Density Functional Study of Neutral and Anionic AlOn and ScOn with High Oxygen Content

The electronic and geometrical structures of neutral and negatively charged AlO5, AlO6, AlO7, AlO8, AlO9, AlO10, AlO11, AlO12, AlO15, AlO16, and AlO18 along with the corresponding series of ScOn and ScOn- oxides were investigated using density functional theory with generalized gradient approximation. We found that these species possess geometrically stable isomers for all values of n = 5-12, 15, 16, 18 and are thermodynamically stable for n = 5-7. The species with n 16 are found to be octa-dioxides M(eta(1)-O-2)(8) while the species with n = 15 and 18 are penta-ozonides (eta(2)-O-3)M(eta(1)-O-3)(4) and hexa-ozonides M(eta(1)-O-3)(6), respectively. Geometrical configurations of a number of the lowest total energy states of Al and Sc oxides are different. Especially, drastic differences are found for the anion AlOn- and ScOn- pairs at n = 9, 10, and 11. The Sc-O bonds are longer than the Al-O bonds by approximate to 0.2A, which, in turn, slightly affects the corresponding interoxygen bond lengths. The charges on metal atoms are close to +2e in both Al series and to +1.5e in both Sc series. As an extra electron is delocalized over ligands in the presence of a large positive charge on the metal atom of the anions, the electron affinity (EA) of the neutrals along with the ionization energies of the anions are large and exceed the EAs of the halogen atoms in a number of cases. (C) 2011 Wiley Periodicals, Inc. J Comput Chem 32: 2974-2982, 2011