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Coupled cluster

About: Coupled cluster is a research topic. Over the lifetime, 6280 publications have been published within this topic receiving 301055 citations.


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TL;DR: The presented method is applied to the calculation of CC and CI harmonic frequencies and nuclear magnetic resonance chemical shifts up to the full CI level for some selected systems, underline the importance of higher excitations in high-accuracy calculations.
Abstract: Analytic second derivatives of energy for general coupled-cluster (CC) and configuration-interaction (CI) methods have been implemented using string-based many-body algorithms. Wave functions truncated at an arbitrary excitation level are considered. The presented method is applied to the calculation of CC and CI harmonic frequencies and nuclear magnetic resonance chemical shifts up to the full CI level for some selected systems. The present benchmarks underline the importance of higher excitations in high-accuracy calculations.

177 citations

Journal ArticleDOI
TL;DR: In this article, the authors performed coupled-cluster calculations for doubly magic nuclei for the chiral effective field theory at order next to next-to-next to-next-to leading order, and found that the coupledcluster approximation including triples corrections binds nuclei within 0.4 MeV per nucleon compared to data.
Abstract: We perform coupled-cluster calculations for the doubly magic nuclei $^{4}\mathrm{He}$, $^{16}\mathrm{O}$, $^{40,48}\mathrm{Ca}$, for neutron-rich isotopes of oxygen and fluorine, and employ ``bare'' and secondary renormalized nucleon-nucleon interactions. For the nucleon-nucleon interaction from chiral effective field theory at order next-to-next-to-next-to leading order, we find that the coupled-cluster approximation including triples corrections binds nuclei within 0.4 MeV per nucleon compared to data. We employ interactions from a resolution-scale dependent similarity renormalization group transformations and assess the validity of power counting estimates in medium-mass nuclei. We find that the missing contributions from three-nucleon forces are consistent with these estimates. For the unitary correlator model potential, we find a slow convergence with respect to increasing the size of the model space. For the $G$-matrix approach, we find a weak dependence of ground-state energies on the starting energy combined with a rather slow convergence with respect to increasing model spaces. We also analyze the center-of-mass problem and present a practical and efficient solution.

176 citations

Journal ArticleDOI
TL;DR: A linear scaling local correlation approach is proposed for approximately solving the coupled cluster doubles (CCD) equations of large systems in a basis of orthogonal localized molecular orbitals (LMOs) and it is demonstrated that the presentLocal correlation approach recovers more than 98.5% of the conventional CCD correlation energy.
Abstract: A linear scaling local correlation approach is proposed for approximately solving the coupled cluster doubles (CCD) equations of large systems in a basis of orthogonal localized molecular orbitals (LMOs). By restricting double excitations from spatially close occupied LMOs into their associated virtual LMOs, the number of significant excitation amplitudes scales only linearly with molecular size in large molecules. Significant amplitudes are obtained to a very good approximation by solving the CCD equations of various subsystems, each of which is made up of a cluster associated with the orbital indices of a subset of significant amplitudes and the local environmental domain of the cluster. The combined effect of these two approximations leads to a linear scaling algorithm for large systems. By using typical thresholds, which are designed to target an energy accuracy, our numerical calculations for a wide range of molecules using the 6-31G or 6-31G* basis set demonstrate that the present local correlation approach recovers more than 98.5% of the conventional CCD correlation energy.

176 citations

Journal ArticleDOI
TL;DR: The Coupled Cluster Green's Function (CCGF) method as mentioned in this paper is intimately connected to both Coupled Clustered Linear Response Theory (CCLRT) and the Normal CoupledCluster Method (NCCM).
Abstract: Diagrammatic and Coupled Cluster techniques are used to develop an approach to the single-particle Green's function G which concentrates on G directly rather than first approximating the irreducible self-energy and then solving Dyson's equation. As a consequence the ionization and attachment parts of the Green's function satisfy completely decoupled sets of equations. The proposed Coupled Cluster Green's Function method (CCGF) is intimately connected to both Coupled Cluster Linear Response Theory (CCLRT) and the Normal Coupled Cluster Method (NCCM). These relations are discussed in detail. © 1992 John Wiley & Sons, Inc.

176 citations

Journal ArticleDOI
TL;DR: In this article, a continuous transition between the Rayleigh-Schrodinger and Brillouin-Wigner perturbation theories is constructed and the Bloch equation for the corresponding wave operator is derived.
Abstract: A continuous transition between the Rayleigh–Schrodinger and Brillouin–Wigner perturbation theories is constructed and the Bloch equation for the corresponding wave operator is derived. Subsequently it is applied to the Hilbert space multireference coupled cluster theory and used to investigate relationships between several versions of multireference coupled cluster methods. Finally, based on those continuous transitions, new size extensivity corrections for the Brillouin–Wigner coupled cluster method are suggested. Numerical tests of size-extensivity and separability of a supermolecule to closed- and open-shell fragments are also presented. Equivalence of some of the multireference coupled cluster methods with single and double excitations to full configuration interaction for two-electron systems is investigated, both theoretically and numerically.

175 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
2023163
2022351
2021267
2020344
2019253
2018244