Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Learning on-top: regressing the on-top pair density for real-space
  visualization of electron correlation   The on-top pair density [$\Pi(\mathrm{\mathbf{r}})$] is a local
quantum-chemical property that reflects the probability of two electrons of any
spin to occupy the same position in space. Being the simplest quantity related
to the two-particle density matrix, the on-top pair density is a powerful
indicator of electron correlation effects, and as such, it has been extensively
used to combine density functional theory and multireference wavefunction
theory. The widespread application of $\Pi(\mathrm{\mathbf{r}})$ is currently
hindered by the need for post-Hartree--Fock or multireference computations for
its accurate evaluation. In this work, we propose the construction of a machine
learning model capable of predicting the CASSCF-quality on-top pair density of
a molecule only from its structure and composition. Our model, trained on the
GDB11-AD-3165 database, is able to predict with minimal error the on-top pair
density of organic molecules, bypassing completely the need for $\textit{ab
initio}$ computations. The accuracy of the regression is demonstrated using the
on-top ratio as a visual metric of electron correlation effects and
bond-breaking in real-space. In addition, we report the construction of a
specialized basis set, built to fit the on-top pair density in a single
atom-centered expansion. This basis, cornerstone of the regression, could be
potentially used also in the same spirit of the resolution-of-the-identity
approximation for the electron density.

18
The categories of this paper are: econ
4
The categories of this paper are: cond-mat
30
The categories of this paper are: q-alg
16
The categories of this paper are: stat
25
The categories of this paper are: patt-sol
20
The categories of this paper are: acc-phys
14
The categories of this paper are: math-ph
28
The categories of this paper are: alg-geom
9
The categories of this paper are: nlin
5
The categories of this paper are: gr-qc
34
The categories of this paper are: chem-ph
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The categories of this paper are: solv-int
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The categories of this paper are: funct-an
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The categories of this paper are: supr-con
12
The categories of this paper are: nucl-th
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The categories of this paper are: eess