A few simple rules governing hydrogenation of graphene dots

Bonfanti, Matteo; Casolo, Simone; Tantardini, Gian Franco; Ponti, Alessandro; Martinazzo, Rocco

doi:10.1063/1.3650693

Cited by 40 publications

(58 citation statements)

References 62 publications

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“…Considering benzene as the simplest building block of graphene, it is easy to realize how adsorption of a H atom breaks the aromatic network and leaves one unpaired electron free to move on the lattice by bond switching: spin-recoupling with a neighbouring double bond creates an unpaired electron in one every two lattice sites. Ab-initio VB calculations (Bonfanti et al, 2008) show that this indeed the case: the 5 π electrons have 5 different ways of couplings ( Fig.6) but only those with the unpaired electron in the so-called ortho and para positions are relevant; an electron in meta position would involve a Dewar-like structure, which has a high energy bond-pattern (see Fig.6). The bond switching mechanism is very useful and well known in basic organic chemistry, where it easily allows predictions for orientation effects, e.g.…”

Section: Chemical Resonance Formulamentioning

confidence: 99%

“…The barrier (which is also present when the substrate is kept planar) has an important, purely electronic origin. Indeed, it has been shown (Bonfanti et al, 2008) that it results from an avoided crossing between a repulsive interaction with the Kekulé-like ground-state and an attractive interaction with the low-lying, Dewar-like excited state (see Fig.4 in Casolo et al (2009a)). This can be nicely understood in terms of the chemical picture above since the Kekulé-like structures do not have unpaired electrons which can readily couple with that of the incoming H atom.…”

Section: Sticking Of Atomic and Molecular Speciesmentioning

confidence: 99%

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The Effect of Atomic-Scale Defects and Dopants on Graphene Electronic Structure

Martinazzo¹,

Casolo²,

Tantardini³

2011

Physics and Applications of Graphene - Theory

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Graphene, being one-atom thick, is extremely sensitive to the presence of adsorbed atoms and molecules and, more generally, to defects such as vacancies, holes and/or substitutional dopants. This property, apart from being directly usable in molecular sensor devices, can also be employed to tune graphene electronic properties.Here we briefly review the basic features of atomic-scale defects that can be useful for material design. After a brief introduction on isolated p z defects, we analyse the electronic structure of multiple defective graphene substrates, and show how to predict the presence of microscopically ordered magnetic structures. Subsequently, we analyse the more complicated situation where the electronic structure, as modified by the presence of some defects, affects chemical reactivity of the substrate towards adsorption (chemisorption) of atomic/molecular species, leading to preferential sticking on specific lattice positions. Then, we consider the reverse problem, that is how to use defects to engineer graphene electronic properties. In this context, we show that arranging defects to form honeycomb-shaped superlattices (what we may call "supergraphenes") a sizeable gap opens in the band structure and new Dirac cones are created right close to the gapped region. Similarly, we show that substitutional dopants such as group IIIA/VA elements may have gapped quasiconical structures corresponding to massive Dirac carriers. All these possible structures might find important technological applications in the development of graphene-based logic transistors.

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Section: Chemical Resonance Formulamentioning

confidence: 99%

Section: Sticking Of Atomic and Molecular Speciesmentioning

confidence: 99%

The Effect of Atomic-Scale Defects and Dopants on Graphene Electronic Structure

Martinazzo¹,

Casolo²,

Tantardini³

2011

Physics and Applications of Graphene - Theory

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“…Its actual shape was chosen -following the line of reasoning of Ref. 39-with the help of Tight-Binding (TB) calculations in such a way to limit the edge localization which does interfere with the defect-induced states at the Fermi level. In the chosen structure, edge states were found sufficiently far in energy from the vacancy-induced states (both at the TB and at the Hartree-Fock (HF) level) to make us confident that the resulting energetics accurately describes the vacancy.…”

Section: B a Finite-size Modelmentioning

confidence: 99%

Spin coupling around a carbon atom vacancy in graphene

Casartelli

Casolo²,

Tantardini³

et al. 2013

Phys. Rev. B

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We investigate the details of the electronic structure in the neighborhoods of a carbon atom vacancy in graphene by employing magnetization-constrained density-functional theory on periodic slabs, and spin-exact, multi-reference, second-order perturbation theory on a finite cluster. The picture that emerges is that of two local magnetic moments (one π-like and one σ-like) decoupled from the π band and coupled to each other. We find that the ground state is a triplet with a planar equilibrium geometry where an apical C atom opposes a pentagonal ring. This state lies ∼0.2 eV lower in energy than the open-shell singlet with one spin flipped, which is a bistable system with two equivalent equilibrium lattice configurations (for the apical C atom above or below the lattice plane) and a barrier ∼0.1 eV high separating them. Accordingly, a bare carbon-atom vacancy is predicted to be a spin-one paramagnetic species, but spin-half paramagnetism can be accommodated if binding to foreign species, ripples, coupling to a substrate, or doping are taken into account.

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“…[3][4][5] The energetics of hydrogen adsorption has been extensively studied, mostly at the Density Functional Theory (DFT) level with the periodic supercell approach [6][7][8][9][10] and more lately with some accurate wavefunction calculations on cluster models. [11][12][13][14] Many different aspects of hydrogen adsorption have been addressed, including adsorption and diffusion in the a) Electronic mail: matteo.bonfanti@unimi.it b) Electronic mail: rocco.martinazzo@unimi.it shallow physisorption well, 11 single and multiple adsorption in the chemisorption well, 9,15-17 carbon vacancy hydrogenation, 18 and binding to edges. 13,19 All these possibilities determine a vast variety of cases which can be well interpreted and rationalized in terms of electronic and structural effects.…”

Section: Introductionmentioning

confidence: 99%

“…[11][12][13][14] Many different aspects of hydrogen adsorption have been addressed, including adsorption and diffusion in the a) Electronic mail: matteo.bonfanti@unimi.it b) Electronic mail: rocco.martinazzo@unimi.it shallow physisorption well, 11 single and multiple adsorption in the chemisorption well, 9,15-17 carbon vacancy hydrogenation, 18 and binding to edges. 13,19 All these possibilities determine a vast variety of cases which can be well interpreted and rationalized in terms of electronic and structural effects.…”

Section: Introductionmentioning

confidence: 99%

Quantum dynamics of hydrogen atoms on graphene. I. System-bath modeling

Bonfanti

Jackson

Hughes

et al. 2015

The Journal of Chemical Physics

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Ab initio molecular dynamics of hydrogen dissociation on metal surfaces using neural networks and novelty sampling J. Chem. Phys. 127, 154716 (2007) An accurate system-bath model to investigate the quantum dynamics of hydrogen atoms chemisorbed on graphene is presented. The system comprises a hydrogen atom and the carbon atom from graphene that forms the covalent bond, and it is described by a previously developed 4D potential energy surface based on density functional theory ab initio data. The bath describes the rest of the carbon lattice and is obtained from an empirical force field through inversion of a classical equilibrium correlation function describing the hydrogen motion. By construction, model building easily accommodates improvements coming from the use of higher level electronic structure theory for the system. Further, it is well suited to a determination of the system-environment coupling by means of ab initio molecular dynamics. This paper details the system-bath modeling and shows its application to the quantum dynamics of vibrational relaxation of a chemisorbed hydrogen atom, which is here investigated at T = 0 K with the help of the multi-configuration time-dependent Hartree method. Paper II deals with the sticking dynamics. C 2015 AIP Publishing LLC. [http://dx

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A few simple rules governing hydrogenation of graphene dots

Cited by 40 publications

References 62 publications

The Effect of Atomic-Scale Defects and Dopants on Graphene Electronic Structure

The Effect of Atomic-Scale Defects and Dopants on Graphene Electronic Structure

Spin coupling around a carbon atom vacancy in graphene

Quantum dynamics of hydrogen atoms on graphene. I. System-bath modeling

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