First-principles study of structural, electronic, and optical properties of the rutile TiO₂(011)-2 × 1 surface

This work investigates surface reconstruction, electronic structure, and optical properties of the rutile TiO₂(011)-2 × 1 surface using means of density functional theory calculations. For the surface reconstruction of the rutile TiO₂(011) surface, a theoretical simulation with forming from bulk truncation to the 2 × 1 reconstruction was carried out. The calculated band structure shows a direct band gap at point, and the band gap of 2.08 eV reproduces the experimental measurement value ∼2.10 eV very well. Analysis of the density of states reveals that no surface state was introduced into the forbidden gap. Not coincidentally, the calculated optical absorption edge at about 2.01 eV further clarifies the band gap narrowing and such an intrinsic band gap nature effectively pushes the optical absorption edge into the visible light. Hence, our theoretical calculations provide evidence that the rutile TiO₂(011)-2 × 1 surface possesses high photocatalytic activity.