锐钛矿型TiO2空位缺陷性质的第一性原理研究

近年来运用减小TiO2禁带宽度的方法来提高TiO2的活性在实验上被广泛研究。本文运用基于局域密度泛函和赝势的第一性原理方法研究了锐钛矿相TiO2点空位缺陷性质和在具有点空位缺陷情况下的晶体结构、能带结构与态密度状况。分析发现缺陷使晶体结构发生畸变；近邻缺陷氧原子有靠近氧空位而远离钛空位的趋势，而近邻缺陷钛原子有靠近钛空位而远离氧空位的趋势；氧空位缺陷使费迷能级升高大约2．6eV而钛空位缺陷使费米能级降低，并在价带顶部产生一个与价带顶能量相差约0．25eV的杂质能级。结果表明，氧空位使导带变宽是n型杂质而钛空位使导带变窄是P型杂质，氧空位附近多余电子的主要贡献在价带，引起电荷布居数变化并改变了晶体中电子局域化运动的性质。

First-principles Study of Point Defects in Anatase TiO2

Recently the way of reducing the TiO2 band gap to enhance the activity of TiO2 has widely been investigated. In this paper the property of point defects in anatase TiO2 is investigated and the character of band structure and density of states is analyzed by using first-principle pseudopotential calculations based on density-functional theory （DFT）. It is discovered that the crystal structure was changed due to pulling into vacancy ; the nearby oxygen atom has the trend of closing to the oxygen vacancy and keeping off the titanium vacancy, whereas the nearby titanium atom has the trend of closing to the titanium vacancy and keeping off the oxygen vacancy. Oxygen vacancy makes Fermi energy rise about 2.6 eV and titanium vacancy makes Fermi energy go down. A defect level appeares in the gap about 0. 25 eV above the top of valence band due to titanium vacancy. Theoretical results show that oxygen vacancy causing conduction band wider is n-type impurity and titanium vacancy causing conduction band narrower is p-type impurity; the redundant electrons nearby oxygen vacancy contributed to valence band, which causes the change of the electric populations and alters the local motional property of electrons.