TY - JOUR
T1 - The characterization of electronic defect states of single and double carbon vacancies in graphene sheets using molecular density functional theory
AU - Pinheiro, Max
AU - Cardoso, Daniely V.V.
AU - Aquino, Adélia J.A.
AU - Machado, Francisco B.C.
AU - Lischka, Hans
N1 - Publisher Copyright:
© 2019, © 2019 The Author(s). Published by Informa UK Limited, trading as Taylor & Francis Group.
PY - 2019/6/18
Y1 - 2019/6/18
N2 - A detailed picture of the electronic states manifolds of single- and double-vacancy defects in molecular models of graphene based on polycyclic aromatic hydrocarbons (PAHs) is presented. DFT calculations using various density functionals including long-range corrected ones have been performed for pyrene, circumpyrene and 7a,7z-periacene. It has been found for pyrene defect models that DFT results reproduced well the set of closely-spaced singlet and triplet states predicted by the CCSD(T) and previous MRCI + Q calculations, indicating the applicability of DFT for accessing the excited states manifolds also for larger graphene models. For the single-carbon vacancy defect, all structures have a triplet ground state. As expected, in the largest system, 7a,7z-periacene-1C, the lowest lying states are much closer in energy. For all double-vacancy defect structures, a significant rearrangement of the electronic states with increasing size of the sheet is observed. The closed-shell 1 A g state in the smallest systems is destabilised in the extended 7a,7z-periacene system, which has the 3 B 2u state as the ground state. As observed for the single-vacancy defect, the lowest lying states are closer in energy for the larger systems, since there are more π orbitals close in energy available. For all states, the formation of the bridging bonds for the double vacancy leads to distances shorter than for the single vacancy defect indicating a larger rigidity of the former structure which does not allow stronger distortions.
AB - A detailed picture of the electronic states manifolds of single- and double-vacancy defects in molecular models of graphene based on polycyclic aromatic hydrocarbons (PAHs) is presented. DFT calculations using various density functionals including long-range corrected ones have been performed for pyrene, circumpyrene and 7a,7z-periacene. It has been found for pyrene defect models that DFT results reproduced well the set of closely-spaced singlet and triplet states predicted by the CCSD(T) and previous MRCI + Q calculations, indicating the applicability of DFT for accessing the excited states manifolds also for larger graphene models. For the single-carbon vacancy defect, all structures have a triplet ground state. As expected, in the largest system, 7a,7z-periacene-1C, the lowest lying states are much closer in energy. For all double-vacancy defect structures, a significant rearrangement of the electronic states with increasing size of the sheet is observed. The closed-shell 1 A g state in the smallest systems is destabilised in the extended 7a,7z-periacene system, which has the 3 B 2u state as the ground state. As observed for the single-vacancy defect, the lowest lying states are closer in energy for the larger systems, since there are more π orbitals close in energy available. For all states, the formation of the bridging bonds for the double vacancy leads to distances shorter than for the single vacancy defect indicating a larger rigidity of the former structure which does not allow stronger distortions.
KW - DFT
KW - Excited states
KW - Periacenes
KW - polycyclic aromatic hydrocarbons
KW - pyrene
UR - http://www.scopus.com/inward/record.url?scp=85060260395&partnerID=8YFLogxK
U2 - 10.1080/00268976.2019.1567848
DO - 10.1080/00268976.2019.1567848
M3 - Article
AN - SCOPUS:85060260395
SN - 0026-8976
VL - 117
SP - 1519
EP - 1531
JO - Molecular Physics
JF - Molecular Physics
IS - 9-12
ER -