Structural properties of caesium encapsulated in carbon nanotubes

Caesium structures encapsulated in CNTs were investigated using a structural optimization process applied to a steepest descent method. As the radius of the CNTs increased, the optimal structures were found in various phases from an atomic strand to multi-shell packs composed of coaxial cylindrical shells, and both helical and layered structures were found. The numbers of helical atom rows composed of coaxial tubes and the orthogonal vectors of the circular rolling of a triangular network can explain the structures of ultra-thin caesium nanowires encapsulated in CNTs.