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Diagrammatic analysis and application of the coupled cluster response approach to ground‐state expectation values
Author(s) -
Nooijen Marcel,
Snijders Jaap G.
Publication year - 1993
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.560470103
Subject(s) - diagrammatic reasoning , coupled cluster , formalism (music) , ground state , cluster (spacecraft) , physics , atomic physics , statistical physics , quantum mechanics , molecule , computer science , art , musical , visual arts , programming language
The response approach to couple cluster ( CC ) expectation values devised by Monkhorst and the normal coupled cluster method ( NCCM ) discussed by Arponen and Bishop are considered from a diagrammatic point of view. The perturbative diagrammatic content of the operator that parametrizes the NCCM bra state is discussed in detail. The method is applied to the calculation of the one‐particle reduced density matrix of the Be atom and the HF molecule for different values of the internuclear distance. Various contributions to the total energy obtained in the NCCM framework are compared to results from accurate multireference configuration interaction calculations. Such a comparison is shown to provide a much more stringent test on the accuracy of the CC formalism than will a comparison of total energy alone. © 1993 John Wiley & Sons, Inc.