The closed‐shell coupled cluster single and double excitation (CCSD) model for the description of electron correlation. A comparison with configuration interaction (CISD) results

1987 ◽  
Vol 86 (5) ◽  
pp. 2881-2890 ◽  
Author(s):  
Gustavo E. Scuseria ◽  
Andrew C. Scheiner ◽  
Timothy J. Lee ◽  
Julia E. Rice ◽  
Henry F. Schaefer
Keyword(s):  
Configuration Interaction ◽  
Electron Correlation ◽  
Closed Shell ◽  
Coupled Cluster ◽  
Double Excitation

Assessment of the Direct Generalized Bloch Approach B0: Application to the Li and Be Atoms and the Molecules LiH, BeH, and the Phenolate Anion

2005 ◽  
Vol 70 (8) ◽  
pp. 1272-1314
Author(s):  
Holger Meissner
Keyword(s):  
Simple Model ◽  
Configuration Interaction ◽  
Closed Shell ◽  
Experimental Results ◽  
Basis Sets ◽  
Coupled Cluster ◽  
Photoactive Yellow Protein ◽  
Energy Calculations ◽  
Molecular Systems ◽  
Reasonable Approach

Besides the necessity of the development of sophisticated methods to calculate correlation energies - be it the coupled-cluster (CC) or the configuration-interaction (CI) methods and their various approaches - one also accentuate the need for efficient and less demanding methods in the area of medium and large molecular systems. Therefore, this article proposes a computational efficient and in our opinion reasonable approach for the calculation of correlation energies for medium and even larger molecules. This approach, named B0, based on the so-called direct generalized Bloch (DGB) equation which has already been successfully applied to small systems. Within those considerations the B0 approach showed promising results so that further investigations are worthwhile. Here, as a further step in the assessment of this method we apply the B0 approach to the Li and Be atoms as well as the LiH and BeH molecules. Molecules which show open and closed shell characteristics in the equilibrium and in the case of dissociation as well. The results are compared with CC and CI and experimental results if available. Since this results are encouraging even when considering small basis sets and with the prospect of larger molecular systems, therefore, we perform also B0 energy calculations for the low-lying states of the phenolate anion which for instance can be used in a simple model of the photoactive yellow protein (PYP) chromophore.

An efficient reformulation of the closed‐shell coupled cluster single and double excitation (CCSD) equations

1988 ◽  
Vol 89 (12) ◽  
pp. 7382-7387 ◽  
Author(s):  
Gustavo E. Scuseria ◽  
Curtis L. Janssen ◽  
Henry F. Schaefer
Keyword(s):  
Closed Shell ◽  
Coupled Cluster ◽  
Double Excitation

Comparison of single and double excitation coupled cluster and configuration interaction theories: determination of structure and equilibrium propertie

1987 ◽  
Vol 139 (2) ◽  
pp. 134-139 ◽  
Author(s):  
Timothy J. Lee ◽  
Gustavo E. Scuseria ◽  
Julia E. Rice ◽  
Andrew C. Scheiner ◽  
Henry F. Schaefer
Keyword(s):  
Configuration Interaction ◽  
Coupled Cluster ◽  
Double Excitation

Excitonic Coupled-cluster Theory: Part I, General Formalism

2017 ◽  
Author(s):  
Yuhong Liu ◽  
Anthony Dutoi
Keyword(s):  
Electron Correlation ◽  
Degrees Of Freedom ◽  
Model Systems ◽  
Coupled Cluster ◽  
Effective Hamiltonian ◽  
Coupled Cluster Theory ◽  
Cluster Theory ◽  
Companion Article ◽  
High Level ◽  
Fragment Interaction

<div> <div>A shortcoming of presently available fragment-based methods is that electron correlation (if included) is described at the level of individual electrons, resulting in many redundant evaluations of the electronic relaxations associated with any given fluctuation. A generalized variant of coupled-cluster (CC) theory is described, wherein the degrees of freedom are fluctuations of fragments between internally correlated states. The effects of intra-fragment correlation on the inter-fragment interaction is pre-computed and permanently folded into the effective Hamiltonian. This article provides a high-level description of the CC variant, establishing some useful notation, and it demonstrates the advantage of the proposed paradigm numerically on model systems. A companion article shows that the electronic Hamiltonian of real systems may always be cast in the form demanded. This framework opens a promising path to build finely tunable systematically improvable methods to capture precise properties of systems interacting with a large number of other systems. </div> </div>

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