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  • 1
    Electronic Resource
    Electronic Resource
    A localized-basis monoexcited configuration interaction technique for extended systems (1991)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 94 (1991), S. 8520-8528 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: It is demonstrated that the monoexcited configuration interaction matrix, constructed from the localized (or Wannier) orbitals for an one-dimensional extended system with translational symmetry can be used to define a series of finite-dimensional matrices whose lowest eigenvalues and eigenvectors converge to the lowest eigenvalues and eigenvectors of the infinite-dimensional full monoexcited configuration interaction problem. As an illustration, the developed monoexcited configuration interaction approach is applied to the π-electronic model of cyclic polyenes (annulenes) in the framework of the Pariser–Parr–Pople approximation. A standard parametrization scheme has been found to yield a value of ∼2.42 eV for the lowest singlet excitation energy of an infinite polyene, which is in good agreement with the experimental estimate of ∼2 eV.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.460085
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  • 2
    Electronic Resource
    Electronic Resource
    Convergence of direct space exchange lattice sums in polymer band structure calculations (1986)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 85 (1986), S. 5286-5298 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A study of the convergence properties associated with direct lattice summations of the exchange contributions to the quantities needed in a restricted Hartree–Fock calculation for a polymer, leads to a detailed analysis of the analytic and asymptotic properties of the Fock–Dirac density matrix in the LCAO representation. The results, obtained simply by means of Fourier analysis, provide an important characterization of the restricted Hartree–Fock method as applied to chain-like systems. As a by-product we obtain a general proof in direct space that a partially filled band, which influences drastically the analyticity properties of the density matrix in reciprocal space, leads to a logarithmically diverging derivative of the orbital energy at the Fermi level. This in turn gives a vanishing density of states at that level. This result, well known for the electron gas model, is thus an inherent property of the restricted Hartree–Fock approximation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.451671
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  • 3
    Electronic Resource
    Electronic Resource
    Electron nuclear dynamics for a zig–zag chain of nitrogen atoms (1995)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 102 (1995), S. 3269-3280 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We study the nitrogen zig–zag chain with two atoms per unit cell within the electron nuclear dynamics (END) formalism. This amounts to an approximate solution of the time-dependent Schrödinger equation for all the particles in the system. In the present approximation the nuclei are treated classically. The time dependence of the electronic motion is brought in through time-dependent linear combinations of fixed Bloch sums. This implies that the immediate mutual interaction between electronic and nuclear motion is taken into account. We investigate in particular the long-range terms of the interaction so as to arrive at convergent lattice sums. Before going to the general case when electronic and nuclear motion is coupled, we investigate the special cases of END traditional lattice dynamics and the random phase approximation (RPA) for the electrons. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.468638
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  • 4
    Electronic Resource
    Electronic Resource
    A model for electron nuclear dynamics of a monatomic chain (1994)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 101 (1994), S. 3989-4003 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The electron nuclear dynamics (END) approach is developed for a linear chain in a parametrized model inspired by the PPP (Pariser–Parr–Pople) model. Particular attention is given to the model parameters, and the choice of basis functions in this time-dependent theory. The resulting equations of motion include electronic–vibrational couplings. Explicit analysis of the simplest model leads to coupling between the highest frequency longitudinal vibrational mode and the electrons.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.467517
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  • 5
    Electronic Resource
    Electronic Resource
    Orbital forms of gap equations and instability conditions (1982)
    Springer
    Theoretical chemistry accounts 61 (1982), S. 135-147 
    Details
    ISSN: 1432-2234
    Keywords: Gap equation ; Instabilities ; Fukutome classes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Previously derived forms of instability conditions at the spin orbital level are specialized to orbital levels of different kinds. Similarly the special forms of the gap equation that are obtained for different types of broken symmetry solutions are analyzed and discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00549139
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  • 6
    Electronic Resource
    Electronic Resource
    Symmetric orthogonalisation in momentum space: A numerical study (1993)
    Springer
    Theoretical chemistry accounts 84 (1993), S. 475-487 
    Details
    ISSN: 1432-2234
    Keywords: Symmetric orthogonalisation ; Momentum space
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Symmetric orthogonalisation is favourable to perform in momentum space, as this article will show. We have used a model of a body centered cubic lattice with 1s- and 2s-Slater orbitals centered at each atom site. Computer programs have been written to calculate the eigenvalues of the overlap matrix which play an important role in constructing symmetrically orthogonalised wavefunctions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01126611
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  • 7
    Electronic Resource
    Electronic Resource
    Fukutome classes in momentum space (1993)
    Springer
    Theoretical chemistry accounts 86 (1993), S. 137-147 
    Details
    ISSN: 1432-2234
    Keywords: Fukutome ; Momentum space
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Fukutome's group theoretical classification scheme for determinants, based on the transformation properties of the Fock-Dirac density matrix under spin rotations and time reversal, has been extended to momentum space. Particular attention is paid to the transformation properties of orbitals and density matrices under inversion in momentum space.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01113520
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  • 8
    Electronic Resource
    Electronic Resource
    Atomic wave functions for the configurations snpm studied by the projection operator technique (1965)
    Springer
    Theoretical chemistry accounts 3 (1965), S. 69-96 
    Details
    ISSN: 1432-2234
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Résumé On a calculé des fonctions propres du moment cinétique ainsi que les matrices correspondantes de l'énergie, pour les configurations atomiques s n pm. Les trois types de couplage, LS, jj et intermédiaire ont été étudiés, ainsi que les matrices de transformation entre ces couplages. Pour tous ces calculs on a utilisé la méthode des projecteurs pour le moment cinétique, introduite par Löwdin.
    Abstract: Zusammenfassung Eigenfunktionen des Drehimpulses und entsprechende Energiematrizen für die Atomkonfigurationen s n pm sind für die drei Kopplungsfälle, LS, jj und intermediär tabelliert. Matrizen für Transformationen zwischen LS- und jj-Kopplung werden angegeben. Alle diese Rechnungen sind auf die von Löwdin eingeführte Projektionsoperatormethode gegründet.
    Notes: Abstract Tables of angular momentum wave functions and energy matrices for the atomic configurations s n pm are given in the cases of strong, weak and intermediate coupling. Also the transformation matrices between LS- and jj-coupling are calculated. All these calculations are carried out as an application of the projection operator method for angular momenta, introduced by Löwdin.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00526534
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  • 9
    Electronic Resource
    Electronic Resource
    Interaction between electronic and nuclear motion in linear chains (1994)
    Springer
    Theoretical chemistry accounts 89 (1994), S. 311-321 
    Details
    ISSN: 1432-2234
    Keywords: Electronic motion ; Nuclear motion ; Linear chains
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The geometrical structure of linear chains is discussed with reference to procedures for treating both electronic and nuclear motion and illustrated with reference to recent density functional calculations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01114104
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  • 10
    Electronic Resource
    Electronic Resource
    Calculation of the electronic structure of ethylene by the SCF-Xα scattered wave method (1975)
    Springer
    Theoretical chemistry accounts 40 (1975), S. 231-236 
    Details
    ISSN: 1432-2234
    Keywords: Ethylene
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The electronic structure of ethylene is investigated by the implementation of the Xα scattered wave method and a comparison is made with SCF LCAO results. Calculations are also carried out for different geometrical configurations of the molecule, in which one HCH plane is rotated through different angles relative to the other.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00548457
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