Semiempirical calculations of titanium dioxide (rutile) clusters

The densities of states for small (TiO2)x-clusters, x = 1, 3, 6, 9, and 14, were calcd. by means of the INDO method. The shape of the valence bands' d. of states (DOS) are discussed in terms of the distribution of coordination nos. A one-slab cluster with uniform distribution of the coordination nos. was used to compare the calcns. with exptl. spectra. The photoelec. DOS and DOS for a cluster with an oxygen vacancy are in very good agreement with exptl. findings for the TiO2 (001) surface. O 1s core level shifts between a surfacelike and a bulklike O atom were estd. The obsd. surface-bulk shift for the TiO2 (001) surface contains a substantial relaxation contribution.