Instruct: Identify the main and secondary category of Arxiv papers based on the titles
Query: First-principles modeling of the interactions of iron impurities with
  graphene and graphite
17
The categories of this paper are: q-fin
15
The categories of this paper are: nucl-ex
9
The categories of this paper are: nlin
25
The categories of this paper are: patt-sol
8
The categories of this paper are: hep-ex
29
The categories of this paper are: funct-an
30
The categories of this paper are: q-alg
27
The categories of this paper are: comp-gas
11
The categories of this paper are: hep-lat
24
The categories of this paper are: dg-ga
5
The categories of this paper are: gr-qc
36
The categories of this paper are: cmp-lg
1
The categories of this paper are: cs
18
The categories of this paper are: econ
28
The categories of this paper are: alg-geom
2
The categories of this paper are: math