On the Tammann–Rule

The validity of Tammann 's rule is related to the fact that the unavoidable thermal generation of point defects leads to defect‐defect interactions and finally to a breakdown of the structure. It is shown that the onset of this defect avalanche, which can be estimated by a cube root law, roughly corresponds to the Tammann temperature. The investigation of simple compounds corroborates this picture and also the observation of a critical defect concentration. Examples are given that Tammann 's rule can be used to systematically search for new solid electrolytes.