Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: The Finite Temperature Structure of the MAPbI3 Perovskite: Comparing
  Density Functional Approximations and Force Fields to Experiment   Determining the finite temperature structure of the hybrid perovskite MAPbI3
is a challenge for both experimental and theoretical methods. A very powerful
computational method that can resolve the atomic structure is molecular
dynamics (MD). The resulting structure depends on the density functional
approximation (DFA) in the case of ab initio MD and the force field in
classical MD. We compare the structure between 250K and 400K obtained with
different DFAs and force fields in one consistent manner. The symmetry of the
PbI3 framework is analyzed as well as the relative ordering of the neighboring
organic molecules inside the framework. The distribution function of the
molecules is used to map out an effective energy surface for the rotation of a
single molecule. This surface is accurately modeled by a pair of cubic
harmonics. Available experimental data in literature are discussed and compared
to the structure obtained with the different methods. The spread in these data
is still too large to uniquely determine the method that 'best' describes the
perovskite, however promising candidates and outliers have been identified.

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The categories of this paper are: physics
26
The categories of this paper are: bayes-an
28
The categories of this paper are: alg-geom
36
The categories of this paper are: cmp-lg
21
The categories of this paper are: adap-org
24
The categories of this paper are: dg-ga
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The categories of this paper are: hep-ph
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The categories of this paper are: quant-ph
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The categories of this paper are: astro-ph
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The categories of this paper are: nucl-ex
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The categories of this paper are: hep-lat
30
The categories of this paper are: q-alg
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The categories of this paper are: patt-sol
31
The categories of this paper are: ao-sci
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The categories of this paper are: nlin
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The categories of this paper are: chao-dyn