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The Jahn–Teller effect (JT effect or JTE) is an important mechanism of spontaneous symmetry breaking in molecular and solid-state systems which has far-reaching consequences in different fields, and is responsible for a variety of phenomena in spectroscopy, stereochemistry, crystal chemistry, molecular and solid-state physics, and materials science.
Second-order Jahn-Teller distortion provides a rigorous and first-principles approach to the distortion problem. The interactions between the HOMOs and LUMOs to afford a new set of molecular orbitals is an example of second-order Jahn-Teller distortion.
In their early 1957 paper on what is now called pseudo Jahn–Teller effect (PJTE), Öpik and Pryce [2] showed that a small splitting of the degenerate electronic term does not necessarily remove the instability and distortion of a polyatomic system induced by the Jahn–Teller effect (JTE), provided that the splitting is sufficiently small (the two split states remain "pseudo degenerate ...
Another example is [Co(H 2 O) 6] 2+. [14] Note that the ligand is the same as the last example. Here the cobalt ion has the oxidation state of +2, and it is a d 7 ion. From the high-spin (left) side of the d 7 Tanabe–Sugano diagram, the ground state is 4 T 1 (F), and the spin multiplicity is a quartet.
English: A conceptual comparison of the Jahn-Teller and pseudo Jahn-Teller effects, showing the mutual relation of two potential energy surfaces (PES) in the two cases. The number of PES is two in this picture but it can be more in actual molecular or solid-state systems.
Known for his "life-long years of experience in theoretical chemistry" [1] working on the electronic structure and properties of coordination compounds, Isaac B. Bersuker is “one of the most widely recognized authorities” [2] in the theory of the Jahn–Teller effect (JTE) and the pseudo-Jahn–Teller effect (PJTE).
Complexes such as this are called "low spin". For example, NO 2 − is a strong-field ligand and produces a large Δ. The octahedral ion [Fe(NO 2) 6] 3−, which has 5 d-electrons, would have the octahedral splitting diagram shown at right with all five electrons in the t 2g level. This low spin state therefore does not follow Hund's rule.
the Jahn-Teller effect is a pretty advanced topic in chemistry and a reader would really benefit from some groundwork, octahedral complex would be preferable over octahedral complex. See also the AXE method, most molecular geometries are still missing. V8rik 20:07, 12 July 2005 (UTC)