Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Crystal structure evolution in the van der Waals transition metal
  trihalides   Most transition-metal trihalides are dimorphic. The representative
chromium-based triad, CrCl3, CrBr3, CrI3, is characterized by the
low-temperature phase adopting the trigonal BiI3 type while the structure of
the high-temperature phase is monoclinic of AlCl3 type (C2/m). The structural
transition between the two crystallographic phases is of the first-order type
with large thermal hysteresis in CrCl3 and CrI3. We studied crystal structures
and structural phase transitions of vanadium-based counterparts VCl3, VBr3, and
VI3 by measuring specific heat, magnetization, and X-ray diffraction as
functions of temperature and observed an inverse situation. In these cases, the
high-temperature phase has a higher symmetry while the low-temperature
structure reveals a lower symmetry. The structural phase transition between
them shows no measurable hysteresis in contrast to CrX3. Possible relations of
the evolution of the ratio c/a of the unit cell parameters, types of crystal
structures, and nature of the structural transitions in V and Cr trihalides are
discussed.

28
The categories of this paper are: alg-geom
31
The categories of this paper are: ao-sci
0
The categories of this paper are: hep-ph
13
The categories of this paper are: quant-ph
2
The categories of this paper are: math
12
The categories of this paper are: nucl-th
15
The categories of this paper are: nucl-ex
30
The categories of this paper are: q-alg
25
The categories of this paper are: patt-sol
19
The categories of this paper are: eess
7
The categories of this paper are: hep-th
5
The categories of this paper are: gr-qc
20
The categories of this paper are: acc-phys
23
The categories of this paper are: solv-int
8
The categories of this paper are: hep-ex
26
The categories of this paper are: bayes-an