Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Density-Functional Theory of the nonlinear optical susceptibility:
  application to cubic semiconductors   We present a general scheme for the computation of the time dependent (TD)
quadratic susceptibility ($\chi^{(2)}$) of an extended insulator obtained by
applying the `$2n+1$' theorem to the action functional as defined in TD density
functional theory. The resulting expression for $\chi^{(2)}$ includes
self-consistent local-field effects, and is a simple function of the linear
response of the system. We compute the static $\chi^{(2)}$ of nine III-V and
five II-VI semiconductors using the local density approximation(LDA) obtaining
good agreement with experiment. For GaP we also evaluate the TD $\chi^{(2)}$
for second harmonic generation using TD-LDA.

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The categories of this paper are: gr-qc
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The categories of this paper are: adap-org
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The categories of this paper are: eess
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The categories of this paper are: alg-geom
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The categories of this paper are: hep-ex
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The categories of this paper are: nlin
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The categories of this paper are: nucl-ex
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The categories of this paper are: hep-ph
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The categories of this paper are: q-bio
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The categories of this paper are: ao-sci
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The categories of this paper are: cs
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The categories of this paper are: physics
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The categories of this paper are: dg-ga
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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: quant-ph