Triplet instability conditions for the restricted Hartree-Fock (RHF) solution for the 4Fe-4S cluster in ferredoxin were examined. The possible generalized HF (GHF) solutions for the cluster were derived on the basis of a general magnetic double group theory. The resulting GHF solutions support the spin structures based on the Heisenberg model, which show antiferromagnetic spin couplings between the iron ions in ferredoxins. The VB and MO pictures provide complementary insight into the type II and III mixed-valence (MV) states of the iron-sulfur clusters. © 1990.
Yamaguchi, K., Fueno, T., Ozaki, M. aki, Ueyama, N., & Nakamura, A. (1990). A general spin-orbital (GSO) description of antiferromagnetic spin couplings between four irons in iron-sulfur clusters. Chemical Physics Letters, 168(1), 56–62. https://doi.org/10.1016/0009-2614(90)85102-I