State‐specific coupled cluster‐type dressing of multireference singles and doubles configuration interaction matrix

1996 ◽  
Vol 104 (11) ◽  
pp. 4068-4076 ◽  
Author(s):  
J. Meller ◽  
J. P. Malrieu ◽  
R. Caballol
Keyword(s):  
Configuration Interaction ◽  
Interaction Matrix ◽  
Coupled Cluster ◽  
Cluster Type

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.

scholarly journals A feasible approach for automatically differentiable unitary coupled-cluster on quantum computers

2021 ◽  
Author(s):  
Jakob S. Kottmann ◽  
Abhinav Anand ◽  
Alán Aspuru-Guzik
Keyword(s):  
Coupled Cluster ◽  
Quantum Computers ◽  
Evaluation Procedures ◽  
Cluster Type

We develop computationally affordable and encoding independent gradient evaluation procedures for unitary coupled-cluster type operators, applicable on quantum computers.

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