Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Icosahedra boron chain and sheets: new boron allotropic structures   The icosahedra boron chain and three icosahedra sheets (with {\alpha},
{\delta}4, and {\delta}6 symmetries), constructed by the icosahedra B12, have
been obtained as new members of boron family using a highly efficient molecular
dynamics scheme based on a transferable and reliable semi-empirical
Hamiltonian. The icosahedral B12 in the icosahedra chain is slightly elongated
along the china direction and directly bonded each other with the two-center
covalent bonds. A deformation of the icosahedra B12 was also found in the
two-dimensional icosahedra sheets. In addition to the three-center bonding
nature inside the icosahedra B12, there are two types of directional
inter-icosahedra bonds in the icosahedra sheet structures, one is the single
strong covalent bond, and the other is a pair of the weak covalent {\delta}
bonds. In contrast to the boron monolayer, there is no buckling found in these
icosahedra sheets. The deformation of the icosahedra B12 and the special
bonding nature in these new icosahedra structures induce the energy band gap of
0.74 eV in the icosahedra chain, 0.52 eV in the icosahedra {\delta}6 sheet,
0.39 eV in the icosahedra {\delta}4 sheet, and the gapless in the icosahedra
{\alpha} sheet, respectively. The energy barrier per atom from the icosahedra
{\delta}6 sheet to the icosahedra {\alpha} sheet is estimated to be 0.17 eV
while it is estimated as 0.38 eV from the icosahedra {\delta}6 sheet to the
icosahedra {\delta}4 sheet and 0.27 eV from the icosahedra {\alpha} sheet to
the icosahedra {\delta}4 sheet, respectively. Such high energy barriers
indicate that these icosahedra sheets are relatively stable.

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The categories of this paper are: alg-geom
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The categories of this paper are: q-fin
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The categories of this paper are: q-alg
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The categories of this paper are: nlin
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The categories of this paper are: nucl-th
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The categories of this paper are: physics
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The categories of this paper are: hep-ph
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The categories of this paper are: gr-qc
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The categories of this paper are: eess
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The categories of this paper are: acc-phys
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The categories of this paper are: astro-ph
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The categories of this paper are: math
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The categories of this paper are: atom-ph
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The categories of this paper are: math-ph
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The categories of this paper are: ao-sci
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The categories of this paper are: hep-lat