First-principles study on the adsorption energy of Fe on the N-doped CNT bus-bar

In this study, the CASTEP program based on the density functional theory was used to investigate the ability of the outside wall of a N-doped CNT (carbon nano tube) bus-bar to adsorb Fe (iron) atoms, under a deformation of the superlattice structure. The calculation results show that the formation energy of the new structure is negative, satisfying the energy conditions of stable existence. The energy of the adsorbing Fe atoms at each point has been significantly increased, indicating the improvement of the bonding strength between the CNTs and the Fe substrate. The doping of electron-rich N atoms makes the density of states at the Fermi level increase, which makes it easier to react with external matter. The Mulliken charge number and the population number show that N atoms have a stronger ability to adsorb electrons, so the strength of the bond between Fe and N is higher. Small amounts of linear tension and compression will not affect the ability of the new structure to adsorb Fe atoms. However, the adsorption abilities drop quickly after the deformation amplitude reaches its critical value, and the adsorption energies become more sensitive to the tensile deformation. The ionic bond of Fe-N is a key factor for raising the ability of the N-doped CNT bus-bar to adsorb Fe atoms.