Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Hybrid density functional study of electronic and optical properties of
  phase change memory material: $\mathrm{Ge_{2}Sb_{2}Te_{5}}$   In this article, we use hybrid density functional (HSE06) to study the
crystal and electronic structures and optical properties of well known phase
change memory material $\mathrm{Ge_{2}Sb_{2}Te_{5}}$. We calculate the
structural parameters, band gaps and dielectric functions of three stable
structures of this material. We also analyze the electron charge distribution
using the Bader's theory of charge analysis. We find that hybrid density
functional slightly overestimate the value of 'C' parameter. However, overall,
our results calculated with the use of hybrid density functional (HSE06) are
very close to available experimental values than calculated with the use of PBE
functional. Specifically, the electronic band gap values of this material
calculated with HSE06 are in good agreement with the available experimental
data in the literature. Furthermore, we perform the charge analysis and find
that naive ionic model fails to explain the charge distribution between the
constituent atoms, showing the complex nature of this compound.

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The categories of this paper are: eess
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The categories of this paper are: math-ph
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The categories of this paper are: funct-an
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The categories of this paper are: dg-ga
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The categories of this paper are: solv-int
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The categories of this paper are: gr-qc
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The categories of this paper are: quant-ph
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The categories of this paper are: nlin
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The categories of this paper are: q-bio
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The categories of this paper are: astro-ph
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The categories of this paper are: chao-dyn
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The categories of this paper are: patt-sol
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The categories of this paper are: hep-ex
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The categories of this paper are: stat
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The categories of this paper are: acc-phys
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The categories of this paper are: supr-con