Analogy of the slow dynamics between the supercooled liquid and the supercooled plastic crystal states of difluorotetrachloroethane

TL;DR

This study uses Molecular Dynamics simulations to compare the slow dynamics of difluorotetrachloroethane in supercooled liquid and plastic crystal states, revealing strong analogies predicted by Mode Coupling Theory.

Contribution

It demonstrates the analogy between supercooled liquids and plastic crystals in their slow dynamics, supported by simulation data and theoretical predictions.

Findings

Alpha-relaxation times are similar in both states.

Non-ergodicity parameters are governed by static correlations.

Mode Coupling Theory accurately predicts the dynamics.

Abstract

Slow dynamics of difluorotetrachloroethane in both supercooled plastic crystal and supercooled liquid states have been investigated from Molecular Dynamics simulations. The temperature and wave-vector dependence of collective dynamics in both states are probed using coherent dynamical scattering functions $S(Q,t)$. Our results confirm the strong analogy between molecular liquids and plastic crystals for which $\alpha$-relaxation times and non-ergodicity parameters are controlled by the non trivial static correlations $S(Q)$ as predicted by the Mode Coupling Theory. The use of infinitely thin needles distributed on a lattice as model of plastic crystals is discussed.