In this work, we studied the effect of uniaxial tension/compression on the electrical properties of carbon nanotube bundles within the framework of density functional theory. The bundles consist of mono-chirality single-walled carbon nanotubes. The band gap response of the bundles shows different electrical characteristics including band gap opening, closing and non-linear behaviors, where the affected band gap is significantly dependent on the chirality of the constituent tubes. Calculations reveal that the bundles express a systematic down-shift in the Fermi energy as a consequence of the applied tension, and a systematic up-shift in the Fermi energy in response to the applied compression. Furthermore, the simulation results show a nonlinear behavior in Fermi energy for bundles under test. This nonlinear behavior in Fermi energy may be caused by asymmetrical electronic effects in both conduction and valance bands. For all bundles, the weak wall-to-wall interactions have considerable effects on electrical properties compared to single-walled carbon nanotubes. We hope this study does not only provide helpful enlightenment on the effects of uniaxial strain on electrical properties of bundles, but also opens exciting opportunities for potential applications of piezoresistive nano-devices.

We investigated the effects of applying an external electric field on the electronic properties of Stone-Wales (SW) defective carbon-boron-nitride nanotubes (CBN) using first principles calculations. The defective CBN nanotubes were modeled by introducing Stone–Wales defects in the boron-nitride segment (BN-SW), the carbon segment (C-SW), and the carbon-boron-nitride interface segment (CBN-SW). Initially, we studied the formation energies and the structural stability for all models. As a result of adding the SW defects, the calculated bandgap values of the C-SW and CBN-SW models showed significant changes compared to the pristine CBN nanotube. Meanwhile, the BN-SW model showed a slight bandgap change because of the strong covalent bonding between the boron and nitrogen atoms. Applying a transverse electric field induced a fast bandgap closing response in all models, indicating a rapid semiconductor-to-metal phase transition. The defective C-SW and CBN-SW models demonstrated unique bandgap closing patterns in response to applied transverse and longitudinal electric fields, while pristine and BN-SW models had similar bandgap responses.