Electronic and optical properties of N-doped, Co-doped as well as N,Co-codoped rutile TiO2

► N-doped rutile TiO2 shows a semiconducting characteristic with an AFM ground state. ► Both Co-doped and N,Co-codoped rutile TiO2 have a stable FM ground state. ► All three doping systems extend the optical absorption in the visible-light region. ► Both Co-doped and N,Co-codoped rutile TiO2 become semiconductors within GGA+U.