Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: A DFT Investigation of the Electronic and Optical Properties of
  Pentadiamond   Recently, a new carbon 3D carbon allotrope named pentadiamond was proposed.
Pentadiamond is composed of carbon atoms in mixed sp$^2$ and sp$^3$-like
hybridization. In this work, we have carried out a detailed investigation of
the electronic and optical properties of pentadiamond structure using
first-principles (DFT) methods. Our results show that pentadiamond has an
indirect bandgap semiconductor of $2.50$ eV with GGA-PBE and $3.31$ eV with
HSE06. Its static dielectric constant is $4.70$ and the static refractive index
is $2.16$. Pentadiamond presents low reflectivity, almost 40$\%$, for
all-optical spectrum, making it a good structure to be used as a UV collector.
Also, pentadiamond exhibits optical activity in the UV range where other carbon
allotropes, such as diamond and 8-tetra(2,2) tubulane show no activity.

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The categories of this paper are: q-alg
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The categories of this paper are: funct-an
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The categories of this paper are: alg-geom
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The categories of this paper are: econ
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The categories of this paper are: cmp-lg
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The categories of this paper are: adap-org
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The categories of this paper are: mtrl-th
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The categories of this paper are: nlin
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The categories of this paper are: dg-ga
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The categories of this paper are: acc-phys
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The categories of this paper are: math
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The categories of this paper are: chao-dyn
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The categories of this paper are: solv-int
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The categories of this paper are: bayes-an
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The categories of this paper are: comp-gas
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The categories of this paper are: ao-sci