Endohedral silicon nanotubes as thinnest silicide wires

Using ab initio calculations, we describe how the smallest silicon nanotubes of (2,2) and (3,0) chiral symmetries are stabilized by the axially placed metal atoms, to form nearly one-dimensional structures with substantial cohesive energy, mechanical stiffness, and metallic density of electronic states. Their further reconstructions lead to thicker and shorter wires, while relative stability can be viewed in a binary field diagram of M _xSi_1-x, and depends on chemical potentials of the components. A comparison with recent epitaxial-growth experiments reveals the equivalence of the (2,2) endohedral nanotubes with the thinnest possible experimental wires.