Dependencies between effective parameters in coarse-grained models for phase separation of DNA-based fluids.

DNA is now firmly established as a versatile and robust platform for achieving synthetic nanostructures. While the folding of single molecules into complex structures is routinely achieved through engineering basepair sequences, very little is known about the emergence of structure on larger scales in DNA fluids. The fact that polymeric DNA fluids can undergo phase separation into dense fluid and dilute gas opens avenues to design hierachical and multifarious assemblies.

Aggregate morphing of self-aligning soft active disks in semi-confined geometry.

We study the dependence of alignment and confinement on the aggregate morphology of self-aligning soft disks(particles) in a planer box (two dimensional) geometry confined along y direction using Langevin dynamics simulations. We show that when the box width decreases, the aggregate wall accumulation becomes non-uniform and displays non-monotonic behaviour in terms of phase behavior and height of these aggregates with an increase in alignment strength. Additionally, we identify two distinct categories of wall aggregates: layered and non-layered structures each exhibiting distinct local structural properties.

Collective behavior of soft self-propelled disks with rotational inertia.

We investigate collective properties of a large system of soft self-propelled inertial disks with active Langevin dynamics simulation in two dimensions. Rotational inertia of the disks is found to favor motility induced phase separation (MIPS), due to increased effective persistence of the disks. The MIPS phase diagram in the parameter space of rotational inertia and disk softness is reported over a range of values of translation inertia and self-propulsion strength of the disks.

Reentrant phase separation of a sparse collection of nonreciprocally aligning self-propelled disks.

We study a model of aligning self-propelled disks that nonreciprocally reorient the self-propulsion directions along the interparticle separation and towards the other disks. In the limit of small inertia and large softness, where conventional motility-induced phase separation is absent, we demonstrate that the homogeneous system at a small area fraction phase-separates into clusters and a low-density phase that, eventually, reenters the homogeneous phase with a monotonic increase in alignment strength. The disks inside the clusters move with a finite space-dependent speed, constantly shuttling between clusters through the surrounding low-density homogeneous phase while maintaining the hexatic structure properties within the clusters.

Motility-induced phase separation of self-propelled soft inertial disks.

The phase diagram of the phenomenon of motility-induced phase separation (MIPS) for a collection of self-propelled interacting disks over a large inertial range is explored using active Langevin dynamics simulation with particular emphasis on disk softness and effective size. It is shown that the parabola-like phase boundary between the homogeneous and MIPS states in the semi-log space of disk softness and effective size moves towards the hard disk limit with increase in inertia, before complete disappearance in the limit of large inertia. With increase in effective size of the disks, re-entrant phase separation, that is the system phase-separating from a homogeneous phase and eventually re-entering the homogeneous phase, is reported.

Phase transition and emergence of active temperature in an active Brownian system in underdamped background.

We explore the role of inertia in the properties of active Brownian particles (ABPs) immersed in an underdamped background in two dimensions using Langevin dynamics computer simulation. Similar to an equilibrium two-dimensional passive interacting particle system, the system of ABPs transits from a liquid phase to a solid phase with the change in the coupling parameter, which is the ratio of interaction potential energy and thermal energy of the background solvent. Important qualitative and quantitative differences are found in the liquid-solid phase transition with increasing strength of activity as compared to those found in the conventional overdamped background limit.