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Theoretical studies of the photoelectron spectroscopy of the fluorinated ethylenes (1986)

Heaton, M. M. ; El-Talbi, M. R.

College Park, Md. : American Institute of Physics (AIP)

The Journal of Chemical Physics 85 (1986), S. 7198-7210

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ISSN: 1089-7690

Source: AIP Digital Archive

Topics: Physics , Chemistry and Pharmacology

Notes: Ab initio molecular orbital calculations within the self-consistent field (SCF) method were effected for the complete series of the fluorinated ethylenes. A "double zeta''-quality basis set was used with complete geometry optimization. Two methods were employed to correlate these calculated results with experimentally obtained vertical ionization potentials: the use of the orbital energies in accordance with Koopmans' theorem and the use of the difference between the SCF energy of the molecule and the respective ion constrained to the molecular geometry. In several cases, an average of the Koopmans' theorem results and the ΔSCF results was employed to approximate the experimental photodetachment energies. Definitive assignments of the molecular orbitals to the experimental bands could not be made on the basis of correspondence of energies. However, the relative ordering of the theoretical energies is considered generally correct. A correspondence also exists between the experimentally determined characteristics of the molecular orbitals, where specified, and the theoretical characteristics as evidenced in the population analyses. The orbital assignments were based upon the latter two factors.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1063/1.451356

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The difluoroethylenes: A reconsideration of the “Cis effect” (1986)

Heaton, M. M. ; El-Talbi, M. R.

New York, NY : Wiley-Blackwell

International Journal of Quantum Chemistry 29 (1986), S. 61-72

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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: Ab initio molecular orbital calculations have been carried out on all three isomers of difluoroethylene with geometry optimization. The calculations were done with a “double-zeta” basis set. After correction of the SCF energies for the effect of electron correlation, the 1,1-isomer is shown to be 8 kcal/mole lower in energy than the cis, which is 1 kcal/mole more stable than the trans. As the stabilization of the isomers increases, the distance between the fluorine atoms decreases: trans, 3.57 Å; cis, 2.77 Å; 1,1-isomer 2.20 Å. A simple explanation for these trends is based upon electrostatics and the small size and high electronegativity of the fluorine atom. As the fluorine atoms come closer together, the destabilization due to nuclear repulsions and electron repulsions is offset by the increased stabilizing electrons-nuclei attractions.

Additional Material: 1 Ill.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1002/qua.560290107

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