  Unusual physical properties of single-wall carbon nanotubes have started a
search for similar tubular structures of other elements. In this paper, we
present a theoretical analysis of single-wall nanotubes of silicon and group
III-V compounds. Starting from precursor graphene-like structures we
investigated the stability, energetics and electronic structure of zigzag and
armchair tubes using first-principles pseudopotential plane wave method and
finite temperature ab-initio molecular dynamics calculations. We showed that
(n,0) zigzag and (n,n) armchair nanotubes of silicon having n > 6 are stable
but those with n < 6 can be stabilized by internal or external adsorption of
transition metal elements. Some of these tubes have magnetic ground state
leading to spintronic properties. We also examined the stability of nanotubes
under radial and axial deformation. Owing to the weakness of radial restoring
force, stable Si nanotubes are radially soft. Undeformed zigzag nanotubes are
found to be metallic for 6 < n < 11 due to curvature effect; but a gap starts
to open for n > 12. Furthermore, we identified stable tubular structures formed
by stacking of Si polygons. We found AlP, GaAs, and GaN (8,0) single-wall
nanotubes stable and semiconducting. Our results are compared with those of
single-wall carbon nanotubes.
