La-N共掺杂锐钛矿相TiO_2的电子结构及光学性质的第一性原理研究

First-principles study on La-N co-doped anatase TiO_2

利用基于密度泛函理论的第一性原理平面波超软赝势方法对锐钛矿相TiO_2、La单掺杂及La-N共掺杂锐钛矿相TiO_2的电子结构进行计算,分析La单掺杂及La-N共掺杂对锐钛矿相TiO_2的晶体结构、能带、态密度、差分电荷密度和光吸收性质的影响.结果表明,掺杂后TiO_2的晶格发生畸变,原子间键长的变化使晶格发生膨胀;掺杂后TiO_2的禁带宽度减小,并在禁带中引入杂质能级,导致TiO_2的吸收图谱产生红移现象;与La单掺杂相比,La-N共掺杂锐钛矿相TiO_2的红移程度增强.

The electronic structures of anatase TiO_2,La-doped and La-N co-doped anatase TiO_2 were calculated by the first-principles plane wave ultra-soft pseudo-potential method based on the density functional theory（DFT）. The effects of doping on crystal structures,energy bands,density of states（DOS）,electron density difference and optical properties were analyzed. The results show that,after doping the lattices of TiO_2 are distorted by the doping and the bond length change of atoms leads to the lattice expansion. The impurity levels in the band gap and the decrease of the forbidden band width lead to the red-shift of absorption band edge in anatase TiO_2. La-N co-doped anatase TiO_2 shows a stronger red-shift in the absorption band edge than the single La-doped samples in the optical spectra.