Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Phase Coexistence in Cs3Bi2I9 Ferroelastics: Optical, Dilatation and
  Ultrasonic Velocity Studies   The results for dilatometric, ultrasonic velocity and the domain struct-ure
studies of Cs3Bi2I9 crystals in the course of ferroelastic phase trans-ition
are presented. It is shown that the phase transition in Cs3Bi2I9 is of the
first order. Basing on the thermal expansion results and the data obtained for
the elastic stiffness of Cs3Bi2I9 crystals, the latent heat Q=79J/kg at Tc is
calculated. The region between 183K and 221K (at cooling) is identified as a
heterostructure region, where ferroelastic and paraelastic phases coexist.

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The categories of this paper are: q-fin
30
The categories of this paper are: q-alg
2
The categories of this paper are: math
21
The categories of this paper are: adap-org
28
The categories of this paper are: alg-geom
20
The categories of this paper are: acc-phys
11
The categories of this paper are: hep-lat
26
The categories of this paper are: bayes-an
12
The categories of this paper are: nucl-th
6
The categories of this paper are: astro-ph
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The categories of this paper are: nlin
3
The categories of this paper are: physics
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The categories of this paper are: math-ph
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The categories of this paper are: stat
7
The categories of this paper are: hep-th
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The categories of this paper are: solv-int