Crystal, electronic and magnetic structure of Co and Ag doped rutile TiO2 from first-principles calculations

The crystal structure, electronic structure and ferromagnetic properties of the transition metals M (where M=Co, Ag) doped rutile TiO2 are studied by using first-principles calculations based on the density functional theory (DFT) and projector augmented wave (PAW) pseudo-potentials (PP) method. In the doped system M2Ti14O32, the two doping atoms tend to align along c axis in the stablest configuration state. When M represents Co atom, the ferromagnetic state is favorable with magnetic moments of 0.99 mu B per Co atom, while Ag2Ti14O32 has no magnetic moment. Doping atoms induce new energy level, which reduces band gap, decreases Fermi energy level and thus considerably affects the optical absorption and photocatalytic activities of TiO2 under visible light irradiation.