Journal ArticleDOI
Multireference coupled‐cluster method: Ionization potentials and excitation energies for ketene and diazomethane
TLDR
In this paper, a linked, size-extensive multireference coupled-cluster method (MRCC) is presented, and has been used to calculate the ionization potentials and excitation energies of the interesting molecules ketene and diazomethane.Abstract:
A linked, size‐extensive multireference coupled‐cluster method (MRCC) is presented, and has been used to calculate the ionization potentials and excitation energies of the interesting molecules ketene and diazomethane. Comparisons are made with experimental numbers and theoretical results from configuration‐interaction (CI) studies. Good agreement is found between the MRCC results, CI calculations, and experiment.read more
Citations
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Journal ArticleDOI
Coupled cluster response functions
Henrik Koch,Poul Jo,rgensen +2 more
TL;DR: The linear and quadratic response functions have been determined for a coupled cluster reference state from the response functions, computationally tractable expressions have been derived for excitation energies, first and second-order matrix transition elements, transition matrix elements between excited states, and second and third-order frequency-dependent molecular properties as discussed by the authors.
Journal ArticleDOI
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
Excitation energies from the coupled cluster singles and doubles linear response function (CCSDLR). Applications to Be, CH+, CO, and H2O
TL;DR: In this paper, the linear response function for a coupled cluster singles and doubles wave function is used to calculate vertical electronic energies for the closed shell system Be, CH+, CO, and H2O.
Journal ArticleDOI
Equation of motion coupled cluster method for electron attachment
TL;DR: The electron attachment equation of motion coupled cluster (EA•EOMCC) method is derived in this paper, which enables determination of the various bound states of an (N+1)-electron system and the corresponding energy eigenvalues relative to the energy of an N•electron CCSD reference state.
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.
References
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Journal ArticleDOI
On the Correlation Problem in Atomic and Molecular Systems. Calculation of Wavefunction Components in Ursell-Type Expansion Using Quantum-Field Theoretical Methods
TL;DR: In this article, a method for the calculation of the matrix elements of the logarithm of an operator which gives the exact wavefunction when operating on the wavefunction in the one-electron approximation is proposed.
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.
Journal ArticleDOI
Towards a full CCSDT model for electron correlation
TL;DR: In this article, the effects of single, double, and triple excitation operators on electron correlation were analyzed and an alternate version of the approximate CCSDT•1 method was implemented.
Journal ArticleDOI
Coupled-cluster method for multideterminantal reference states
TL;DR: In this paper, a general coupled-cluster method valid for arbitrary multideterminantal reference states is formulated and the resulting cluster expansion for the wave function is a generalization of that introduced by Silverstone and Sinano and applied by Sinano\ifmmode \check{g}else \v{g}\fi{}lu and collaborators.