1962/05/01 by R. McWeeny · 35 citations
Materials Science · Mathematics · Physics and Astronomy · #Advanced Chemical Physics Studies #Density matrix #Eigenvalues and eigenvectors #Fock matrix #Fock space #Hamiltonian (control theory) #Hamiltonian matrix #Magnetism in coordination complexes #Mathematical physics #Mathematics #Perturbation (astronomy) #Physics #Quantum #Quantum and electron transport phenomena #Quantum mechanics #Symmetric matrix
paper · doi:10.1103/physrev.126.1028
openalex publication_date 1962/05/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
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 (\ensuremathρ) is idempotent and commutes with the Hamiltonian (h). The change in \ensuremathρ, accompanying a change \ensuremathΔ 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.