Dynamic simulations of colloids by core-modified dissipative particle dynamics.

Area of Science:

• Colloid Science
• Computational Physics
• Materials Science

Background:

• Dissipative Particle Dynamics (DPD) is a mesoscale simulation technique.
• Understanding colloidal system behavior under shear is crucial for materials design.
• Depletion forces significantly impact colloidal system structure and dynamics.

Purpose of the Study:

• To develop and validate a core-modified DPD model for colloidal systems.
• To investigate the influence of volume fraction on fluid structure and diffusion.
• To accurately simulate and characterize colloid rheology under shear flow.

Main Methods:

• Core-modified dissipative particle dynamics (DPD) simulations.
• Incorporation of an additional term to counteract depletion forces.
• Analysis of radial distribution functions, diffusion coefficients, and stress correlation functions.
• Comparison of various auxiliary thermostats for nonequilibrium simulations.

Main Results:

• Radial distribution functions change significantly with increasing colloid volume fraction.
• Anomalous short-time diffusion coefficients were observed.
• A thermostat based on relative particle velocities successfully reproduced the four classical regions of colloid rheology.
• The core-modified DPD model without an auxiliary thermostat showed similar rheological behavior despite temperature increases.

Conclusions:

• The core-modified DPD model provides a robust framework for simulating colloidal systems.
• Accurate temperature control is essential for DPD simulations, but the model shows resilience.
• The study successfully characterized the complex rheological behavior of colloids across different shear rates.