A Fully Atomistic Reactive Molecular Dynamics Study on the Formation of Graphane from Graphene Hydrogenated Membranes
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A Fully Atomistic Reactive Molecular Dynamics Study on the Formation of Graphane from Graphene Hydrogenated Membranes. Pedro A. S. Autreto1 , Marcelo Z. Flores1, Sergio B. Legoas2, Ricardo P. B. Santos1,3 and Douglas S. Galvao1 1 Instituto de Física “Gleb Wataghin, Universidade Estadual de Campinas, Campinas - SP, 13083-970, Brazil 2 Departamento de Física, CCT, Universidade Federal de Roraima, 69304-000, Boa Vista - RR, Brazil. 3 Departamento de Engenharia Agrícola, Universidade Estadual de Maringá, 82020-900, Maringá - PR, Brazil. ABSTRACT Recently, Elias et al. (Science 323, 610 (2009).) reported the experimental realization of the formation of graphane from hydrogenation of graphene membranes under cold plasma exposure. In graphane, the carbon-carbon bonds are in sp3 configuration, as opposed to the sp2 hybridization of graphene, and the C–H bonds exhibit an alternating pattern (up and down with relation to the plane defined by the carbon atoms). In this work we have investigated, using reactive molecular dynamics simulations, the role of H frustration (breaking the H atoms up and down alternating pattern) in graphane-like structures. Our results show that a significant percentage of uncorrelated H frustrated domains are formed in the early stages of the hydrogenation process, leading to membrane shrinkage and extensive membrane corrugations. This might explain the significant broad distribution of values of lattice parameter experimentally observed. For comparison purposes we have also analyzed fluorinated graphanelike structures. Our results show that similarly to H, F atoms also create significant uncorrelated frustrated domains on graphene membranes. INTRODUCTION The discovery of new carbon-based materials has been frequent in recent decades. Examples of these materials are colossal nanotubes [1] and graphene [2]. Graphene is a two dimensional array of hexagonal units of sp2 bonded C atoms with very unusual and interesting electronic and mechanical properties [2]. Because of its electronic properties, graphene is considered one of the most promising materials for future electronics [3]. However since graphene is a gapless material, its use becomes restrict in some electronic applications [4]. One possibility towards opening graphene gap is through chemical functionalization, using hydrogen or fluorine atoms [5-14]. Fully hydrogenated graphene, named graphane, was theoretically predicted by Sofo, Chaudhari, and Barber [5], and experimentally realized by Elias et al. [7]. In their experiments, graphene membranes were submitted to H+ exposure from cold plasma. The H incorporation into the membranes results in altering the carbon hybridizations from sp2 to sp3. The experiments were also made with graphene membranes over SiO2 substrates, producing a material with different properties [7]. Perfect idealized graphane consists of a single-layer structure with fully saturated (sp3 hybridization) carbon atoms and with C-H bonds in an alternating pattern (up and down with
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relation to the plane defined by the carb
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