Non-negative Interfacial Tension in Phase-Separated Active Brownian Particles.

Area of Science:

• Statistical Mechanics
• Soft Matter Physics
• Active Matter

Background:

• Active Brownian particles exhibit unique collective behaviors not seen in passive systems.
• Understanding the thermodynamics and stability of interfaces in active matter is crucial for predicting their macroscopic properties.

Purpose of the Study:

• To develop a microscopic theory for the nonequilibrium interfacial tension of active Brownian particles.
• To theoretically investigate the stability of the gas-liquid interface in active Brownian systems.

Main Methods:

• A square gradient approach was employed to model the system.
• The force balance at the interface was split into flow and structural contributions.
• The theory applies to inhomogeneous nonequilibrium steady states.

Main Results:

• The derived interfacial tension (γ_gl) was found to be non-negative (γ_gl ≥ 0).
• This finding contradicts previous theoretical claims.
• The results provide theoretical support for observed interfacial stability in simulations.

Conclusions:

• The microscopic theory provides a robust framework for understanding interfacial phenomena in active matter.
• The non-negative interfacial tension ensures the stability of the gas-liquid interface.
• This work reconciles theoretical predictions with experimental observations in active Brownian systems.