Influence of Tension and Compression on the Band Structure of Carbon Nanotubes as Probed by the Cylindrical Wave Method

Abstract

The effect of uniaxial deformation on the band structure of chiral ((8,7), (9,6), (10,5), and (12,1)) and achiral ((7,7), (13,0), (12,0), and (13,0)) nanotubes ~10 Å in diameter of different geometry has been calculated by linearized augmented cylindrical wave method. The results have been compared with the effects of nanotube twisting on the electronic properties of these compounds. It has been found that perturbation of the band structure under the action of these two types of mechanical deformations can be sharply different. In the armchair (7,7) tube and the (8,7) tube, which is sometimes called “the almost armchair” tube because of the proximity of indices n₁ = 8 and n₂ = 7, the band structure changes sharply upon tube twisting, but remains almost unperturbed upon uniaxial tension and compression. On the contrary, in semiconducting zigzag (13,0) and (11,0) tubes and “almost zigzag” (12,1) tubes, the effect of tube twisting is very weak, while axial stretching is accompanied by strong changes in dispersion curves near the Fermi level up to a change in the alternation of the frontier bands. In quasi-metallic (12,0) and (9,6) nanotubes, all types of deformation—tension, compression, and twisting—induce a sharp broadening of the band gap to give semiconductors. In the semiconductor chiral (10,5) nanotubes, both twisting and uniaxial deformations lead to strong changes in the band structure.