the effect of uniaxial and torsional strains on the density of states of single walled carbon nanotubes

In this paper, we investigate the effect of uniaxial and torsional strains on the density of states (dos) of single walled carbon nanotubes (swcnts). we employ the nearest neighbor and the third nearest neighbor πtb (tight binding) models for our investigation. it is shown that uniaxial and torsional strains in some cases of metallic swcnts not only open a band gap but also effectively increase the dos of swcnt. it is also shown that, the mentioned types of strain have different effects on the dos of chiral swcnts; in some types, they increase the dos at the band edges, while they decrease it at the band edges in other types.