ATOMIC AND ELECTRONIC-STRUCTURE OF THE CORUNDUM(0001) SURFACE - COMPARISON WITH SURFACE SPECTROSCOPIES

The electronic structure and geometry of the Al-terminated corundum (0 001) surface were studied using a slab model within the ab-initio Hart ree-Fock technique. The distance between the top Al plane and the next O basal plane is found to be considerably reduced on relaxation (by 0 .57 Angstrom i.e. by 68% of the corresponding interlayer distance in t he bulk). An interpretation of experimental photoelectron spectra (UPS He I)and metastable impact electron spectra (MIES) is given using the calculated total density of states of the slab and the projections to the atoms, atomic orbitals, and He Is Boating atomic orbital at diffe rent positions above the surface. Calculated projected densities of st ates exhibit a strong dependence on the relaxation of surface atoms. T he good agreement of simulated and experimental UPS and MIES spectra s upports the correctness of calculated surface relaxation.