First-principles study of electronic structure of deformed carbon nanotubes

On the basis of density functional theory, we study the electronic structures of five types of carbon nanotubes: the non-deformed (6,6) tube, the uniformly stretched tube along the tube axis, the uniformly compressed tube, the partially stretched tube and the partially compressed tube. The electron charge density increases at the compressed C-C bond of the partially stretched tube, while the density decreases at the stretched C-C bond of the partially stretched tube. In addition, the a1 and e1 states of the (6,6) tube contribute to the bonding along the tube axis and the a2 and e2 states are the bonds connecting the atoms in the same layers. Thus, the energy bands of the a1 and e1 states are sensitively affected by the deformation of the tubes along the tube axis.