GREEN-FUNCTION CALCULATION OF IONIZATION ENERGIES OF HYPERMETALLIC MOLECULES

Vertical ionization and electron capture energies (electron affinities) are obtained for the hypermetallic molecules Al2O, Al3O, Al4O, Al4C, CAl2Si2, NAl3Si and BAlSi3 and some related compounds from ab initio calculations with large basis sets. Many-body effects are taken into account by the Green function technique. The results agree with the photoelectron data on Al2O. Koopmans' approximation gives good agreement with the Green function results for the first few ionization energies. However, the one-particle ionization model breaks down for the lower valence levels. Electron correlation and relaxation contributes strongly to the electron capture energies.