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The Semiempirical LCAO‐MO Method of Energy Spectrum and Electronic Structure Calculation for Open‐Shell Clusters
Author(s) -
Shashkin S. Yu.,
Nikiforov A. E.,
Cherepanov V. I.
Publication year - 1980
Publication title -
physica status solidi (b)
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.51
H-Index - 109
eISSN - 1521-3951
pISSN - 0370-1972
DOI - 10.1002/pssb.2220970205
Subject(s) - open shell , hamiltonian (control theory) , linear combination of atomic orbitals , coupling constant , computation , atomic orbital , cluster (spacecraft) , spectral line , physics , coupled cluster , diagonalizable matrix , unpaired electron , atomic physics , electron , quantum mechanics , eigenvalues and eigenvectors , mathematics , molecule , computer science , algorithm , mathematical optimization , symmetric matrix , programming language
A semiempirical method is proposed of open‐shell cluster calculation which is based upon Roothaan's rigorous theory and does not contain any variable parameters. It is shown that approximations used for Hamiltonian matrix elements in previous semiempirical calculations must be made more accurate. An estimation technique for Roothaan's coupling operator matrices is developed. Optical transition energies are calculated by a many‐electron way in the “frozen orbital” approximation with configuration interaction taking into account. Numerical computations are made for [NiF 6 ] 4− and [TiF 6 ] 3− complexes. Comparison of cluster spectra and also of the spin—orbit coupling constant λ cr , unpaired spin densities ƒ s , ƒ σ , and neutron scattering form factor for [NiF 6 ] 4− with the experimental data proves the applicability of the method proposed.