Journal ArticleDOI
The linked-cluster theorem in the open-shell coupled-cluster theory for incomplete model spaces
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The linked-cluster theorem (LCT) holds for incomplete model spaces as discussed by the authors, provided the intermediate normalization condition (IN) for the eigenfunctions is abandoned.About:
This article is published in Chemical Physics Letters.The article was published on 1986-04-04. It has received 198 citations till now. The article focuses on the topics: Operator theory & Operator (computer programming).read more
Citations
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The equation-of-motion coupled-cluster method: Excitation energies of Be and CO
TL;DR: In this paper, an equation of motion coupled-cluster (EOM-CC) method for the calculation of excitation energies is presented, which is based upon representing an excited state as an excitation from a ground state and the excitation energy is obtained by solving a non-Hermitian eigenvalue problem.
Journal ArticleDOI
Multireference nature of chemistry: the coupled-cluster view.
Journal ArticleDOI
On the connectivity criteria in the open-shell coupled-cluster theory for general model spaces
TL;DR: In this article, the authors study the open-shell coupled-cluster theories and examine the current theoretical status regarding the existence or non-existence of a linked-clusters theorem, ensuring the connectedness of the cluster amplitudes and the effective Hamiltonian.
Journal ArticleDOI
Multi-reference averaged quadratic coupled-cluster method: a size-extensive modification of multi-reference CI
TL;DR: In this article, an extension of the earlier multi-reference linearized coupled-cluster method to include quadratic EPV terms in an averaged way is presented, which is conceptually similar to the averaged coupled pair functional but offers superior performance particularly with small reference spaces.
Book ChapterDOI
Use of Cluster Expansion Methods in the Open-Shell Correlation Problem
Debashis Mukherjee,Sourav Pal +1 more
TL;DR: The open-shell many-body perturbation theory (MBPT) and the propagator or the Green's function methods have now developed into vast computational technology, generating softwares that are cost-effective and competitive with the CI-based codes as mentioned in this paper.
References
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Journal ArticleDOI
The effective interaction in nuclei and its perturbation expansion: An algebraic approach
T.H Schucan,Hans A. Weidenmüller +1 more
TL;DR: In this paper, the authors consider a finite-dimensional model for the Hilbert space of the A -nucleon problem and construct the energy-independent effective interaction W first introduced by Des Cloiseaux and Brandow.
Journal ArticleDOI
Quantum chemistry in Fock space. I. The universal wave and energy operators
TL;DR: In this paper, the wave operator W and the energy operator L were constructed in terms of perturbation theory both in the strictly degenerate and the quasidegenerate version.
Journal ArticleDOI
Application of cluster expansion techniques to open shells: Calculation of difference energies
TL;DR: In this article, a nonperturbative open-shell formalism has been proposed for generating difference energies such as ionization potential (I. P), electron affinity (E. A), and excitation energy (E.).
Journal ArticleDOI
Correlation problem in open-shell atoms and molecules
TL;DR: In this article, a non-perturbative approach to the calculation of correlation energies of open-shell systems is presented, which utilizes an Ursell-type expansion about a multi-determinant starting wave function.