Magnetism in defected single-walled boron nitride nanotubes

We have investigated the electronic properties of defected boron nitride nanotubes (BNNTs) for spin-up and spin-down electrons by using the first-principle density functional theory. Two types of defects have been considered, vacancy and substitution of carbon and oxygen by boron or nitrogen. The formation energy calculation shows that for both vacancies defected zigzag and armchair BNNTs, the probability of the nitrogen vacancy case is higher than that of the boron vacancy. Also in the carbon doping process of BNNTs, the substitution of boron by carbon is more possible with respect to nitrogen by carbon. In the oxygen doping substitution process, substitution of boron by oxygen is less favorable than nitrogen by oxygen. For the higher-probability cases the spin-up and spin-down band structures show different features. For the first and second cases, the spin-up band structure shows a n-type semiconductor, while the spin-down band structure illustrates a wide band gap semiconductor. But for the oxygen-doped BNNTs case, the spin-up band structure shows a wide band gap semiconductor, while the spin-down band structure illustrates a n-type semiconductor. All defected BNNTs have a 1.0μB total magnetic moment