The orientational glass instability and localization in (KCN) x (KBr)1−x and (KCN) x (NaCN)1−x

Substitutional disorder in mixed crystals with orientational and translational degrees of freedom leads to the appearance of random strain fields. The strains act as static scattering centers for dynamic modes. Near a ferroelastic phase transition where the crystal is very soft, internal friction processes dominate the dynamic restoring forces. The resulting nonergodic instability marks the onset of the orientational glass state, which is characterized by a freezing-in of orientational and translational modes without long range order. The method is based on the study of dynamic equations of mode-coupling type and was originally developed by Götze for the Anderson localization.Dedicated to Professor Harry Thomas on the occasion of his 60th birthday