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Perturbation Theory for the Fock-Dirac Density Matrix

McWeeny, R.·1962·Physical Review

Abstract

In Hartree-Fock theory and its various generalizations, it is customary to solve an eigenvalue problem involving an effective one-body Hamiltonian. The eigenvectors determine the Fock-Dirac density matrix, which also appears in the effective Hamiltonian, and solution proceeds iteratively until self-consistency is achieved.An alternative (necessary and sufficient) condition for a solution is that the density matrix ($\ensuremath{\rho}$) is idempotent and commutes with the Hamiltonian (h). The change in $\ensuremath{\rho}$, accompanying a change $\ensuremath{\Delta}$ in h, can then be expressed as a perturbation series. Formulas for the perturbation, to all orders, are obtained in terms of the unperturbed Hamiltonian and density matrix. It is also shown that the whole perturbation may be obtained directly, without separating the orders, and that the approach is related to earlier steepest-descent methods.

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Metadata

Authors
McWeeny, R.
Venue
Physical Review
Published
1962-05-01
Volume
126
Issue
3
Pages
1028-1034
ISSN
0031-899X (ISSN-L)
OpenAlex
W2148080533
Cited by
833
References
6
FWCI
1.14
Type
journal article
Language
en
Open access
closed

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CoChat. (2026). Citation check: Perturbation Theory for the Fock-Dirac Density Matrix. https://app.cochat.ai/papers/10.1103/physrev.126.1028
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McWeeny, R. (1962). Perturbation Theory for the Fock-Dirac Density Matrix. Physical Review. https://doi.org/10.1103/physrev.126.1028

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