Effect of bond lifetime on the dynamics of a short-range attractive colloidal system

TL;DR

This study uses molecular dynamics simulations to explore how bond lifetime influences the relaxation dynamics of short-range attractive colloids, revealing a crossover from percolation-driven to glassy behavior.

Contribution

It introduces a method to control bond lifetime in simulations and demonstrates its impact on the transition from percolation to glassy dynamics in colloidal systems.

Findings

Permanent bonds lead to divergence of relaxation time near percolation threshold.

Short-lived bonds exhibit typical glassy dynamics with increasing packing fraction.

Intermediate bond lifetimes show a crossover from percolation to glassy behavior.

Abstract

We perform molecular dynamics simulations of short-range attractive colloid particles modeled by a narrow (3% of the hard sphere diameter) square well potential of unit depth. We compare the dynamics of systems with the same thermodynamics but different bond lifetimes, by adding to the square well potential a thin barrier at the edge of the attractive well. For permanent bonds, the relaxation time $\tau$ diverges as the packing fraction $\phi$ approaches a threshold related to percolation, while for short-lived bonds, the $\phi$-dependence of $\tau$ is more typical of a glassy system. At intermediate bond lifetimes, the $\phi$-dependence of $\tau$ is driven by percolation at low $\phi$, but then crosses over to glassy behavior at higher $\phi$. We also study the wavevector dependence of the percolation dynamics.