Theoretical study of native defects in BN nanotubes

Antisites, carbon substitutionals, and vacancy defects in BN nanotubes have been investigated by first-principles total energy calculations, based on a density functional spin-polarized method. All defects introduce localized energy levels inside the band gap. For some open-shell systems (carbon substitutionals and vacancy defects) the levels in the gap region present an exchange splitting greater than 0.5 eV. The C-B and N-B defects, in N-rich growth condition, and C-N in B-rich growth condition, are the ones that present the lower formation energies.