Is 2-D Graphite an Ultimate Large Hydrocarbon? 1. Energy Spectra of Giant Polycyclic Aromatic Hydrocarbons

Tyutyulkov, N.; Madjarova, Galia; Dietz, F.; Müllen, Kläus

doi:10.1021/jp982651b

Cited by 45 publications

(42 citation statements)

References 47 publications

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“…Again one expects there is some delocalization of the unpaired electron away from the defect, though again there is a net of 1 unpaired electron. And again this is in agreement with various theoretical studies 25,26,70,71,72,73,74 , as well as some experimental electron tunnelling microscopy measurements 75,76,77 . A generally sized and shaped hole may be viewed to arise from deletion of some benzenoid molecular network R so that we might denote the so defected graphite by G R − .…”

Section: Issn 1424-6376supporting

confidence: 92%

Mean-field resonance-theoretic view of benzenoid networks

Klein¹,

Ivanciuc²

2005

Arkivoc

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A simple classically based "mean field" resonance-theoretic approach is described to anticipate the effects of various modes of electron pairing (as in π-bond formation) for general "alternant" benzenoid conjugated π-networks. This simplified approach avoids generation and manipulation of individual resonance structures, whence application is facilitated, even for very large systems -so large that there might be hundreds or millions or moles or even substantially greater numbers of resonance structures. Some of the predictions so facilitated for several general circumstances are conveniently manifested as explicit algebraic formulas for numbers of unpaired electrons. The simplicity (and apparent reliability) of these algebraic formulas is emphasized; they involve no more than counts of different "kinds" of π-center carbons, e.g., the numbers of π-centers of different functionalities (primary, secondary, or tertiary) which are "starred" (in an "alternant" system) as well as those which are "unstarred". The argumentation also provides some information about rough locations for the (unpaired) spin densities, and ultimately also about the presence of low-lying excited states, magnetic moments, reactivities, and more. In particular these easily used ideas, which are extensions of those already familiar in "classical" organic chemistry should then aid in nano-technological developments.

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Section: Issn 1424-6376supporting

confidence: 92%

Mean-field resonance-theoretic view of benzenoid networks

Klein¹,

Ivanciuc²

2005

Arkivoc

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“…The same qualitative results have been obtained for three classes of 2-D polybenzenoid hydrocarbons with a large number N of 7r-Downloaded by [University of Nebraska, Lincoln] at 13:58 02 January 2015 m = 1, 2, 3, ... centers [12]. In the asymptotic limit N -+ 00, the EG A E ( N -t 00) is different from zero [12].…”

Section: Introductionsupporting

confidence: 75%

“…In the asymptotic limit N -+ 00, the EG A E ( N -t 00) is different from zero [12]. In this relation arises the principal question whether alternant 1-D and 2-D 7r-systems, in particular CZuv systems, with zero energy gap might exist.…”

Section: Introductionmentioning

confidence: 99%

Structure and Energy Spectra of a Class of Polybenzenoid Clar's Hydrocarbons and 1-D Polymers

Dietz

Tyutyulkov

Karabunarliev³

et al. 2000

Polycyclic Aromatic Compounds

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The energy spectra of a class of 2-D polybenzenoid Clar's hydrocarbons with a large number N(N-104) of carbon atoms is studied theoretically. It is shown that at the asymptotic case N -D Z the energy gap (EG) A E (N-m) is different from zero, i.e., the a-systems should possess semiconductor properties. The results for the EG A E ( N -w)#O of the hydrocarbons are in qualitative agreement with the results for the EG calculated for a class of 1-D ladder polymers having the same edge structure as the hydrocarbons. With increasing the number ( M ) of the a-centers of the elementary unit of the polymers, the band gap AE(M+ m) approaches also to a value different from zero. The quantitative results on the equilibria geometries of the hydrocarbons and the polymers correspond to Clar's qualitative characterization of benzenoids composed of disjoint "n-sextets". The energetics of the hydrocarbons with different types of defects and the corresponding Tamm and Frenkel states were also investigated.

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“…Within the Stoner mechanism 49 , ferromagnetism is possible if the local electron-electron interaction term (the so-called Hubbard term) 50 , U , is large than a critical value given by:…”

Section: Magnetic Response and The Role Of Short Range Coulomb Inmentioning

confidence: 99%

Electronic properties of disordered two-dimensional carbon

2006

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Two-dimensional carbon, or graphene, is a semi-metal that presents unusual low-energy electronic excitations described in terms of Dirac fermions. We analyze in a self-consistent way the effects of localized (impurities or vacancies) and extended (edges or grain boundaries) defects on the electronic and transport properties of graphene. On the one hand, point defects induce a finite elastic lifetime at low energies with the enhancement of the electronic density of states close to the Fermi level. Localized disorder leads to a universal, disorder independent, electrical conductivity at low temperatures, of the order of the quantum of conductance. The static conductivity increases with temperature and shows oscillations in the presence of a magnetic field. The graphene magnetic susceptibility is temperature dependent (unlike an ordinary metal) and also increases with the amount of defects. Optical transport properties are also calculated in detail. On the other hand, extended defects induce localized states near the Fermi level. In the absence of electron-hole symmetry, these states lead to a transfer of charge between the defects and the bulk, the phenomenon we call selfdoping. The role of electron-electron interactions in controlling self-doping is also analyzed. We also discuss the integer and fractional quantum Hall effect in graphene, the role played by the edge states induced by a magnetic field, and their relation to the almost field independent surface states induced at boundaries. The possibility of magnetism in graphene, in the presence of short-range electron-electron interactions and disorder is also analyzed.

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Is 2-D Graphite an Ultimate Large Hydrocarbon? 1. Energy Spectra of Giant Polycyclic Aromatic Hydrocarbons

Cited by 45 publications

References 47 publications

Mean-field resonance-theoretic view of benzenoid networks

Mean-field resonance-theoretic view of benzenoid networks

Structure and Energy Spectra of a Class of Polybenzenoid Clar's Hydrocarbons and 1-D Polymers

Electronic properties of disordered two-dimensional carbon

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