Doped ways of boron and nitrogen doped carbon nanotubes: A theoretical investigation

The B- and N-doped (4,4)i and (8,0)i (i = 3-5) carbon nanotubes, BCyN (y = 1-4, 6 and 8), B3CyN3 (y = 2 and 4), B2CN2, as well as BN nanotubes have been investigated using B3LYP/6-31G∗ method. The lowest energy structures of BxCyNx nanotubes of doped (8,0)i carbon nanotubes indicate that the B and N atoms prefer to dope (8,0)i carbon nanotubes from bottom to top layer by layer. When the number of BN layers of doping (4,4)i carbon nanotube is equal to i − 1, the B and N atoms are situated in the middle positions of BxCyNx nanotube and carbon atoms locate on its top and bottom. Otherwise, the doped ways of B- and N-doped (4,4)i carbon nanotubes are similar to those of (8,0)i. Calculated energy gaps of (4,4)i and (8,0)i (i = 3-5) BN nanotubes are between 5.51 and 6.38 eV, which are in good agreement with the experimental energy gap of 5.5 eV. In addition, the energy gaps of BC2N and BCN nanotubes are consistent with the previous theoretical and experimental results. The variety of energy gaps of BxCyNx nanotubes of doped (4,4)i and (8,0)i (i = 3-5) carbon nanotubes follows the same trend. However, the energy gaps of doped (4,4)i carbon nanotubes are greater than those of doped (8,0)i ones.