Conversion of stable crystals to metastable crystals in a solution by periodic change of temperature

Using a Becker-D\"oring type model including cluster incorporation, we study the possibility of conversion of stable crystals to metastable crystals in a solution by a periodic change of temperature. At low temperature, both stable and metastable crystals grow by coalescence with abundant clusters. At high temperature, a large amount of small clusters produced by the dissolution of crystals inhibits the dissolution of crystals, and the imbalance in the amount of crystals increases. By repeating this process, the periodic temperature change can convert stable crystals into metastable crystals

Effect of immobile impurities on two-dimensional nucleation

We study the dependence of the critical size of the nucleus on the density of impurity by carrying out a Monte Carlo simulation. We assume that the impurities are fixed on a crystal surface, and neglect restoration of bonds between an impurity atom and an adsorbed atom. We initially prepare one cluster in the system and investigate the change of the cluster size. When the cluster size is the critical value, the frequency of increasing the cluster size is equal to that of decreasing the size. With increasing the impurity density, the critical nucleus becomes large. When the impurity density is sufficiently high, regardless of the initial cluster size, the cluster vanishes after a long time interval, namely, the critical cluster size is diverged. © 2011 American Physical Society

Cluster diffusion on two-dimensional surface with immobile impurities

We study diffusion of a two-dimensional cluster on a two-dimensional surface with immobile impurities. We perform a kinetic Monte Carlo simulation using a simple square lattice model. In our model, not only atoms forming an edge of two-dimensional cluster but also atoms in the cluster, which is neighboring impurities in the cluster, are able to evaporate. The cluster diffusion coefficient in the system with a high impurity concentration is larger than that with no impurities. © 2013 Elsevier B.V. All rights reserved

Machine learning refinement of in situ images acquired by low electron dose LC-TEM

We study a machine learning (ML) technique for refining images acquired during in situ observation using liquid-cell transmission electron microscopy (LC-TEM). Our model is constructed using a U-Net architecture and a ResNet encoder. For training our ML model, we prepared an original image dataset that contained pairs of images of samples acquired with and without a solution present. The former images were used as noisy images and the latter images were used as corresponding ground truth images. The number of pairs of image sets was $1,204$ and the image sets included images acquired at several different magnifications and electron doses. The trained model converted a noisy image into a clear image. The time necessary for the conversion was on the order of 10ms, and we applied the model to in situ observations using the software Gatan DigitalMicrograph (DM). Even if a nanoparticle was not visible in a view window in the DM software because of the low electron dose, it was visible in a successive refined image generated by our ML model.Comment: 33 pages, 9 figure

Effect of difference in interaction strength on two-dimensional lattice structure in a binary system with DNA nanoparticles

Keeping two-dimensional lattice structures formed by nanoparticles covered with DNA in mind, we carry out Brownian dynamics simulations to study the effect of interaction strength on a two-dimensional lattice structure formed in a binary system. In our previous study [H. Katsuno, Y. Maegawa, and M. Sato, J. Phys. Soc. Jpn. 85, 074605 (2016)], we carried out simulations using the Lennard-Jones potential, in which the difference in interaction length was taken into account. When the interaction length between different species, σ$, is smaller than that between the same species, σ, various lattice structures were formed with changing the ratio σ$/σ. In this paper, taking the difference in the interaction strength into account, we study the effect of the difference in interaction strength on the two-dimensional lattice structure. © 2017 The Japan Society of Applied PhysicsEmbargo Period 12 month

Three-dimensional lattice structure formed in a binary system with DNA nanoparticles

Keeping the formation of lattice structures by nanoparticles covered with DNA in mind, we carry out Brownian dynamics simulations and study three-dimensional lattice structures formed by two species of particles. In our previous study [H. Katsuno, Y. Maegawa, and M. Sato, J. Phys. Soc. Jpn. 85, 074605 (2016)], we used the Lennard-Jones potential and studied two-dimensional structures formed in a binary system. When the interaction length between the different species, σ′, is shorter than that between the same species, σ, the lattice structure changes with the ratio σ′/σ. In this paper, we use the same potential and study the formation of three-dimensional structures. With decreasing ratio σ′/σ, the mixture of the face-centered-cubic (fcc) structure and hexagonal-close-packed (hcp) structure is changed to the bodycentered-cubic (bcc) structure and the NaCl structure. © 2017 The Physical Society of Japan.Embargo Period 12 month

Two-dimensional crystal structure formed by two components of DNA nanoparticles on a substrate

We study the two-dimensional crystal structure of two components of DNA nanoparticles on a substrate by Brownian dynamics simulation. We use the Lennard-Jones potential as the interaction potential between particles and assume that the interaction length between different types of particles, σAB , is smaller than that between the same types of particles, σ. Two types of particles form an alloy structure. With decreasing σAB =σ, the crystal structure changes from a triangular lattice, to a square lattice, a honeycomb lattice, a rectangular lattice, and a triangular lattice. © 2016 The Physical Society of Japan

Ordering of Brownian particles from walls due to an external force

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

Formation of a crystal of Brownian particles under a uniform external force

To keep the formation of colloidal crystal under a centrifugation in mind, we study ordering of Brownian particles under a uniform external force. When the force is added to Brownian particles distributing uniformly in the system, the particles drift and the density of particles near walls increases. Ordering of particles on the walls occurs at first and ordering in bulk occurs in succession. In bulk, both the clusters with face-centered cubic structure and those with the hexagonal close-packed structure appear. The distribution of cluster sizes changes with the direction of external force. © 2013 American Physical Society