Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Determination of the exchange interaction energy from the polarization
  expansion of the wave function   The exchange contribution to the energy of the hydrogen atom interacting with
a proton is calculated from the polarization expansion of the wave function
using the conventional surface-integral formula and two formulas involving
volume integrals: the formula of the symmetry-adapted perturbation theory
(SAPT) and the variational formula recommended by us. At large internuclear
distances $R$, all three formulas yield the correct expression $-(2/e)Re^{-R}$,
but approximate it with very different convergence rates. In the case of the
SAPT formula, the convergence is geometric with the error falling as $3^{-K}$,
where $K$ is the order of the applied polarization expansion. The error of the
surface-integral formula decreases exponentially as $a^K/(K+1)!$, where $a=\ln2
-\tfrac{1}{2}$. The variational formula performs best, its error decays as
$K^{1/2} [a^{ K}/(K+1)!]^2$. These convergence rates are much faster than those
resulting from approximating the wave function through the multipole expansion.
This shows the efficiency of the partial resummation of the multipole series
effected by the polarization expansion. Our results demonstrate also the
benefits of incorporating the variational principle into the perturbation
theory of molecular interactions.

2
The categories of this paper are: math
19
The categories of this paper are: eess
20
The categories of this paper are: acc-phys
10
The categories of this paper are: q-bio
12
The categories of this paper are: nucl-th
37
The categories of this paper are: supr-con
5
The categories of this paper are: gr-qc
33
The categories of this paper are: plasm-ph
23
The categories of this paper are: solv-int
4
The categories of this paper are: cond-mat
35
The categories of this paper are: mtrl-th
16
The categories of this paper are: stat
32
The categories of this paper are: atom-ph
1
The categories of this paper are: cs
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The categories of this paper are: hep-ex
6
The categories of this paper are: astro-ph