Comparison of the Properties of Bent and Straight Single-Walled Carbon Nanotube Intramolecular Junctions

The properties of four finite-length bent and straight intramolecular junctions (IMJs) connecting two armchair and zigzag single-walled carbon nanotube segments, viz. (3,3)-(6,0) and (4,4)-(8,0), were investigated. Their structures were calculated using the density functional theory (DFT) methods at the B3LYP/6-31G(d) level of theory. The results indicate that the bent junctions are more stable than the straight ones due to the energetically favored defect structures. Remarkable differences of the HOMO and LUMO orbitals appear between the straight and the bent IMJs. The spin-unrestricted calculations at the same level of theory were also performed to obtain the antiferromagnetic-type ground state, suggesting that the spin polarizations mainly occur on the zigzag edge and the defect rings of the straight (4,4)-(8,0) IMJ and induce marked changes of the electronic structures. Additionally, the energy band structures of the four junctions with periodic boundary conditions were calculated based on DFT calculations using generalized gradient approximation with the Perdew and Wang function. The calculated band gaps suggest that the conductance of the straight IMJs is higher than the bent ones.