Ordering of Brownian particles from walls due to an external force

• The ordering of Brownian particles under a uniform external force is studied by Brownian dynamics method.
• The ordering along walls first occurs and then ordering in bulk occurs.
• Due to solidification domains with the face-centered cubic and hexagonal close-packed structures are created in bulk.
• By controlling the direction and strength of external force, the ratio of the two types of structures changes.

Keeping the formation of colloidal crystal under a centrifugal force in mind, we study the ordering of Brownian particles under a uniform external force. Owing to the external force, the particles move in the direction of the external force. Near walls, the density of particles increases and the ordering of particles occurs on the walls at first. Then, the ordering in bulk proceeds gradually. Domains with the face-centered cubic and hexagonal close-packed structures are created in bulk. By controlling the direction and strength of external force, the ratio of the two types of structures changes.