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:
We present nonlocal density-functional calculations for a model of the [Fe4S4]3+ cluster found in high potential iron proteins, which consists formally of a ferric pair Fe 3+Fe3+ and a mixed-valence pair Fe 2.5+—Fe2.5+. Three Spin Hamiltonian parameters, J (the interlayer Heisenberg interaction), B (a resonance delocalization term) and ΔJ12 (associated with the ferric pair) have been estimated using density-functional energies of a high-spin state as well as two different broken symmetry states. We obtain J=673 cm-1, B=878 cm-1, and Δ J12=160 cm-1. These results are discussed in the light of experimental work on a model compound in the same oxidation state, in which the temperature dependence of the magnetic susceptibility was analyzed with this sort of spin Hamiltonian. Good overall agreement between theory and experiment (J=652 cm-1, B=592 cm-1), and ΔJ12=145 cm-1 is found. In particular, the antiferromagnetic spin coupling constant for the ferric pair exceeds in magnitude all other Heisenberg-type interactions (ΔJ12 〉 0) as expected from previous theoretical and experimental work; this is the first time that the broken symmetry method has been used to analyze a spin Hamiltonian with multiple coupling constants in an Fe4S4 cluster. © 1995 John Wiley & Sons, Inc.
Additional Material:
1 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/qua.560560710
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