Formation energies of topological defects in carbon nanotubes

Tight-binding calculations are presented for the formation energies of a type of topological defect called the 5-77-5 defect in achiral carbon nanotubes. The calculations show that the defect formation energy is dependent on the chirality and radius of a tube as well as the different orientations of a 5-77-5 defect in a tube. We also presented trends of the defect formation energy varying with tube size in the whole size range of the achiral carbon nanotubes. Moreover, it is indicated that a positive bond length deviation originating from a 5-77-5 defect in a tube can improve the sp(2)-like hybridization towards sp(2) hybridization locally, which enhances the stability of the system.