Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Electronic structure of vacancy-ordered iron-selenide
  K$_{0.5}$Fe$_{1.75}$Se$_2$   The electronic structure of the vacancy-ordered K$_{0.5}$Fe$_{1.75}$Se$_2$
iron-selenide compound (278 phase) is studied using the first-principles
density functional method. The ground state of the 278 phase is stripe-like
antiferromagnetic, and its bare electron susceptibility shows a large peak
around $(\pi, \pi)$ in the folded Brillouin zone. Near Fermi level, the density
of states are dominated by the Fe-3d orbitals, and both electron-like and
hole-like Fermi surfaces appear in the Brillouin zone. Unfolded band structure
shows limited similarities to a hole doped 122 phase. With 0.1e electron
doping, the susceptibility peak is quickly suppressed and broadened; while the
two-dimensionality of the electron-like Fermi surfaces are greatly enhanced,
resulting in a better nesting behavior. Our study should be relevant to the
recently reported superconducting phase K$_{0.5+x}$Fe$_{1.75+y}$Se$_2$ with
both $x$ and $y$ very tiny.

2
The categories of this paper are: math
17
The categories of this paper are: q-fin
31
The categories of this paper are: ao-sci
16
The categories of this paper are: stat
25
The categories of this paper are: patt-sol
8
The categories of this paper are: hep-ex
26
The categories of this paper are: bayes-an
30
The categories of this paper are: q-alg
5
The categories of this paper are: gr-qc
29
The categories of this paper are: funct-an
36
The categories of this paper are: cmp-lg
0
The categories of this paper are: hep-ph
32
The categories of this paper are: atom-ph
15
The categories of this paper are: nucl-ex
35
The categories of this paper are: mtrl-th
13
The categories of this paper are: quant-ph