Tubular Structures of Siloxenes

Using density-functional tight-binding theory we demonstrate that silicon-based tubular nanostructures in the form of siloxenes are stable and energetically viable. The structures studied here have a semiconducting gap which is independent of the chirality, but showing an increase of the gap size with increasing diameter towards that of the corresponding siloxene layer. The Si-based nanotubes are less stiff than tubes of other chemical compositions so far studied, but having Young's modulus of a magnitude similar to the bulk modulus of diamond silicon.