Stability and energy characteristics of extended nitrogen nanotubes: density functional theory study

We apply the density functional theory with B3LYP exchange-correlation energy functional and the basis set 6-31G(d) to investigate structural, energetic, and electronic properties and stability of extended armchair and zigzag nitrogen nanotubes with a length of approximate to 3 nm. The capping effect, as well as the passivation of nanotubes' ends by hydrogen atoms and hydroxyl groups on their stability, are studied. According to our calculations, pristine nitrogen nanotubes are unstable. Both capping and passivation of the nanotube ends provide thermodynamic stability only for (3,0) and (4,0) zigzag nitrogen nanotubes. Moreover, the calculated frequency spectra of considered systems confirm their dynamic stability. We stress the fact that some extended nitrogen nanotubes are found to be stable under ambient conditions, i.e., in the absence of external factors such as pressure, spatial confinement, etc. The calculated HOMO-LUMO gaps for these stable extended systems are of the order of 4 eV, so they can be assigned to the class of insulators. It is shown that nitrogen nanotubes are able to store a large amount of energy and can be used as a basis for new high-energy-density materials. We expect that the all-nitrogen tubes with the longer effective length of similar chiralities are also should be stable.