High-order excitations in state-universal and state-specific multireference coupled cluster theories: Model systems

2006 ◽  
Vol 125 (15) ◽  
pp. 154113 ◽  
Author(s):  
Francesco A. Evangelista ◽  
Wesley D. Allen ◽  
Henry F. Schaefer
Keyword(s):  
High Order ◽  
Model Systems ◽  
Coupled Cluster

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>

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>

scholarly journals The spin-half XXZ antiferromagnet on the square lattice revisited: A high-order coupled cluster treatment

2017 ◽  
Vol 428 ◽  
pp. 178-188 ◽  
Author(s):  
R.F. Bishop ◽  
P.H.Y. Li ◽  
R. Zinke ◽  
R. Darradi ◽  
J. Richter ◽  
...  
Keyword(s):  
High Order ◽  
Square Lattice ◽  
Coupled Cluster

Relaxed active space: Fixing tailored-CC with high order coupled cluster. I

2012 ◽  
Vol 137 (21) ◽  
pp. 214103 ◽  
Author(s):  
Anna Melnichuk ◽  
Rodney J. Bartlett
Keyword(s):  
High Order ◽  
Coupled Cluster ◽  
Active Space

scholarly journals Quantum phase transitions of a square-lattice Heisenberg antiferromagnet with two kinds of nearest-neighbor bonds: A high-order coupled-cluster treatment

2000 ◽  
Vol 61 (21) ◽  
pp. 14607-14615 ◽  
Author(s):  
Sven E. Krüger ◽  
Johannes Richter ◽  
Jörg Schulenburg ◽  
Damian J. J. Farnell ◽  
Raymond F. Bishop
Keyword(s):  
Phase Transitions ◽  
Nearest Neighbor ◽  
Quantum Phase Transitions ◽  
High Order ◽  
Quantum Phase ◽  
Square Lattice ◽  
Coupled Cluster ◽  
Heisenberg Antiferromagnet
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