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Generalized open shell SCF theory
Author(s) -
Caballol Rosa,
Gallifa Ramóan,
Riera Josep M.,
Carbóa Ramóan
Publication year - 1974
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.560080306
Subject(s) - open shell , formalism (music) , excited state , cndo/2 , singlet state , hamiltonian (control theory) , quantum mechanics , physics , operator (biology) , computational chemistry , theoretical physics , chemistry , mathematics , molecule , art , musical , mathematical optimization , visual arts , biochemistry , repressor , transcription factor , gene
A generalized form of the coupling operator technique in SCF theory has been developed. In the formalism presented here, the monoconfigurational problem may be treated as a particular case of the multiconfigurational framework. The matrix form of the operators has been analyzed; in the LCAO context a structure has been found which is very adequate for computational purposes. Some examples are also presented which show the usefulness of the theory, emphasising the CNDO and INDO approximations. Within the application of the method to ab initio calculations, some He and second row atoms states have been studied. The He first excited singlet is also studied, the result of the analysis of such a problem being that the nonorthogonality between the singlet functions of the fundamental and of the first excited states play a primordial role in the efficiency of the method. In no case have the calculation problems, appearing in the application of the theory, been of a more difficult nature than those normally found in the application of the formalism for closed shells.