N和硫属元素掺杂及共掺杂TiO_2第一性原理计算

采用密度泛函理论(DFT)计算了N、S、Se和Te掺杂及共掺杂金红石TiO2的电子结构。针对DFT方法存在对过渡金属氧化物带隙能的计算结果与实际值严重偏离的缺陷,采用DFT+U(Hubbard系数)方法对掺杂体系的电子结构进行了计算。优化结构的结果表明,掺杂造成二氧化钛的体积膨胀和晶格畸变很明显。相比较于其他元素而言,Te更难掺杂进二氧化钛中是由于其大的原子半径和较大的取代能。能带总态密度图和分态密度图的分析表明,Ti 3d和O 2d轨道与N 2p、S 3p、Se 4p和Te 5p强烈地杂化在一起。与S、Se、Te单掺杂后带隙能比较,由计算的结果(S:2.43;Se:2.42;Te:2.46)可以看出,N/S、N/Se和N/Te共掺杂能明显地改善材料的电子结构及带隙。DFT+U计算结果与实验测量结果较好地吻合。

First principle calculation on electronic properties of rutile TiO2 doped and co-doped by N and X

The structural and electronic properties of N, S, Se and Te doped and （N/S）, （N/Se）, （N/Te） co-doped rutile TiO2 were calculated based on the density functional theory （DFT）. Since DFT calculations performed on transition metal oxides al- ways lead to a severe underestimation of the band gap, DFTq-U （Hubbard coefficient） method was also adopted to calculate the electronic structures. The optimized geometries show that the doping causes a TiO2 obvious volume expansion and lattice distortion. Te is more difficult to incorporate into TiO2 compared to other elements due to the large atom radius and the large substitution energy. From the analysis of the band structure and total density of states （DOS） and the corresponding partial DOS （PDOS） of N, Se and Te doped and （N/S）, （N/Se）, （N/Te） co-doped TiO2, Ti 3d and O 2p states are strongly hybrid- ized with impurity states of N 2p, S 3p, Se 4p, and Te 5p. The calculated results indicate that, compared to the band gaps of the S, Se and Te doped （S：2.43; Se,2.42; Te：2.46）, those of （N/S）, （N/Se） and （N/Te） co-doped rutile TiOz obviously improve the electronic structure and band gap of materials. Results from DFTq-U calculations accord well with some experi- mental results.