Double-walled silicon nanotubes: an ab initio investigation

Abstract

The synthesis of silicon nanotubes realized in the last decade demonstrates multi-walled tubular structures consisting of Si atoms in and the hybridizations. However, most of the theoretical models were elaborated taking as the starting point structures analogous to carbon nanotubes. These structures are unfavorable due to the natural tendency of the Si atoms to undergo . In this work, through ab initio simulations based on density functional theory, we investigated double-walled silicon nanotubes proposing layered tubes possessing most of the Si atoms in an hybridization, and with few atoms localized at the outer wall. The lowest-energy structures have metallic behavior. Furthermore, the possibility to tune the band structure with the application of a strain was demonstrated, inducing a metal-semiconductor transition. Thus, the behavior of silicon nanotubes differs significantly from carbon nanotubes, and the main source of the differences is the distortions in the lattice associated with the tendency of Si to make four chemical bonds.