Ground state wave vectors for thed5 (Fe3+) configuration in symmetriesC4vandC2v. Application to ferrihemoglobins and related compounds

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Abstract
Complete wave vectors for the d5 energy levels were computed on the basis of the 252‖SLJMJ〉 kets of the configuration for D4h, C4v, and C2v symmetries. The interelectronic repulsion Hamiltonian with B=800 cm−1, C=3.7B, the spin–orbit coupling Hamiltonian with ζ=400 cm−1, and a crystal field Hamiltonian written in Wybourne’s tensor operator formalism with the five parameters B40, B44, B42, B20, B22, were used in combination. The free atom parameters used correspond to Fe3+ in solids. Maps of the ground state multiplicity versus B40, B44, and B20, (C4v) were established. Two zones, where the three multiplicities (2S+1) =2, 4, and 6 meet are apparent, one corresponds to low values of B20 and medium values of B40, B44 (30 000 cm−1). The positive D factor for zero‐field splitting of the 6S5/2 state was computed as a function of crystal field parameters. g∥ and g⊥ were computed for the low‐spin domain in C4v; gx, gy, gz were calculated in C2v symmetry in the low‐spin domain near the border with four and six multiplicities. Comparison with experimental results shows that high spin ferrihemoglobins, and related compounds with large D factors, correspond to a borderline situation with multiplicity 4. g values for low spin ferrihemoglobins can be reproduced with crystal field parameters values corresponding either to the low spin domain close to the borders, or for C2v distortion of the C4v symmetry in high or intermediate spin domains. In the border areas, the g’s are very sensitive to changes in the crystal field parameters because of the rapid variation of composition of the wave vectors in crossover situations.