Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: An efficient basis set representation for calculating electrons in
  molecules   The method of McCurdy, Baertschy, and Rescigno, J. Phys. B, 37, R137 (2004)
is generalized to obtain a straightforward, surprisingly accurate, and scalable
numerical representation for calculating the electronic wave functions of
molecules. It uses a basis set of product sinc functions arrayed on a Cartesian
grid, and yields 1 kcal/mol precision for valence transition energies with a
grid resolution of approximately 0.1 bohr. The Coulomb matrix elements are
replaced with matrix elements obtained from the kinetic energy operator. A
resolution-of-the-identity approximation renders the primitive one- and
two-electron matrix elements diagonal; in other words, the Coulomb operator is
local with respect to the grid indices. The calculation of contracted
two-electron matrix elements among orbitals requires only O(N log(N))
multiplication operations, not O(N^4), where N is the number of basis
functions; N = n^3 on cubic grids. The representation not only is numerically
expedient, but also produces energies and properties superior to those
calculated variationally. Absolute energies, absorption cross sections,
transition energies, and ionization potentials are reported for one- (He^+,
H_2^+ ), two- (H_2, He), ten- (CH_4) and 56-electron (C_8H_8) systems.

22
The categories of this paper are: chao-dyn
9
The categories of this paper are: nlin
4
The categories of this paper are: cond-mat
12
The categories of this paper are: nucl-th
6
The categories of this paper are: astro-ph
29
The categories of this paper are: funct-an
34
The categories of this paper are: chem-ph
36
The categories of this paper are: cmp-lg
27
The categories of this paper are: comp-gas
15
The categories of this paper are: nucl-ex
24
The categories of this paper are: dg-ga
10
The categories of this paper are: q-bio
7
The categories of this paper are: hep-th
32
The categories of this paper are: atom-ph
31
The categories of this paper are: ao-sci
1
The categories of this paper are: cs