Shrinking stacking fault through glide of the Shockley partial dislocation in hard-sphere crystal under gravity

Mori, Ayumi; Suzuki, Yoshihisa; Yanagiya, Shin-ichiro; Sawada, Tsutomu; Ito, Katsura

doi:10.1080/00268970701348725

Cited by 17 publications

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References 40 publications

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“…We have already found a glide mechanism for shrinking a stacking fault through a Shockley partial dislocation in fcc (001) stacking in HS crystals by Monte Carlo (MC) simulations. 3 This mechanism has also been suggested by MC simulations of colloidal epitaxy on a square pattern under gravity. 4,5 In the present work, we study the possibility of gravity-induced tempering based on MC simulations.…”

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confidence: 85%

“…The pattern on the bottom wall was the same as that used in a previous study. 3 The groove width was 0.707106781· and the side-to-side separation between two adjacent grooves was 0.338·. 18 The diagonal length of the intersection of the longitudinal and transverse grooves was 0.9999999997·.…”

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confidence: 99%

“…3 One of the shortcomings of this simulation was that the fcc (001) stacking was driven by stress from a small simulation box with horizontal periodic boundary conditions (PBC). One of the purposes of our successive simulations was to resolve this artifact.…”

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Possibility of Gravitational Tempering in Colloidal Epitaxy to Obtain a Perfect Crystal

2012

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We have performed Monte Carlo simulations of hard spheres on a pattern under gravity. We found that a crystal formed at a moderate gravity strength contains essentially no defects while the one formed at a higher gravity strength contains a significant amount of defects. This result suggests the possibility of using gravitational tempering in a colloidal epitaxy to reduce the number of defects in the colloidal crystals. Moreover, we wish to emphasize on the possibility of obtaining a perfect crystal.Colloidal epitaxy was first proposed in 1997 by van Blaaderen et al.1 as a method to reduce stacking disorders in colloidal crystals. The basic idea of colloidal epitaxy is that the uniqueness of the stacking sequence for face-centered cubic (fcc) (001) stacking reduces the stacking disorders. Fcc (001) stacking was forced in a colloidal epitaxy by using a pattern on the substrate. Additionally, Zhu et al.2 in 1997 found that gravity reduces the stacking disorder in hard-sphere (HS) colloidal crystals. We have already found a glide mechanism for shrinking a stacking fault through a Shockley partial dislocation in fcc (001) stacking in HS crystals by Monte Carlo (MC) simulations. 3This mechanism has also been suggested by MC simulations of colloidal epitaxy on a square pattern under gravity. 4,5 In the present work, we study the possibility of gravity-induced tempering based on MC simulations. The number of defects is reduced with increasing gravity for a small range of gravity strength. But, it decreases with decreasing gravity in other ranges. In other words, the relationship between the number of defects and the strength of gravity is not monotonic; the amount of defects reaches a minimum at an optimum gravity strength. Similarly, up to a certain gravity strength, the crystallinity improves with the increasing gravity. In particular, no defects were observed in the bottom region at this gravity. We propose that settling a colloidal crystal at an optimum gravity strength reduces the number of defects. In other words, one can obtain a perfect crystal with the gravitational tempering.In 1957, the existence of a crystalline phase in an HS system was shown by MC 6 and molecular dynamics (MD) 7 simulations. In the HS system, the phase behavior is governed only by the particle number density. The fluid and the crystalline phases are separated by a coexistence region of 0.494 < º < 0.545 8 (In 1998, the coexistence densities were revised by Davidchack and Laird 9 as º f = 0.491 and º s = 0.542 by an MD simulation of a direct crystal-fluid coexistence). Here, º Ô (³/6)· 3 (N/V) is the volume fraction of the HSs with · being the HS diameter; N, the number of particles; and V, the volume of the system. As the density increases, the HS system crystallizes. Accordingly, the HS colloids, and also the charge-stabilized colloids with repulsive screened Coulombic interaction, crystallize by sedimentation.10 Defects contained in the colloidal crystals obtained without invention are, however, inevitable.In applications such as produc...

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Possibility of Gravitational Tempering in Colloidal Epitaxy to Obtain a Perfect Crystal

2012

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“…After some pioneering experiments, extensive fundamental studies on colloidal crystals have been conducted so far [3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21]. On the other hand, the application of colloidal crystals as photonic bandgap (PBG) crystals has also received much attention.…”

Section: Introductionmentioning

confidence: 99%

“…However, almost all systems reported so far have mainly utilized repulsive interactions between particles for colloidal crystallization basically [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18]20,21,[25][26][27][28][29][30][31][32][33][34][35][36][37][38][39][40][42][43][44], whereas the growth of crystals of atoms or molecules usually proceeds via attractive interactions. In such systems, in situ observation of growth interfaces of colloidal crystals by optical microscopy is usually difficult because of high particle concentrations.…”

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Adsorption, Desorption, Surface Diffusion, Lattice Defect Formation, and Kink Incorporation Processes of Particles on Growth Interfaces of Colloidal Crystals with Attractive Interactions

et al. 2016

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Abstract:Good model systems are required in order to understand crystal growth processes because, in many cases, precise incorporation processes of atoms or molecules cannot be visualized easily at the atomic or molecular level. Using a transmission-type optical microscope, we have successfully observed in situ adsorption, desorption, surface diffusion, lattice defect formation, and kink incorporation of particles on growth interfaces of colloidal crystals of polystyrene particles in aqueous sodium polyacrylate solutions. Precise surface transportation and kink incorporation processes of the particles into the colloidal crystals with attractive interactions were observed in situ at the particle level. In particular, contrary to the conventional expectations, the diffusion of particles along steps around a two-dimensional island of the growth interface was not the main route for kink incorporation. This is probably due to the number of bonds between adsorbed particles and particles in a crystal; the number exceeds the limit at which a particle easily exchanges its position to the adjacent one along the step. We also found novel desorption processes of particles from steps to terraces, attributing them to the assistance of attractive forces from additionally adsorbing particles to the particles on the steps.

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Monte Carlo simulation of growth of hard-sphere crystals on a square pattern

Mori

2011

Journal of Crystal Growth

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a b s t r a c tMonte Carlo simulations of the colloidal epitaxy of hard spheres (HSs) on a square pattern have been performed. This is an extension of previous simulations; we observed a shrinking intrinsic stacking fault running in an oblique direction through the glide of a Shockley partial dislocation terminating its lower end in fcc (0 0 1) stacking [A. Mori, Y. Suzuki, S.i. Yanagiya, T. Sawada, K. Ito, Mol. Phys. 105 (2007) 1377], which was an answer to a question why the defect in colloidal crystals reduced by gravity [J. Zhu, M. Li, R. We have resolved one of the shortcomings of the previous simulations; the driving force for fcc (0 0 1) stacking, which was a stress from a small periodic boundary simulation box, has been replaced with the stress from a pattern on the bottom. We have observed disappearance of stacking fault in this realizable condition. Sinking of the center of gravity has been smooth and of a single relaxation mode under the condition that the gravitational energy mgs is slightly less than the thermal energy k B T. In the snapshots tetrahedral structures have appeared often, suggesting formation of staking fault tetrahedra.

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Shrinking stacking fault through glide of the Shockley partial dislocation in hard-sphere crystal under gravity

Cited by 17 publications

References 40 publications

Possibility of Gravitational Tempering in Colloidal Epitaxy to Obtain a Perfect Crystal

Possibility of Gravitational Tempering in Colloidal Epitaxy to Obtain a Perfect Crystal

Adsorption, Desorption, Surface Diffusion, Lattice Defect Formation, and Kink Incorporation Processes of Particles on Growth Interfaces of Colloidal Crystals with Attractive Interactions

Monte Carlo simulation of growth of hard-sphere crystals on a square pattern

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