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Application of the valence‐universal coupled‐cluster method based on various model spaces to 1 S states of Be
Author(s) -
Jankowski K.,
Malinowski P.
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.560550308
Subject(s) - excited state , valence (chemistry) , coupled cluster , basis set , basis (linear algebra) , ground state , physics , cluster (spacecraft) , state (computer science) , basis function , atomic physics , quantum mechanics , theoretical physics , statistical physics , mathematics , density functional theory , computer science , molecule , geometry , algorithm , programming language
The recently formulated atomically oriented valence‐universal theory ( VU – CCSD / R ) based on various complete model spaces is applied to the accurate description of the 2 s 2 1 S , 2 s 3 s 1 S , 2 p 2 1 S, and 3 s 2 1 S states of Be. Two extensive 9 s 9 p 7 d 7 f 5 g STO basis sets that differ by one s ‐type function are employed. Both standard and nonstandard solutions of the VU – CC equations are considered. The eight values of the ground‐state energies obtained when considering various model spaces and basis sets were found to differ very little. The energies of the individual excited states disclosed a relatively weak dependence on the choice of model spaces defining the method (or, equivalently, on the fact whether they correspond to standard or nonstandard solutions). In turn, the energies of the excited states strongly depend on the STO basis set used in the calculations. To obtain a reliable description of both the ground state and excited states, well‐balanced STO basis sets have to be employed. © 1995 John Wiley & Sons, Inc.