Dynamics of a quadrupolar glass

Abstract

Substitutional disorder in an orientationally disordered crystal generates static random strain fields. Strains cause scattering of orientational and displacive waves. The resulting friction processes may lead to structural arrest (nonergodic instability) at a threshold temperature ${\mathit{T}}_{\mathit{f}}$. The slow dynamics associated with structural arrest is studied. The scattering law exhibits a dynamic central peak. The influence of microscopic relaxation processes on the dynamics of structural arrest is investigated. Phonon resonances and ultrasonic attenuation are calculated. A comparison with experiments in K(CN${)}_{\mathit{x}}$ ${\mathrm{Br}}_{1\mathrm{-}\mathit{x}}$ ranging from high- to low-frequency methods is made.