Influence of nitrogen doping on the radial breathing mode in carbon nanotubes

The influence of nitrogen doping in semiconducting carbon nanotubes is investigated by first-principles calculations considering a wide variety of substitution sites and concentrations. The frequency of the radial breathing mode of a (8,0) nanotube is calculated using density-functional theory and frozen-phonon approximation for different doping concentrations, substitution sites, and vacancies. The results are compared to a one-dimensional first-neighbor spring constant model using experimental parameters. We estimate the effect of doping in Raman spectra by examining the electronic band structure of doped carbon nanotubes.