Nuclear Bound States of Molecular Hydrogen Physisorbed on Graphene: An Effective Two-Dimensional Model.

Abstract

Using the periodic dlDF+Das ab initio scheme, the interaction potential between molecular hydrogen and a graphene sheet was computed and validated against experimental nuclear bound-state energies for H2, D2, and HD on graphite. The H2–graphene interaction was found to be effectively two-dimensional, with the molecule–surface distance and the tilt angle of the diatomic axis as the key degrees of freedom. The global energy minimum occurs when the molecule is oriented perpendicular to the surface, yielding an equilibrium distance of 3.17 Å and a binding energy of −51.9 meV. Numerically calculated 2D bound-state energies agreed with experimental values to within a maximum absolute deviation of 1.7 meV, demonstrating superior accuracy compared with van der Waals-corrected DFT approaches for weak surface interactions.

Mechanism

Dispersion contributions were extracted via DFT-based symmetry-adapted perturbation theory on surface cluster models and combined with periodic dispersionless DFT calculations to accurately describe the weak H2–graphene interaction potential.