Empirical potential for the interaction between molecular hydrogen and graphite

High level ab initio results on the interaction between H2 and graphite have recently become available, and in this paper, H2 -graphite potentials have been fitted to model such interactions. The popular Lennard-Jones formula is found to be inadequate, and its strong repulsive part must be replaced to fit the full range of interactions, from the long range attraction to the short range repulsion. Two isotropic empirical forms are obtained, and both produce excellent fit to the ab initio results and should provide good description for the interactions between hydrogen and graphitic materials, both in the physisorption and the high pressure regimes. Our calculations also show that density functional theory is inadequate to describe the H2 -graphite interactions in high pressure. The newly obtained exp-6-8-10 is also applied to the problem of trapping H2 in graphite, and the calculated critical pressure is considerably higher than that obtained before by density functional theory calculations.