In order to understand the photocatalytic mechanisms of N-doped TiO2 with different doping positions of N, this research performed ab-initio calculations based on density functional theory (DFT) without and with Hubbard U correction, concentrate on the electronic structure of the materials. | JOURNAL OF SCIENCE OF HNUE DOI Mathematical and Physical Sci. 2016 Vol. 61 No. 7 pp. 157-164 This paper is available online at http A DFT STUDY ON N-DOPED TiO2 ANATASE Duong Quoc Van Le Minh Thu Nguyen Manh Nghia and Nguyen Minh Thuy Faculty of Physics Hanoi National University of Education Abstract. In order to understand the photocatalytic mechanisms of N-doped TiO2 with different doping positions of N this research performed ab-initio calculations based on density functional theory DFT without and with Hubbard U correction concentrate on the electronic structure of the materials. The adopted value of effective Hubbard U for Ti 3d is eV the corresponding calculated band-gap value of TiO2 with this value of U is eV in a good agreement with experiment value. The calculated results show that substitutional doping is easier to form than interstitial doping in the N-doped TiO2 material. Band-gap of defective models are decreasing lead to the shifting of edges of absorption to the visible light region. Keywords N-doped TiO2 substitutional interstitial oxygen vacancy DFT and DFT U. 1. Introduction Since the first demonstration of Fujishima and Honda in 1972 1 TiO2 has been considered as one of most important material due to nontoxic chemical and physical stability low cost and photocatalytic activity. However band-gap value of pure anatase TiO2 is approximates eV and only absorbs ultraviolet light with wavelengths shorter than 387 nm. The limitation due to wide band-gap lead to the ineffective of TiO2 photocatalytic activity in the region of visible light. To reduce this limitation modified TiO2 has been studied for the extending of optical absorption to the visible light region. After Asahi et al. 2 reported that doping N into TiO2 lead the optical absorption extends to the visible region N-doped TiO2 has been studied widely all over the world. N-doped TiO2 has been prepared in different shapes such as .
