Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Nonlinear optical properties of TeO$_2$ crystalline phases from first
  principles   We have computed second and third nonlinear optical susceptibilities of two
crystalline bulk tellurium oxide polymorphs: $\alpha$-TeO$_{2}$ (the most
stable crystalline bulk phase) and $\gamma$-TeO$_{2}$ (the crystalline phase
that ressembles the more to the glass phase. Third order nonlinear
susceptibilities of the crystalline phases are two orders of magnitude larger
than $\alpha$-SiO$_{2}$ cristoballite, thus extending the experimental
observations on glasses to the case of crystalline compounds. While the
electronic lone pairs of Te contribute to those large values, a full
explanation of the anisotropy of the third order susceptibility tensor requires
a detailed analysis of the structure, in particular the presence of helical
chains, that seems to be linked to cooperative non-local polarizabilty effects.
Our results demonstrate that first-principles simulations are a powerful
predictive tool to estimate nonlinear optical susceptibilitites of materials.

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The categories of this paper are: eess
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The categories of this paper are: plasm-ph
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The categories of this paper are: stat
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The categories of this paper are: physics
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The categories of this paper are: comp-gas
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The categories of this paper are: hep-lat
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The categories of this paper are: nucl-ex
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The categories of this paper are: gr-qc
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The categories of this paper are: econ
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The categories of this paper are: chao-dyn
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The categories of this paper are: hep-th
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The categories of this paper are: math-ph
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The categories of this paper are: alg-geom
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The categories of this paper are: ao-sci
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The categories of this paper are: mtrl-th
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The categories of this paper are: hep-ex