|
393. 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
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-
center parameters, which take care of all one-center-
pair correlation energies, have been determined from
atomic spectroscopy. The two-center 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.
_________
Reference:
1. L. Åsbrink, C. Fridh, E. Lindholm, S. de Bruijn
and D. P. Chong, submitted to Physica Scripta for
publication.
_________
FORTRAN IV
Lines of Code: 4100
Recommended Citation: L. Åsbrink et al., QCPE 13, 393
(1981).
|
