Instruct: Identify the main and secondary category of Arxiv papers based on the titles
Query: Flexoelectricity from density-functional perturbation theory
23
The categories of this paper are: solv-int
3
The categories of this paper are: physics
27
The categories of this paper are: comp-gas
19
The categories of this paper are: eess
22
The categories of this paper are: chao-dyn
1
The categories of this paper are: cs
2
The categories of this paper are: math
29
The categories of this paper are: funct-an
21
The categories of this paper are: adap-org
31
The categories of this paper are: ao-sci
13
The categories of this paper are: quant-ph
35
The categories of this paper are: mtrl-th
37
The categories of this paper are: supr-con
34
The categories of this paper are: chem-ph
0
The categories of this paper are: hep-ph
18
The categories of this paper are: econ