Gd掺杂锐钛矿型二氧化钛的第一性原理研究

First-principles Study of Gd-doped Anatase TiO_2

采用基于密度泛函理论(DFT)平面波超软赝势方法并选择GGA水平上的PW91相关能泛函,模拟计算了Gd掺杂前后锐钛矿型TiO2的几何结构、能带结构、态密度和光吸收系数,并与实验结果进行比较。结果表明:Gd掺杂锐钛矿型TiO2晶体后,对称性不变,晶格常数变大,价带顶部主要由O-2p和Gd-4f轨道上的电子共同构成,导带底部主要由Ti-3d轨道上的电子构成;主要由于价带上移使得禁带宽度(Eg)变小,TiO2吸收带边红移,可见光区的光吸收强度增加。可见,Gd掺杂有助于提高TiO2催化剂的光催化活性,扩展其光响应范围。

Using density function theory（DFT）,the geometry,the band structure,the densitiy of states and the photocatalytic activity of anatase TiO_2 and Gd-doped anatase TiO_2 were calculated at plane wave ultra-soft pseudo-potential level.The exchange-correlation interaction was treated within the generalized gradient approximation（GGA） with the functional parameters of PW91.The theoretical results fit well with the experimental results.It shows that the symmetry of Gd-doped anatase TiO_2 maintains the same as that of pure TiO_2,but the lattice parameters a and c become larger.For Gd-doped anatase TiO_2,the top of value bands involves O-2p and Gd-4f electrons,and the bottom of conduction bands contains Ti-3d electrons.The O-2p and Gd-4f electrons make the forbidden band narrower,therefore there is a red shift in the absorption spectrum.It may lead us to the conclusion that Gd-doped anatase TiO_2 has a better photocatalytic ability than that of pure TiO_2.