Energetics and electronic structures of pyridine-type defects in nitrogen-doped carbon nanotubes

We investigate atomic and electronic structures and energetics of the pyridine-type defects in the nitrogen-doped carbon nanotubes (CNTs) using first-principles density-functional calculations. To discuss the stability of pyridine-type configurations, we calculate the total energies of the possible nitrogen formations in the nitrogen-doped (10,0) CNT. From the results of total-energy calculations, it is found that the pyridine-type defects in the nitrogen-doped (10,0) CNT is energetically preferred to the substitutional nitrogen defects under the existence of the vacancy in the nanotube. We also discuss the impurity states induced by the pyridine-type configurations in the nitrogen-doped nanotube. (C) 2010 Elsevier B.V. All rights reserved.