Thermal stability of hydrogen clusters at graphene and Stone–Wales graphene surfaces

In the framework of the nonorthogonal tight-binding model, the possibility to form different thermally stable elements of the hydrogen pattern at graphene and Stone–Wales graphene surfaces is studied. The latter material is the recently predicted allotrope of graphene. The migration of a hydrogen atom adsorbed on these structures is numerically analyzed. The activation energies of migration of a hydrogen atom on the surfaces of graphene and Stone–Wales graphene are equal to 0.52 and 0.84 eV, respectively. The thermal stability of hydrogen clusters having the form of hexatomic rings and located on the surface of graphene, as well as the stability of the pent-, hex-, and heptatomic rings on the surface of Stone–Wales graphene, is estimated. The corresponding activation energies (1.61, 1.25, 1.36, and 1.27 eV, respectively), as well as the frequency-dependent factors in the Arrhenius formula characterizing the thermal decay, are determined. The lifetimes of these clusters at freezing and boiling temperatures of water are estimated.