R10-Graphene: A Predicted Two-Dimensional Metallic Carbon

A two-dimensional rectangular carbon formed by four-, eight- and ten-membered carbon rings, named R10graphene, is found by the particle swarm optimization method. Studies indicate that R10-graphene is metallic, possessing dynamical, thermal and mechanical stability. Its metallicity comes mainly from the pz orbital of the carbon atoms, as that in graphene. It is mechanically anisotropic, having a larger elastic constant along the a axis than that along the b axis. Calculated ideal in-plane strength along the a axis is also considerably higher than that along the b axis although the critical strains along these two directions are almost the same. Investigations reveal that it has greater differential quantum capacitance and charge storage capacity than graphene, especially at negative voltage, which make it a promising cathode material for supercapacitors.