中文摘要：

碳纳米管作为最先进的纳米材料之一,在电子和光学器件领域有潜在的应用前景,因此引起了广泛关注.掺杂、变形及形成超晶格为调制纳米管电子、光学性质提供了有效途径.为了理解相关机理,利用第一性原理方法研究了不同剪切形变下扶手椅型硼氮交替环状掺杂碳纳米管超晶格的空间结构、电子结构和光学性质.研究发现,剪切形变会改变碳纳米管的几何结构,当剪切形变大于12%后,其几何结构有较大畸变.结合能计算表明,剪切形变改变了掺杂碳纳米管超晶格的稳定性,剪切形变越大,稳定性越低.电荷布居分析表明,硼氮掺杂碳纳米管超晶格中离子键和共价键共存.能带和态密度分析发现硼氮交替环状掺杂使碳纳米管超晶格从金属转变为半导体.随着剪切形变加剧,纳米管超晶格能隙逐渐减小,当剪切形变大于12%后,碳纳米管又从半导体变为金属.在光学性能中,剪切形变的硼氮掺杂碳纳米管超晶格的光吸收系数及反射率峰值较未受剪切形变的均减小,且均出现了红移.

英文摘要：

Carbon nanotubes, one of the most advanced nanoscale materials, have attracted much research attention since they exhibited semiconductor, metal or insulator properties depending on their geometric structures. Carbon nanotubes have great potential in various applications in electronic and optical device. Dopants to the carbon nanotubes intentionally could offer a possible route to change and tune their electronic, optical properties. Another important and effective method is to deform the carbon nanotubes structure. Superlattice structures can offer extra degrees of freedom in designing electronic, optical devices. To understand the involved mechanism, in this paper, the geometry structures, electronic structures and optical properties of the armchair carbon nanotube superlattices doped cyclic alternately with B and N under different shear deformations are investigated by the first-principles method through using the CASTEP code in MS 6.0. It is found that the structures of carbon nanotube superlattices can be dramatically changed by shear deformation. When the shear deformation is less than 9%, the optimization geometry structures of carbon nanotube superlattices are still similar to tubular structures, when the shear deformation is greater than 12%, the geometry structures of these systems have large distortions. The results about the binding energy show that the shear deformation changes the stability of the armchair doped carbon nanotube superlattice. The larger the shear deformation, the lower the stability of the doped carbon nanotube superlattices is. The analysis of charge population show that the covalent bond and ionic bond coexist in the armchair carbon nanotube superlattices doped cyclically alternately with B and N. The band gap of the carbon nanotube superlattice is affected by N, B dopants, as a result, the carbon nanotube superlattice changes from a metal to a semiconductor. Compared with the （5, 5） nanotube superlattices, the band gaps of the （7, 7）, （9, 9） doped carbon nanotube super