We present diffusion Monte Carlo calculations of ${\mathrm{D}}_2$ adsorbed inside a narrow carbon nanotube. The one-dimensional ${\mathrm{D}}_2$ equation of state is reported, and the one-dimensional character of the adsorbed ${\mathrm{D}}_2$ is analyzed. The isotopic dependence of the constitutive properties of the quantum fluid are studied by comparing ${\mathrm{D}}_2$ and ${\mathrm{H}}_2.$ 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 ${\mathrm{D}}_2$ and ${}^4\mathrm{He}$ 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.

• Received 13 February 2001

DOI:https://doi.org/10.1103/PhysRevB.65.014503