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Manuscript Title: HPAM: Hirshfeld Partitioned Atomic Multipoles
Authors: Dennis M. Elking, Lalith Perera, Lee G. Pedersen
Program title: HPAM
Catalogue identifier: AEKP_v1_0
Distribution format: tar.gz
Journal reference: Comput. Phys. Commun. 183(2012)390
Programming language: C.
Computer: Any.
Operating system: Linux.
RAM: Typically, a few hundred megabytes.
Keywords: Atomic multipoles, Hirshfeld charges, dipole, quadrupole.
Classification: 16.13.

External routines: The program requires 'formatted checkpoint' files obtained from the Gaussian 03 or Gaussian 09 quantum chemistry program.

Nature of problem:
An ab initio molecular charge density ρmol(r) is partitioned into Hirshfeld (HD) and Hirshfeld-Iterated (HD-I) atomic charge densities ρa(r) on a grid. Atomic charges qa and multipoles Qlma are calculated from the partitioned atomic charge densities ρa(r) by numerical integration.

Solution method:
Molecular and isolated atomic grids are generated for the molecule of interest. The ab initio density matrix Pμν and basis functions χμ(r) are read in from 'formatted checkpoint' files obtained from the Gaussian 03 or 09 quantum chemistry programs. The ab initio density is evaluated for the molecule and the isolated atoms/atomic ions on grids and used to construct Hirshfeld (HD) and Hirshfeld-I (HD-I) partitioned atomic charges densities ρa(r), which are used to calculate atomic charges qa and atomic multipoles Qlma by integration.

The ab initio density matrix can be calculated at the HF, DFT, MP2, or CCSD levels with ab initio Gaussian basis sets that include up to s, p, d, f, g functions for either closed shell or open shell molecules.

Running time:
The running time varies with the size of the molecule, the size of the ab initio basis set, and the coarseness of the desired grid. The run time can range from a minute or less for water to ~15 minutes for neopentane.