SWCNTs: A fast method to calculate the band gap under lattice deformation

In this paper we calculate the band gap of the mechanically deformed lattice of single-walled carbon nanotubes (SWCNTs) by generating some types of virtual sub-bands which are considerably lower in number, while maintaining the value of the band gap precisely. Using this method, the computational time needed to calculate the change in the band gap of the strained structure is reduced considerably which is a desirable issue in simulation of these types of lattice deformations. The accuracy of the method depends on the precision of π-tight binding (π-TB) approximation, where this precision in turn depends on the number of neighbors which are included. In this paper we included both the nearest-neighbor and the third-nearest-neighbor π-TB approximations.