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A new procedure to optimize core orbitals in the spin‐coupled wave function
Author(s) -
Sironi M.
Publication year - 1999
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/(sici)1097-461x(1999)74:2<145::aid-qua11>3.0.co;2-c
Subject(s) - atomic orbital , core electron , valence bond theory , wave function , core charge , modern valence bond theory , electron , core (optical fiber) , valence (chemistry) , valence electron , generalized valence bond , spin (aerodynamics) , molecular orbital theory , minification , chemistry , physics , atomic physics , quantum mechanics , computer science , thermodynamics , optics , programming language
The spin‐coupled theory developed by Joseph Gerratt is the modern version of the valence‐bond theory. It has been applied to study a large variety of systems, characterized by very different chemical situations. The important results obtained so far encourage its application to large systems. For this purpose, the spin‐coupled method has been used to correlate some valence electrons in a field generated by the frozen‐core electrons. To overcome this approximation, algorithms to relax the core orbitals have been proposed. In this work, a new procedure to optimize core orbitals in the spin‐coupled wave function is presented, based on a two‐step minimization scheme where the core orbitals are optimized with a first‐order procedure. The correct convergence of the algorithm has been checked by comparison with second‐order algorithms. The success of this new minimization procedure points to its application to systems possessing a large number of core electrons. ©1999 John Wiley & Sons, Inc. Int J Quant Chem 74: 145–151, 1999