Forces due to changes of electronic density: A complementary view of the Jahn–Teller effect

The E ⊗ e Jahn–Teller (JT) effect in an octahedral complex is explored in this work looking directly at forces on ligand ions. It is shown that distortions at adiabatic minima are driven by a force associated with the difference between the real electronic density and that coming from a closed shell ion keeping the same number of electrons. Through this more direct approach main characteristics of tetragonal distortions are shown to be well reproduced in a simple case. As a salient feature the existence of an infinity of equivalent distortions when anharmonicity of vibrations is ignored is also found in the present approach. The way of applying these ideas to other JT systems as well as to excited states of transition-metal complexes is also briefly discussed.