Jahn–Teller effect

The Jahn–Teller effect is a principle in chemistry and physics, named after Hermann Arthur Jahn and Edward Teller, who proved it. It says that any non-linear molecule or ion in a state of electronic degeneracy will distort in a way that lowers its symmetry and removes the degeneracy, thereby reducing its energy. The theorem explains why many complexes of transition metals, such as those of copper in the +2 state, have octahedra that are stretched or squashed rather than perfectly regular. The effect has consequences for the colors, magnetic properties and structures of many compounds and solids. It also has a role in modern materials, including some high-temperature superconductors and manganese oxides with colossal magnetoresistance.

Open on the timeline