ABSTRACT
This chapter presents a method for calculating any nanotubes, regardless of their chirality and the number of atoms in the translation cells. Every carbon (C) single-walled nanotube can be generated by first mapping only two nearest-neighbor C atoms onto the surface of a cylinder and using the rotational and helical symmetry operators to determine the remainder of the tubule. The nanotubes radii and chirality angles of these tubules are noticeably larger than those of the corresponding tubules, and the gaps of the tubes are about 30% smaller. The transition from zigzag tubule with 9th order rotational axis to the low-symmetry chiral tubule is accompanied by dramatic simplification of band structure, but it almost does not affect the band gap. The nanotubes with optical gaps falling within the terahertz (THz) range are identified that can be of importance for application of nanotubes in the THz nanodevices.
