Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Peierls Mechanism of the Metal-Insulator Transition in Ferromagnetic
  Hollandite K2Cr8O16   Synchrotron X-ray diffraction experiment shows that the metal-insulator
transition occurring in a ferromagnetic state of a hollandite
K$_2$Cr$_8$O$_{16}$ is accompanied by a structural distortion from the
tetragonal $I4/m$ to monoclinic $P112_{1}/a$ phase with a
$\sqrt{2}\times\sqrt{2}\times 1$ supercell. Detailed electronic structure
calculations demonstrate that the metal-insulator transition is caused by a
Peierls instability in the quasi-one-dimensional column structure made of four
coupled Cr-O chains running in the $c$-direction, leading to the formation of
tetramers of Cr ions below the transition temperature. This furnishes a rare
example of the Peierls transition of fully spin-polarized electron systems.

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The categories of this paper are: math
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The categories of this paper are: chem-ph
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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: cmp-lg
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The categories of this paper are: hep-lat
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The categories of this paper are: chao-dyn
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The categories of this paper are: quant-ph
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The categories of this paper are: gr-qc
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The categories of this paper are: astro-ph
12
The categories of this paper are: nucl-th
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The categories of this paper are: funct-an
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The categories of this paper are: atom-ph
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The categories of this paper are: patt-sol
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The categories of this paper are: hep-ph
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The categories of this paper are: bayes-an