Mn掺杂锐钛矿型TiO2电子结构的第一性原理研究

First-principles study of Mn doped anatase TiO_2

[目的]研究Mn掺杂对锐钛矿TiO_2晶体可见光区催化活性的影响。[方法]采用基于密度泛函理论(DFT)框架下的第一性原理平面波赝势(PWPP)方法,研究掺杂对锐钛矿TiO_2晶体的晶体结构、能带结构、态密度的改变。同时我们也进行了Mn掺杂TiO_2的实验研究,从实验方面对掺杂后TiO_2光吸收性能变化进行研究。[结果]Mn掺杂TiO_2后,晶体的对称性和点群没有改变。通过对比纯TiO_2,Mn掺杂TiO_2的能带和态密度可以得出:Mn掺杂TiO_2后导带发生较大下移,且导带底部主要是Mn-3d的贡献,使禁带宽度变小,从而可见光吸收增强。实验结果也表明Mn掺杂后可见光吸收增强,和理论的红移结果一致。[结论]通过我们的计算和实验,说明Mn掺杂可以改善和提高TiO_2在可见光区的活性,这种材料具有很好的应用前景,值得做进一步的实验研究。

[objective]To investigate the optical catalytic property of Mn doped TiO2 crystal,[method]Using density function theory（DFT）,the geometry,the band structure and the electronic density of states of pure TiO2 and Mn doped TiO2 were calculated at plane wave ultra-soft pseudo-Potential level（PWPP）.Experiments of Mn doped anatase TiO2 were also carried out at the same time.Based on these results,the optical catalytic properties of them could be predicted and compared,[result]It showed that the symmetry of Mn doped anatase TiO2 maintains the same as pure TiO2＇s,while the lattice parameters a and c become larger.It also showed that the 3d orbitals of the doped Mn at the bottom of the conduction bands make the conduction bands shift downwards,then the forbidden band becomes narrower to enhance the optical absorption in the visible-light range.The results of experiments showed that the Mn doped TiO2 crystal possesses better visible absorbency in the ultraviolet-visible spectrogram, the red-shift of Mn doped TiO2 in the experiments agreed with our calculation result,[conclusion]Mn doped TiO2 crystal has narrower band gap than the pure TiO2 crystal,and its optical catalytic property is remarkably improved during visible-light range.These results had important implications for the understanding and further development of photocatalytic materials that are active under visible-light irradiation.