Relativistic state-specific multireference coupled cluster theory description for bond-breaking energy surfaces

2016 ◽  
Vol 145 (12) ◽  
pp. 124303 ◽  
Author(s):  
Anirban Ghosh ◽  
Rajat K. Chaudhuri ◽  
Sudip Chattopadhyay
Keyword(s):  
Coupled Cluster ◽  
Bond Breaking ◽  
Coupled Cluster Theory ◽  
Cluster Theory ◽  
Breaking Energy ◽  
Energy Surfaces

Frozen Natural Orbitals: Systematic Basis Set Truncation for Coupled-Cluster Theory

2005 ◽  
Vol 70 (6) ◽  
pp. 837-850 ◽  
Author(s):  
Andrew G. Taube ◽  
Rodney J. Bartlett
Keyword(s):  
Small Molecules ◽  
Potential Energy Surfaces ◽  
Equilibrium Structure ◽  
Virtual Space ◽  
Basis Set ◽  
Coupled Cluster ◽  
Coupled Cluster Theory ◽  
Cluster Theory ◽  
Equilibrium Structures ◽  
Energy Surfaces

The method of frozen natural orbital (FNO) basis set truncation for coupled-cluster theory is described. Numerical comparisons of the FNO potential energy surfaces of a group of small molecules at the CCSD(T) level in DZP, cc-pVTZ, cc-pVQZ bases show that truncation of up to 50% of the virtual space yields CC correlation energies that are accurate to 90 or 95% when added to the full MBPT(2) basis result. The FNO truncation method is also applied to dimethylnitramine (DMNA): both the equilibrium structure and dimer interactions, yielding results at the CCSD(T) level in both a DZP and cc-pVTZ basis set that agree with literature values. CCSD(T) calculations at two possible equilibrium structures of 1,3,5-trinitrohexahydro-1,3,5-triazine (RDX) in a truncated DZP basis are also reported.

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 Orbital optimized unitary coupled cluster theory for quantum computer

2020 ◽  
Vol 2 (3) ◽  
Author(s):  
Wataru Mizukami ◽  
Kosuke Mitarai ◽  
Yuya O. Nakagawa ◽  
Takahiro Yamamoto ◽  
Tennin Yan ◽  
...  
Keyword(s):  
Quantum Computer ◽  
Coupled Cluster ◽  
Coupled Cluster Theory ◽  
Cluster Theory

scholarly journals Focal-point approach with pair-specific cusp correction for coupled-cluster theory

2021 ◽  
Vol 154 (23) ◽  
pp. 234103
Author(s):  
Andreas Irmler ◽  
Alejandro Gallo ◽  
Andreas Grüneis
Keyword(s):  
Focal Point ◽  
Coupled Cluster ◽  
Coupled Cluster Theory ◽  
Cluster Theory
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