Isotopic effects of hydrogen adsorption in carbon nanotubes

Abstract

We present diffusion Monte Carlo calculations of D2 adsorbed inside a narrow carbon nanotube. The one-dimensional D2 equation of state is reported, and the one-dimensional character of the adsorbed D2 is analyzed. The isotopic dependence of the constitutive properties of the quantum fluid are studied by comparing D2 and H2. Quantum effects due to their different masses are observed both in the energetic and the structural properties. The influence of the interatomic potential in one-dimensional systems is also studied by comparing the properties of D2 and 4He which have nearly the same mass but a sizeably different potential. The physics of molecular hydrogen adsorbed in the interstitial channels of a bundle of nanotubes is analyzed by means of both a diffusion Monte Carlo calculation and an approximate mean-field method.