Reduced and n-Type Doped TiO 2 : Nature of Ti 3+ Species

Defect states in reduced and n-type doped titania are of fundamental importance in several technologically important applications. Still, the exact nature of these states, often referred to as “Ti3+ centers”, is largely unclear and a matter of debate. The problem is complicated by the fact that electronic structure calculations based on density functional theory (DFT) in the local density approximation (LDA) or semilocal generalized gradient approximation (GGA) provide results that do not account for many of the experimentally observed fingerprints of the formation of Ti3+ centers in reduced TiO2. Here, we investigate the properties of at least four different types of Ti3+ centers in bulk anatase, (1)…