Formation of silicon-fullerene-linked nanowires inside carbon nanotubes: A molecular-dynamics and first-principles study

We study the formation of Si nanowires inside carbon nanotubes by using a combination of empirical molecular-dynamics and first-principles approaches. Molecular-dynamics simulations demonstrate that liquid Si encapsulated into a (13,0) nanotube crystallizes into a nanowire composed of linked Si₁₆ fullerene cages. On the other hand, a nanowire composed of linked Si₂₀ fullerene cages forms inside a (14,0) nanotube. The stabilities of these nanowires are further confirmed by first-principles calculations. We also find that the freestanding Si₁₆-linked nanowire is a metal, while the Si₂₀-linked nanowire is a semiconductor. The present findings suggest that the choice of the nanotube size allows us to control the structure of Si nanowires, and therefore to tailor the material properties.