Balance between physical and chemical interactions of second-row diatomic molecules with graphene sheet

We present a computational investigation of adsorption on graphene concerning the second-row diatomic molecules (Li-2, B-2, C-2, O-2, N-2 and F-2). The adsorption energies and the nature of the interaction between guest molecules and graphene, in both periodic and non-periodic approaches, were evaluated using dispersion-corrected density functional theory calculations (DFT/PBE-D3). A periodic graphene model, used to tune the coverage, is compared with a cluster model in which the graphene sheet is represented by coronene. The results of both energetic and electronic state analyses reveal a variety of adsorption processes. While B-2 and C-2 adsorb in a bridge position in order to establish two covalent bonds with the surface, O-2 and N-2 are clearly physisorbed in positions parallel to the surface. Li-2 and F-2 show intermediate behavior, with strong physisorption accompanied by charge transfer. (C) 2016 Elsevier Ltd. All rights reserved.