Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Bromination of Graphene and Graphite   We present a density functional theory study of low density bromination of
graphene and graphite, finding significantly different behaviour in these two
materials. On graphene we find a new Br2 form where the molecule sits
perpendicular to the graphene sheet with an extremely strong molecular dipole.
The resultant Br+-Br- has an empty pz-orbital located in the graphene
electronic pi-cloud. Bromination opens a small (86meV) band gap and strongly
dopes the graphene. In contrast, in graphite we find Br2 is most stable
parallel to the carbon layers with a slightly weaker associated charge transfer
and no molecular dipole. We identify a minimum stable Br2 concentration in
graphite, finding low density bromination to be endothermic. Graphene may be a
useful substrate for stabilising normally unstable transient molecular states.

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The categories of this paper are: hep-ex
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The categories of this paper are: cmp-lg
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The categories of this paper are: comp-gas
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The categories of this paper are: mtrl-th
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The categories of this paper are: q-bio
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The categories of this paper are: dg-ga
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The categories of this paper are: gr-qc
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The categories of this paper are: hep-th
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The categories of this paper are: adap-org
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The categories of this paper are: stat
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The categories of this paper are: ao-sci
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The categories of this paper are: acc-phys
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The categories of this paper are: quant-ph
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The categories of this paper are: econ
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The categories of this paper are: math-ph
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The categories of this paper are: nucl-th