Theoretica chimica acta

, Volume 30, Issue 1, pp 45–58 | Cite as

Molecular orbital structure, Mössbauer isomer shift, and quadrupole splitting in iron complexes

  • Alfred Trautwein
  • Frank E. Harris
Commentationes

Abstract

Molecular orbital calculations are made on six iron complexes, using iterative Hückel methods and, where required for proper description of spin states, a spin-projected semi-empirical configuration interaction (CI). Many integrals are avoided in the CI studies by making direct calculation of energy differences between states. From the calculations are obtained charge and spin bond order matrices, dipole moments, and atomic orbital charges. These quantities are used to calculate charge densities at the Fe nucleus, nuclear quadrupole splittings, and spin populations. From calculations of all six complexes we estimate an Fe57 Mössbauer isomer-shift calibration α ≡ Δδ/Δϱ(0)=−0.31 to −0.38 a03mm/sec.

Zusammenfassung

Mit Hilfe iterativer Hückel-Methoden werden MO-Rechnungen für sechs Eisenkomplexe durchgeführt. Wo es für die Beschreibung der Spinzustände notwendig ist, wird nach einem CI-Verfahren mit Spinprojektion gearbeitet. Durch direkte Berechnung von Energiedifferenzen zwischen den einzelnen Zuständen werden viele Integrale in den CI-Berechnungen vermieden. Aus den Rechnungen erhält man die Matrizen der Ladungs- und Spin-Bindungsordnungen, Dipolmomente und AO-Ladungsverteilungen. Diese Größen werden zur Berechnung der Ladungsdichte am Fe-Kern, der Kernquadrupolaufspaltung und der Spinpopulation verwendet. Aufgrund der Berechnungen aller sechs Komplexe wird die Fe57-Mößbauer-Isomerieverschiebung auf αε Δδ/Δϱ(0)=−0,31 bis −0,38 a03mm/sec geschätzt.

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Copyright information

© Springer-Verlag 1973

Authors and Affiliations

  • Alfred Trautwein
    • 1
  • Frank E. Harris
    • 2
  1. 1.Institut für MetallphysikUniversität des SaarlandesSaarbrückenWest Germany
  2. 2.Department of PhysicsUniversity of UtahSalt Lake City

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