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采用基于密度泛函理论(DFT)的平面波超软赝势(PWPP)方法,对Ni-N共掺杂前后锐钛矿型TiO_2的超晶胞体系进行了几何结构优化,从理论上给出了掺杂体系的晶格参数。讨论了Ni掺杂、N掺杂、Ni-N共掺杂对锐钛矿型TiO_2的晶体结构、能带结构、态密度等的影响。结果表明:Ni-N共掺杂对锐钛矿型TiO_2的晶格参数和晶体结构的影响不大,从能带结构和态密度看,Ni掺杂后TiO_2价带和导带之间出现了主要由O-2p和Ni-3d共同作用而产生的杂质能级,N的掺入使得TiO_2导带下移。Ni、N的共同作用导致禁带宽度变窄,吸收带红移,拓宽了光响应范围。这些计算结果很好地解释了Ni-N共掺杂锐钛矿型TiO_2在可见光下具有良好的光催化性能的内在原因。本文从理论上对纯TiO_2,以及Ni掺杂、N掺杂、Ni-N共掺杂进行了较系统的研究,其中纯TiO_2和N掺杂TiO_2的结果与前人的一致;Ni掺杂和Ni-N共掺杂是这个系列的新内容。从理论上对这个系列的TiO_2光催化材料进行了比较,得出Ni掺杂和Ni-N共掺杂可以使TiO_2的禁带宽度变窄,有助于光催化活性提高这一结论,与我们的紫外可见吸收实验结果一致,与前人实验中发现Ni-N共掺杂TiO_2在可见光区的活性比纯TiO_2高1倍的实验事实相符。
The geometry optimization of the super-cell system of anatase TiO_2 with and without Ni-N co-doping was performed by using the plane wave super soft pseudopotential (PWPP) method based on density functional theory (DFT) Doping system lattice parameters. The effects of Ni doping, N doping and Ni-N co-doping on the crystal structure, energy band structure and density of state of anatase TiO 2 were discussed. The results show that the Ni-N co-doping has little effect on the lattice parameters and crystal structure of anatase TiO 2. From the energy band structure and the density of states, The impurity level mainly caused by the interaction of O-2p and Ni-3d, the incorporation of N makes the conduction band of TiO 2 down. The combined effect of Ni and N results in a narrow bandgap, a red shift of the absorption band, and a widening of the photoresponse range. These results explain well the intrinsic reason that Ni-N codoped anatase TiO 2 has good photocatalytic activity in visible light. In this paper, pure TiO 2, Ni doping, N doping and Ni-N co-doping have been systematically studied theoretically. The results of pure TiO 2 and N-doping TiO 2 are consistent with those of previous ones. The Ni doping and Ni-N co-doped is the new content of this series. This series of TiO 2 photocatalytic materials are compared theoretically, and it is concluded that Ni doping and Ni-N co-doping can narrow the forbidden band width of TiO 2 and contribute to the improvement of photocatalytic activity. UV-visible absorption experiment results are consistent with previous experiments found that Ni-N co-doped TiO 2 in the visible region of activity than pure TiO 2 1 times higher than the experimental fact.