Instruct: Identify the main and secondary category of Arxiv papers based on the titles
Query: A DFT+U study on the contribution of 4f electrons to oxygen vacancy
  formation and migration in Ln-doped CeO2
13
The categories of this paper are: quant-ph
11
The categories of this paper are: hep-lat
16
The categories of this paper are: stat
22
The categories of this paper are: chao-dyn
7
The categories of this paper are: hep-th
21
The categories of this paper are: adap-org
34
The categories of this paper are: chem-ph
25
The categories of this paper are: patt-sol
33
The categories of this paper are: plasm-ph
10
The categories of this paper are: q-bio
29
The categories of this paper are: funct-an
37
The categories of this paper are: supr-con
15
The categories of this paper are: nucl-ex
1
The categories of this paper are: cs
35
The categories of this paper are: mtrl-th
2
The categories of this paper are: math