Grain boundaries with octagonal defects in graphene nanoribbons and nanotubes

We study graphene nanoribbons and carbon nanotubes containing ordered defect lines built of octagonal rings. We show that octagonal defect lines are a robust source of state localization at the Fermi energy, in some cases leading to spontaneous magnetization. We also prove that the localization at chains of octagons is a consequence of the zigzag nature of the graphene edges forming the defect lines. © 2013 American Physical Society.This work was supported by the Polish National Science Center (Grant No. DEC-2011/03/B/ST3/00091), the Basque Departamento de Educación and the UPV/EHU (Grant No. IT-366-07), the Spanish Ministerio de Innovación, Ciencia y Tecnología (Grant Nos. TEC2007-68065-C03-03 and FIS2010-19609-C02-02), and the ETORTEK research program (NANO-IKER Grant No. IE11-304) funded by the Basque Departamento de Industria and the Diputación Foral de Guipuzcoa.Peer Reviewe