LSDA + U calculations of the electronic and optical properties of rutile TiO2(1 1 0) vs (0 1 1)-2 × 1 surfaces

We present a study concerning the effect of the on-site Coulomb interaction term U on the electronic and optical properties of the rutile TiO2(1 1 0) surface as compared with those of the rutile TiO2(0 1 1)-2 × 1 surface. The calculations were performed using the so-called LSDA + U approach, in which U = 5 eV was added for the treatment of the Ti-3d electrons. For the rutile TiO2(1 1 0) surface, the conventional LSDA calculations give an underestimated band gap and there was no obvious improvement on the band gap after the treatment of U approximation was considered in LSDA. However, for the rutile TiO2(0 1 1)-2 × 1 surface, the conventional LSDA calculations could reproduce the optimal agreement with the experimental band gap ∼2.10 eV, leading to the LSDA + U calculations giving an overestimation to the band gap. Finally, the calculated optical properties of the rutile TiO2(1 1 0) and (0 1 1)-2 × 1 surfaces further proved the above same.