Electromechanical properties of zigzag-shaped carbon nanotubes.

Atomic structural models of zigzag-shaped carbon nanotubes (Z-CNTs) were constructed by periodically introducing pentagons and heptagons into pristine CNTs. In terms of formation energies, the Z-CNTs present comparable energetic stabilities to those of the pristine CNTs and are more stable than C60 fullerene. The mechanical properties of these Z-CNTs, including the Young's modulus, intrinsic strength and failure behaviour, were systematically investigated by first-principles computations. Compared with the pristine CNTs with an average Young's modulus of about 1.0 TPa, incorporation of pentagons and heptagons in the Z-CNTs will reduce the average Young's modulus to several hundreds of GPa. Moreover, the computational results also showed that under uniaxial tensile strain, the intrinsic strength and failure strain of the Z-CNTs are also lower than those of the pristine CNTs. Generally, the Young's modulus and intrinsic strength of the Z-CNTs are exponentially inverse to curvature, which can be expressed by simple formulae. In particular, the electronic properties of the armchair Z-CNTs can be tailored by uniaxial tensile strain. It was also found that through applying tensile strain, a semiconductor-metal or metal-semiconductor transition can be triggered. The localized-delocalized partial charge distribution near the Fermi energy for the strained Z-CNTs can explain the semiconductor-metal or metal-semiconductor transition. This significant electromechanical coupling effect suggests the Z-CNTs have potential applications in nanoscale electromechanical sensors and switches.