An ab initio study of cluster-assembled hydrogenated silicon nanotubes

► H-SiNTs can be constructed by proper assembly of hydrogenated silicon clusters. ► The stability and electronic properties of H-SiNTs are systematically studied. ► The chemical formulas of H-SiNTs are exact defined for the first time. ► H-SiNTS show a large energy gap due to hydrogen passivation. ► A direct-indirect-direct band gap transition has been revealed.