A study of the influence of structural imperfection on the electronic structure of carbon nanotubes by X-ray spectroscopy and quantum-chemical methods

It is demonstrated that the CKalpha x-ray fluorescence spectra of carbon nanotubes synthesized by electric-arc evaporation of graphite and the spectra of carbon nanotubes produced using catalytic decomposition of hydrocarbons differ in the intensity of the short-wavelength lines. In order to interpret the obtained data, the electronic structures of perfect and defect-containing nanotubes are calculated in the framework of the tight-binding method with optimized parameters. The density of localized states that correspond to the observed increase in the intensity of the fluorescence spectrum of catalytic nanotubes can be obtained in the case when 15-20% of the total number of carbon atoms are absent in the carbon network. It is shown that defects of this type can bring about a decrease in the band gap of the nanotubes. (C) 2002 MAIK "Nauka/Interperiodica".