STRUCTURES OF THE ALUMINUM-OXIDES STUDIED BY ABINITIO METHODS WITH NATURAL BOND ORBITAL ANALYSIS

We present a comprehensive theoretical analysis for the low-lying isomeric structures, energetics, and vibrational properties of dinuclear aluminum oxides Al2On (n = 1-4) to aid interpretation of experimental spectroscopic data for these species. We also carried out natural population and natural bond orbital (NBO) analysis of the correlated and uncorrelated ab initio wave functions in order to elucidate the general bonding principles governing these species. We find that the equilibrium structures generally exhibit high ionic character (viz., effective Al3+ and O2- ionic units), but with significant modifications due to covalency, which is generally enhanced by electron correlation. Although certain previous experimental assignments are confirmed by our studies, in other cases the theoretical results strongly contradict suggested assignments. For a significant number of the reported experimental lines, we currently have no good theoretical candidate species.