Simulation Study on the Mechanism of Intermediate Subdiffusion of Diffusive Particles in Crowded Systems

Area of Science:

• Statistical Physics
• Soft Matter Physics
• Computational Physics

Background:

• Particle diffusion in crowded environments is crucial for understanding various physical and biological processes.
• Intermediate subdiffusion is a phenomenon observed in complex systems, deviating from standard Brownian motion.
• Existing models often simplify the complexities of particle-environment interactions.

Purpose of the Study:

• To investigate the intermediate subdiffusion of particles in crowded systems using two distinct theoretical models.
• To elucidate the conditions under which intermediate subdiffusion transitions to normal diffusion.
• To identify the key parameters governing subdiffusion in these models.

Main Methods:

• Analysis of the Continuous Time Random Walk (CTRW) model with a finite longest waiting time (τmax).
• Simulation and analysis of the obstruction-binding model with randomly distributed attractive obstacles.
• Comparison of diffusion behavior across different parameter regimes (waiting times, binding energies, obstacle densities).

Main Results:

• In the CTRW model, particles exhibit subdiffusion below τmax and normal diffusion above it.
• In the obstruction-binding model, diffusion is dependent on binding energy and obstacle density; curves can be rescaled to show a transition from subdiffusion to normal diffusion.
• Both models demonstrate that intermediate subdiffusion is limited by a characteristic timescale (longest waiting time or effective binding strength).

Conclusions:

• Intermediate subdiffusion is a transient phenomenon in these models, occurring below a specific timescale threshold.
• Long timescale subdiffusion requires an infinitely long waiting time in CTRW or infinite binding strength in the obstruction-binding model.
• The findings provide insights into the dynamics of particles in complex, heterogeneous environments.