Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: The Density Matrix Renormalization Group Studies of Metal-Halogen Chains
  within a Two-Band Extended Peierls-Hubbard Model   The phase diagram of halogen-bridged mixed-valent metal complexes ($MX$) has
been studied using a two-band extended Peierls-Hubbard model employing the
recently developed Density Matrix Renormalization Group method. We present the
energies, charge and spin density distributions, bond orders, charge-charge and
spin-spin correlations, in the ground state for different parameters of the
model. The effect of bond alternation and site-diagonal distortion on the
ground state properties are considered in detail. We observe that the
site-diagonal distortion plays a significant role in deciding the nature of the
ground state of the system. We find that while the $CDW$ and $BOW$ phases can
coexist, the $CDW$ and $SDW$ phases are exclusive in most of the cases. We have
also studied the doped $MX$ chains both with and without bond alternation and
site-diagonal distortion in the $CDW$ as well as $SDW$ regimes. We find that
the additional charge in the polarons and bipolarons for hole doping are
confined to a few sites, in the presence of bond alternation and site-diagonal
distortion. For electron doping, we find that the additional charge(s) is(are)
smeared over the entire chain length and although energetics imply a
disproportionation of the negatively charged bipolaron, the charge and spin
density distributions do not reflect it. Positively charged bipolaron
disproportionates into two polarons in the $SDW$ region. There is also bond
order evidence for compression of bond length for the positively charged
polaronic and bipolaronic systems and an elongation of the bonds for systems
with negatively charged polarons and bipolarons.

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The categories of this paper are: adap-org
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The categories of this paper are: nlin
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The categories of this paper are: funct-an
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The categories of this paper are: patt-sol
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The categories of this paper are: math-ph
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The categories of this paper are: hep-ex
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The categories of this paper are: nucl-ex
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The categories of this paper are: bayes-an
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The categories of this paper are: econ
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The categories of this paper are: math
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The categories of this paper are: astro-ph
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The categories of this paper are: solv-int
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The categories of this paper are: quant-ph
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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: comp-gas