DFT Study of the Stability and Electronic Properties of Ni-Doped Defected (6,0) and (8,0) Single-Walled Carbon Nanotubes.

The interaction of Ni with (6,0) and (8,0) zigzag carbon nanotube exterior surfaces containing two vacancies was studied using density functional theory (DFT). A two-vacancy defect was analysed in order to anchor Ni, and the pristine nanotube was also considered as a reference for each chirality. The adsorbed Ni stability and the nanotube's geometry and electronic structure were analysed before and after the adsorption. We compared calculations performed using a general gradient functional with those conducted using two semi-classical dispersion methods to assess the van der Waals forces (PBE-D2 and PBE-D3). In addition, the inclusion of the Hubbard parameter for the correction of Ni d electron self-interaction energy was included, and we evaluated energy and electronic structure changes through atomic-level calculations. Adsorption energy, the density of states, and the charge distribution were obtained to establish the Ni binding on the defective nanotube's dominating mechanisms. The effect of curvature and applied functional influence was also considered. Furthermore, a bonding analysis was performed to complement our comprehension of the interaction between Ni and the nanotube surfaces. The electronic results show that Ni-doped two-vacancy (6,0) and (8,0) carbon nanotubes can be applied for the development of low-resistance contact materials and spintronic devices, respectively.