椅型碳纳米管电子结构与长度效应

Electronic Structures and the Length Effects of Armchair Carbon Nanotubes

采用PM3方法对含帽及不含帽结构的三种 (5 ,5 )椅型有限长碳纳米管的构型和电子结构进行了系统研究 ,结果表明 ,随着管长度的增加 ,除了最高占据轨道 (HOMO)和最低空轨道 (LUMO)之间的能隙 (Eg)出现周期性的变化外 ,纳米管端“表面” (管的末端和管帽 )构型也出现周期振荡现象 ,通过研究同种类型纳米管三组不同的长度效应 ,发现属于同一组的纳米管具有相似的构型和电子结构变化规律 .此外 ,研究表明纳米管帽的尺寸效应可以看成为一定长度管壁的简单延伸 ,揭示了含帽与不含帽纳米管电子结构之间的相似性 .本文还对处在管末端以及管帽上的表面态及其化学反应性进行了探讨 .

The geometries and electronic structures of three kinds of (5,5) armchair carbon nanotubes with open or capped ends were studied by PM3 method. The results indicate, as the length of the tube increases, in addition to the periodical variation of the energy gap between the HOMO and LUMO, the geometries of tube also exhibit oscillation and can be divided into three groups. For die nanotubes belonged to the same group, their geometries and the electronic structures are very similar. For the cap of nanotube, it can be seen as the prolongation of the tube wall, therefore, the electronic structures of tube with capped ends are close to the tube,with open ends. Furthermore, the surface states located at the ends of nanotube were also discussed in this paper.