Effects of hydrogen chemisorption on the structure and deformation of single-walled carbon nanotubes

We report results of molecular-dynamics simulations for the effects of atomic hydrogen chemisorption on the structure and deformation of single-walled carbon nanotubes. Upon hydrogenation, the nanotubes expand and the degree of expansion depends on the hydrogen coverage. There is a critical hydrogen coverage, similar to 25%-30%, that marks the onset of a structural transition associated with the sp(2)-to-sp(3) bonding transition: at lower-than-critical coverage, sp(2) C-C bonding dominates and nanotube swelling is negligible; at higher-than-critical coverage, however, sp(3) C-C bonding dominates and radial and axial strains increase monotonically with coverage. This behavior is independent of nanotube chirality and diameter and of temperature.