First-principles density functional calculations in the beyond local spin density

LSD+U approximation were performed in order to investigate the properties of

bridging hydroxyls (OHb) at the rutile (110) and anatase (101) surfaces as well as

those of bulk oxygen vacancies (VOx) and Ti–OH defects in the same two

materials. The aim was to deepen the understanding of the properties of these

defects in rutile and anatase and to reveal similar behaviours by VOx and OH

defects. In the case of rutile OHb, good agreement was found between the present

results and those of a recent scanning tunnelling microscopy study. Anatase OHb

exhibited properties which were similar to those of rutile OHb. On the other hand, a

marked difference was found between the structural and electronic properties of

bulk VOx in rutile and anatase. This was suggested to explain the higher electron

mobility and photocatalytic activity observed in the latter compound. Bulk Ti–OH

defects were predicted to form easily via the insertion of atomic H into TiO2

lattices. In the case of rutile, these defects were expected to exhibit properties quite

similar to those of VOx. These results proved the importance of using beyond local

spin density methods when dealing with defects in TiO2.

Oxygen Vacancies and OH Species in Rutile and Anatase TiO2 Polymorphs.

A.A.Bonapasta, F.Filippone, G.Mattioli, P.Alippi: Catalysis Today, 2009, 144[1-

2], 177-82