Theoretical simulations of regular and defective aluminium nitride nanotubes

For theoretical simulation on AlN nanotubes (NTs) of different chiralities (armchair-and zigzag-type) and uniform diameters, we have considered their single-walled (SW) 1D periodic models. For this aim, we have performed ab initio DFT calculations on AlN SW NTs using formalism of the localized Gaussian-type atomic functions as implemented in CRYSTAL-03 computer code. We have shown that the smaller the diameter of AlN single-walled nanotube is, the closer its electronic and structural properties to AlN bulk. We have analysed an influence of N vacancies (neutral F centres) created by either soft irradiation of nanotubes or under experimental conditions of their growth, on the atomic and electronic structure of AlN SW NTs. We have found the small inward relaxation of the Al nearest neighbours and the N next-nearest neighbours around each point defect formed on 1 nm AlN NTs of both chiralities. Presence of N vacancy in both types of nanotubes has resulted in appearance of the two defect energy levels in their band gaps consisting of mainly 3s and 3p states of the nearest Al atoms.