In this paper, the Young’s modulus of single-walled carbon nanotubes (SWCNTs) under uniaxial strain is studied by using the tight-binding method in the nearest neighbor approximation while the curvature effect take into account. Also, the effect of an external electric field on the Young’s modulus of carbon nanotubes is investigated. The strain dependent tight-binding parameters are obtained by comparing the tight-binding band structure of graphene with DFT calculations. In the next step, total energy and then the Young’s modulus of single-walled carbon nanotubes are calculated. Our results indicate the dependence of Young’s modulus on the tube diameter and the external electric field. By applying the axial electric field, the dependency of Young’s modulus to the diameter becomes less important. Also, by increasing the axial electric field, the Young’s modulus decreases. The axial electric field becomes much more important in the armchair nanotubes.

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