Dependence of the Apex Angle of an Inverted Pyramidal-Shaped Container on Crystallization of Brownian Particles
Journal of the Physical Society of Japan
Large grains of a close-packed colloidal crystal have been experimentally shown to form in an inverted pyramidal pit by sedimentation [S. Matsuo, T. Fujine, K. Fukuda, S. Juodkazis, and H. Misawa, Appl. Phys. Lett. 82, 4285 (2003)]. Keeping this experiment in mind, we study the crystallization of Brownian particles. We carry out Brownian dynamics simulations in an inverted pyramidal-shaped container. The Brownian particles settle out toward the apex of the container by a uniform external force.
... orm external force. If the apex angle is suitable, large grains with the face-centered cubic (fcc) structure are formed [Y. Kanatsu and M. Sato, J. Phys. Soc. Jpn. 84, 044601 (2015) ]. When the apex angle deviates from a suitable value, the number of hexagonal close-packed (hcp) structured particles, N hcp , increases with increasing angle deviation. The formation of the hcp structure is induced by disordered particles remaining in the center region of the container. Introduction Recently, colloidal crystals have been studied as materials for photonic devices. Since the radius of colloidal particles is as large as the wavelength of visible light, the colloidal crystals are expected to be used as devices such as optical filters and switches. In particular, a closepacked colloidal crystal with the face-centered cubic (fcc) structure is used as a template for an inverse opal with a three-dimensional full photonic band gap. 1) Many groups have tried to form large grains of close-packed colloidal crystals with the fcc structure. From a theoretical study 2) and an experiment, 3) it was found that the fcc structure is more stable than the hexagonal close-packed (hcp) structure. However, during growth by sedimentation, a mixture of both structures is often formed. 4) *