Molecular-Orbital Calculation of 10Dq in Some Transition-Metal Fluorides

Abstract

Using the ionic Hamiltonian model, the antibonding orbital separation 10Dq has been calculated for the tripositive metal hexafluorides CrF₆³⁻ and FeF₆³⁻, and for the dipositive metal hexafluoride NiF₆⁴⁻. The calculated 10Dq is found to be about half of the experimental value in all three cases. Isotropic and anisotropic spin densities at the fluoride nuclei have also been calculated; the agreement between theory and experiment is poor in all cases. The results are discussed in the light of the approximations made in the ionic Hamiltonian model. A comparison of the present molecular‐orbital method with the configuration‐interaction approach of Hubbard et al. is given; it is shown that molecular‐orbital theory is capable of taking into account all relaxation and polarization effects included in the configuration‐interaction approach.