Universal critical-like scaling of dynamics in plastic crystals

Abstract

Many theoretical models for the glassy dynamics have been proposed so far describing the changes in molecular dynamics along the extraordinary slowing down in the vitrification process of a disordered phase on cooling. Many of these theories share the concept of cooperative rearranging regions firstly proposed by Adam and Gibbs. Among them, the dynamical scaling model (DSM) is based on the random diffusion of free volume which creates random walking clusters formed by cooperatively rearranging entities.

Within this framework a critical phenomenon relating a hidden phase transition at TC (below Tg) implies the divergence of the relaxation time (τ) or viscosity (η) τ, η ∝ (T − TC) − phi with a universal scaling exponent φ → 9. In this work we apply the DSM model to orientational glasses, obtained from the quenching of orientationally disordered phases (plastic crystals) via the application of the linearized derivative-based transformation of dielectric spectroscopy τ(T) data.