Journal ArticleDOI
The closed‐shell coupled cluster single and double excitation (CCSD) model for the description of electron correlation. A comparison with configuration interaction (CISD) results
TLDR
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).read more
Citations
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Journal ArticleDOI
A fifth-order perturbation comparison of electron correlation theories
TL;DR: In this paper, a new augmented version of coupled-cluster theory, denoted as CCSD(T), is proposed to remedy some of the deficiencies of previous augmented coupledcluster models.
Journal ArticleDOI
Coupled-cluster theory in quantum chemistry
Rodney J. Bartlett,Monika Musiał +1 more
TL;DR: In this article, the essential aspects of coupled-cluster theory are explained and illustrated with informative numerical results, showing that the theory offers the most accurate results among the practical ab initio electronic-structure theories applicable to moderate-sized molecules.
Journal ArticleDOI
Coupled cluster theory for high spin, open shell reference wave functions
TL;DR: In this paper, the coupled cluster method restricted to single and double excitations (CCSD) is considered for the case of a spin restricted Hartree-Fock open shell reference determinant.
Journal ArticleDOI
An efficient reformulation of the closed‐shell coupled cluster single and double excitation (CCSD) equations
TL;DR: In this article, the closed-shell CCSD equations were reformulated in order to achieve superior computational efficiency using a spin adaptation scheme based on the unitary group approach (UGA).
Journal ArticleDOI
A comparison of the efficiency and accuracy of the quadratic configuration interaction (QCISD), coupled cluster (CCSD), and Brueckner coupled cluster (BCCD) methods
TL;DR: In this article, the Brueckner coupled-cluster (BCCD) method with single and double excitations from a closed-shell reference function (CCSD) and the corresponding quadratic configuration interaction method (QCISD) are formulated in terms of quantities which can be computed directly from the two-electron integrals in AO basis.
References
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Journal ArticleDOI
A full coupled‐cluster singles and doubles model: The inclusion of disconnected triples
TL;DR: The coupled cluster singles and doubles model (CCSD) as discussed by the authors is derived algebraically, presenting the full set of equations for a general reference function explicitly in spin-orbital form, and the computational implementation of the CCSD model, which involves cubic and quartic terms, is discussed and results are compared with full CI calculations for H2O and BeH2.
Journal ArticleDOI
Gaussian Basis Functions for Use in Molecular Calculations. III. Contraction of (10s6p) Atomic Basis Sets for the First‐Row Atoms
TL;DR: In this paper, the effects of contraction on the energies and one-electron properties of the water and nitrogen molecules were investigated, and the authors obtained principles which can be used to predict optimal contraction schemes for other systems without the necessity of such exhaustive calculations.
Journal ArticleDOI
Configuration interaction calculations on the nitrogen molecule
TL;DR: In this article, a contracted Gaussian basis set capable of describing about 63% of the correlation energy of N2 has been used in a detailed configuration-interaction calculation, and second-order perturbation theory overestimated the correlated energy by 23-50% depending on how H0 was chosen.
Journal ArticleDOI
Many-Body Perturbation Theory and Coupled Cluster Theory for Electron Correlation in Molecules
TL;DR: Manybody perturbation theory (MBPT) and coupled-cluster methcoder (CCM) were defined in this paper as a subset of the N-body problem.
BookDOI
Methods of Electronic Structure Theory
TL;DR: In this paper, the authors present a method for determining configuration interaction wave functions for the Electronic States of Atoms and Molecules: the Vector Method, which is a general computer program for ab initio calculations.