Heptagraphene: Tunable Dirac Cones in a Graphitic Structure.
We predict the existence and dynamical stability of heptagraphene, a new graphitic structure formed of rings of 10 carbon atoms bridged by carbene groups yielding seven-membered rings. Despite the rectangular unit cell, the band structure is topologically equivalent to that of strongly distorted graphene. Density-functional-theory calculations demonstrate that heptagraphene has Dirac cones on symmetry lines that are robust against biaxial strain but which open a gap under shear. At high deformation values bond reconstructions lead to different electronic band arrangements in dynamically stable configurations. Within a tight-binding framework this richness of the electronic behavior is identified as a direct consequence of the symmetry breaking within the cell which, unlike other graphitic structures, leads to band gap opening. A combined approach of chemical and physical modification of graphene unit cell unfurls the opportunity to design carbon-based systems in which one aims to tune an electronic band gap.
Argonne National Laboratory, 9700 S. Cass Avenue, Lemont, Illinois, 60439, United States.
Alejandro
A
Lopez-Bezanilla
Argonne National Laboratory, 9700 S. Cass Avenue, Lemont, Illinois, 60439, United States.
Ivar
I
Martin
Argonne National Laboratory, 9700 S. Cass Avenue, Lemont, Illinois, 60439, United States.|James Franck Institute, University of Chicago, Chicago, Illinois 60637, United States.
Peter B
PB
Littlewood