ABSTRACT
In their simplest form, the defect-free single-walled carbon nanotubes are the hexagonal networks of covalently bound carbon atoms in various cylindrical structures with helical and rotational symmetries. The proposed method of calculating nanotubes with point impurities is that the band structure of the ideal nanotube is first calculated using the linearized augmented cylindrical wave (LACW) technique. The polyynic carbyne is a linear chain of carbon atoms with alternating single and triple bonds. The LACW band structure shows that the polyynic carbyne is the direct gap semiconductor. In the case of the local densities of states (DOS) of boron impurity, there is not the peak, but a well-defined dip in Muffin-Tin region; for the nitrogen, a noticeable smoothing of the resonance is observed. The main effect of the nitrogen impurity is about 50% virtually constant increase in the DOS; in the case of boron, there is further growth of the DOS.
