Electronic features induced by Stone-Wales defects in zigzag and chiral carbon nanotubes

It has been recently shown [P. Partovi-Azar, A. Namiranian, J. Phys.: Condens. Matter, 24 (2012) 035301.] that Stone-Wales (SW) defects induce different electronic features when they are formed with different angels with respect to the axis of armchair carbon nanotubes. However, the electronic features introduced by SW defects in metallic zigzag and chiral carbon nanotubes is less considered in the literature. In this paper, by means of density functional calculations, we study the electronic effects induced by SW defects in metallic zigzag and chiral tubes. We inspect how these effects change with defect orientation and concentration. We show that two and three distinctive orientations of SW defects, respectively in the case of zigzag and chiral tubes, unlike those in armchair ones, behave the same and both introduce a semiconducting gap and an electron-rich region around the defects. For zigzag tubes, the longitudinal defects open wider band gaps than circumferential ones. The value of the gaps in zigzag and chiral tubes are attributed to the degree of deformation caused by the defects.