Structures of hydrogen molecules in single-walled carbon nanotubes

Molecular-dynamics simulations were used to investigate the structures of hydrogen molecules formed within (5,5), (9,0) and (10,10) single-walled carbon nanotubes (SWNT). In the (5,5) and (9,0) SWNTs, H2 molecules preferably form linear lines and helical curves, showing the strong confinement of small-diameter SWNTs. The structure of H2 molecules in the (5,5) and (9,0) SWNTs is different, showing the dependence on the helicities of the SWNTs. The accumulation process of H2 molecules in the (10,10) SWNT is also presented, showing the formation of H2 molecules cylindrical shells.