Abstract: Based on density functional theory, we calculated the modulation of the electronic structure of vacancy defects of different concentration points on the armchair and zigzag carbon nanotubes, and analyzed the bond length, the defect formation energy, the bandgap and the electron state density. The results show that with the increase of concentration of defects, the bond length of the neighboring carbon atoms decreases, the bandgap of the armchair carbon nanotube opens, the metallic properties change to the semiconductor properties, and the bandgap of the zigzag carbon nanotubes gradually decreases. The absence of carbon atoms causes the nonbonding unpaired electrons near the defects to form additional electronic state near Fermi energy levels, which changes the electronic structure of the carbon nanotubes.

Key words: vacancy defect, electronic structure; density functional theory, carbon nanotube