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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Theoretical chemistry accounts 33 (1974), S. 79-86 
    ISSN: 1432-2234
    Keywords: Atomic screening constants ; Mean values of r 1 r and r 12 r in two-electron atoms ; Scaling ; Helium isoelectronic sequence, screening in the ∼
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Mean values of r 1 r and r r 12 for the ground and several excited states of the helium isoelectronic sequence are used to demonstrate that a simple scaling which superimposes the distribution function f(r 12) as a function of the atomic number leads to a similar result for the electron density distribution D(r1). On the basis of a screening interpretation of the scaling parameter δ, it is concluded that screening is greater in the singlet than the triplet state of a particular configuration, that screening is greater in the P states than the corresponding S states, and that the screening approaches the limiting value of 1 for the highly excited states. The perturbation expansions of Scherr and Knight are used to determine the limiting value of δ when Z→∞ and the relationship between the scaling parameter and the scale factor, chosen so that a trial wave function satisfies the virial theorem, is discussed. A brief discussion of the scaling of the Coulomb hole is presented.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Theoretical chemistry accounts 53 (1979), S. 309-317 
    ISSN: 1432-2234
    Keywords: Additivity model ; UHF spin densities and charge densities ; Heteroatom model ; Radical cations
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract By use of a heteroatom model for the methyl group and an additivity model for spin densities, the unrestricted Hartree-Fock after annihilation (UHFAA) results for the radical cations of naphthalene, 1-methylnaphthalene and 2-methylnaphthalene are used to predict the spin densities in the π-electron approximation in the corresponding cations of di-, tri- and tetramethylnaphthalenes. The additivity model approach is shown to be equally successful for charge densities.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 10 (1989), S. 367-375 
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: The topological properties of the electron density and the properties of an atom in a molecule are calculated by means of second-order Møller-Plesset perturbation theory (MP2) and compared with the results of configuration interaction calculations (C12) which include all single and double substitutions from the Hartree-Fock reference configuration. A software package for analyzing the effects of electron correlation on the topological properties of the electron density of molecules is described. H2CO is used to provide a numerical example and to indicate that the number of bond critical points is unaffected by the inclusion of electron correlation. Correlation leads to only a small shift in the positions of bond critical points and a small change in the electron density at bond critical points. It is further shown that the energy of an atom in a molecule can be calculated to an accuracy of 1 kcal/mol and the electron population of an atom to about 0.001e. A statistical method is used to show that the deviation of the MP2 correlation correction relative to the CI2 correlation correction for a variety of atomic properties is about 25%.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 8 (1987), S. 489-498 
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: The bond critical points and associated electronic properties of the diatomic hydrides of the twenty-one main group elements from lithium to bromine have been calculated with large basis sets. As part of a systematic study of the polarity of chemical bonds, the position of the bond critical point, the charge density at the bond critical point, the Laplacian of the charge density at the bond critical point, and the molecular dipole moment of each molecule have been calculated. Particular attention has been paid to the effect of bond length elongation and contraction on the electronic properties. Variation of the bond length reveals that with atoms of low electronegativity, the bond critical point of AH tends to follow atom A, whereas with atoms of high electronegativity, the bond critical point tends to follow the hydrogen atom as the bond lengthens. Furthermore, it is shown that some properties of the diatomic hydrides vary monotonically within each row of the periodic table, while others effect a classification according to the character of the bond.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
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