Theoretical Calculations of the Effect of Finite Length on the Structural Properties of Pristine and Nitrogen-doped Carbon Nanotubes

The effect of impurities on quantum chemical parameters of single-walled nanotubes (SWNTs) was studied using density functional theory (DFT). The density of states (DOS), Fermi energy and thermodynamic energies of (5,5) carbon nanotubes were calculated in the presence of nitrogen impurity. It was found that this nanotube remains metallic after being doped with one nitrogen atom. The partial density of states (PDOS) of spin up and spin down electrons shows that the SWNTs and nitrogen doped single-walled nanotubes (N-SWNTs) are anti-ferromagnetic. Comparing the results of SWNTs with N-SWNTs, it can be shown that there is a relationship between the energy gap and the DOS. The relationship between the thermodynamic properties and the binding energies of nanotubes is similar to the energy gap and the DOS relation.