The characterization of electronic defect states of single and double carbon vacancies in graphene sheets using molecular density functional theory

Author(s)

Pinheiro, Max, Jr. ; Cardoso, Daniely V. V. ; Aquino, Adelia J. A. ; Machado, Francisco B. C. ; Lischka, Hans

• Document type: Journal article
• Source: Molecular Physics; v. 117, n. 9-12, p. 13-pg., 2019-06-18.

Abstract

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 B-3(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 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. [GRAPHICS] . (AU)

• FAPESP's process: 17/50157-4 - The development of biradicaloid systems and functionalized materials for organic semiconductors: accurate molecular information from multireference quantum theory
• Grantee: Francisco Bolivar Correto Machado
• Support Opportunities: Regular Research Grants
• FAPESP's process: 12/11857-7 - Study of elementary reactions present in the decomposition mechanisms of sulfur containing organic materials
• Grantee: Daniely Verônica Viana Cardoso
• Support Opportunities: Scholarships in Brazil - Doctorate
• FAPESP's process: 17/07707-3 - Excited states and biradicalar nature of poliacenes and periacenes
• Grantee: Francisco Bolivar Correto Machado
• Support Opportunities: Regular Research Grants