Ab initio studies of Nb doping effect on the formation of oxygen vacancy in rutile TiO2

► Nb doping can suppress the formation of oxygen vacancy and the growth of TiO2. ► The optimum content of Nb is in the vicinity of CNb=11.1 at%. ► The trend of the formation energy is mainly determined by the structural relaxation. ► The distribution of the excess electrons strongly influences the structural relaxation.