### Abstract

Experimental observations indicate that removing bridging oxygen atoms from the TiO2 rutile (1 1 0) surface produces a localised state approximately 0.7 eV below the conduction band. The corresponding excess electron density is thought to localise on the pair of Ti atoms neighbouring the vacancy; formally giving two Ti3+ sites. We consider the electronic structure and geometry of the oxygen deficient TiO2 rutile (1 1 0) surface using both gradient-corrected density functional theory (GGA DFT) and DFT corrected for on-site Coulomb interactions (GGA + U) to allow a direct comparison of the two methods. We show that GGA fails to predict the experimentally observed electronic structure, in agreement with previous uncorrected DFT calculations on this system. Introducing the +U term encourages localisation of the excess electronic charge, with the qualitative distribution depending on the value of U. For low values of U (⩽4.0 eV) the charge localises in the sub-surface layers occupied in the GGA solution at arbitrary Ti sites, whereas higher values of U (⩾4.2 eV) predict strong localisation with the excess electronic charge mainly on the two Ti atoms neighbouring the vacancy. The precise charge distribution for these larger U values is found to differ from that predicted by previous hybrid-DFT calculations.

Original language | English |
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Pages (from-to) | 5034-5041 |

Journal | Surface Science |

Volume | 601 |

Issue number | 21 |

DOIs | |

Publication status | Published - 1 Nov 2007 |

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## Cite this

Morgan, B. J., & Watson, G. W. (2007). A DFT+U description of oxygen vacancies at the TiO2 rutile (110) surface.

*Surface Science*,*601*(21), 5034-5041. https://doi.org/10.1016/j.susc.2007.08.025