A first principles survey of stoichiometric (1 x 2) reconstructions on the rutile surface

First principles slab calculations on the reconstructed stoichiometric (110) surface of rutile TiO2 are reported. Motivated by experimental observations, this systematic density functional survey has yielded 36 low energy (1 x 2) reconstructions (DeltaE(Surf) < 1.0 J m(-2)). Some isomers show only slight differences in energy, so that careful estimation of the surface energy is necessary: by computing both singly and doubly reconstructed slabs we are confident in comparing surface energies to within +/-0.04 J m(-2). The bulk-terminated unreconstructed surface is confirmed to be the most stable for the stoichiometric oxide. However, reconstructions featuring tetrahedrally-coordinated Ti cations at the vertically-oriented interstitial sites are computed to occur on top of any bulk-terminated surface section and destabilise the surface by just 0.04 J m(-2). Destabilisation is calculated to be greater for the rich variety of other possible reconstructions, such as incomplete bulk-terminated sections, or reconstructed Ti at the other interstitial site. Oxide anions generally occupy positions of the bulk sub-lattice. (C) 2001 Elsevier Science B.V. All rights reserved.