Glassy Colloids

Dynamics of dense hard sphere colloidal systems: A numerical analysis” Paolo Sibani, Carsten Svaneborg. Phys. Rev. E. 99, 042607 (2019).

Abstract: The applicability to dense hard sphere colloidal suspensions of a general coarse-graining approach called Record Dynamics (RD) is tested by extensive molecular dynamics simulations. We reproduce known results as logarithmic diffusion and the logarithmic decay of the average potential energy per particle. We provide quantitative measures for the cage size and identify the displacements of single particles corresponding to intermittent cage breakings. We then partition the system into spatial domains and show that, within each domain, a subset of such intermittent events called quakes constitutes a log-Poisson process, as predicted by RD. Specifically, quakes are shown to be statistically independent and Poisson distributed with an average depending on the logarithm of time. Finally, we discuss the nature of the dynamical barriers surmounted by quakes and link RD to the phenomenology of aging hard sphere colloids.

Figure 1

Mean square displacements for a polydisperse colloidal model just above and below the glass-transition density (phi=0.620) illustrating the cross-over from diffusive behaviour to diffusion in MSD(t) ~ log(time) in the glassy regime.