Quantum simulation of hydrogen adsorption to various carbon nanotubes

We perform the quantum simulation of adsorption of a hydrogen molecule to various kinds of single-walled carbon nanotubes (SWNTs). The potential energy barrier height (PBH) for the dissociative adsorption of a hydrogen molecule onto the outer wall of nanotube decreases as the tube diameter decreases. H-2, however, dose not adsorb to the inner wall of any type of nanotubes. While, the PBH for H2 penetration into the open-ended nanotube increases as the tube diameter decreases, which is independent of the atomic geometry. These results on the structure-dependent H2 adsorption to SWNTs are reasonably interpreted by a transition in the local electronic states from sp(2) to sp(3) bondings caused by the interaction between an adsorbing hydrogen and carbon atoms of SWNTs.