How do packing defects modify the cooperative motions in supercooled liquids ?

Abstract

We use molecular dynamic simulations to investigate the relation between the presence of packing defects in a glass-former and the spontaneous cooperative motions called dynamic heterogeneity. For that purpose we use a simple diatomic glass-former and add a small number of larger or smaller diatomic probes. The diluted probes modify locally the packing, inducing structural defects in the liquid, while we find that the number of defects is small enough not to disturb the average structure. We find that a small packing modification around a few molecules can deeply influence the dynamics of the whole liquid, when supercooled. When we use small probe molecules, the dynamics accelerates and the dynamic heterogeneity decreases. In contrast, for large probes the dynamics slows down and the dynamic heterogeneity increases. The induced heterogeneities and transport coefficient modification increase when the temperature decreases and disappear around the onset temperature of the cage dynamics.

arXiv comment7 pages, 12 figures

References in corpus (24)

• Testing Mode-Coupling Theory for a Supercooled Binary Lennard-Jones Mixture I: The van Hove Correlation Function
• String-like Clusters and Cooperative Motion in a Model Glass-Forming Liquid
• Direct experimental evidence of a growing length scale accompanying the glass transition
• Glassy dynamics of kinetically constrained models
• Scaling behavior in the $\beta$-relaxation regime of a supercooled Lennard-Jones mixture
• The Physics of the Colloidal Glass Transition
• Dynamics on the Way to Forming Glass: Bubbles in Space-time
• Geometrical explanation and scaling of dynamical heterogeneities in glass forming systems
• Spontaneous and induced dynamic fluctuations in glass-formers I: General results and dependence on ensemble and dynamics
• Spontaneous and induced dynamic correlations in glass-formers II: Model calculations and comparison to numerical simulations
• Fundamental differences between glassy dynamics in two and three dimensions
• Liquid-glass transition of a fluid confined in a disordered porous matrix: A mode-coupling theory
• Spatially heterogeneous dynamics and dynamic facilitation in a model of viscous silica
• Temperature dependence of spatially heterogeneous dynamics in a model of viscous silica
• An introduction to the colloidal glass transition
• Analysis of a growing dynamic length scale in a glass-forming binary hard-sphere mixture
• Manifestations of Dynamical Facilitation in Glassy Materials
• Statistical mechanics of homogeneous partly pinned fluid systems
• Slow dynamics in an azopolymer molecular layer studied by x-ray photon correlation spectroscopy
• Cooperative motions in a finite size model of liquid silica: an anomalous behavior
• A simple diatomic potential that prevents crystallization in supercooled liquids simulations
• Simple physics of the partly pinned fluid systems
• Enhanced diffusion in finite-size simulations of a fragile diatomic glass former
• Kinetic Monte Carlo Simulations for Birefringence Relaxation of Photo-Switchable Molecules on a Surface