中文摘要：

近年来的理论和实验研究表明，通过不同离子共掺杂TiO2是减小其禁带宽度的一种有效方法．本文采用基于第一性原理的平面波超软赝势方法研究了C和zn共掺杂TiO2的能带结构、态密度和光学性质．计算结果表明C-Zn共掺杂导致导带相对Fermi能级发生了明显的下降，同时在TiO2的导带下方与价带上方形成了新的杂质能级，使TiO2的禁带宽度变小，TiO2的光学吸收带边产生红移．杂质能级可以降低光激发产生的电子-空穴对的复合概率，提高TiO2的光催化效率．此外，掺杂后TiO2在可见光区的吸收系数有明显增加，能量损失也明显减小．

英文摘要：

In recent years, many theoretical and experimental researches have reported that different atoms doping TiO2 is one of the effective methods to reduce the gap. In this paper, the band structure, density of states and optical property of C-Zn co-doped rutile TiO2 are studied by the plane-wave ultrasoft pseudopotenfial method based on the first-principles density functional theory. The calculations show that C-Zn co-doped TiO2 results in the conductor band apparently shifted down to the Fermi level. Some impurity energy levels of co-doped TiO2 are below the conduction band minimum, and others are above the valence band maximum. The distance between them narrows down, which results in the redshift of the optical absorption edges to visible-light region. These impurity energy levels can reduce the recombination rate of photoexcited carriers and improve the photocatalytic efficiency of TiO2. Besides, the optical absorption coefficient becomes larger in visible-light region and the energy loss decreases clearly.