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Open Access item Strong covalent bonding between two graphene layers

Authors:Andres, P. L. de
Ramírez, Rafael
Vergés, José A.
Keywords:few graphene layers
Issue Date:14-Jan-2008
Publisher:American Physical Society
Citation:Phys Rev B 77 (4) 045403 (2008)
Abstract:We show that two graphene layers stacked directly on top of each other (AA stacking) form strong chemical bonds when the distance between planes is 0.156 nm. Simultaneously, C-C in-plane bonds are considerably weakened from partial double-bond (0.141 nm) to single bond (0.154 nm). This polymorphic form of graphene bilayer is meta-stable w.r.t. the one bound by van der Waals forces at a larger separation (0.335 nm) with an activation energy of 0.16 eV/cell. Similarly to the structure found in hexaprismane, C forms four single bonds in a geometry mixing 90 and 120 angles. Intermediate separations between layers can be stabilized under external anisotropic stresses showing a rich electronic structure changing from semi-metal at van der Waals distance, to metal when compressed, to wide gap semiconductor at the meta-stable minimum.
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