On the electronic structure of WS2 nanotubes

Electronic properties of WS2 nanotubes have been studied using the Density Functional Based Tight Binding method (DFTB). We show that WS2 nanotubes are all semiconducting possessing a non zero moderate gap. Only for zig-zag (n, 0) nanotubes the band gap tends to vanish for very small tube diameters (< 10 إ). The (n, n) tubes exhibit an indirect gap of similar size as the direct gap in (n, 0) nanotubes of comparable diameter.