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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Theoretical chemistry accounts 36 (1975), S. 163-180 
    ISSN: 1432-2234
    Keywords: Hartree-Fock problem ; Frontier molecular orbital model
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The commutator relation between the Hartree-Fock matrix and the one-electron density matrix in Fukui's frontier molecular orbital model has been used to investigate the various kinds of ending of the customary iterative SCF procedure. Step by step description of the iterative SCF procedure has been given in an illustrative graphical way. There is a close connection among the symmetry nonadapted RHF solution for symmetrical molecules, the UHF solution for the closed shell molecules, the complex HF solution and the occurrence of oscillation for the iterative procedure. It has been explicitly shown that the nonconvergence of the usual iterative procedure occurs when the Coulombic interaction between not fully coupled spins of the molecular systems with a certain amount of diradical character is sufficiently weak. The results of the analysis concerning the properties of the Hartree-Fock approach are generalized for the asymmetrical molecules.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Theoretical chemistry accounts 36 (1975), S. 149-161 
    ISSN: 1432-2234
    Keywords: Hartree-Fock-problem ; Frontier molecular orbital model
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The general Hartree-Fock energy in the frontier orbital model in the terms of independent variables is given. The existence conditions for extrema of this expression are derived and their relation with various types of solutions of the HF problem as RHF, UHF and complex wavefunctions is shown. The connection between overall properties of the energy surface and the local properties i.e. the stability and instability conditions of various kinds is demonstrated. The conditions for the occurrence of “strange” HF solutions are expressed in terms of quantities characterizing the correlation effects. This shows explicitly that the lack of respecting the electronic correlation is the reason for the occurrence of the “strange” HF solutions for the molecular configurations which exhibit a certain amount of diradical character.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
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