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On invariant procedures in approximate SCF MO theories
Author(s) -
Jug Karl
Publication year - 2009
Publication title -
international journal of quantum chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.484
H-Index - 105
eISSN - 1097-461X
pISSN - 0020-7608
DOI - 10.1002/qua.560030727
Subject(s) - cndo/2 , invariant (physics) , unitary state , atomic orbital , dipole , basis set , computational chemistry , atomic units , physics , basis (linear algebra) , chemistry , quantum mechanics , atomic physics , mathematics , density functional theory , molecule , geometry , electron , political science , law
The CNDO and subsequent methods by Pople are analyzed with regard to a possible refinement. It is emphasized that the invariance requirements for atomic integrals under local rotations and local hybridization are not essential for the theory, but that the SCF equations have to be invariant under unitary transformations of the atomic basis set. The removal of this restriction yields the possibility of introducing different scale factors for the various 2 s‐ and 2 p ‐orbitals at the same center. For aromatic systems it is predicted that little improvement will result for ground state properties which are average values of the σ‐ and π‐part, e.g. total dipole moments. The neccessity of the application of the more recent scale factors for calculations on spectra is pointed out.