Self-consistent theory of collective Brownian dynamics: theory versus simulation

Area of Science:

• Colloid science
• Soft matter physics
• Statistical mechanics

Background:

• Collective diffusion is crucial for understanding colloidal suspension dynamics.
• Hydrodynamic interactions often complicate theoretical models.
• Isolating direct interactions is key to understanding microscopic relaxation mechanisms.

Purpose of the Study:

• To quantitatively assess a new theory of collective diffusion.
• To evaluate the theory's accuracy in monodisperse colloidal systems without hydrodynamic interactions.
• To isolate and analyze the effects of direct inter-particle forces.

Main Methods:

• Numerical solution of a self-consistent theory.
• Brownian dynamics simulations.
• Analysis of the van Hove function G(r,t) and intermediate scattering function F(k,t).

Main Results:

• The theory accurately describes collective dynamics for systems with short- and long-ranged repulsive interactions.
• Excellent agreement was found, particularly in the short- and intermediate-time regimes.
• The theory outperforms single exponential approximation and mode-coupling theory.

Conclusions:

• The developed theory provides a robust and accurate framework for collective diffusion in colloidal systems.
• The theory effectively captures the dynamics governed by direct inter-particle interactions.
• This work validates the theory's predictive power without adjustable parameters.