Intermediate-Spin State of a 3d Ion in the Octahedral Environment and Generalization of the Tanabe–Sugano Diagrams

Electronic spectra of 3dⁿ transition ions in an octahedral ligand surrounding have been studied using the modified crystal field approach (MCFA), which includes a relativistic spin–orbital interaction. A new variable parameter, the effective nuclear charge Z_eff of a metal ion that allows accounting implicitly the covalence degree of a metal–ligand bond, has been introduced. Energy diagrams similar to the Tanabe–Sugano ones have been calculated. To study the spin state evolution of the metal ion in an arbitrary distorted octahedral complex, a spin state diagram approach has been proposed. The intermediate-spin (IS) state problem for 3d⁴, 3d⁵, and 3d⁶ metal ions has been considered and conditions for the IS state realization have been formulated. The regions of the mixed high-, intermediate-, and low-spin states have been found. The possibility of coexistence of the different spin states of 3d ions in the octahedral complexes has been considered using crystallography data for the YBaCo₂O_5.5 layered cobaltite.

 

Intermediate-Spin State of a 3d Ion in the Octahedral Environment and Generalization of the Tanabe–Sugano Diagrams. Karina V. Lamonova, Elena S. Zhitlukhina, Roman Yu. Babkin, Sergei M. Orel, Sergei G. Ovchinnikov, and Yurii G. Pashkevich. The Journal of Physical Chemistry A 2011 115 (46), 13596-13604.