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Applicability of single-reference coupled-cluster methods to excited states. A model study

✍ Scribed by J. Jankowski; K. Kowalski; P. Jankowski

Publisher: Elsevier Science
Year: 1994
Tongue: English
Weight: 637 KB
Volume: 222
Category: Article
ISSN: 0009-2614
DOI: 10.1016/0009-2614(94)00391-2

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✦ Synopsis

It is demonstrated that standard single-reference coupled-cluster @R-CC) theories can be successfully applied to the studies of some excited states not belonging to the lowest energy in their symmetry class. The prerequisite of such applications is that a proper reference state configuration and orbital set are employed for the parametrization of the SR-CC method. The 2 *A, and 5 'A, states of the simple H4 model system are considered for geometries related to various degrees of quasidegeneracy of these states. It is found that the efficiency of various versions of the SR-CC method (except the linearized versions) is similar to that of standard applications to the closed-shell ground state of H4.

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