Another advantage of IGMH over NCI and IRI is that it defines quantitative indices to measure the contribution of atoms and atom pairs to the interactions shown in the IGMH map. Although these indices are very simple and may not have a direct positive correlation with the contribution to the interaction energy, they can still be used to identify which atoms and atom pairs are relatively important and therefore worthy of attention. Specifically, G pair is used to quantify the contribution of an atom pair to the interaction between two specific fragments, A and B: