Zigzag Single-Walled Carbon Nanotubes Substitutionally Doped by Silicon: A Density Functional Theory Study

In this article, the nanotubes obtained by silicon atoms substitutionally doping the single-walled carbon nanotubes were investigated by quantum chemistry calculations under the framework of density functional theory. The geometrical structures, relative stabilities and electronic properties of the Si-doped tubes were studied in details and compared with those of the pristine (12, 0) tubes. It is found that the Si atoms in the doped tubes have obviously larger π-orbital axis vector angles than carbon atoms, and they also tend to “pop out” from the original positions. The Si-doped nanotubes exhibit lower thermodynamic stability than those of the undoped tubes from the viewpoint of both cohesive energy and Gibbs free energy. The energy levels of the frontier orbitals vary within 0.25 eV when the silicon atom is introduced into the nanotubes. However, most hybrid nanotubes present larger energy gaps than those of the pristine ones.