Super-Arrhenius diffusion in a binary colloidalmixture at low volume fraction: An effect ofdepletion interaction

Area of Science:

• Soft Matter Physics
• Computational Chemistry
• Colloidal Science

Background:

• Understanding particle dynamics in complex environments is crucial for various applications.
• Colloidal mixtures offer a model system to study fundamental transport phenomena.
• External potentials significantly influence particle motion and diffusion characteristics.

Purpose of the Study:

• To investigate the effect of asymmetric external potential barriers on the diffusion dynamics of a binary colloidal mixture.
• To analyze the behavior of smaller and larger particles separately under varying potential asymmetries.
• To explore the transition in diffusion regimes (Arrhenius, sub-Arrhenius, super-Arrhenius).

Main Methods:

• Molecular dynamics simulations were employed.
• A binary colloidal mixture at low volume fraction ($\phi$=0.2) was simulated.
• An external potential barrier was applied along one spatial direction with varying asymmetry.

Main Results:

• Smaller particles exhibited consistent Arrhenius diffusion, unaffected by potential asymmetry.
• Larger particles showed a crossover from sub-Arrhenius to super-Arrhenius diffusion as potential asymmetry increased.
• This crossover was observed at low temperatures and low volume fractions.

Conclusions:

• The asymmetry of external potentials can induce complex diffusion behaviors in colloidal systems.
• The findings are relevant for understanding molecular transport in confined and asymmetric environments.
• This model provides insights into transport across biological membranes and in nano/micro-channels.