Geometric Isomers of the (3,1) Carbon Nanotube: A Theoretical Study

This paper presents the results of density functional theory calculations for the (3,1) carbon nanotube ensuing in two structural configurations, representing two local energy minima. To be sure in this conclusion, we used two distinct density functional theory implementations and three different structure optimization algorithms. The interatomic distances of the two kinds of (3,1) carbon nanotubes do not differ too much, but the other properties are more pronounced. We found that the HOMO–LUMO energy gap of the lower energy configuration is 0.69 eV, whereas the second configuration possesses the 0.36 eV HOMO–LUMO gap. Both isomers have been obtained by optimization because the calculations started either with a different initial configuration or with different starting parameters critical for convergence, efficiency and/or accuracy.