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MCSCF optimization through combined use of natural orbitals and the brillouin–levy–berthier theorem
Author(s) -
Ruedenberg K.,
Cheung L. M.,
Elbert S. T.
Publication year - 1979
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.560160511
Subject(s) - atomic orbital , linear combination of atomic orbitals , eigenvalues and eigenvectors , complete active space , context (archaeology) , wave function , natural bond orbital , molecular orbital , brillouin zone , chemistry , computer science , computational chemistry , quantum mechanics , physics , molecule , density functional theory , paleontology , biology , electron
A novel approach is developed for optimizing molecular orbitals within the context of a multiconfiguration self‐consistent‐field problem. The MCSCF wave function is determined through a sequence of eigenvalue problems in the multiconfiguration space and the single‐excitation space. They are used to iteratively improve the natural orbitals, which in turn are related, by successively improved transformations, to the MCSCF orbitals. The mathematical problems arising out of this general concept are solved and the computational implementation is discussed. In many applications the method has proven itself as a powerful approach in forcing rapid convergence. Adaptation to spin and spatial symmetry is maintained throughout and the procedure is applicable to excited states as well as to ground states.