Two-dimensional colloidal aggregation: concentration effects

Area of Science:

• Colloid and Surface Science
• Computational Physics
• Materials Science

Background:

• Colloidal aggregation is a fundamental process in various scientific and industrial applications.
• Understanding the factors influencing aggregate structure, such as fractal dimension and cluster size, is crucial.
• Diffusion-limited aggregation (DLCA) and reaction-limited aggregation (RLCA) represent two distinct mechanisms governing this process.

Purpose of the Study:

• To investigate the concentration dependence of fractal dimension and average cluster sizes in 2D colloidal aggregation.
• To compare results from on-lattice and off-lattice simulations to ensure algorithm independence.
• To analyze the scaling behavior of cluster size distribution functions.

Main Methods:

• Extensive numerical simulations were conducted for both DLCA and RLCA in two dimensions.
• Both on-lattice and off-lattice simulation models were employed.
• A wide range of concentrations (2.5 orders of magnitude) was studied.

Main Results:

• In DLCA, the fractal dimension (d(f)) increases linearly with concentration (phi), following d(f)=d(fo)+aphi(c).
• Exponents (z, z') for average cluster size growth in DLCA also depend linearly on concentration.
• In RLCA, a similar linear increase in fractal dimension with concentration was observed, but cluster size exponents could not be definitively determined within the studied regime.

Conclusions:

• The fractal dimension and cluster growth dynamics in colloidal aggregation are significantly influenced by particle concentration.
• Simulation results are robust across different lattice structures and algorithms.
• Master curves for cluster size distribution provide insights into the universality of aggregation scaling.