Electronic structure degeneracy

The role of electronic structure in Mn and Co site preference and mobility can to some extent be understood through ligand-field theory (LFT). LET qualitatively explains how the degeneracy of the 3d orbitals is broken when a free TM ion is surrounded by coordinating anions. The ligand-field splitting of d orbitals in octahedral and tetrahedral coordination is pictured in Figure 6. ... 

A special feature of these JT-induced SB is that they emerge directly from the electronic structure of the system that determines the degeneracy and pseudodegeneracy and the parameters of instability (which in turn determine the SB), and it is quite clear how these SB are controlled by the electronic structure. 

This correlation between symmetry and degeneracy of energy levels is fundamental to understanding the electronic structure of atoms and molecules. This relationship is valid not only when increasing symmetry renders the energy levels degenerate but also when energy levels are split as molecular symmetry decreases. 

The wave functions are products of radial function R i(r) and spherical harmonics y, -( ,) and the energy levels are highly degenerate. The energy levels are labeled by the principal quantum number, n and the orbital quantum number l. This degeneracy is removed by perturbation effects. The properties of the electrons in an unfilled shell only are considered since electrons in filled subshells do not contribute to the electronic structure of the low-lying levels. 

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