Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: The two-fold superstructure of titanium(III)-oxybromide at T = 17.5 K   The low-temperature (T = 17.5 K) structure of titanium(III)-oxybromide,
TiOBr, is reported as a two-fold superstructure of the crystal structure at
room temperature. Weak superlattice reflections could be measured with
synchrotron radiation x-rays, and they were analysed by structure refinements
employing superspace techniques. Both the low temperature and room temperature
tructures of TiOBr are isostructural to the corresponding structures of TiOCl.
The results indicate that at low temperatures TiOBr is in a spin-Peierls state
similar to TiOCl, but with the modulations and relevant interactions smaller
than in the latter compound.

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The categories of this paper are: acc-phys
5
The categories of this paper are: gr-qc
1
The categories of this paper are: cs
30
The categories of this paper are: q-alg
22
The categories of this paper are: chao-dyn
8
The categories of this paper are: hep-ex
28
The categories of this paper are: alg-geom
3
The categories of this paper are: physics
36
The categories of this paper are: cmp-lg
15
The categories of this paper are: nucl-ex
10
The categories of this paper are: q-bio
2
The categories of this paper are: math
11
The categories of this paper are: hep-lat
35
The categories of this paper are: mtrl-th
13
The categories of this paper are: quant-ph
6
The categories of this paper are: astro-ph