Scaling properties of dynamic response in orientational glasses

The freezing transition in dipolar and quadrupolar glasses is characterized by the presence of local random electric and strain fields generated by substitutional disorder. The dynamic response in the ergodic phase above the freezing temperature T_F is studied in terms of Langevin dynamics applied to the recently formulated symmetry-adapted random-bond-random-field (SARBRF) model of orientational glasses. Following the theory of spin glasses it is assumed that for T≥T_F the response can be written in a dynamic scaling form by introducing a scaling exponent v and a frequency scaling variable. The value of v(T) is explicitly evaluated for the quadrupolar (100) SARBRF model, and its relation to the experimentally observed effective exponent u_eFF(T) in dipolar and quadrupolar glasses is discussed.