The first systematic survey of the surface structure of reduced rutile TiO2-x by first-principles calculations was reported. Motivated by the reconstructions observed in experiment, rows of ions were considered on the (110) surface so as to satisfy (1 x 2) periodicity. The surface was reduced by the removal of one O anion per (1 x 2) cell and over 100 reconstructed surfaces were computed with cations at both bulk and interstitial sites. These spin-polarized density-functional calculations revealed that the most stable reconstruction was the so-called added row +Ti2O3 structure of Onishi & Iwasawa (1994), at a surface energy of 3.29J/m2. This was described as being a twinned dislocation; stabilized by relaxation of the cations away from the surface. All other reconstructions were calculated to be at least 0.3J/m2 less stable. Many of them featured rutile-like Ti-O half-ribbons and rocksalt-like dislocations. Some of these might account for less stable (1 x 2) surface phases.

Assigning the (1 x 2) Surface Reconstruction on Reduced Rutile by First-Principles Energetics. Elliott, S.D., Bates, S.P.: Physical Review B, 2002, 65[24], 245415