Brownian dynamics simulation of the structural evolution in monodisperse hard-sphere suspensions during drying and sedimentation processes.

This article focuses on the drying behavior and microstructural evolution of monodisperse colloidal films, emphasizing the combined effects of evaporation and sedimentation using Brownian dynamics (BD) simulations. The study employs dimensionless numbers—the Péclet number (Pe), representing the ratio of evaporation to diffusion, and the sedimentation number (Ns), indicating the relative influence of sedimentation—to systematically analyze particle distributions and crystalline structures during drying. Results show that low Pe favors uniform particle distribution and face-centered cubic (FCC) crystalline structures, while high Pe leads to particle accumulation near the liquid–gas interface and predominantly amorphous films; increased sedimentation promotes dense packing near the substrate and can enhance FCC ordering at intermediate Pe. Comparisons with continuum models reveal that the Wang and Brady (W-B) model aligns well with BD simulations across a range of conditions, whereas the Routh and Zimmermann (R-Z) model is limited to low Pe and Ns regimes. The findings highlight limitations in current continuum models for predicting crystalline structures and underscore the need for advanced modeling that incorporates sedimentation effects, while noting that hydrodynamic and capillary interactions were not included and remain areas for future research.