Classical Nucleation Theory Description of Active Colloid Assembly.

Area of Science:

• Statistical Mechanics
• Soft Matter Physics
• Non-equilibrium Systems

Background:

• Nonaligning self-propelled particles with repulsive interactions exhibit motility-induced phase separation (MIPS).
• MIPS leads to distinct dilute gas and dense cluster phases.
• Understanding the kinetics of dense phase formation in these active systems is crucial.

Purpose of the Study:

• To investigate the kinetics of dense phase formation in athermal MIPS.
• To determine if classical nucleation theory can describe this nonequilibrium phase transition.
• To develop a theoretical framework for predicting the dynamics of active matter self-organization.

Main Methods:

• Employed enhanced sampling computational methods to simulate particle behavior.
• Developed an analytic theory based on classical nucleation theory principles.
• Compared theoretical predictions with simulation results for validation.

Main Results:

• The kinetics of dense phase formation can be described by an effective free energy, analogous to equilibrium systems.
• The theory accurately predicts the binodal location, nucleation rates, and cluster size distributions.
• Discrepancies in the metastable region offer insights into early-stage active crystal formation.

Conclusions:

• A framework similar to equilibrium thermodynamics can be derived from the microdynamics of active systems.
• Classical nucleation theory provides a successful model for describing MIPS kinetics.
• This approach facilitates the study of evolution towards nonequilibrium steady states in active matter.