Energetic stability of graphene nanoflakes and nanocones

Wohner, Natalie; Lam, Pui K.; Sattler, K.

doi:10.1016/j.carbon.2013.10.064

Cited by 37 publications

(31 citation statements)

References 139 publications

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“…This finding is very general, holding also for their unsaturated counterparts, namely graphene nanoribbons and nanoflakes (see e.g. [105][106][107]) and can be understood also in terms of Hückel molecular orbital theory and organic chemistry concepts such as Clar aromatic sextets and Kekulé structures [108,109].…”

Section: Prototypical Molecular Solidsmentioning

confidence: 77%

Exciton dispersion in molecular solids

Cudazzo¹,

Sottile²,

Rubio³

et al. 2015

J. Phys.: Condens. Matter

119

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The investigation of the exciton dispersion (i.e. the exciton energy dependence as a function of the momentum carried by the electron-hole pair) is a powerful approach to identify the exciton character, ranging from the strongly localised Frenkel to the delocalised Wannier-Mott limiting cases. We illustrate this possibility at the example of four prototypical molecular solids (picene, pentacene, tetracene and coronene) on the basis of the parameter-free solution of the many-body Bethe-Salpeter equation. We discuss the mixing between Frenkel and charge-transfer excitons and the origin of their Davydov splitting in the framework of many-body perturbation theory and establish a link with model approaches based on molecular states. Finally, we show how the interplay between the electronic band dispersion and the exchange electron-hole interaction plays a fundamental role in setting the nature of the exciton. This analysis has a general validity holding also for other systems in which the electron wavefunctions are strongly localized, as in strongly correlated insulators.

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Section: Prototypical Molecular Solidsmentioning

confidence: 77%

Exciton dispersion in molecular solids

Cudazzo¹,

Sottile²,

Rubio³

et al. 2015

J. Phys.: Condens. Matter

119

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“…Experimentally, GNFs have been studied due to their unique properties and potential applications [27][28][29][30]. In particular, for large GNFs with lateral dimensions up to 20 nm, the de-Theoretically, the structural and electronic properties of small GNFs with up to hundreds of atoms have been studied with first-principles calculations [21][22][23][24][25]. The stability and the HOMO-LUMO energy gaps have been calculated.…”

Section: Introductionmentioning

confidence: 99%

“…Therefore, many bandgap engineering techniques have been developed both experimentally and theoretically to open a small band gap in graphene [4][5][6]. One of these techniques involves cutting 2D graphene into finite-sized one-dimensional (1D) graphene nanoribbons (GNRs) [7][8][9][10][11][12][13][14][15][16][17] and zero-dimensional (0D) graphene nanoflakes (GNFs) [18][19][20][21][22][23][24][25]. Theoretically, significant efforts [12][13][14][15][16][17] based on first-principles calculations have been made to characterize properties of GNRs with respect to the atomic configuration of their edges, which are of either the armchair (AC) or zigzag (ZZ) types.…”

Section: Introductionmentioning

confidence: 99%

Electronic structure and aromaticity of large-scale hexagonal graphene nanoflakes

Lin

Yang

et al. 2014

The Journal of Chemical Physics

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With the help of the recently developed SIESTA-PEXSI method [J. Phys.: Condens. Matter 26, 305503 (2014)], we perform Kohn-Sham density functional theory (DFT) calculations to study the stability and electronic structure of hexagonal graphene nanoflakes (GNFs) with up to 11,700 atoms. We find the electronic properties of GNFs, including their cohesive energy, HOMO-LUMO energy gap, edge states and aromaticity, depend sensitively on the type of edges (ACGNFs and ZZGNFs), size and the number of electrons. We observe that, due to the edge-induced strain effect in ACGNFs, large-scale ACGNFs' cohesive energy decreases as their size increases. This trend does not hold for ZZGNFs due to the presence of many edge states in ZZGNFs. We find that the energy gaps Eg of GNFs all decay with respect to 1/L, where L is the size of the GNF, in a linear fashion. But as their size increases, ZZGNFs exhibit more localized edge states. We believe the presence of these states makes their gap decrease more rapidly. In particular, when L is larger than 6.40 nm, we find that ZZGNFs exhibit metallic characteristics. Furthermore, we find that the aromatic structures of GNFs appear to depend only on whether the system has 4N or 4N + 2 electrons, where N is an integer.

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“…Indeed, this hexagonal nano-flake has attracted great interest with respect to its interesting properties like electronic absorption spectra, 119 and it has been successfully applied for modeling graphene in previous theoretical work. [120][121][122][123][124] Several theoretical studies have focussed on acenes [125][126][127] and oligoacenes [128][129][130][131][132] using DFT and ab-initio methods. However, because of the polyradical character of oligoacenes, 125,126 the spin ground state of these molecules have to be checked.…”

Section: Graphene Modelmentioning

confidence: 99%

Chemical Bonding and Electronic Properties of the Co Adatom and Dimer Interacting with Polyaromatic Hydrocarbons

2015

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The density functional calculations presented here elucidate the nature of the interaction between the Co atom and dimer with a polyaromatic hydrocarbon (PAH). The results are analyzed in terms of structural, electronic and magnetic properties. The bonding character of the Co atom and dimer adsorbed on the PAH exhibits a strong covalent bonding, arising from a hybridization between the d orbitals of Co and the p z orbitals of the carbon atoms, which cause an in-plane distortion in the PAHs. A small charge transfer takes place from the Co atom and dimer to the PAH surface, which creates a positive charge on the metal atoms and thereby change their catalytic activity. Upon adsorption, the magnetic moment of the Co adatom is reduced depending on the adsorption site. For the perpendicular Co dimer to the PAH plane, the projected magnetic moment of the Co atom further from the PAH is increased, which is due to antiferromagnetic coupling between the Co atoms in this configuration. Density of state analysis shows that the main contribution of magnetic moment reduction is due to promotion of electrons from the 4s states to the 3d states of the Co adatom upon adsorption.

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Energetic stability of graphene nanoflakes and nanocones

Cited by 37 publications

References 139 publications

Exciton dispersion in molecular solids

Exciton dispersion in molecular solids

Electronic structure and aromaticity of large-scale hexagonal graphene nanoflakes

Chemical Bonding and Electronic Properties of the Co Adatom and Dimer Interacting with Polyaromatic Hydrocarbons

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