Phase behaviour and dynamics of three-dimensional active dumbbell systems

Abstract

We present a comprehensive numerical study of the phase behavior and dynamics of a three- dimensional active dumbbell system with attractive interactions. We demonstrate that attraction is essential for the...

Phase separation kinetics and cluster dynamics in two-dimensional active dumbbell systems

“…A distinguishing aspect of the rotating aggregates is that the velocity and orientational patterns are distinct: the former is a vortex and the latter is a spiral. 41 On the experimental side, colloidal particles with non-convex shapes have been proposed to serve as the building blocks for active colloidal molecules with a dynamical function. [42][43][44]…”

“…The dynamic phase diagram of an (rather dilute) active attractive dumbbell model was recently established in ref. 41, where the motion of a dumbbell cluster was also characterized. The phase separation in a mixture of ''hot'' and ''cold'' three-dimensional dumbbells was analyzed in ref.…”

“…In sum, they are more stable objects and the dynamics does not create holes within them, nor let pieces easily detach, as one can see happening in ABP clusters. 41 In Fig. 11, we plot the individual cluster mass against its radius of gyration, considering configurations taken in the scaling regime for Pe = 100 at the density of Fig.…”

“…In ref. 41, we used the cluster tracking algorithm to calculate the mean-square displacement of the center of mass of clusters of spherical particles and we found diffusive behavior with a mass dependent diffusion coefficient. Consequently, the average over them all also resulted in diffusion.…”

“…The former contributes to the change in direction, while the latter to the directed motion only. A good approximation 41 is to consider the tangential component of the active force almost fully counterbalanced by the drag force F t act % M m d g d _ R cm ; setting in this direction the time derivative to zero in eqn (18). The remaining small mismatch gives rise to a force F r act = F act + F drag (21) equal to the inertial contribution of the motion and directed radially towards the center of the trajectory.…”