Computational studies on carbon nanotube–graphene nanoribbon hybrids by density functional theory calculations

We have performed Density Functional Theory (DFT) calculations to investigate the influence of carbone nanotube (CNT) size on the properties of the electronic structure of various junction models constructed from (6, 0) CNT and graphene nanoribbon (GNR) units via covalent linkage. Chemical shielding tensors and the HOMO–LUMO gap have been calculated for different models of the investigated hybrids of CNT and GNR. Our results indicate that the HOMO–LUMO gap strongly depends on the number of atoms and tube length, showing a decreasing trend with increasing the length of the tube and approaching zero in Model 7. The isotropic and anisotropic Chemical Shift (CS) parameters are divided into some layers, based on detecting similar electronic environments for the atomic sites of each layer.