摘要:
采用基于密度泛函理论的平面波超软赝势法研究了Magneli相亚氧化钛Ti8O15的电子结构和光学性能.计算出的能带结构显示Ti_8O_（15）相比锐钛型TiO_2禁带宽度大幅度降低.态密度分析表明,其原因在于Ti_8O_（15）的O原子的2p轨道以及Ti原子的3p,3d轨道相对于TiO_2的相应轨道向左产生了偏移,同时由于O原子的缺失使得Ti原子的3d,3p轨道多余电子在Fermi能级附近聚集形成新的电子能级.态密度分析结果还显示,相对于TiO_2,Ti_8O_（15）Fermi能级附近电子格局发生了如下变化：O原子的2p轨道电子贡献减少,Ti原子的3d轨道的电子对Fermi能级贡献增大.光吸收计算图谱表明,TiO_2仅在紫外光区有较高的光吸收能力,而Ti_8O_（15）由于禁带宽度变窄引起光吸收范围红移到可见光区,从而在紫外光区和可见光区都有较高的光吸收能力,计算结果与实验得到的紫外-可见漫反射吸收光谱结果一致.
Abstract:
The electronic structure and the optical properties of Magneli phase titanium suboxide Ti_8O_（15） are studied by using the plane-wave ultrasoft pesudopotential method based on the density functional theory.The band structure reveals that the energy band gap of Ti_8O_（15） is reduced a lot compared with that of anatase TiO_2,which is due to the fact that O 2p,Ti 3p and Ti 3d of TigOis shift toward the left compared with those of TiO_2,and a new electron energy level formed by the redundant electrons of Ti 3d and Ti 3p of Ti_8O_（15） due to the lack of oxygen atom in lattice.The results from DOS analysis show that electron distribution near the Fermi level of Ti_8O_（15） is different from that of anatase TiO_2,contribution of O 2p to Fermi level decreases and that of Ti 3d increases.Compared with anatase TiO_2 which only has high ultraviolet light absorption,Ti_8O_（15） has high light absorptivity both in ultraviolet spectrum and visible spectrum, because its narrow forbidden band width results in the red shift toward visible-light region.The light absorptivity calculated results are consistent with those from UV-vis diffuse absorption test results of anatase TiO_2 and Magneli phase titanium suboxides.
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