Faceted silicon nanotubes: Structure, energetic, and passivation effects

We report the favorable configurations of double-walled silicon nanotubes (DWSiNTs) with faceted wall surfaces, determined from first-principles calculations. These tubes have higher energetic favorability than the conventionally adopted cylindrical configurations of single-walled silicon nanotubes (SWSiNTs) and compare well with the synthesized silicon nanowires. The hexagonal (h-) and tetrahedral (t-) like structures of these DWSiNTs are almost energetically equivalent, but quite different in their electronic structures. The hydrogen passivation effects on the geometries and electronic structures of these DWSiNTs are also investigated.