Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Bipolar expansions and overlap corrections to the electrostatic
  interaction energy   We use the multipole technique to derive four equivalent expressions for the
bipolar expansion of the inverse distance, valid in all the regions of
configuration space. Using the first-order perturbation theory, we calculate
the overlap correction to the long-range electrostatic energy between two
hydrogen atoms and between a hydrogen atom and a proton.

9
The categories of this paper are: nlin
10
The categories of this paper are: q-bio
37
The categories of this paper are: supr-con
36
The categories of this paper are: cmp-lg
12
The categories of this paper are: nucl-th
32
The categories of this paper are: atom-ph
31
The categories of this paper are: ao-sci
3
The categories of this paper are: physics
27
The categories of this paper are: comp-gas
15
The categories of this paper are: nucl-ex
19
The categories of this paper are: eess
6
The categories of this paper are: astro-ph
23
The categories of this paper are: solv-int
24
The categories of this paper are: dg-ga
20
The categories of this paper are: acc-phys
25
The categories of this paper are: patt-sol