Solving the single-reference coupled-cluster equations involving highly excited clusters in quasidegenerate situations

Journal Article · Fri Apr 15 00:00:00 EDT 1994 · Journal of Chemical Physics; (United States)

DOI:https://doi.org/10.1063/1.467149· OSTI ID:5015941

Piecuch, P; Adamowicz, L ^[1]

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1. Department of Chemistry, University of Arizona, Tucson, Arizona 85721 (United States)

A new procedure for improving the convergence of the reduced linear equation method for solving the single-reference (SR) coupled-cluster (CC) equations in highly degenerate cases, where the convergence of the iterative process is often destabilized by dangerous'' denominators, is discussed and implemented. Emphasis is placed on the SR CC methods involving highly excited clusters, such as the CC method with singles, doubles, triples, and quadruples (CCSDTQ). The new algorithm is based on rearranging and quasilinearizing the nonlinear terms and correcting the energy denominators by the quasilinearized terms. The method is tested in the SR CCSDTQ calculations for a dissociating single bond.

• DOE Contract Number: FG03-93ER61605
• OSTI ID: 5015941
• Journal Information: Journal of Chemical Physics; (United States), Vol. 100:8; ISSN 0021-9606
• Country of Publication: United States
• Language: English

Related Subjects

74 ATOMIC AND MOLECULAR PHYSICS
EQUATIONS
ITERATIVE METHODS
SOLID CLUSTERS
ACCURACY
ALGEBRA
ALGORITHMS
CALCULATION METHODS
EXCITED STATES
NONLINEAR PROBLEMS
ENERGY LEVELS
MATHEMATICAL LOGIC
MATHEMATICS
664100* - Theory of Electronic Structure of Atoms & Molecules- (1992-)