Evidence for graphene edges beyond zigzag and armchair

The edges of nanoscopic objects determine most of their properties. For this reason the edges of honeycomb carbon-always considered either zigzag- or armchairlike-need special attention. In this Brief Report we provide experimental evidence confirming a previous unexpected prediction: zigzag is a metastable edge as its planar reconstruction lowers energy and forms the most stable graphene edge. Our evidence is based on reanalyzing a recent experiment. Since the reconstructed edge, along with other unconventional edges we discuss, has distinct chemical properties, this discovery urges for care in experiments and theory-we must enter the realm beyond zigzag and armchair.