Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
  • 1
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 102 (1995), S. 8040-8047 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Extension of weak orthogonality (WO) techniques developed by Szalewicz et al. and coupled pair equations derived by Jeziorski et al. to positronium compounds are presented. These methods enable us to calculate many-electronic positronium compounds with explicitly correlated functions. These methods were applied to positronium hydride (PsH) with Hylleraas-type functions (HTF's), and the total energies, the positron-electron two-photon annihilation rates, and the positronium binding energies were calculated. Extended coupled pair equations were solved by CEPA(2)-type, complete coupled pair (CCP) procedures, and independent pair approximation (IPA) of CCP. For the total energies, IPA, CEPA(2), and CCP procedures gave −0.78899, −0.78238, and −0.77471 au, respectively. For the two-photon annihilation rates, the respective procedure gave 2.088, 2.064, and 1.972 ns−1, respectively. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 2
    ISSN: 1432-2234
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung Die einfache Hückelsche Methode ist auf die Elektronenstruktur der Eisen-Porphyrin-Komplexe zuerst von Pullman et al. [12] angewandt worden. In der folgenden Arbeit wird ihr Verfahren auf (a) die Wirkung eines Dipols oder einer Punktladung an der sechsten Koordinationsstelle und (b) die eines Stickstoffatoms an der fünften erweitert. Ein Satz neuer Parameterwerte wird verwandt, bei deren Bestimmung besonders auf ihre Abhängigkeit von der Ladungsverteilung geachtet wird. Die erhaltene Ladungsverteilung für Ferroporphyrin erscheint vernünftig. Die Unempfindlichkeit der Lage der Soret-Bande gegen den sechsten Liganden ist aus den erhaltenen Energieniveaus zu verstehen. Die Schwierigkeit, eine vernünftige Ladungsverteilung für Ferriporphyrin zu finden, wird diskutiert.
    Abstract: Résumé La simple méthode de Hückel a été appliquée à la structure électronique des complexes fer-porphyrine pour la première fois par Pullman et al. [12]. Dans l'article suivant, leur travail est étendu afin d'inclure (a) l'effet d'un dipôle ou d'une charge ponctuelle sur la sixième position coordinative, et (b) l'effet d'un atome de nitrogène sur la cinquième position. Un jeu de nouvelles valeurs des paramètres est usé qu'on détermine en tenant compte spécialement de leur dépendance de la distribution des charges atomiques. La distribution de charge obtenue pour la ferroporphyrine semble être raisonnable. Le fait que la position de la bande Soret est insensitive contre le sixième ligand, peut être compris à l'aide des énergies des orbitales calculées. La difficulté de trouver une distribution de charge raisonnable pour la ferriporphyrine est discutée.
    Notes: Abstract The simple Hückel method was first applied to the electronic structure of the iron-porphyrin complexes by Pullman et al. [12]. In this paper, their work is extended to include (a) the effect of a dipole or a point charge placed at the sixth coordination position, and (b) the effect of a nitrogen atom placed at the fifth coordination position. A set of new parameter values is used, whose estimation is made by directing special attention to their dependence on the charge distribution among the atoms. The resulting charge distribution for ferro-porphyrin seems to be reasonable. The fact that the position of the Soret peak is insensitive to the sixth ligand can be understood from the resulting orbital energy levels. The difficulty of finding a reasonable charge distribution for ferri-porphyrin is discussed.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 3
    ISSN: 1432-2234
    Keywords: Key words: Electron affinity ; Excitation energy ; Ionization potential ; Energy convergence ; Transition metal atoms
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract. The electron affinities of the Sc and Ti atoms have been obtained by configuration interaction calculations. Energy convergence with respect to the systematic expansion of both the one-electron basis set and the configuration space was investigated for valence electrons, and the inclusion of correlation contributions from core electrons and relativistic effects gave the electron affinities of 0.181 eV and 0.163 eV for Sc and Ti, respectively. These are in excellent agreement with the observed values of 0.189 ± 0.020 eV and 0.080 eV. The same approach was applied for the first excited states and positive ions of both atoms. Excellent agreement with the experimental results was also obtained for these states.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 4
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A method is proposed for the calculation of matrix elements among various states of atoms. A set of tensor operators is the only entity in the formalism, and all formulas involve merely the vacuum expectation values of these tensor operators and the recoupling transformation coefficients. Some numerical examples are given for the Coulomb interaction matrix elements.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 5
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The transformation of two-electron integrals from an atomic orbital basis to a symmetry orbital basis is a straightforward procedure, but becomes a time-consuming process when the system has high symmetry. In the conventional transformation algorithm, the number of multiplications is proportional to the fifth power of the basis size. To reduce the computer time, a new transformation algorithm is proposed. In this method, the number of multiplications for the transformation is proportional to the fourth power of the number of atomic orbitals in an equivalent orbital group. A new transformation program has been completed and tested against the conventional n5 method. The present method may be regarded as extension of Almlöf's method to any molecular point group. The program cuts the CPU time for the transformation to one-third in calculations for C4H8 and NiF6. This reduction is quite significant for large systems having high symmetry.
    Additional Material: 2 Tab.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 6
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A series of basis sets and configuration interaction (CI) wave functions, both of which were constructed so as to systematically approach to the complete set limit and the full CI limit, were used for the ground state of Ne. These calculations yielded an estimated correlation energy of -0.3891 au, which is 99.6% of a recent theoretical estimate of -0.3905 au. The CI value, -0.3821 au, was obtained by SDCI calculation with seven reference configurations by using Slater-type orbitals (STOs) from s to h functions. © 1994 John Wiley & Sons, Inc.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 7
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In this work, we propose a new orbital set based on density matrices of subsystems. Most of the resultant orbitals are localized in the subsystems and resemble the natural orbitals of the subsystems. Correlation between two electrons, each in a distant localized orbital, should be small and the corresponding configurations can be neglected in a calculation. Test calculations are performed on hexatriene and the usefulness of these orbitals is shown. © 1996 John Wiley & Sons, Inc.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 8
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A study of X-ray and fast electron scattering by light atoms and ions has been carried out in the first Born approximation. Coherent and incoherent scattering factors calculated with configuration interaction wave functions are compared with those obtained with Hartree-Fock wave functions. These configuration interaction wave functions involve only L-shell correlation. It is shown that the changes in the coherent scattering factors due to configuration interaction are not negligible and that the electron correlation effects on the incoherent scattering factors are important. Tables of coherent and incoherent scattering factors for light atomic systems are given.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 9
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Wave functions of the 1S (ground state), 3P and 1P states for the beryllium isoelectronic sequence have been obtained in various approximations.The HF 2p orbitals for the 1P and 3P states are similar except for Be, where the 2p orbital is quite diffuse for the 1P state.The difference between the experimental E(1P) - E(3P) and the HF E(1P) - E(3P) is 0.62 eV for Be and 1.17 ∼ 1.40 eV for B+ ∼ F5+. The disagreements are attributed to the correlation effects between the 2s and 2p electrons. This is confirmed by ci calculations.It is shown that a limited basis SCF calculation reproduces the above feature of the HF results if we treat the orbital exponents as the variational parameters. The use of the Slater values for the orbital exponents is shown to be inadequate especially for the Be 1P state.The conclusions of this paper will be useful for discussing the V-T separations of H2 and C2H4.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 10
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Configuration-interaction calculations, with an extended basis, are carried out on the ground and lower excited states of O2 and O2+ at and near the equilibrium internuclear distance (R = 2.3 a.u.) of the ground state of O2. Particular attention has been paid to the two lowest 3Σu- states, and the mixing of the valence and Rydberg characters in these states are studied. The lowest 3Σu- state is a Rydberg-type state for R 〈 2.3 a.u., but becomes valence-type for R ≳ 2.3 a.u. The second 3Σu- state, which is 1.6 eV above the lowest 3Σu- at R = 2.3 a.u., changes its character from Rydberg to valence, valence to Rydberg, and then to valence again when R increases from 1.9 to 3.1 a.u. Satisfactory agreement between the calculated and experimental vertical excitation energies is obtained.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...