Showing papers by "Poul Jo published in 1978"
TL;DR: In this article, the Hartree-Fock procedure can be brought to converge for stable states of a given symmetry if the blocks of the Fock matrix, which are not determined by the Brillouin theorem, are chosen in an appropriate fashion.
Abstract: The problem of finding orbitals, which make the total energy stationary, when the ground state or reference state is of the multiconfigurational form, is analyzed in this paper. Particular attention is given to the quadratically convergent methods. Orbital variations are generated by unitary transformations and an expansion of the total energy through second order in the parameters used to define these transformations provides a characterization of the stationary point, which is reached at convergence, as well as estimates of second order properties. Effective one‐particle potentials are analyzed and it is emphasized that only certain blocks of the Fock matrix are determined by the generalized Brillouin theorem. In an analysis of the convergence properties of the various methods it is shown that the Hartree–Fock procedure can be brought to converge for stable states of a given symmetry if the blocks of the Fock matrix, which are not determined by the Brillouin theorem, are chosen in an appropriate fashion...
255 citations
TL;DR: In this article, the second order optical properties are obtained directly from the propagator without calculating the individual excitation energies and transition moments which appear in the sum-over-states procedures, and expressions for the frequency-dependent polarizability, the Verdet constant, and the energy sum rules have been derived consistent through third order in the electronic repulsion using an analytical polarization propagator method.
Abstract: Expressions for the frequency‐dependent polarizability, the Verdet constant, and the energy sum rules have been derived consistent through third order in the electronic repulsion using an analytical polarization propagator method. In this approach, the second order optical properties are obtained directly from the propagator without calculating the individual excitation energies and transition moments which appear in the sum‐over‐states procedures.
40 citations
TL;DR: In this paper, the frequency dependent polarizabilities and Verdet constants for He, Be, CO, and FH have been calculated within a first (coupled Hartree-Fock) and second order polarization propagator approach.
Abstract: Frequency dependent polarizabilities and Verdet constants for He, Be, CO, and FH have been calculated within a first (coupled Hartree–Fock) and second order polarization propagator approach. Except for regions close to excitation thresholds, small differences are found between frequency‐dependent polarizabilities calculated in the two orders. The improvements in the polarizability near an excitation threshold are caused by the better description of the excitation spectrum in the second order theory. The trends in the Verdet constants are similar to those found for the polarizability except that the improvements in the second order approach are substantial also away from an excitation threshold (up to 60% of the difference between the coupled Hartree–Fock and the experimental result).
39 citations