Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Synthesis, crystal structure, and properties of novel perovskite
  oxychalcogenides, Ca2CuFeO3Ch (Ch = S, Se)   Two new perovskite oxychalcogenides, Ca2CuFeO3S and Ca2CuFeO3Se, have been
synthesized in evacuated quartz tubes. They crystallize in P4/nmm space group
with lattice parameters a = 3.8271(1), c = 14.9485(2) {\AA} and a = 3.8605(1),
c = 15.3030(2) {\AA} for Ca2CuFeO3S and Ca2CuFeO3Se, respectively. They appear
to be the first layered chalcogenide perovskites involving calcium and are
structural analogs of the corresponding Sr and Ba compounds. The new compounds
exhibit semiconducting properties with energy gap decreasing from the
oxysulfide to the oxyselenide. Possibility of introducing Ca2+ into structures
of known layered oxychalcogenides and oxypnictides is discussed.

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The categories of this paper are: nucl-ex
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The categories of this paper are: stat
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The categories of this paper are: chao-dyn
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The categories of this paper are: alg-geom
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The categories of this paper are: nlin
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The categories of this paper are: solv-int
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The categories of this paper are: hep-th
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The categories of this paper are: q-bio
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The categories of this paper are: acc-phys
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The categories of this paper are: dg-ga
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The categories of this paper are: atom-ph
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The categories of this paper are: mtrl-th
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The categories of this paper are: bayes-an
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The categories of this paper are: gr-qc
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The categories of this paper are: patt-sol
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The categories of this paper are: adap-org