Equilibrium and non-equilibrium cluster phases in colloids with competing interactions

Area of Science:

• Colloid science
• Soft matter physics
• Computational materials science

Background:

• Colloidal systems exhibit complex phase behavior governed by interparticle interactions.
• Understanding phase transitions is crucial for designing materials with specific properties.

Purpose of the Study:

• To investigate the phase behavior of colloids with competing short-range attraction and long-range repulsion.
• To map equilibrium and non-equilibrium cluster phases in the interaction strength-density parameter space.
• To elucidate the distinct gelation mechanisms arising from different preparation routes.

Main Methods:

• Computer simulations were employed to model colloidal interactions.
• Systematic variation of attractive interaction strength (ε) and colloid density (ρ).
• Analysis of cluster morphology, size, and phase transitions.

Main Results:

• A stable equilibrium colloidal cluster phase with compact crystalline structures was identified.
• Non-equilibrium cluster phases, featuring elongated Bernal spiral-like clusters, were observed under specific conditions.
• Mean cluster size showed a linear dependence on colloid density.
• Two distinct gelation pathways were revealed: a glass transition of compact clusters and percolation of elongated clusters.

Conclusions:

• The study delineates the regions of equilibrium and non-equilibrium cluster phases relative to fluid-solid coexistence.
• Gelation mechanisms are critically dependent on the preparation route, highlighting the role of interaction parameters and density.
• Findings provide insights into controlling colloidal self-assembly and material properties.