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Application of quadratic CI with singles, doubles, and triples (QCISDT): An attractive alternative to CCSDT
Author(s) -
He Zhi,
Kraka Elfi,
Cremer Dieter
Publication year - 1996
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(1996)57:2<157::aid-qua2>3.0.co;2-x
Subject(s) - chemistry , quadratic equation , character (mathematics) , computational chemistry , physics , mathematics , geometry
The size‐extensive quadratic CI method with single(s), double( D ), and triple ( T ) excitations, QCISDT , is compared with QCISD, QCISD ( T ), CCSDT ‐ n , and CCSDT . It is shown that QCISDT results are more accurate than are either QCISD or QCISD ( T ) results. In particular, QCISDT turns out to be more stable than are QCISD and QCISD ( T ) in cases with considerable multireference character. QCISDT and CCSDT results are of similar accuracy with slight advantages for the former method. Since QCISDT is much easier to implement on a computer than is CCSDT , it is an attractive alternative to CCSDT . © 1996 John Wiley & Sons, Inc.