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  • 1
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 116 (2002), S. 7012-7026 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: An exhaustive investigation of the outer-valence ionization spectra of azulene, phenanthrene, pyrene, chrysene, triphenylene, and perylene is presented. The analysis is based on one-particle Green's function calculations performed upon correlated [density-functional theory/Becke three-parameter Lee–Yang–Parr (DFT/B3LYP)] geometries using the third-order outer-valence Green's function [OVGF] and algebraic-diagrammatic construction [ADC(3)] schemes, as well as basis sets of improving quality (6-31G, 6-31G*, cc-pVDZ). The ionization bands of polycyclic aromatic hydrocarbons show a great diversity, which reflects the strong impact of the molecular architecture on orbital energies. Despite the intricacy of ionization spectra and the extent of the shake-up contamination in the π- and σ-band systems, the ADC(3) results enable consistent insights into available ultraviolet photoelectron measurements, up to the inner-valence region. They also indirectly support recent assignments of low-lying π*←π doublet excitations in the electronic absorption spectrum of the pyrene and perylene cations by means of time-dependent density functional theory [J. Chem. Phys. 111, 8904 (1999)]. It has been found that OVGF pole strengths smaller than 0.85 very systematically foretell a breakdown of the orbital picture of ionization at the ADC(3) level. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 115 (2001), S. 5859-5882 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The valence ionization bands of benzene and of polyacenes ranging from naphthalene to pentacene have been entirely assigned by means of one-particle Green's function calculations, performed using the third-order algebraic-diagrammatic construction [ADC(3)] scheme and series of basis sets of improving quality. For the sake of consistency, the computations are based on correlated (DFT/B3LYP) rather than uncorrelated geometries. Ionization bands pertaining to π-orbitals are subject to a severe shake-up contamination at already quite low binding energies (e.g., down to 8.0 eV in the case of pentacene). In sharp contrast, the orbital picture of ionization holds to a much greater extent within the σ-band system (e.g., for pentacene, up to binding energies of 14.6 eV). Despite the intricacy of ionization bands, and, possibly, vibrational complications, ADC(3) spectra consistently match photoionization measurements up to the inner-valence region, where the orbital picture completely breaks down. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 102 (1995), S. 6128-6144 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The perturbed electron propagator is discussed as a means of obtaining static linear response properties. The dynamic self-energy is derived at first order in the field and second order in correlation using a diagrammatic method. We discuss the invariance properties of the first-order perturbed electron density which may be obtained from the perturbed electron propagator formalism. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 102 (1995), S. 8967-8977 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The size-consistency and the size-extensivity aspects of linear response properties obtained using the coupled electron propagator approach are examined in the limit of a complex system dissociating into noninteracting fragments, and in the thermodynamic limit of a periodic inhomogeneous system with finite densities. This analysis is carried out considering forms of the perturbed electron propagator exact up to first-order and second-order in the correlation potential. Conclusions obtained can be extrapolated to higher orders on the basis of the topology of self-energy and perturbed one-electron density diagrams. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 5
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 103 (1995), S. 3578-3588 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Various approximations are used currently to evaluate the static part Σ(∞) of the self-energy or optical potential in molecular Green's function calculations. Since its expansion is ruled out by the linked-cluster theorem, one generally assumes a size-intensive behavior of Σ(∞) in the thermodynamic limit of an infinite system. A detailed analysis of this size-dependence property is conducted using the formulation of crystalline orbitals (CO) for stereoregular polymers. In spite of the linked-cluster theorem, this study provides evidence for a logarithmic divergence with respect to the size of a chain for some forms of Σ(∞), computed with common approximation schemes. This is the direct outcome of the long-range character of the Coulombic interaction and can be related to a violation in the number of particles within the system. A proper size-intensive behavior implies an exact cancellation of the logarithmically divergent behavior of antigraphs. The conclusions drawn from CO analysis are confirmed by numerical tests on model oligomer systems. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 105 (1996), S. 7583-7596 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The x-ray photoionization spectra of large saturated hydrocarbons have been investigated by means of one-particle Green's function calculations. These spectra saturate overall rather quickly to their asymptotic form with increasing system size. The results obtained indicate a severe breakdown of the molecular orbital picture of ionization above a binding energy threshold of about 23 eV, for n-alkane chains ranging from n-propane to n-nonane, or cycloalkane compounds such as cyclobutane, cyclopentane, and cyclohexane. In spite of the fast multiplication of satellite solutions, shake-up lines remain confined above that threshold, as a result of the delocalization properties of one-electron canonical states. The ring closure is shown to emphasize the dispersion of photoionization intensity into satellites. Conformational changes, on the other hand, have only marginal effects on the convoluted correlation bands. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    The @journal of physical chemistry 〈Washington, DC〉 97 (1993), S. 5115-5123 
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
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  • 9
    ISSN: 1432-2234
    Keywords: Green's function ; Ionization potential ; Orbital relaxation ; Electron correlation ; Polarization
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The vertical ionization potential and the related pole strength of a model alternant chain of 14 hydrogen atoms subject to a homogeneous electric field, parallel to the chain and of increasing intensity are calculated, in the framework of a 6–31G** basis set, at the second-order level of the many-body Green's function theory. Trends observed with orbital relaxation, pair removal and pair relaxation effects are interpreted in terms of deformations of the electron density.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 41 (1992), S. 243-255 
    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 vertical ionization potentials of model hydrogen chains have been calculated, in the framework of STO-3G and 4-31G bases, at the second-order level of the many-body Green's function theory. Compared to the second-order many-body perturbation theory, this approach provides a qualitative description of trends observed with orbital relaxation, pair removal, and pair relaxation effects when studying oligomeric systems of increasing size with varying bond length.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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