Surface States and Catalysis ond-Band Perovskites

It is demonstrated that surface states derived from the lower conduction band of $d$-band perovskites produce a square-root singularity peak in the density of surface states at energies which lie in the forbidden gap. These surface states are highly localized and have nearly pure $d$-state character. It is suggested that these surface states provide the necessary orbitals to facilitate an important class of symmetry-forbidden chemical reactions.