AB-INITIO STUDIES OF STATIONARY-POINTS OF THE AL2O3 MOLECULE

We report a theoretical ab initio investigation on energetically low-l ying stationary points of the Al2O3 molecular system. The calculations were performed at the Hartree-Fock (HF) and second-order Moller-Pless et (MP2) frozen core level of approximation using the standard 6-31G(d ) basis set. Several isomeric singlet as well as higher spin states of Al2O3 which lie close to each other within an energy range of about 8 eV (at MP2) are characterised. The lowest of these stationary points is in fact a triplet state of planar C-2v symmetry. It is by 0.08 eV ( MP2) lower than the often discussed linear D-infinity h singlet state. Atomisation energies for all species are quite large showing that the system is strongly bound. Energies, harmonic vibrational modes, and g eometric parameters are compared with the results of earlier work by S olomonik and Sliznev [1] Nemukhin and Weinhold [2], Andrews et al. [3] and Desai et al. [4]. Based on our calculations we give a tentative a ssignment of some selected vibrational wave numbers and an interpretat ion of some features of the photoelectron spectrum.