Atomistic study of sodium nanowires encapsulated in carbon nanotubes

We have investigated the structural phases of sodium encapsulated in carbon nanotubes by using a structural optimization process applied to an atomistic simulation method. As the radius of the carbon nanotubes is increased, the structures are found in various phases from an atomic strand to multi-shell packs composed of coaxial cylindrical shells and in both helical and layered structures. The numbers of helical atom rows composed of coaxial tubes and the orthogonal vectors of a circular rolling of a triangular network can explain multi-shell phases of sodium in carbon nanotubes