Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Effect of high pressure on multiferroic BiFeO3   We report experimental evidence for pressure instabilities in the model
multiferroic BiFeO3 and namely reveal two structural phase transitions around 3
GPa and 10 GPa by using diffraction and far-infrared spectroscopy at a
synchrotron source. The intermediate phase from 3 to 9 GPa crystallizes in a
monoclinic space group, with octahedra tilts and small cation displacements.
When the pressure is further increased the cation displacements (and thus the
polar character) of BiFeO3 is suppressed above 10 GPa. The above 10 GPa
observed non-polar orthorhombic Pnma structure is in agreement with recent
theoretical ab-initio prediction, while the intermediate monoclinic phase was
not predicted theoretically.

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The categories of this paper are: math
11
The categories of this paper are: hep-lat
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The categories of this paper are: gr-qc
14
The categories of this paper are: math-ph
18
The categories of this paper are: econ
35
The categories of this paper are: mtrl-th
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The categories of this paper are: hep-ex
22
The categories of this paper are: chao-dyn
10
The categories of this paper are: q-bio
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The categories of this paper are: eess
31
The categories of this paper are: ao-sci
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The categories of this paper are: adap-org
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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: comp-gas
32
The categories of this paper are: atom-ph