Electronic properties of α-graphyne nanotubes

We constructed alpha-graphyne nanotubes (alpha GyNTs) and performed density functional theory calculations to investigate the electronic properties of zigzag and armchair alpha GyNTs. We found that all zigzag graphyne nanotubes (Z-alpha GyNTs) were semiconductors. In particular, the band gap of Z-alpha GyNTs showed an oscillatory dependence on tube size which could be further classified into three families with N-z = 3 m - 1, 3 m and 3 m + 1 where m is a positive integer. This resulted in band gap magnitudes in the following rank order: 3 m - 1 > 3 m + 1 > 3 m. Armchair alpha GyNTs were also calculated to be semiconductor with very small band gaps when tube size is small, though they become metallic as the tube size increases. (C) 2014 Elsevier Ltd. All rights reserved.