Crystallization and structural rearrangement in nearly hard-sphere model colloidal suspensions: A long-time study across concentration regimes

Colloidal crystallization provides a flexible framework for studying how order develops or disappears in response to thermodynamic and kinetic constraints. Despite some studies on the formation of colloidal crystals near the glass transition, their evolution over ultra-long timescales remains largely unknown. In this work, we follow the structural and dynamical aging of a nearly hard-sphere suspension for about four years. Slow solvent evaporation provides a continuous, gentle densification that gradually drives the system across the fluid-crystal coexistence region and into the glassy regime. Light scattering measurements indicate that total crystallinity decreases as the remaining crystallites grow and become denser. The random hexagonal close-packed structure slowly changes into face-centered cubic ordering, while smaller or flawed domains turn into amorphous regions. This slow restructuring reflects a balance between densification, kinetic frustration, and defect annealing, leading to partial crystal amorphization instead of standard ripening. Our findings reveal a previously unobserved route of structural aging in colloidal glasses, relevant for understanding long-term reorganization and disordering processes in dense soft materials.