Structural and electronic properties of zigzag and armchair WSe2 nanotubes

The structural and electronic properties of zigzag and armchair WSe2 nanotubes are investigated systematically by first-principles calculations. It is found that the armchair (n, n) nanotubes have an indirect (direct) band gap when n <= 15 (n > 15), while the zigzag (n, 0) ones always possess a direct band gap regardless of n. The band gaps of both nanotubes increase with their diameter increasing, being totally different from the case of carbon nanotubes. The varying range of the band gap can be from 0.44 to 1.98 eV, covering the energies from near-infrared to orange light. This strong modulation of band gap by changing the diameter is due to the large wall thickness and the resulting curvature-induced charge redistribution. Our results imply potential applications of WSe2 nanotubes in future optoelectronic nanodevices. (C) 2016 Elsevier B.V. All rights reserved.