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QCMP005. HAM/3: Molecular Orbital Calculations by the
HAM/3 Method
by L. Åsbrink, C. Fridh and E. Lindholm,
Physics Department, The Royal Institute of
Technology, S-10044 Stockholm, Sweden
Converted by D. P. Chong, Department of
Chemistry, University of British Columbia,
Vancouver, B.C., Canada V6T 1Y6
The HAM/3 program constitutes a parameterized
approximate version of the HAM model. The
HAM model can be deduced1 from the Hartree-
Fock model if the idempotency of the density
matrix is exploited and the Slater-type
shielding constants are introduced. HAM and
Hartree-Fock are thus equivalent, although
not equal. The advantages of the new model
can easily be shown: 1) most of the
correlation energy can be incorporated into
the Slater shielding constants in a very
simple and direct way which is suitable for
parameterization from atomic spectroscopy and
2) the compensation of the self-repulsion
takes place with a term (-1), also in a
simple and direct way. The one-centre
parameters, which take care of all one-
centre-pair correlation energies, have been
determined from atomic spectroscopy. The
two-centre parameters have been determined
from photoelectron spectra, excitation
spectra and electron affinity of many
molecules.
HAM/3 calculates the following properties of
molecules: ionization energies, electron
affinities, excitation energies, and CI
between excited configurations. It gives
approximate results for the following
properties: ESCA energies (ls ionization
energies), heat of formation, dipole moment
and intensities of excitation processes. The
system can handle the following atoms: H, C,
N, O, F. As delivered by QCPE, it can handle
60 atoms and 122 orbitals.
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Reference:
1. L. Åsbrink, C. Fridh, E. Lindholm, S. de
Bruijn and D. P. Chong, submitted to Physica
Scripta for publication.
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FORTRAN 77 (Microsoft FORTRAN)
Lines of Code: 4100
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