Electronic states of the Cr2O3(0001) surface from ab initio embedded cluster calculations

The electronic structure of the Cr2O3(0001) surface is studied by means of ab initio embedded cluster calculations. Charge distributions and local d-d excitations are analysed for different geometrical relaxations of the surf ace. In the ground state there is considerable delocalization of electrons from the oxygen 2p band into the partly occupied 3d AOs of the Cr cations a t the surface such that their ionicity is reduced to Cr2+ as compared to Cr 3+ in the bulk. The calculated d-d and charge transfer excitations agree ve ry well with the prominent loss peaks observed experimentally by means of e lectron energy loss spectroscopy (EELS) at the Cr2O3 (0001) surface.