Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Pressure-Induced Effects on the Structure of the FeSe Superconductor   A polycrystalline sample of FeSe, which adopts the tetragonal PbO-type
structure (P4/nmm) at room temperature, has been prepared using solid state
reaction. We have investigated pressure-induced structural changes in
tetragonal FeSe at varying hydrostatic pressures up to 0.6 GPa in the
orthorhombic (T = 50 K) and tetragonal (T = 190 K) phases using high resolution
neutron powder diffraction. We report that the structure is quite compressible
with a Bulk modulus around 31 GPa to 33 GPa and that the pressure response is
anisotropic with a larger compressibility along the c-axis. Key bond angles of
the SeFe4 pyramids and FeSe4 tetrahedra are also determined as a function of
pressure.

37
The categories of this paper are: supr-con
20
The categories of this paper are: acc-phys
22
The categories of this paper are: chao-dyn
36
The categories of this paper are: cmp-lg
29
The categories of this paper are: funct-an
2
The categories of this paper are: math
34
The categories of this paper are: chem-ph
0
The categories of this paper are: hep-ph
15
The categories of this paper are: nucl-ex
30
The categories of this paper are: q-alg
19
The categories of this paper are: eess
35
The categories of this paper are: mtrl-th
3
The categories of this paper are: physics
5
The categories of this paper are: gr-qc
13
The categories of this paper are: quant-ph
12
The categories of this paper are: nucl-th