H2 in the interstitial channels of nanotube bundles

TL;DR

This study uses diffusion Monte Carlo simulations to analyze hydrogen adsorption in carbon nanotube bundles, revealing minimal lattice dilation and a predominantly one-dimensional behavior of H2 at equilibrium.

Contribution

It provides a detailed computational analysis of H2 in nanotube interstitial channels, highlighting the importance of the C-H2 potential and challenging previous estimates of lattice dilation.

Findings

H2 exhibits minimal lattice dilation in nanotube bundles.

H2 remains highly unidimensional near equilibrium density.

Radial degrees of freedom become significant at higher densities.

Abstract

The equation of state of H2 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 H2 adsorption, has been analyzed by modeling the cohesion energy of the bundle. The influence of factors like 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-H2 potential. Using the same model than in planar graphite, which is expected to be also accurate in nanotubes, the dilation is observed to be smaller than in previous estimations or even inexistent. H2 is highly unidimensional near the equilibrium density, the radial degree of freedom appearing progressively at higher densities.