Distribution of local relaxation events in an aging three-dimensional glass: Spatiotemporal correlation and dynamical heterogeneity

Abstract

We investigate the spatiotemporal distribution of microscopic relaxation events, defined through particle hops, in a model polymer glass using molecular dynamics simulations. We introduce an efficient algorithm to directly identify hops during the simulation, which allows the creation of a map of relaxation events for the whole system. Based on this map, we present density-density correlations between hops and directly extract correlation scales. These scales define collaboratively rearranging groups of particles and their size distributions are presented as a function of temperature and age. Dynamical heterogeneity is spatially resolved as the aggregation of hops into clusters, and we analyze their volume distribution and growth during aging. A direct comparison with the four-point dynamical susceptibility χ(4) reveals the formation of a single dominating cluster prior to the χ(4) peak, which indicates maximally correlated dynamics. An analysis of the fractal dimension of the hop clusters finds slightly noncompact shapes in excellent agreement with independent estimates from four-point correlations.

Universal scaling in the aging of the strong glass former SiO2

“…6 and 7 respectively. Similar to previous results in fragile glass formers [13,20,21,[23][24][25] χ α max and t α max increase with increasing t w . It is possible that χ α max reaches a plateau for large t w , but the noise in the results is too large to allow for any definite conclusions to be drawn.…”

Dynamical heterogeneity in periodically deformed polymer glasses

“…As expected, polymer chain ends are more mobile; however, the mobility does not necessarily propagate along the backbone of the chains [8]. More recently, the spatiotemporal distribution of monomer hopping events was investigated in an aging polymer glass quenched below the glass transition temperature [9].…”

“…It was shown that before merging into a single dominating cluster, the volume distribution of clusters of hopping monomers follows a power-law decay with an exponent of two, and the clusters have slightly noncompact shapes [9].…”

Deformation and flow of amorphous solids: Insights from elastoplastic models

“…-simple numerical glass models like Lennard-Jones glasses (Falk and Langer, 1998;Maloney and Lemaître, 2004;Maloney and Lemaître, 2006;Tanguy et al, 2006) and other systems (Gartner and Lerner, 2016), -numerical models of metallic glasses (Rodney and Schuh, 2009;Srolovitz et al, 1983), -numerical models of silicon glasses (amorphous silicon) (Albaret et al, 2016;Fusco et al, 2014), -numerical models of polymer glasses (Papakonstantopoulos et al, 2008;Smessaert and Rottler, 2013) -dense colloidal suspensions (Chikkadi and Schall, 2012;Jensen et al, 2014;Schall et al, 2007), -concentrated emulsions (Desmond and Weeks, 2015), -dry and wet foams (Biance et al, 2009(Biance et al, , 2011Debregeas et al, 2001;Kabla and Debrégeas, 2003), -granular matter (Amon et al, 2012(Amon et al, , 2013Denisov et al, 2016;Le Bouil et al, 2014).…”