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Integral processing in beyond‐Hartree‐Fock calculations
Author(s) -
Taylor Peter R.
Publication year - 1987
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.560310322
Subject(s) - coulomb , matrix (chemical analysis) , extension (predicate logic) , scheme (mathematics) , work (physics) , computational science , computer science , implementation , mathematics , physics , chemistry , quantum mechanics , mathematical analysis , chromatography , programming language , electron
The increasing rate at which improvements in processing capacity outstrip improvements in input/output performance of large computers has led to recent attempts to bypass generation of a disk‐based integral file. The “direct” SCF method of Almlöf and co‐workers represents a very successful implementation of this approach. The present work is concerned with the extension of this general approach to CI and MCSCF calculations. After a discussion of the particular types of MO integrals for which — at least for most current generation machines — disk‐based storage seems unavoidable, it is shown how all the necessary integrals can be obtained as matrix elements of Coulomb and exchange operators that can be calculated using a direct approach. Computational implementations of such a scheme are discussed.