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Kramers‐restricted closed‐shell CCSD theory
Author(s) -
Visscher Lucas,
Dyall Kenneth G.,
Lee Timothy J.
Publication year - 1995
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.560560844
Subject(s) - formalism (music) , open shell , physics , amplitude , coupled cluster , wave function , quantum mechanics , classical mechanics , mathematical physics , molecule , art , musical , visual arts
A Kramers‐restricted version of the closed‐shell coupled cluster singles and doubles theory is presented. The theory can be used in conjunction with two‐ or four‐component relativistic reference wave functions, where the intrinsic treatment of the spin–orbit coupling gives rise to a maximum of eight times more independent quantities (amplitudes and integrals) than found in a spin‐independent formalism. The number of operations required to evaluate the equations is at most 32 times larger than in the optimal spin‐independent closed‐shell formalism, which is eight times smaller than found when using a spin‐dependent unrestricted formalism. © 1995 John Wiley & Sons, Inc.