The electronic states of a double carbon vacancy defect in pyrene: a model study for graphene

Machado, Francisco B. C.; Aquino, Adélia J. A.; Lischka, Hans

doi:10.1039/c4cp05751a

Cited by 17 publications

(25 citation statements)

References 60 publications

(99 reference statements)

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“…Using this model, chemical bonding and the manifold of electronic states were investigated by multireference configuration interaction (MRCI) calculations. [13][14][15][16] In case of the SV defect, 13 the calculations showed four electronic states (two singlet and two triplet) within a narrow margin of 0.1 eV, whereas for the DV structure, 14 a gap of ~1 eV to the lowest excited state was found. For the DV defect, comparison with density functional theory using the hybrid Becke three-parameter Lee, Yang, and Parr (B3-LYP) density functional 17 showed good agreement with the MRCI results.…”

Section: Introductionmentioning

confidence: 99%

Structure and electronic states of a graphene double vacancy with an embedded Si dopant

Nieman

Aquino

Hardcastle

et al. 2017

The Journal of Chemical Physics

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Silicon represents a common intrinsic impurity in graphene, bonding to either three or four carbon neighbors, respectively, in a single or double carbon vacancy. We investigate the effect of the latter defect (Si-C) on the structural and electronic properties of graphene using density functional theory. Calculations based both on molecular models and with periodic boundary conditions have been performed. The two-carbon vacancy was constructed from pyrene (pyrene-2C) which was then expanded to circumpyrene-2C. The structural characterization of these cases revealed that the ground state is slightly non-planar, with the bonding carbons displaced from the plane by up to ±0.2 Å. This non-planar structure was confirmed by embedding the defect into a 10 × 8 supercell of graphene, resulting in 0.22 eV lower energy than the previously considered planar structure. Natural bond orbital analysis showed sp hybridization at the silicon atom for the non-planar structure and spd hybridization for the planar structure. Atomically resolved electron energy loss spectroscopy and corresponding spectrum simulations provide a mixed picture: a flat structure provides a slightly better overall spectrum match, but a small observed pre-peak is only present in the corrugated simulation. Considering the small energy barrier between the two equivalent corrugated conformations, both structures could plausibly exist as a superposition over the experimental time scale of seconds.

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Section: Introductionmentioning

confidence: 99%

Structure and electronic states of a graphene double vacancy with an embedded Si dopant

Nieman

Aquino

Hardcastle

et al. 2017

The Journal of Chemical Physics

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“…Pentagon and hexagon are two basic structures for carbon nanostructure. The topological defect or geometrical frustration in carbon, are usually has a pentagon form [9][10].…”

Section: Introductionmentioning

confidence: 99%

Computing the band structure and energy gap of penta-graphene by using DFT and G0W0 approximations

Einollahzadeh

Dariani

Fazeli

2016

Solid State Communications

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In this paper, we consider the optimum coordinate of the penta-graphene. Penta-graphene is a new stable carbon allotrope which is stronger than graphene. Here, we compare the band gap of penta-graphene with various density functional theory (DFT) methods. We plotthe band structure of penta-graphene which calculated with the generalized gradient approximation functional HTCH407, about Fermi energy. Then, one-shot GW (G 0 W 0 ) correction for precise computations of band structure is applied. Quasi-direct band gap of penta-graphene is obtained around 4.1-4.3eV by G 0 W 0 correction. Penta-graphene is a semiconductor and can be expected to have broad applications in future, especially in nanoelectronics and nanomechanics.

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“…The geometries of each pyrene structure (Scheme 1) were optimized using complete active space (CAS) self-consistent field (CASSCF) theory [17,18]. Based on the experience with previous pyrene defect calculations [14,15] a CAS(5,5) was used comprised of five electrons in five orbitals where, in C s symmetry, three orbitals belonged to the A' irreducible representation and two orbitals belonged to the A" irreducible representation. The CAS(4,4) is chosen for the description of the isolated pyrene defect and one active orbital and electron is added to account for the hydrogen atom.…”

Section: Computational Detailsmentioning

confidence: 99%

“…The electronic structures of both single vacancy (SV) and double vacancy (DV) pyrene (Scheme 1) which has been used as a prototype for a graphene defect structure, have recently been described using multireference configuration interaction (MRCI) [14,15] and DFT [16].…”

Section: Introductionmentioning

confidence: 99%

“…The single vacancy investigation of pyrene using MRCI calculations [14] showed several closely spaced electronic states of triplet and singlet multiplicity (Scheme 1, Pyrene-1C) with the weight of the main configurations not exceeding a value of ~70%. The electronic ground state of the double vacancy defect [15] (Scheme 1, pyrene-2C) possesses 50% closed shell character which indicates a significantly different character as compared to the SV case. Nevertheless, the justmentioned percentages of the contributions of the dominating configuration to the total wavefunction for both types of defects demonstrate the importance of other configurations and the consequent need for a multireference approach, especially because of the goal of describing all closely spaced states simultaneously.…”

Section: Introductionmentioning

confidence: 99%

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Single and double carbon vacancies in pyrene as first models for graphene defects: A survey of the chemical reactivity toward hydrogen

et al. 2017

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Graphene is regarded as one of the most promising materials for nanoelectronics applications. Defects play an important role in modulating its electronic properties and also enhance its chemical reactivity. In this work the reactivity of single vacancies (SV) and double vacancies (DV) in reaction with a hydrogen atom H r is studied. Because of the complicated open shell electronic structures of these defects due to dangling bonds, multireference configuration interaction (MRCI) methods are being used in combination with a previously developed defect model based on pyrene. Comparison of the stability of products derived from C-H r bond formation with different carbon atoms of the different polyaromatic hydrocarbons is made. In the single vacancy case the most stable structure is the one where the incoming hydrogen is bound to the carbon atom carrying the dangling bond. However, stable C-H r bonded structures are also observed in the five-membered ring of the single vacancy. In the double vacancy, most stable bonding of the reactant H r atom is found in the five-membered rings. In total, C-H r bonds, corresponding to local energy minimum structures, are formed with all carbon atoms in the different defect systems and the pyrene itself. Reaction profiles for the four lowest electronic states show in the case of a single vacancy a complex picture of curve crossings and avoided crossings which will give rise to a complex nonadiabatic reaction dynamics involving several electronic states.

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The electronic states of a double carbon vacancy defect in pyrene: a model study for graphene

Cited by 17 publications

References 60 publications

Structure and electronic states of a graphene double vacancy with an embedded Si dopant

Structure and electronic states of a graphene double vacancy with an embedded Si dopant

Computing the band structure and energy gap of penta-graphene by using DFT and G0W0 approximations

Single and double carbon vacancies in pyrene as first models for graphene defects: A survey of the chemical reactivity toward hydrogen

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