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  • 1
    Electronic Resource
    Electronic Resource
    Theory of one-dimension rotational isomerization: A study of thecis-trans isomerization of HS-NS compared to that of HO-NO (1992)
    Springer
    Molecular engineering 2 (1992), S. 17-27 
    Details
    ISSN: 1572-8951
    Keywords: Rotational isomerization ; NSeH ; NO2H ; potential barriers ; potential functions ; local potentials ; ionization potentials ; dipole moments ; π bonding ; transition states ; Brønsted coefficients
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract A theoretical approach, in which the potential functions representing rotational isomerization processes are expressed in terms of linear combinations of local potentials, is presented. Partitioning the torsional potential allows identification of specific contributions that are at the origin of the shape of potential curves at different regions along the torsional variable. Key properties, such as barrier heights, may then be expressed parametrically in terms of properties associated to the stable conformations. Simple analytical expressions intended to explore, quantitatively and qualitatively, the main characteristics of the transition states connecting stable isomers are formulated. As a first step towards the study of complex systems, we use this procedure to analyseab initio results concerning thecis-trans isomerization reaction of two simple prototype molecules: HSNS and HONO. We determine the relative stabilities of the different isomers and molecular structures and evaluate the associated potential barriers. It is shown that the mathematical procedure used to get potential functions is quite convenient and may be applied to the study of more complex isomerization reactions. Numerical results concerning molecular structures, potential barriers, ionization potentials and dipole moments are discussed. Comparing the values for barrier heights suggests that S(O)-S(O) π bonding through the mechanism of hyperconjugation may be present, to some extent, especially in HSNS.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00999519
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  • 2
    Electronic Resource
    Electronic Resource
    The fundamental syntopy of quasi-symmetric systems: Geometric criteria and the underlying syntopy of a nuclear configuration space (1993)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 45 (1993), S. 177-187 
    Details
    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: Point symmetry is a discrete concept; A nuclear configuration for a given stoichiometry either has or has not a particular point symmetry. By contrast, both static and dynamic properties of actual molecules exhibit continuous features. Using the formalism of fuzzy-set theory, we had previously proposed the concept of syntopy as a continuous extension of the symmetry concept for quasi-symmetric systems: This was based on an energetic criterion taking into account the energy costs of nuclear rearrangements. This extension of symmetry was necessarily dependent on the considered electronic state: For a given geometric arrangement of the nuclei, the energy cost of some rearrangement is dependent on the actual potential surface, that is, on the electronic state, in the Born-Oppenheimer approximation. In the extension of the syntopy model reported in the present work, we consider a syntopy criterion that is common to all electronic states. The syntopy thus defined - called the fundamental syntopy of the reduced nuclear configuration space - is independent of the potential surface and of the electronic state: It is defined only in terms of a geometric condition, which makes it more appropriate to rationalize mesoscopic structures. This new syntopy model provides a connection between all possible syntopies generated by the various potential-energy surfaces supported by the considered family of atomic nuclei. © 1993 John Wiley & Sons, Inc.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560450205
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  • 3
    Electronic Resource
    Electronic Resource
    A semiclassical density functional evaluation of the smoothly varying part of the Hartree-Fock binding energy in atoms (1994)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 52 (1994), S. 1349-1368 
    Details
    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 semiclassical density functional approach is used to evaluate the smooth part of the variation of the Hartree-Fock (HF) binding energy in atoms, from helium through xenon. The energy density functional is chosen with an improved form for the kinetic energy functional (KEF). The variation of the HF binding energy is split into smooth and oscillating (shell-structure) parts, in accordance with Strutinskyøs self-consistent averaging procedure, which is equivalent to a semiclassical ħ-expansion of the KEF. This enables a well-grounded evaluation of the oscillating part of the HF binding energy, which displays a quasi-periodic behavior expressing clearly the shell structure of atoms. © 1994 John Wiley & Sons, Inc.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560520610
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