Strain energy and electronic structures of silicon carbide nanotubes: Density functional calculations

We perform density functional calculations for the geometries, strain energy, and electronic structures of silicon carbide nanotubes (SiCNT's). We find that the strain energy in SiCNT's is as higher as 0.686 eV/atom relative to 3C-SiC for (5,5) SiCNT and decreases with increasing tube diameter. All the SiCNT's are semiconductors, the band gap of which increases with increasing tube diameter. In contrast to 3C-SiC, zigzag SiCNT has a direct band gap at the Gamma point, whereas armchair and chiral tubes have an indirect band gap. The highest occupied valance band and the lowest unoccupied conduction band highly localize to C and Si atoms, respectively. Hydrogen-decorated SiCNT's display the characters of p- or n-type semiconductors depending on the adsorbing site.