Kinetic heterogeneities at dynamical crossovers

• Published in: Europhysics letters Vol. 90; no. 6; p. 66004
• Main Authors: Haxton, T. K, Liu, A. J
• Format: Journal Article
• Language: English
• Published: IOP Publishing 01.06.2010; EDP Sciences
• Subjects: 64.70.pm; 64.70.ps; 64.70.Q; Crossovers; Diffusion; Dynamics; Glass transition; Heterogeneity; Liquids; Maxima; Molecular dynamics
• ISSN: 0295-5075; 1286-4854
• DOI: 10.1209/0295-5075/90/66004

We perform molecular dynamics simulations of a model glass-forming liquid to measure the size of kinetic heterogeneities, using a dynamic susceptibility χss(a, t) that quantifies the number of particles whose dynamics are correlated on the length scale a and time scale t. By measuring χss(a, t) as a function of both a and t, we locate local maxima χ⋆ at distances a⋆ and times t⋆. Near the dynamical glass transition, we find two types of maxima, both correlated with crossovers in the dynamical behavior: a smaller maximum corresponding to the crossover from ballistic to sub-diffusive motion, and a larger maximum corresponding to the crossover from sub-diffusive to diffusive motion. Our results indicate that kinetic heterogeneities are not necessarily signatures of an impending glass or jamming transition.