Mapasha, Refilwe EdwinUkpong, Aniekan M.Chetty, Nithaya2012-06-202012-06-202012-05Mapasha, RE, Ukpong, AM & Chetty, N 2012, 'Ab initio studies of hydrogen adatoms on bilayer graphene', Physical Review B, vol. 85, no. 20.1098-0121 (pint)1550-235x (online)10.1103/PhysRevB.85.205402http://hdl.handle.net/2263/19212We present a comparative density functional study of the adsorption of hydrogen on bilayer graphene. Six different exchange-correlation functionals are employed to explore the possible configurations of hydrogen ad- sorption at 50% coverage. Using the four variants of the non-local van derWaals density functional, we identify three distinct competing configurations that retain the coupled bilayer structure at 0 K. One of the configurations undergoes a spontaneous transformation from hexagonal to tetrahedral structure, under hydrogenation, with heat of formation ranging between -0.03 eV (vdW-DF) and -0.37 eV (vdW-DFC09x). This configuration has a finite band gap of around 3 eV, whereas all other competing configurations are either semi-metallic or metallic. We also find two unique low-energy competing configurations of decoupled bilayer graphene, and therefore suggest the possibility of graphene exfoliation by hydrogen intercalation.en© 2012 American Physical SocietyHydrogen adatomsBilayer grapheneGraphene -- Absorption and adsorptionAdsorptionPostprint Article