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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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Journal ArticleDOI
TL;DR: A single and double excitation coupled cluster (CCSD) method restricted to closed-shell single configuration reference functions is described in explicit detail in this article, where significant simplifications resulting from the restriction to closedshell systems are exploited to achieve maximum computational efficiency.
Abstract: A single and double excitation coupled cluster (CCSD) method restricted to closed‐shell single configuration reference functions is described in explicit detail. Some significant simplifications resulting from the restriction to closed‐shell systems are exploited to achieve maximum computational efficiency. Comparisons for energetic results and computational requirements are made with the single and double excitation configuration interaction (CISD) method. The specific molecules considered include N2, H2O, H3O+, H5O+2, HSOH, and s‐tetrazine (C2N4H2).

330 citations

Journal ArticleDOI
TL;DR: In this paper, a new method for the perturbative calculation of the correlation energy due to connected triple excitations (T) in the framework of local coupled cluster theory is presented, for which all computational resources scale linearly with molecular size.
Abstract: A new method for the perturbative calculation of the correlation energy due to connected triple excitations (T) in the framework of local coupled cluster theory is presented, for which all computational resources scale linearly with molecular size. One notable complication in the formalism for connected triples introduced by the local approach is the nondiagonality of the Fock matrix in the localized MO (LMO) and projected AO (PAO) basis, which leads to couplings between individual triples amplitudes via the internal–internal and external–external blocks of the Fock matrix, respectively. Further complications and couplings arise due to the nonorthogonality of the PAOs. While the couplings via the external–external block can easily be dealt with, this is more difficult for the internal–internal couplings. In a previous paper we already published preliminary results of an approximation of the method, which neglects these internal–internal couplings entirely and recovers about 97% of the total local triples ...

329 citations

Journal ArticleDOI
TL;DR: The CCSDT model for general single determinant reference functions for open and closed shell electronic states has been implemented for the first time and has been used to compute the electron affinity of the F atom, the CH2, 3B1-1A1 energy difference, and the ionization potentials of 1A1-CH2 as discussed by the authors.
Abstract: The CCSDT model for general single determinant reference functions for open and closed‐shell electronic states has been implemented for the first time and has been used to compute the electron affinity of the F atom, the CH2, 3B1–1A1 energy difference, and the ionization potentials of 1A1 CH2. The results compare very well with FCI and are markedly superior to those of simpler coupled‐cluster methods.

324 citations

Journal ArticleDOI
TL;DR: A series of molecular applications of many-body perturbation theory (MBPT) and the coupled-cluster doubles (CCD) model are described in this paper, including correlation energies, including contributions from single, double, and quadruple excitations diagrams in fourth-and higher-order; dissociation energies; potential energy surfaces; and molecular polarizabilities and hyperpolarizabilities.
Abstract: A series of molecular applications of many-body perturbation theory (MBPT) and the coupled-cluster doubles (CCD) model are described. Even though these methods have been available for sometime, only recently have large scale, MBPT molecular calculations become available. In the case of CCD, the results presented here are among the first obtained from a general purpose ab initio program. The intention of this paper is to present an overview of the current state of the many-body approach to ground state properties of molecules. The properties studied are correlation energies, including contributions from single, double, and quadruple excitations diagrams in fourth-and higher-order; dissociation energies; potential energy surfaces; and molecular polarizabilities and hyperpolarizabilities. Examples are taken from studies of a variety of molecules including HF, H2O, HCO, C6H6, B2H6, CO2, and N2. In many cases, it is found that quantitatively accurate dissociation energies, geometries, and force constants can be obtained. In an illustration of the X1Σg+ potential energy curve of N2, it is shown that a single UHF or RHF reference function MBPT/CCD approach is inadequate at some internuclear separation.

322 citations

Book ChapterDOI
01 Sep 1995

318 citations


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