Al3O4 and Al3O4- clusters:: Structure, bonding, and electron binding energies

Structure and bonding in neutral and anionic Al3O4 clusters are studied with electronic structure calculations. Geometry optimizations with the B3LYP/6-311+G(2d) density functional method produce several minima, some with distinct multiplicities, for each molecule and anion. The most stable anionic structures are confirmed with additional geometry optimizations at the QCISD level. Equilibrium geometries, harmonic frequencies, and atomic charges are presented. These results, in combination with assignments of photoelectron spectra based on ab initio electron propagator theory, explain the energetic preference of anions for planar structures, while, in contrast, uncharged clusters favor three-dimensional geometries.