基于密度泛函理论的第一性原理平面波超软赝势方法,计算了zn吸附到Ti02(101)清洁表面、含有氧空位(%)的缺陷表面以及既含有氧空位(%)又含有羟基(-OH)表面的能量、Mulliken重叠布居数以及电子结构,并找到了zn在每种表面的最稳定结构(分别为模型(c),模型(aI)以及模型(a11)).通过对三种表面稳定结构的分析、对比发现:首先,zn原子吸附到清洁Ti02(101)表面上,主要与表面氧相互作用,形成Zn-0共价键:其次,当Zn原子吸附到缺陷表面时,吸附能减小到-1.75eV,说明zn更容易吸附到氧空位上(模型(aI));最后,纵观表面模型的能带结构以及态密度图发现,OH的引入并没有引进新的杂质能级,zn吸附此表面,即Zn—Ti02-Vo.OH,使得禁带宽度缩短到最小(1.85eV),从而有望提高Ti02的光催化活性.
The energies, atomic Mulliken charges, and electronic structures of Zn adsorbed on the pure surface, and on the surfaces with an oxygen vacancy (Zn-TiO2-Vo) and one hydroxyl group (Zn-TiO2-Vo-OH) are investigated by density functional theory, plane-wave pseudo-potential method, and the most stable surface structures (namely model (c), model (aI), and model (alI) are found. The results indicate that firstly, Zn interacts mainly with the surface oxygen by Zn--O covalent bond; secondly, when Zn atoms are adsorbed on the defective surface, the adsorption energy is reduced down to -1.75 eV, showing that Zn atoms are prone to being adsorbed on the oxygen vacancy surface. Finally, although no impurity states are introduced in to the gap when the Zn atoms are adsorbed to the surface with hydroxyl group, the band gap is reduced down to a minimum (1.85 eV), which is expected to improve the photocatalytic activity of TiO2.