Off-center defects in crystals revisited: dynamic features

A survey is presented of the dynamic features of non-itinerant off-center defects in crystals, such as rotation-like reorientation of isolated species by either impurity or host ions. The occurrence of off-center displacements in electron-vibrational mode systems is regarded as due to the vibronic effects. It is extendable to systems in other fields of physics, e.g. nuclear matter. The latter extension is found to be effective through re-scaling of energies and separations.