Studies on the stability of on-top Al₁₃i_n^m (n = 1∼12, m = -1, 0, +1) clusters

Energetic and electronic structures of the on-top Al₁₃l _n^m (n = 1 ∼ 12, m = -1, 0, +1) clusters have been investigated by employing a first-principles pseudo-potential plane wave method. Several parameters such as binding energies, second differences of energy and vertical-electron detachment energies have been adopted to characterize and evaluate the structure stability of Al₁₃I_n^- (n = 1 ∼ 12) clusters. The optimized models show that the Al₁₃ moieties in the clusters can not retain the original regular icosahedron structure. Results from binding energy and second difference of energy show that Al₁₃I_n and Al₁₃I_n^- clusters with even n are more stable than those with odd n in contrast with Al₁₃I_n⁺ clusters. The calculation of vertical-electron detachment energies (VDE) of Al₁₃I ⁿ,clusters indicates that Al₁₃I_n and Al ₁₃I_n^- clusters with even n are closer to the closed shell of the Jellium model. Further analysis of electron density of states and electron density differences reveals that the enhanced stability of Al₁₃I_n^- clusters is not only associated with the closed shell of valence electrons but also with the bonding type between I and associated Al atoms.