Hydrogen adsorption on graphite and in carbon slit pores from path integral simulations

A method for computing adsorption isotherms for quantum fluids by combining grand canonical Monte Carlo with the path integral technique is presented. The method is used to compute the isosteric heat of adsorption for H-2, HD, and D-2 as a function of coverage for several different graphite-hydrogen potentials, and these results are compared with available experimental data. Adsorption isotherms for H-2, HD, and D-2 on graphite are computed and compared with experiment. The agreement between simulations and experiment is very good in most cases. Adsorption of para-hydrogen in graphite slit pores is studied by grand canonical path integral Monte Carlo. Comparison with classical hydrogen at the same absolute and reduced temperatures indicates that the quantum effects suppress capillary condensation for some values of the slit width.