N／F掺杂和N-F双掺杂锐钛矿相TiO2（101）表面电子结构的第一性原理计算

采用密度泛函理论(DFT)平面波赝势方法计算了N/F掺杂和N-F双掺杂锐钛矿相TiO2(101)表面的电子结构.由于DFT方法存在对过渡金属氧化物带隙能的计算结果总是与实际值严重偏离的缺陷,本文也采用DFT+U(Hubbard系数)方法对模型的电子结构进行了计算.DFT的计算结果表明N掺杂后,N2p轨道与O 2p和Ti 3d价带轨道的混合会导致TiO2带隙能的降低,而F掺杂以及氧空位的引入对材料的电子结构没有明显的影响.DFT+U的计算却给出截然不间的结果,N掺杂并没有导致带隙能的降低,而只是在带隙中引入一个孤立的杂质能级,反而F掺杂以及氧空位的引入带来明显的带隙能降低.DFT+U的计算结果与一些实验测量结果能够较好地符合.

First-Principles Calculations on Electronic Structures of N/F-Doped and N-F-Codoped TiO2 Anatase(101)Surfaces

Electronic structures of nitrogen(N)/fluorine(F)-doped and N-F-codoped TiO2 anatase(101)surfaces were investigated by density functional theory(DFT)plane-wave pseudopotential method.Since DFT calculations performed on transition metal oxides always lead to a severe underestimation of the band gap,DFT+U(Hubbard coefficient)method was also adopted to calculate the electronic structures.DFT results demonstrated that mixing of N 2p states with O 2p and Ti 3d valence band(VB)states contributes to the band gap reduction of TiO2 whereas F doping and the introduction of oxygen vacancies have no obvious effect on the electronic structure.However,from DFT+U,no obvious band gap narrowing was observed by N-doping except for the isolated N 2p states lying in the gap.In DFT+U calculation,F-doping as well as the introduction of oxygen vacancies leads to an obvious band gap narrowing.Results from DFT+U calculations accord well with some experimental results.