The Pair-Correlation Problem and the Coupled-Cluster Approach

1982 ◽  
pp. 381-423
Author(s):  
Ingvar Lindgren ◽  
John Morrison
Keyword(s):  
Pair Correlation ◽  
Coupled Cluster ◽  
Cluster Approach ◽  
Correlation Problem

Coupled-pair theories and Davidson-type corrections for quasidegenerate states: The H4 model revisited

1988 ◽  
Vol 53 (9) ◽  
pp. 1919-1942 ◽  
Author(s):  
Josef Paldus ◽  
Paul E. S. Wormer ◽  
Marc Benard
Keyword(s):  
Electron Correlation ◽  
Model System ◽  
Coupled Cluster ◽  
Electron Model ◽  
Hydrogen Molecules ◽  
Double Zeta ◽  
Correlation Problem ◽  
Variational Approaches ◽  
Cluster Type ◽  
The Many

The performance of various variational and non-variational approaches to the many-electron correlation problem is examined for a simple four-electron model system consisting of two stretched hydrogen molecules in trapezoidal, rectangular and linear configurations, in which the degree of quasi-degeneracy can be continuously varied from a non-degenerate to an almost degenerate situation. In contrast to an earlier work (K. Jankowski and J. Paldus, Int. J. Quantum Chem. 18, 1243 (1980)) we employ a double-zeta plus polarization basis and examine both single reference and multireference configuration interaction and coupled-cluster-type approaches. The performance of various Davidson-type corrections is also investigated.

Valence bond corrected single reference coupled cluster approach

1994 ◽  
Vol 89 (1) ◽  
pp. 33-57 ◽  
Author(s):  
J. Planelles ◽  
J. Paldus ◽  
X. Li
Keyword(s):  
Valence Bond ◽  
Coupled Cluster ◽  
Cluster Approach

A coupled-cluster approach to the relative strains in [1.1.1]propellane, its derivatives and hetero[1.1.1]propellanes

2012 ◽  
Vol 110 (19-20) ◽  
pp. 2349-2357 ◽  
Author(s):  
Hanying Xu ◽  
Svein Saebo ◽  
Charles U. Pittman
Keyword(s):  
Coupled Cluster ◽  
Cluster Approach

An orbital-invariant internally contracted multireference coupled cluster approach

2011 ◽  
Vol 134 (11) ◽  
pp. 114102 ◽  
Author(s):  
Francesco A. Evangelista ◽  
Jürgen Gauss
Keyword(s):  
Coupled Cluster ◽  
Cluster Approach

Time-Independent Coupled-Cluster Theory of the Polarization Propagator

2005 ◽  
Vol 70 (8) ◽  
pp. 1109-1132 ◽  
Author(s):  
Robert Moszynski ◽  
Piotr S. Żuchowski ◽  
Bogumił Jeziorski
Keyword(s):  
Order Term ◽  
Cluster Method ◽  
Coupled Cluster ◽  
Cluster Approach ◽  
Coupled Cluster Theory ◽  
Cluster Theory ◽  
Polarization Propagator ◽  
Apparent Correlation ◽  
Moller Plesset ◽  
New Formulation

A novel, time-independent formulation of the coupled-cluster theory of the polarization propagator is presented. This formulation, unlike the equation-of-motion coupled-cluster approach, is fully size-extensive and, unlike the conventional time-dependent coupled-cluster method, is manifestly Hermitian, which guarantees that the polarization propagator is always real for purely imaginary frequencies and that the resulting polarizabilities exhibit time-reversal symmetry (are even functions of frequency) for purely real or purely imaginary perturbations. This new formulation is used to derive compact expressions for the three leading terms in the Møller-Plesset expansion for the polarization propagator. The true and apparent correlation contributions to the second-order term are analyzed and separated at the operator level. Explicit equations for the polarization propagator at the non-perturbative, singles and doubles level (CCSD) are presented.

scholarly journals Reply to comment on: Coupled cluster approach or quadratic configuration interaction?

1990 ◽  
Vol 93 (2) ◽  
pp. 1486-1487 ◽  
Author(s):  
Krishnan Raghavachari ◽  
Martin Head‐Gordon ◽  
John A. Pople
Keyword(s):  
Configuration Interaction ◽  
Coupled Cluster ◽  
Cluster Approach
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