The structure evolution process and the electronic properties of armchair boron nitride nanotubes

• The (n,n)@(2n,2n) tubes have large binding energies per atom.
• All tubes are semiconductors.
• Band gaps decrease with the increase of diameter and from short to long nanotubes.

We report the results of density functional calculations on the structural evolution and electronic properties of armchair boron nitride nanotubes (BNNTs), including SWBNNTs and DWBNNTs. Our results show that the initial structural configuration of the BNNTs was determined by the small boron nitride clusters. The evolution process of the BNNTs is through forming tubular clusters with a global reconstruction from structure of the double-rings. Then, it elongates through the layer-by-layer growth process with local reconstructions. Eventually, the infinite BNNTs can be constructed with corresponding repeat unit, designed by the periodic characteristics on the basis of tubular clusters. From the band structure of armchair BNNTs, it can be found the gap slightly increases with increasing diameter of the tube, decrease with the increasing of the walls. Moreover, the evolution process provides a better way to understand the growth mechanism of armchair BNNTs in atomic-level and guide the production of armchair BNNTs in industrial.