scholarly journals Discontinuities-free complete-active-space state–specific multi–reference coupled cluster theory for describing bond stretching and dissociation

2015 ◽  
Vol 143 (2) ◽  
pp. 024109 ◽  
Author(s):  
Irina A. Zaporozhets ◽  
Vladimir V. Ivanov ◽  
Dmitry I. Lyakh ◽  
Ludwik Adamowicz
Keyword(s):  
Coupled Cluster ◽  
Coupled Cluster Theory ◽  
Cluster Theory ◽  
Complete Active Space ◽  
Active Space ◽  
Bond Stretching ◽  
Space State

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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