Precursor-mediated crystallization process in suspensions of hard spheres

Area of Science:

• Physical Chemistry
• Computational Physics
• Materials Science

Background:

• Crystal nucleation is fundamental to materials formation.
• A two-step crystallization process involving amorphous precursors was previously observed in systems with attractive interactions, like protein solutions.
• This mechanism was often attributed to metastable fluid-fluid demixing.

Purpose of the Study:

• To investigate the mechanism of crystal nucleation in a system with purely repulsive interactions (hard spheres).
• To determine if the two-step crystallization process observed in attractive systems also occurs in purely repulsive systems.
• To elucidate the fundamental pathways of crystal nucleation independent of attractive forces.

Main Methods:

• Large-scale computer simulations of hard sphere systems.
• Combined analysis of real-space and reciprocal-space data.
• Characterization of intermediate cluster formation and crystallite nucleation.

Main Results:

• The study supports a two-step crystallization process in hard spheres.
• Dense, amorphous clusters were observed to form first.
• These clusters acted as precursors for the nucleation of well-ordered crystallites.

Conclusions:

• The two-step crystallization mechanism is not exclusive to systems with attractive interactions.
• Purely repulsive systems, like hard spheres, can crystallize via a similar pathway involving amorphous cluster precursors.
• This finding suggests a more universal mechanism for crystal nucleation than previously thought.