TiO$lt;sub$gt;2$lt;/sub$gt;纳米管电子结构和光学性质的第一性原理研究

运用基于密度泛函理论的第一性原理方法, 系统研究了小尺寸锐钛矿相(n,0)型TiO₂纳米管(D<16 Å)的几何构型、电子结构和光学性质. 结果表明: 随着管径增大, 体系单位TiO₂分子的形成能降低, 体系趋于稳定; 在管径14 Å左右, (n,0)型TiO₂纳米管会发生一次构型的转变. 能带分析显示, TiO₂纳米管的电子态比较局域化, 小管径下(D<14 Å)其导电性更好; 随着构型的转变, TiO₂纳米管由直接带隙转变为间接带隙, 并且带隙值随着管径的增大而增大, 这是由于π轨道重叠效应的影响大于量子限域效应所导致的结果. 两种效应的竞争, 使得TiO₂纳米管的介电函数虚部ε₂ (ω)谱的峰值位置随管径增大既可能红移也可能蓝移, 管径大于9 Å (即(8, 0)管)之后, TiO₂纳米管的光吸收会出现明显的增强.关键词：2纳米管')" href="#">TiO₂纳米管第一性原理电子结构光学性质

First-principles study of electronic structure and optical properties of TiO2 nanotubes

Using first-principles calculations based on the density functional theory, we systematically study the geometry structure, electronic structure and optical properties of the small size (n, 0)-type TiO₂ nanotubes (D<16 Å) derived from anatase. The calculation results indicate that the formation energy of each TiO₂ unit decreases with the diameter increasing, and the nanotubes become more stable. At a diameter of about 14 Å, a configuration change occurs. Band structure analysis shows that electronic states of TiO₂ nanotubes are localized, and the conductivity is better for nanotubes with small diameters (D<14 Å). According to the configuration change, TiO₂ nanotubes shift from direct band gap to indirect band gap. And the band gap increases with diameter increasing, because π orbital overlap effect is greater than the quantum confinement effect. Owing to the competition between the two effects, the peaks of the dielectric function ε₂(ω) will become redshifted or blueshifted. When its diameter is larger than 9 Å ((8, 0) tube), the optical absorption of TiO₂ nanotubes will be significantly enhanced.
Keywords：2 nanotubes')" href="#">TiO₂ nanotubesfirst-principleselectronic structureoptical properties