|
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). |