Transient dynamical responses of a charged binary colloid in an electric field

Abstract

In a model system of oppositely charged colloids we study via Brownian dynamics simulation the dynamical response as the system approaches steady states upon application of a constant electric field. The system is known to form patterns of like charges in the transverse plane to the field that are elongated along the field as lanes. We show that an increase in structural heterogeneity leads to non-Gaussian tails in the probability distribution of particle displacements [self van Hove functions (self-vHfs)]. The self-diffusion coefficient depends upon the time of the observations and consequently indicates aging in the system. However, the anomalies in the self-vHfs and diffusion do not appear during the melting of the structures.

Length-scales of Dynamic Heterogeneity in a Driven Binary Colloid

“…Our studies show non-Gaussian behaviour in the probability distributions of particle displacements and anomalous structural relaxation in this plane 25 . Such behaviour has been phenomenologically ascribed to heterogeneity in the single-particle diffusion 2 and has been observed in our studies also 25,28 . However, there has not been attempt so far to examine the spatial distribution of particles with different diffusivity which we study here.…”

“…These studies suggest heterogeneity in the dynamics of particles where particles in the lanes are dynamically different from those not in the lanes 3,13,28 . In recent studies 25,28 , we have considered structural patterns in the plane perpendicular to the electric field. Our studies show non-Gaussian behaviour in the probability distributions of particle displacements and anomalous structural relaxation in this plane 25 .…”

“…When an aqueous suspension of binary colloid with opposite charges is driven by a time-independent and uniform electric field, the system evolves to micro-phase segregation with like charged particles proliferated along the electric field forming lanes 12 . The laning transition in colloids has been observed experimentally [12][13][14][15] , and extensively studied in numerous simulations and theoretically [16][17][18][19][20][21][22][23][24][25][26][27][28] as a prototype of pattern formation away from equilibrium 3,25,28 . These studies suggest heterogeneity in the dynamics of particles where particles in the lanes are dynamically different from those not in the lanes 3,13,28 .…”

“…The laning transition in colloids has been observed experimentally [12][13][14][15] , and extensively studied in numerous simulations and theoretically [16][17][18][19][20][21][22][23][24][25][26][27][28] as a prototype of pattern formation away from equilibrium 3,25,28 . These studies suggest heterogeneity in the dynamics of particles where particles in the lanes are dynamically different from those not in the lanes 3,13,28 . In recent studies 25,28 , we have considered structural patterns in the plane perpendicular to the electric field.…”

“…We take an equimolar symmetric binary mixture of oppositely charged colloidal suspension in water, subject to a constant unidirectional electric field as in our earlier studies 28 . We perform Brownian Dynamics (BD) simulation [37][38][39] on the system repeating over a number of noise realizations.…”