Showing papers by "Ernest R. Davidson published in 1983"
TL;DR: In this article, the rupture de symetrie resultant de croisements evites Von Neumann-Wigner ou Jahn-Teller, ou d'effets pseudo-Jahn Teller.
Abstract: Revue de travaux recents sur la rupture de symetrie resultant de croisements evites Von Neumann-Wigner ou Jahn-Teller, ou d'effets pseudo-Jahn-Teller. Exemples de fonctions d'onde approchees presentant une symetrie brisee pour des arrangements symetriques des noyaux
263 citations
01 Jan 1983
TL;DR: Efficiency must be judged in terms of the ability to solve a variety of eigenvalue problems on computers of widely different architecture, memory size, and data transfer rates.
Abstract: Widespread use of the linear variation method in quantum mechanics leads to the need for efficient matrix eigenvalue methods for real symmetric matrices. Efficiency must be judged, however, in terms of the ability to solve a variety of eigenvalue problems on computers of widely different architecture, memory size, and data transfer rates. To further confuse the situation, cost rather than system throughput, is usually of paramount concern. Additionally, algorithms vary widely in ease of programming, simplicity, reliability, portability and availability as part of standard packages. Consequently there are a wide variety of eigenvalue algorithms in use, and a typical quantum laboratory will incorporate several of these into their program package.
103 citations
97 citations
79 citations
TL;DR: In this paper, a second-order Rayleigh-Schrodinger B K method (RS B K ) is described and applied to computing the lower electronic states of pyrrole, which is more nearly size consistent than the previously used Brillouin-Wigner B K (BW B K) method.
60 citations
TL;DR: In this paper, the rank annihilation for multi-component determinations is extended to a three-dimensional data araay and the possibility of improved sensitivity over the two-dimensional method is shown.
32 citations
TL;DR: In this article, error estimates for the approximate complex eigenvalues of the dilated Schrodinger operators are derived for the resonances of the dc Stark effects in hydrogen, and they are calculated for the σ-approximation of the complex Eigenvalues.
Abstract: Error estimates for the approximate complex eigenvalues of the dilated Schr\"odinger operators are derived. They are calculated for the resonances of the dc Stark effects in hydrogen.
28 citations
TL;DR: In this article, the energy difference between 3A i2 trimethylenemethane (TMM) and 1Ag butadiene was calculated using the pi configuration interaction (CI) values obtained when excitations of sigma electrons are permitted.
Abstract: Ab initio configuration interaction (CI) calculations have been carried out in order to determine the energy difference between 3A i2 trimethylenemethane (TMM) and 1Ag butadiene. The pi CI value of 38.3 kcal/mol is very similar to the CI values obtained when excitations of the sigma electrons are permitted. This finding suggests that correlation effects involving sigma orbitals make at most a small contribution to the energy differences between non-Kekule hydrocarbon diradicals and their closed-shell isomers. Possible complications in the experimental measurement of this energy difference are discussed. It is pointed out that methylenecyclopropane might be formed in attempts to deprotonate the 2-methallyl cation, without the involvement of TMM. From the experimental heats of formation of methylenecyclopropane and butadiene, an energy difference of 14–16 kcal/mol between 3A i2 TMM and methylenecyclopropane is estimated. This is in excellent agreement with a previous energy difference obtained by direct calculation.
23 citations
TL;DR: In this article, the chemical potential for harmonically interacting spin-½ fermions in three dimensions was examined and the energy and chemical potential were shown to be discontinuous functions of the particle number if the most straightforward equation was used to define the energy for a noninteger particle number.
Abstract: The chemical potential μ, as it appears in density functional theory, is examined extensively for harmonically interacting spin-½ fermions in three dimensions. For this system the energy and chemical potential are discontinuous functions of the particle number if the most straightforward equation is used to define the energy for a noninteger particle number.
16 citations
13 citations
TL;DR: In this article, the MRD-CI and MC-SCF are used to calculate the surface de potentiel relativement plate le long de la coordonnee de distorsion de la liaison C-C asymetrique, ou la densite de spin dans l'espace π depend fortement de la difference des deux longueurs de liaison C -C asymptotic.
Abstract: Calculs ab initio MRD-CI et MC-SCF sur l'etat 3 A″ du vinylmethylene. Mise en evidence d'une surface de potentiel relativement plate le long de la coordonnee de distorsion de la liaison C-C asymetrique, ou la densite de spin dans l'espace π depend fortement de la difference des deux longueurs de liaison C-C
TL;DR: In this paper, the MC-SCF d'une courbe de potentiel semi-quantitative for dissociation is calculated, and a minimum stable stable for C 2 H 4 and a barrière for the dissociation of deux methylenes is constructed.
Abstract: Calcul MC-SCF d'une courbe de potentiel semi-quantitative pour la dissociation D 2h du 1er etat excite 1 Ag de C 2 H 4 en deux methylenes 1 A 1 : contrairement a des travaux anterieures, le caractere Rydberg de l'etat 1 Ag conduit a un minimum stable pour C 2 H 4 et a une barriere pour la dissociation
TL;DR: In this paper, interchange and many-body perturbation theory are applied to the calculation of the radiative lifetime of the 3B1 state of SO2, which is predicted to be 7.6 msec in excellent agreement with the experimental collision-free phosphorescence lifetime.
Abstract: Interchange and many-body perturbation theory are applied to the calculation of the radiative lifetime of the 3B1 state of SO2. The radiative lifetime of 3B1 SO2 is predicted to be 7.6 msec, in excellent agreement with the experimental collision-free phosphorescence lifetime. As a separate calculation, interchange perturbation theory is used to determine the radiative lifetime of the 1A1 state of CH2.
TL;DR: In this paper, an alternative definition of the reduced mass, which differs from the usual μ=1 convention, is examined with respect to its ability to provide insight into the type of motion taking place along the reaction coordinate.
Abstract: An alternative definition of the reduced mass, which differs from the usual μ=1 convention, is examined with respect to its ability to provide insight into the type of motion taking place along the reaction coordinate.
TL;DR: In this paper, an empirical correction based on the known deficiencies of the basis set and CI method in atomic calculations, suggests that this estimate should be increased to approximately 0.63 eV, which provides further evidence in favor of a reinterpretation of the photoelectron spectrum work of Zittel et al.
Abstract: Large basis set configuration interaction calculations yield an electron affinity of 0.42 eV for CH2(3B1). Application of an empirical correction, based on the known deficiencies of the basis set and CI method in atomic calculations, suggests that this estimate should be increased to approximately 0.63 eV. This provides futher evidence in favor of a reinterpretation of the photoelectron spectrum work of Zittel et al., which indicated an electron affinity of only 0.210 eV while giving a 3B1–1A1 energy gap of 19.6 kcal/mol.
University of South Carolina1, Michigan Technological University2, University of Oxford3, University of New Orleans4, Argonne National Laboratory5, Technical University of Denmark6, University of Washington7, University of Cologne8, University of Oslo9, University of Alberta10, University of Michigan11, Southern Illinois University Carbondale12, Max Planck Society13, Folkwang University of the Arts14, University of Kassel15, University of Bristol16, University of Erlangen-Nuremberg17
TL;DR: In this paper, a bound-state perturbation theory for a relativistic spinless (Klein-Gordon) and Dirac particle in central fields due to scalar or fourth-component vector-type interactions for an arbitrary bound state is presented.
Abstract: We present summary results of a bound-state perturbation theory for a relativistic spinless (Klein-Gordon) and a relativistic spin-half (Dirac) particle in central fields due to scalar or fourth-component vector-type interactions for an arbitrary bound state. The reduction of the wave equations to Ricatti form enables a decoupling between the pair of coupled first order differential equations on the large and small component Dirac wave functions or a decoupling of the second order differential equation in the Klein-Gordon case. All corrections to the energies and wave functions, including corrections to the positions of the nodes in excited states, are expressed in quadratures in a hierarchical scheme, without the use of either the Green function or the sum over intermediate states.