Electronic Structure of Defect States in Hydroxylated and Reduced Rutile TiO 2 ( 110 ) Surfaces

It has been experimentally observed that a bridging oxygen vacancy on the rutile ${\mathrm{TiO}}_{2}(110)$ surface introduces localized ${\mathrm{Ti}}^{3+}$ $3{d}^{1}$ states about 1 eV below the conduction band which are not removed upon dissociation of a water molecule and formation of a pair of hydroxyl groups. Density functional calculations based on pure exchange-correlation functionals have not been able to satisfactorily reproduce and analyze these findings. Here we show that a correct description of the localized defect states on reduced and hydroxylated ${\mathrm{TiO}}_{2}(110)$ is achieved only if proper geometry relaxation is accounted for using hybrid exchange functionals. We confirm the electron…