  Resonant graphene dopants, such as hydrogen adatoms, experience long-range
effective interaction mediated by conduction electrons. As a result of this
interaction, when several adatoms are present in the sample, hopping of adatoms
between sites belonging to different sublattices involves significant energy
changes. Different inelastic mechanisms facilitating such hopping -- coupling
to phonons and conduction electrons -- are considered. It is estimated that the
diffusion of hydrogen adatoms is rather slow, amounting to roughly one hop to a
nearest neighbor per millisecond.
