A comparative density functional theory (DFT) study of a series of neutral and negative-ionic lithium and aluminum clusters doped with iodine atom is presented. The I atom is found to preserve the same position at Li-13 with and without the negative charge and Li-13 to vary its shape from prolate to oblate with changing spin state of Li13I. Both the Mulliken and natural charges are considered, the natural-charge separation between the metal and halogen moieties being generally much larger (except for Al13I-). In LinI-, the additional electron is strongly localized on the metal moiety starting from n = 1, even though the electron affinity of Li-n is much smaller than that of I. Such a super-halogen behavior of Li-n is induced by highly electronegative iodine making the two components charged in LinI and leading to a charge-dipole interaction with the additional electron. In AlnI-, similar factors result in Al-n being more negative than I already for n = 3, even though the electron affinity of I is higher, the effect escalating for n = 13.
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