Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Density functional study of the electronic and vibrational properties of
  TiOCl   We present the phonon spectrum of TiOCl computed using hybrid density
functional theory (DFT). A complete analysis of the spectrum is performed for
the space group Pmmn (high symmetry phase) and the space group P2_1/m (low
symmetry phase), which is the symmetry of the spin-Peierls phase. We show that
the nonlocal correlations present in the hybrid DFT approach are important for
understanding the electron-lattice interactions in TiOCl. The computed
frequencies compare well with those observed in Raman and infrared spectroscopy
experiments and we identify the origin of an anomalous phonon observed in Raman
spectroscopy. The relationship between relevant zone boundary phonons in the
high symmetry phase and the zone center counterparts in the P2_1/m symmetry
allow us to speculate about the origin of the spin-Peierls phonon.

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The categories of this paper are: gr-qc
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The categories of this paper are: mtrl-th
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The categories of this paper are: patt-sol
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The categories of this paper are: acc-phys
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The categories of this paper are: stat
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The categories of this paper are: astro-ph
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The categories of this paper are: math-ph
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The categories of this paper are: q-bio
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The categories of this paper are: q-alg
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The categories of this paper are: ao-sci
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The categories of this paper are: physics
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The categories of this paper are: atom-ph
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The categories of this paper are: hep-ex
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The categories of this paper are: nucl-th
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The categories of this paper are: alg-geom
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The categories of this paper are: quant-ph