Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Modeling vacancies and hydrogen impurities in graphene: A molecular
  point of view   We have followed a "molecular" approach to study impurity effects in
graphene. This is thought as the limiting case of an infinitely large cluster
of benzene rings. Therefore, we study several carbon clusters, with increasing
size, from phenalene, including three benzene rings, up to coronene 61, with 61
benzene rings. The impurities considered were a chemisorbed H atom, a vacancy,
and a substitutional proton. We performed HF and UHF calculations using the
STO-3G basis set. With increasing cluster size in the absence of impurities, we
find a decreasing energy gap, here defined as the HOMO-LUMO difference. In the
case of H chemisorption or a vacancy, the gap does not decrease appreciably,
whereas it is substantially reduced in the case of a substitutional proton. The
presence of an impurity invariably induces an increase of the density of states
near the HOMO level. We find a zero mode only in the case of a substitutional
proton. In agreement with experiments, we find that both the chemisorbed H, the
substitutional proton, and the C atom near a vacancy acquire a magnetic moment.
The relevance of graphene clusters for the design of novel electronic devices
is also discussed.

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The categories of this paper are: quant-ph
33
The categories of this paper are: plasm-ph
30
The categories of this paper are: q-alg
25
The categories of this paper are: patt-sol
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The categories of this paper are: comp-gas
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The categories of this paper are: acc-phys
3
The categories of this paper are: physics
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The categories of this paper are: chao-dyn
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The categories of this paper are: funct-an
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The categories of this paper are: econ
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The categories of this paper are: dg-ga
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The categories of this paper are: cmp-lg
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The categories of this paper are: q-fin
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The categories of this paper are: eess
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The categories of this paper are: q-bio
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The categories of this paper are: math-ph