Crystallization of Brownian Particles in a Pyramidal Pit by a Uniform External Force

Self Cite

The formation of a large close-packed colloidal crystal with the fcc structure was observed during the sedimentation of colloidal particles in an inverted pyramidal pit [S. Matsuo et al., Appl. Phys. Lett. 82, 4285 (2003)]. Carrying out Brownian dynamics simulations, we confirmed that large grains with the fcc structure are formed when the apex angle of the inverted pyramidal container is suitable and the force direction is parallel to the the center axis [Y. Kanatsu and M. Sato, J. Phys. Soc. Jpn. 84, 044601 (2015)].To form a high-quality colloidal crystal without defects, it is important to investigate in detail how the quality of a colloidal crystal is affected by the force direction and container shape. In this paper, we focus on the effect of the force direction on crystal quality and investigate how the ratio of the number of the hcp structured particles, N hcp , to that of fcc structured particles, N fcc , is affected by the force direction.In our simulation, the ratio of N fcc to N hcp is hardly changed when the force direction deviates from the central axis: N fcc is much larger than N hcp irrespective of the force direction. Thus, our results show that the crystal structure is insensitive to the force direction in forming a colloidal crystal by sedimentation in an inverted pyramidal container.

Section: Model and Order Parametersmentioning

confidence: 68%

“…20) In the simulation, the force direction was parallel to the central axis. When the force direction deviates from the central axis, the growing interface is tilted from the {100} face of the fcc structure, which may cause the increase in the number of defects in the bulk.…”

Section: Introductionmentioning

confidence: 99%

Dependence of crystallization of Brownian particles by sedimentation on the force direction

Sato¹,

Widianto²,

Kanatsu³

2015

Self Cite

“…In our previous studies, 7,8,[10][11][12][13][14][15] we neglected the inertial term mr i for simplicity, but this term may affect the crystallization of particles. Thus, we take account of the inertial term and carry out simulations using a simple Verlet-type algorithm.…”

Section: /13mentioning

confidence: 99%

“…Owing to the unique stacking on the {100} face, grains with the hcp structure hardly appear, irrespective of the particle size, when the apex angle of the pyramidal pit is suitable. The hcp-structured grains, which act as defects in the fcc-structured crystal, increase in number with increasing deviation of the apex angle 7,8) but their number hardly depends on the inclination of the force direction. 7) In the growth of colloidal particles in a V-shaped groove, 6) the growth interface is directed toward the ⟨110⟩ direction if the external force bisects the angle between the two walls of the groove.…”

Section: Introductionmentioning

confidence: 99%

Effect of direction of an external force on crystallization of colloidal particles in a V-shaped groove by sedimentation

Sato

2016

Self Cite

We carried out Langevin dynamics simulations to study the effect of the direction of a uniform external force on the crystallization of colloidal particles in a V-shaped groove. When the inclination of the side walls of a groove was set to a suitable value and the external force bisected the angle, the face-centered-cubic (fcc) structure grew with a {100} growth interface. When the external force was inclined, the number of solidified particles decreased with increasing inclination, which is different from the growth in an inverted pyramidal container.

“…[7][8][9][10][11][12] We consider that particles receive a strong frictional force proportional to their velocity.…”

Section: 5)mentioning

confidence: 99%

Removal of defects in a colloidal crystal grown in an inverted pyramidal container by changing the external force

Kanatsu¹,

Sato²

2015

Self Cite

Keeping the formation of colloidal crystals by sedimentation in mind, we carry out Brownian dynamics simulations and study the crystallization of colloidal particles in an inverted pyramidal container. When an external force is added, the sedimentation of particles occurs and the particle density increases in the low region of the inverted pyramidal container. The crystallization of particles occurs and the face-centered cubic structure is formed in the container. When the force is large, the particles with the hexagonal close-packed structure and disordered particles are also formed and act as defects in bulk. After the sedimentation finishes, we decrease the force transiently. The defects in bulk are removed from the bulk.A close-packed colloidal crystal with the face-centered cubic (fcc) structure is considered as a coordinate of an inverted opal with a three-dimensional full photonic band gap, 1) and the sedimentation of colloidal particles 2) is a useful method to form close-packed colloidal crystals. During sedimentation, particles form a triangular lattice when they deposit on the flat bottom. The lattice acts as the {111} face of the fcc structure and the growth of grains with the fcc structure occurs. However, there are two stacking ways on the triangular lattice. Thus, grains with the hexagonal closepacked (hcp) structure can also grow on the lattice 2, 3) although the fcc structure is more stable than the hcp structure. 4, 5)To prevent the formation of grains with the hcp structure, Matsuo et al. used an inverted pyramidal pit 6) as a container. When the inclination of the pyramidal surfaces of the pit is suitable and the direction of an external force inducing the sedimentation is parallel to the central axis, the triangular lattice is formed on the pyramidal surfaces and the growing interface, which is perpendicular to the external force, becomes the {100} face of the fcc structure. Since the stacking way is unique on the {100} face, the crystal with the fcc structure grows without forming the grains with the hcp structure. Keeping the experiment of Matsuo et al. 6) in mind, we have carried out