The difference of these energies with respect to those calculated with the full CS can then be associated with the contribution of the L i ligand to the Zn(II)-interaction energy, ∆E Zn Int (L i ), and to the coordination-shell formation energy, ∆E CS f (L i ). Finally, the total interaction energy ∆E T Int (L i ) associated with a specific ligand in a given coordination shell is the sum of these two terms, namely,