HPAM: Hirshfeld partitioned atomic multipoles

An implementation of the Hirshfeld (HD) and Hirshfeld-Iterated (HD-I) atomic charge density partitioning schemes is described. Atomic charges and atomic multipoles are calculated from the HD and HD-I atomic charge densities for arbitrary atomic multipole rank lmaxlmax on molecules of arbitrary shape and size. The HD and HD-I atomic charges/multipoles are tested by comparing molecular multipole moments and the electrostatic potential (ESP) surrounding a molecule with their reference ab initio values. In general, the HD-I atomic charges/multipoles are found to better reproduce ab initio electrostatic properties over HD atomic charges/multipoles. A systematic increase in precision for reproducing ab initio   electrostatic properties is demonstrated by increasing the atomic multipole rank from lmax=0lmax=0 (atomic charges) to lmax=4lmax=4 (atomic hexadecapoles). Both HD and HD-I atomic multipoles up to rank lmaxlmax are shown to exactly reproduce ab initio molecular multipole moments of rank L   for L⩽lmaxL⩽lmax. In addition, molecular dipole moments calculated by HD, HD-I, and ChelpG atomic charges only   (lmax=0lmax=0) are compared with reference ab initio values. Significant errors in reproducing ab initio molecular dipole moments are found if only HD or HD-I atomic charges used.Program summaryProgram title: HPAMCatalogue identifier: AEKP_v1_0Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AEKP_v1_0.htmlProgram obtainable from: CPC Program Library, Queenʼs University, Belfast, N. IrelandLicensing provisions: GNU General Public License v2No. of lines in distributed program, including test data, etc.: 500 809No. of bytes in distributed program, including test data, etc.: 13 424 494Distribution format: tar.gzProgramming language: CComputer: AnyOperating system: LinuxRAM: Typically, a few hundred megabytesClassification: 16.13External 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)ρmol(r) is partitioned into Hirshfeld (HD) and Hirshfeld-Iterated (HD-I) atomic charge densities ρa(r)ρa(r) on a grid. Atomic charges qaqa and multipoles Qlma are calculated from the partitioned atomic charge densities ρa(r)ρa(r) by numerical integration.Solution method: Molecular and isolated atomic grids are generated for the molecule of interest. The ab initio   density matrix PμνPμν and basis functions χμ(r)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)ρa(r), which are used to calculate atomic charges qaqa and atomic multipoles Qlma by integration.Restrictions: 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.