High sectors in the Fock space coupled-cluster method

Hughes, S. R.; Kaldor, Uzi

doi:10.1016/0009-2614(92)85749-z

Cited by 54 publications

(13 citation statements)

References 42 publications

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“…Its main shortcoming is the limitation to states obtained from a closed shell configuration by adding and/or removing two electrons at most. Efforts have been made [126] to extend the method to sectors of the Fock space with a larger number of electrons or holes. Other work in progress includes the further development of the Hilbert-space and mixed-sector IHCC [127], as well as the double FSCC formalism mentioned in the introduction, which will include higher QED terms and allow a more precise treatment of SHEs, especially in the case of highly ionized species.…”

Section: Discussionmentioning

confidence: 99%

“…The sector (m, n) of the Fock space includes all states obtained from the reference determinant by removing m electrons from designated occupied orbitals, called valence holes, and adding n electrons in designated virtual orbitals, called valence particles. The practical current limit is m + n ≤ 2, although higher sectors have also been considered [126]. The excitation operator S, defined by the exponential parametrization of , is partitioned into sector operators S = m≥0 n≥0 S (m,n) .…”

Section: Electron Correlation: Fock-space (Fs) and Intermediate Hamilmentioning

confidence: 99%

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Electronic structure theory of the superheavy elements

2015

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Section: Discussionmentioning

confidence: 99%

Section: Electron Correlation: Fock-space (Fs) and Intermediate Hamilmentioning

confidence: 99%

Electronic structure theory of the superheavy elements

2015

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“…Hence, excluding some attempts addressing special cases or introducing various simplifying assumptions, the existing MR-CC methods can be roughly classified into two categories. The first one consists of the valence-universal ͑VU͒ or Fock-space ͑FS͒ theories, [3][4][5][6][7][8][9][10][11][12][13] in which a universal wave operator is defined as a consequence of having one vacuum. The important feature of these approaches is that they simultaneously describe a hierarchy of systems with different numbers of electrons starting with a system for which the Fermi vacuum is the zero-order approximation.…”

Section: Introductionmentioning

confidence: 99%

Application of the intermediate Hamiltonian valence-universal coupled-cluster method to the magnesium atom

Malinowski

Meissner

Nowaczyk

2002

The Journal of Chemical Physics

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Renormalized coupled-cluster methods exploiting left eigenstates of the similarity-transformed HamiltonianPerformance of the general-model-space state-universal coupled-cluster methodThe atomically oriented valence-universal coupled-clusters method in the intermediate Hamiltonian formulation with one-and two-body part͑s͒ included in the cluster operator ͑VU-CCSD/R͒ is applied to describe the ground state and some excited states of the Mg atom. Two Slater-type orbitals ͑STO͒ basis sets are employed to see the effect of the basis set on the results. In addition to that, several complete model spaces are used in the calculation starting with (3s,3p) and ending with (3s,3p,3d,4s,4p) orbitals as active. It has been found that the quality of the description of the ground-and excited states depends on the STO basis set used in the calculation. In order to obtain reliable excitation energies, special attention has been paid to the construction of well-balanced basis sets in which functions necessary for adequate description of both the ground state and excited states under consideration are included. Therefore, in spite of the moderate size of the orbital basis, our results compare quite well in terms of the total energy as well as in energy differences with results of other methods which, in some cases, use significantly larger basis sets.

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“…The sector (m, n) of the Fock space includes all states obtained from the reference determinant by removing m electrons from designated occupied orbitals, called valence holes, and adding n electrons in designated virtual orbitals, called valence particles. The practical limit is m + n ≤ 2, although higher sectors have also been tried [13]. The excitation operator is partitioned into sector operators…”

Section: The Fock Space Coupled Cluster Methodsmentioning

confidence: 99%

Potential Functions of Al2 by the Relativistic Fock-Space Coupled Cluster Method

Landau

Eliav

Visscher

et al. 2002

IJMS

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somewhat too weak, with D e 0.14 eV below experiment, R e too high by 0.08Å, and ω e 21 cm −1 too low. It is speculated that the better agreement obtained in earlier calculations may be due to neglect of basis set superposition errors. The description of bonding in the molecule may be improved by the use of a better basis and the inclusion of more correlation by the intermediate Hamiltonian coupled cluster method, which makes it possible to handle larger P spaces and extend the potential functions to the whole range of internuclear separations.

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High sectors in the Fock space coupled-cluster method

Cited by 54 publications

References 42 publications

Electronic structure theory of the superheavy elements

Electronic structure theory of the superheavy elements

Application of the intermediate Hamiltonian valence-universal coupled-cluster method to the magnesium atom

Potential Functions of Al2 by the Relativistic Fock-Space Coupled Cluster Method

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