EHF cycle = 7). The overall RMSD of the ESP and EHF charges is only 0.072e. This, in turn, is because the fragments in G 4 are relatively weakly interacting, and thus the ESP charges of the isolated fragments are already rather close to self-consistency.