An ab initio coupled cluster theory of quantum spin lattices and their quantum critical behaviour

<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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Excitonic Coupled-cluster Theory: Part I, General Formalism

10.26434/chemrxiv.5330773.v1 ◽

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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Dispersion-Weighted Explicitly Correlated Coupled-Cluster Theory [DW-CCSD(T**)-F12]

Journal of Chemical Theory and Computation ◽

10.1021/ct200600p ◽

2011 ◽

Vol 7 (12) ◽

pp. 3978-3982 ◽

Cited By ~ 32

Author(s):

Michael S. Marshall ◽

C. David Sherrill

Keyword(s):

Coupled Cluster ◽

Coupled Cluster Theory ◽

Cluster Theory ◽

Explicitly Correlated

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