Electronic and optical properties of single-walled silicon nanotubes: the sp3 tight-binding model

In this paper, we investigate the curvature effects on the electronic band structure and dielectric function of single-walled silicon nanotubes and carbon nanotubes, based on tight-binding method. The curvature nature of nanotubes causes radius-dependent σ-π-orbital hybridization which leads to optimization of tight-binding model for each radii. First, the effects of orbitals overlap and the structural optimization on the electronic band structure of small radius nanotubes are investigated. Second, the imaginary part of dielectric function of nanotubes, which is related to optical absorption coefficient, is obtained by calculating the interband optical matrix elements using gradient approximation. It is shown that the σ-π-tight-binding model optimization due to the curvature effects, introduces small changes to the optical transition energies obtained by simple π-band tight-binding model. The results show that the curvature effects are more important in small radius tubes.