Time-Independent Coupled-Cluster Theory of the Polarization Propagator

2005 ◽  
Vol 70 (8) ◽  
pp. 1109-1132 ◽  
Author(s):  
Robert Moszynski ◽  
Piotr S. Żuchowski ◽  
Bogumił Jeziorski
Keyword(s):  
Order Term ◽  
Cluster Method ◽  
Coupled Cluster ◽  
Cluster Approach ◽  
Coupled Cluster Theory ◽  
Cluster Theory ◽  
Polarization Propagator ◽  
Apparent Correlation ◽  
Moller Plesset ◽  
New Formulation

A novel, time-independent formulation of the coupled-cluster theory of the polarization propagator is presented. This formulation, unlike the equation-of-motion coupled-cluster approach, is fully size-extensive and, unlike the conventional time-dependent coupled-cluster method, is manifestly Hermitian, which guarantees that the polarization propagator is always real for purely imaginary frequencies and that the resulting polarizabilities exhibit time-reversal symmetry (are even functions of frequency) for purely real or purely imaginary perturbations. This new formulation is used to derive compact expressions for the three leading terms in the Møller-Plesset expansion for the polarization propagator. The true and apparent correlation contributions to the second-order term are analyzed and separated at the operator level. Explicit equations for the polarization propagator at the non-perturbative, singles and doubles level (CCSD) are presented.

The cohesive energy of superheavy element copernicium determined from accurate relativistic coupled-cluster theory

2017 ◽  
Vol 19 (48) ◽  
pp. 32286-32295 ◽  
Author(s):  
K. G. Steenbergen ◽  
J.-M. Mewes ◽  
L. F. Pašteka ◽  
H. W. Gäggeler ◽  
G. Kresse ◽  
...  
Keyword(s):  
Cohesive Energy ◽  
Superheavy Element ◽  
Coupled Cluster ◽  
Cluster Approach ◽  
Coupled Cluster Theory ◽  
Cluster Theory ◽  
Incremental Method

The cohesive energy of bulk copernicium is accurately determined using the incremental method within a relativistic coupled-cluster approach.

Multireference State-Specific Coupled-Cluster Theory and Multiconfigurationality Index. BH Dissociation

2005 ◽  
Vol 70 (7) ◽  
pp. 1017-1033 ◽  
Author(s):  
Vladimir V. Ivanov ◽  
Ludwik Adamowicz ◽  
Dmitry I. Lyakh
Keyword(s):  
Wave Function ◽  
Numerical Results ◽  
Cluster Method ◽  
Coupled Cluster ◽  
Coupled Cluster Method ◽  
Coupled Cluster Theory ◽  
Cluster Theory ◽  
Computer Aided

Multiconfigurationality index calculated for the coupled-cluster wave function based on an algorithm developed using a computer-aided generation approach is applied to analyze the multireference state-specific coupled-cluster method with the CAS reference (i.e. the so called the CAS(n,m)CCSD approach). The numerical results concern dissociation of the BH molecule where at larger displacement from the equilibrium significant quasi-degeneracy arises. The analysis shows that the CAS(n,m)CCSD approach performs very well in such a situation.

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
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