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, $∼25%–30%$⁠, that marks the onset of a structural transition associated with the $sp2-to-sp3$ bonding transition: at lower-than-critical coverage, $sp2$ C–C bonding dominates and nanotube swelling is negligible; at higher-than-critical coverage, however, $sp3$ 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.