Geometric structure of TiO_{2}(110)(1×1): Confirming experimental conclusions (original) (raw)
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Geometric structure of TiO2(110)(1×1): Achieving experimental consensus
Physical Review B, 2007
Surface x-ray diffraction has been employed to elucidate the surface structure of TiO 2 ͑110͒͑1 ϫ 1͒. The atomic coordinates emerging from this study are in excellent agreement with those derived in other recent quantitative structure determinations of this surface. Most importantly, debate over the relaxation of the surface bridging oxygen has been resolved. In a previous surface x-ray diffraction study, it was concluded that this atom relaxes toward the bulk by 0.27± 0.08 Å, whereas in this present work we determined this displacement to be 0.10± 0.04 Å away from the bulk, which is in accord with the results of other experimental techniques.
Geometric Structure of TiO2(011)(2×1)
Physical Review Letters, 2008
Surface x-ray diffraction has been employed to elucidate the surface structure of the ð011Þ À ð2 Â 1Þ termination of rutile TiO 2 . The data are inconsistent with previously proposed structures. Instead, an entirely unanticipated geometry emerges from the structure determination, which is terminated by zigzag rows of twofold coordinated oxygen atoms asymmetrically bonded to fivefold titanium atoms. The energetic stability of this structure is demonstrated by ab initio total energy calculations.
Photoelectron diffraction investigation of the structure of the clean TiO2(110)(1×1) surface
Physical Review B, 2007
The surface relaxations of the rutile TiO 2 (110)(1x1) clean surface have been determined by O 1s and Ti 2p 3/2 scanned-energy mode photoelectron diffraction. The results are in excellent agreement with recent low energy electron diffraction (LEED) and medium energy ion scattering (MEIS) results, but in conflict with the results of some earlier investigations including one by surface X-ray diffraction. In particular, the bridging O atoms at the surface are found to relax outwards, rather than inwards, relative to the underlying bulk. Combined with the recent LEED and MEIS results a consistent picture of the structure of this surface is provided. While the results of the most recent theoretical total-energy calculations are qualitatively consistent with this experimental consensus, significant quantitative differences remain.
The geometric structure of intrinsic defects at TiO2(110) surfaces: an STM study
Surface Science, 1995
We report on a scanning tunneling microscopy study of TiO2(ll0) surfaces. Different types of intrinsic defects are produced by a high-temperature treatment at T > 1070 K in UHV, i.e. (001) single-steps, (001) line defects, and oxygen vacancies occur as predominant types of defects. Atomically resolved STM images make it possible to determine their geometric structures. With additional input from voltage-dependent (STS) images, simple structural models are derived for electrostatically neutral (001) single-steps at TiO2(ll0) surfaces and for line defects. The latter may formally be described by titanium vacancies and oxygen vacancies along the [001] direction. * Corresponding author.
Physical Review B, 2005
Many transition-metal monoxides formally having an fcc rock-salt structure exhibit a relatively high degree of vacancies, in particular, the most stable structure of stoichiometric titanium monoxide corresponds to a monoclinic phase, ␣-TiO, showing 15% vacancies. The role of such vacancies on the stability of the solid has been the subject of speculations for the last 30 years. We report in this work a theoretical study of the electronic structure of ␣-TiO based on generalized gradient approximation density functional calculations. Analysis of electron distribution changes induced by the creation of defects on the ideal rock-salt structure allows us to clarify the significant function played by both O and Ti ordered vacancies that work together on stabilization of the material. Stabilization of the monoclinic phase with respect to the cubic one involves a noticeable repolarization of the Ti 3d orbitals that simultaneously contribute to two cooperative mechanisms, ͑i͒ enhancement of the Ti-Ti bonding interactions through and around the oxygen vacancies, and ͑ii͒ electrostatic stabilization resulting from electron density accumulation in a oxygen vacancy ͑cation environment͒ together with electron density depletion in titanium vacancy ͑anionic environment͒.
Structure and New Substructure of α-Ti2O3: X-ray Diffraction and Theoretical Study
Journal of Modern Materials
The Crystal structure of both α-Ti2O3 and its new substructure with a halved c-axis has been investigated by single-crystal X-ray diffraction and density functional theory (DFT) calculations. The α-Ti2O3 substructure described in the R-3m space group, reveals an unusual 12-fold high coordination of Ti atoms forming edge and face-sharing distorted hexagonal prisms TiO12 stacking along the c-axis. The Hubbard-corrections predict a close bandgap for both α-Ti2O3 and its substructure; whereas a comparative study of their relative stability indicates that the substructure is thermodynamically less stable.
The Journal of Chemical Physics, 2006
We investigate the effects of constraining the motion of atoms in finite slabs used to simulate the rutile TiO 2 ͑110͒ surface in first-principles calculations. We show that an appropriate choice of fixing atoms in a slab eliminates spurious effects due to the finite size of the slabs, leading to a considerable improvement in the simulation of the ͑110͒ surface. The method thus allows for a systematic improvement in convergence in calculating both geometrical and electronic properties. The advantages of this approach are illustrated by presenting the first theoretical results on the displacement of the surface atoms in agreement with experiment.
Electronic structure of TiO2(110) surface as a function of surface ligand configuration
Applied Surface Science, 1998
Ž. Electronic structure of TiO 110 surface is studied by a first-principles molecular dynamics calculation with the 2 Ž. Vanderbilt pseudopotential. Three types of the surface are concerned: stoichiometric surface, defect 1 = 1 surface, and Ti O added row surface. STM simulation as well as electronic band structures are presented. The simulated STM images 2 3 show that the surface Ti atom which has less ligand dominates the tunnel current.
Surface structure of TiO2(011)-(2x1)
Physical review letters, 2004
A combined experimental and first principles study of the (2x1)-reconstructed rutile TiO2(011) surface is presented. Our results provide evidence that the surface structure is described by a model that includes onefold coordinated (titanyl) oxygen atoms giving rise to double bonded Ti=O species. These species should play a special role in the enhanced photocatalytic activity of the TiO2(011) surface.
New structural and electronic properties of (TiO2)10
The Journal of chemical physics, 2016
We present, based on state of the art density functional theoretic calculations, a new putative ground state (GS) for the cluster (TiO2)10, which results more than 1 eV lower in energy than all those previously reported in the literature. The geometric and electronic properties of this new cluster are discussed in detail and in comparison with the rest. We analyze the implications of the new GS in the context of recent experiments of reactivity regarding oxygen exchange with gaseous CO2 in TiO2 nanostructures, and also in connection with a recent interpretation of photoelectron spectroscopic measurements of the band gap of gas phase TiO2 (-) clusters.