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

Sonia Taamalli (1, 2) , Hafed Belmabrouk (2) , Vo van Hoang , Victor Teboul (1)

1 LPHIA - Laboratoire de Photonique d'Angers
2 UM - Université de Monastir - University of Monastir

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 hetero- geneity increases. The induced heterogeneities and transport coefficient modification increase when the temperature decreases and disappear around the onset temperature of the cage dynamics. 

Mots clés: Dynamic heterogeneity; Glass-transition

Domaines: Matière Condensée [cond-mat]

Sonia Taamalli, Hafed Belmabrouk, Vo van Hoang, Victor Teboul. How do packing defects modify the cooperative motions in supercooled liquids?. Chemical Physics, 2017, 490, pp.55-61. ⟨10.1016/j.chemphys.2017.04.006⟩. ⟨hal-01516583⟩