Hydrogen and deuterium chemisorption on a single layer of graphene was studied by path-integral molecular-dynamics simulations. Finite-temperature properties of these point defects were analyzed in the range from 200 to 1500K by using a tight-binding potential fitted to density-functional calculations. On one hand, vibrational properties of the adatoms were studied at their equilibrium positions linked to C atoms. The vibrations display an appreciable anharmonicity, as derived from the comparison between kinetic and potential energies, as well as between vibrational energy for hydrogen and deuterium. On the other hand, the adatom motion was studied by quantum transition-state theory. At room temperature, quantum effects were found to enhance the hydrogen diffusivity on the graphene sheet by a factor of 20.

Vibrational Properties and Diffusion of Hydrogen on Graphene. Herrero, C.P., Ramírez, R.: Physical Review B, 2009, 79[11], 115429