1. Catalan Institute of Nanoscience and Nanotechnology (ICN2), Av. de Serragalliners, s/n, 08193 Bellaterra (Barcelona), Spain
2. Institut für Chemie und Biochemie, Physikalische und Theoretische Chemie, Freie Universität Berlin, Arnimallee 22, 14195 Berlin, Germany
3. Computing Center, Technical University of Denmark, DK-2800 Kongens Lyngby, Denmark
4. CNR Institute for Microelectronics and Microsystems (CNR-IMM), Strada VIII, 5, 95121 Catania, Italy
5. Departament de Ciència de Materials i Química Física & Institut de Química Teòrica i Computacional (IQTCUB), Universitat de Barcelona, c/Martí i Franquès 1-11, 08028 Barcelona, Spain
6. Department of Physics, Technical University of Denmark, DK-2800 Kongens Lyngby, Denmark
7. Center for Nanostructured Graphene (CNG), DK-2800 Kongens Lyngby, Denmark