H2 in the interstitial channels of nanotube bundles -: art. no. 125421

The equation of state of H-2 adsorbed in the interstitial channels of a carbon nanotube bundle has been calculated using the diffusion Monte Carlo method. The possibility of a lattice dilation, induced by H-2 adsorption, has been analyzed by modeling the cohesion energy of the bundle. The influence of factors such as the interatomic potentials, the nanotube radius, and the geometry of the channel on the bundle swelling is systematically analyzed. The most critical input is proved to be the C-H-2 potential. Using the same model than in planar graphite, the dilation is smaller than in previous estimations or even inexistent. H-2 is highly unidimensional near the equilibrium density, the radial degree of freedom appearing progressively at higher densities.