研究者詳細 - 中村　有花

論文 - 中村　有花

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Spatial distribution of reduced density of hard spheres near a hard-sphere dimer: Results from three-dimensional Ornstein–Zernike equations coupled with several different closures and from grand canonical Monte Carlo simulation 査読

Mika Matsuo, Yuka Nakamura, Masahiro Kinoshita, Ryo Akiyama

Physica A: Statistical Mechanics and its Applications 2024年5月

Nonadditivities of the Particle Sizes Hidden in Model Pair Potentials and Their Effects on Physical Adsorptions 査読

Ken Ichi Amano, Satoshi Furukawa, Yuto Kubo, Yuka Nakamura, Rina Ishii, Ayane Tanase, Masahiro Maebayashi, Tomohiko Hayashi, Naoya Nishi, Tetsuo Sakka

Langmuir 39 ( 37 ) 12999 - 13007 2023年9月

掲載種別：研究論文（学術雑誌）

It is important to understand the mechanism of colloidal particle assembly near a substrate for development of drug delivery systems, micro-/nanorobots, batteries, heterogeneous catalysts, paints, and cosmetics. Understanding the mechanism is also important for crystallization of the colloidal particles and proteins. In this study, we calculated the physical adsorption of colloidal particles on a flat wall mainly using the integral equation theory, wherein small and large colloidal particles were employed. In the calculation system, like-charged electric double-layer potentials were used as pair potentials. In some cases, it was found that the small particles are more easily adsorbed. This result is unusual from the viewpoint of the Asakura-Oosawa theory, and we call it a “reversal phenomenon”. Theoretical analysis revealed that the reversal phenomenon originates from the nonadditivities of the particle sizes. Using the knowledge obtained from this study, we invented a method to analyze the size nonadditivity hidden in model pair potentials. The method will be useful for confirmation of various simulation results regarding the adsorption and development of force fields for colloidal particles, proteins, and solutes.

DOI： 10.1021/acs.langmuir.3c00968

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A Microscopic Theory for Preferential Solvation Effects on Viscosity 査読

Shota Arai, Akira Yoshimori, Yuka Nakamura, Ryo Akiyama

Journal of the Physical Society of Japan 91 ( 9 ) 2022年9月

Solvation effects on diffusion processes of a macromolecule: Accuracy required for radial distribution function to calculate diffusion coefficient 査読国際誌

Yuka Nakamura, Akira Yoshimori, Ryo Akiyama

JOURNAL OF CHEMICAL PHYSICS 154 ( 154 ) 084501 - 084501 2021年2月

担当区分：筆頭著者,　責任著者記述言語：英語掲載種別：研究論文（学術雑誌）

We investigate the dependence of the diffusion coefficient of a large solute particle on the solvation structure around a solute. The diffusion coefficient of a hard-sphere system is calculated by using a perturbation theory of large-particle diffusion with radial distribution functions around the solute. To obtain the radial distribution function, some integral equation theories are examined, such as the Percus-Yevick (PY), hypernetted-chain (HNC), and modified HNC theories using a bridge function proposed by Kinoshita (MHNC) closures. In one-component solvent systems, the diffusion coefficient depends on the first-minimum value of the radial distribution function. The results of the MHNC closure are in good agreement with those of calculation using the radial distribution functions of Monte Carlo simulations since the MHNC closure very closely reproduces the radial distribution function of Monte Carlo simulations. In binary-solvent mixtures, the diffusion coefficient is affected by the larger solvent density distribution in the short-range part, particularly the height and sharpness of the first peak and the depth of the first minimum. Since the HNC closure gives the first peak that is higher and sharper than that of the MHNC closure, the calculated diffusion coefficient is smaller than the MHNC closure result. In contrast, the results of the PY closure are qualitatively and quantitatively different from those of the MHNC and HNC closures.

DOI： 10.1063/5.0038894

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Dynamical scaling analysis on critical universality class for fully frustrated XY models in two dimensions 査読

Yukiyasu Ozeki, Yuri Yajima, Yuka Nakamura

PHYSICAL REVIEW B 101 ( 9 ) 2020年3月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：AMER PHYSICAL SOC

Critical properties of the fully frustrated XY models on square and triangular lattices are investigated by means of the nonequilibrium relaxation (NER) method. We examine the validity of the conclusion on the universality class of the chiral transition previously obtained by the NER method, in which that belongs to a non-Isingtype one. To clarify it, we analyze the NER of fluctuations for longer Monte Carlo steps on lager lattices than those performed previously. The calculation is made at the chiral transition temperatures estimated carefully by the use of recently improved dynamical scaling analysis. The result indicates that the asymptotic behavior of the time-dependent exponents, which should converge to the critical exponents, show the same tendency as those obtained previously in shorter times. We also apply the improved dynamical scaling analysis to the estimation of Kosterlitz-Thouless (KT) transitions and confirm the existence of the double transitions for the chiral and KT phases with more reliable estimations.

DOI： 10.1103/PhysRevB.101.094437

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Reduced density profile of small particles near a large particle: Results of an integral equation theory with an accurate bridge function and a Monte Carlo simulation 査読

Yuka Nakamura, Shota Arai, Masahiro Kinoshita, Akira Yoshimori, Ryo Akiyama

JOURNAL OF CHEMICAL PHYSICS 151 ( 4 ) 2019年7月

担当区分：筆頭著者,　責任著者記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：AMER INST PHYSICS

Solute-solvent reduced density profiles of hard-sphere fluids were calculated by using several integral equation theories for liquids. The traditional closures, Percus-Yevick (PY) and the hypernetted-chain (HNC) closures, as well as the theories with bridge functions, Verlet, Duh-Henderson, and Kinoshita (named MHNC), were used for the calculation. In this paper, a one-solute hard-sphere was immersed in a one-component hard-sphere solvent and various size ratios were examined. The profiles between the solute and solvent particles were compared with those calculated by Monte Carlo simulations. The profiles given by the integral equations with the bridge functions were much more accurate than those calculated by conventional integral equation theories, such as the Ornstein-Zernike (OZ) equation with the PY closure. The accuracy of the MHNC-OZ theory was maintained even when the particle size ratio of solute to solvent was 50. For example, the contact values were 5.7 (Monte Carlo), 5.6 (MHNC), 7.8 (HNC), and 4.5 (PY), and the first minimum values were 0.48 (Monte Carlo), 0.46 (MHNC), 0.54 (HNC), and 0.40 (PY) when the packing fraction of the hard-sphere solvent was 0.38 and the size ratio was 50. The asymptotic decay and the oscillation period for MHNC-OZ were also very accurate, although those given by the HNC-OZ theory were somewhat faster than those obtained by Monte Carlo simulations.

DOI： 10.1063/1.5100040

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Stick boundary condition at large hard sphere arising from effective attraction in binary hard-sphere mixtures 査読

Yuka Nakamura, Akira Yoshimori, Ryo Akiyama, Tsuyoshi Yamaguchi

JOURNAL OF CHEMICAL PHYSICS 148 ( 12 ) 2018年3月

担当区分：筆頭著者,　責任著者記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：AMER INST PHYSICS

We have studied the diffusion of a large hard-sphere solute immersed in binary hard-sphere mixtures. We reveal how the boundary condition at the solute surface is affected by the solvent density around the solute. Solving equations for a binary compressible mixture by perturbation expansions, we obtain the boundary condition depending on the size ratio of binary solvent spheres. When the size ratio is 1: 2, the boundary condition lies close to the slip boundary condition. By contrast, when the size ratio becomes large, the boundary condition approaches the stick boundary condition with the addition of larger solvent spheres. We find that the transition to the stick boundary condition is caused by the increase in the solvent density around the solute due to an entropic effect. Published by AIP Publishing.

DOI： 10.1063/1.5025202

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Effects of the solvation structure on diffusion of a large particle in a binary mixture studied by perturbation theory 査読

Y. Nakamura, A. Yoshimori, R. Akiyama

JOURNAL OF MOLECULAR LIQUIDS 200 85 - 88 2014年12月

担当区分：筆頭著者,　責任著者記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：ELSEVIER SCIENCE BV

We study the effects of the solvation structure on the diffusion of a large particle in a binary mixture. Using our recently developed perturbation theory, we calculate the diffusion coefficient of a large hard-sphere solute particle immersed in a binary solvent mixture of hard spheres with two different sizes. The calculation results show that the Stokes-Einstein (SE) relation breaks down in the hard-sphere system. When the size ratio of binary solvent spheres is three or more, the deviation from the SE relation increases with the packing fraction of larger solvent spheres. In contrast, at the size ratio of two, the diffusion coefficient approaches the value predicted by the SE relation as larger solvent spheres are added. We show that the large deviation from the SE relation is caused by the high density of larger solvent spheres around the solute sphere. (C) 2014 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.molliq.2014.06.021

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Perturbation Theory of Large-Particle Diffusion in a Binary Solvent Mixture 査読

Yuka Nakamura, Akira Yoshimori, Ryo Akiyama

JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN 83 ( 6 ) 2014年6月

担当区分：筆頭著者,　責任著者記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：PHYSICAL SOC JAPAN

We study the diffusion of a large spherical particle immersed in a binary compressive liquid mixture using a perturbation theory. We focus on the breakdown of the Stokes-Einstein (SE) relation caused by the microscopic solvation structure of binary solvent particles around a solute particle. In order to consider the solvation structure, we solve multicomponent generalized Langevin equations by singular perturbation expansion. Then, we assume that solvent particles are much smaller than the solute particle. Solving the equations, we express the diffusion coefficient analytically using the radial distribution functions of a binary mixture. The expression shows the breakdown of the SE relation if the density distribution of a binary solvent is inhomogeneous around a solute particle. Actually, we show that the SE relation breaks down when a large hard sphere diffuses in a binary hard-sphere mixture. We observe the large deviation from the SE relation, which is a result specific to the binary solvent.

DOI： 10.7566/JPSJ.83.064601

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A Perturbation Theory for Friction of a Large Particle Immersed in a Binary Solvent 査読

Yuka Nakamura, Akira Yoshimori, Ryo Akiyama

JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN 81 2012年9月

担当区分：筆頭著者,　責任著者記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：PHYSICAL SOC JAPAN

A new theory of a binary solvent is developed to study the effects of the density of solvent particles around a large solute particle on friction. To develop the theory, the solvent particles are assumed to be much smaller than the solute particle, and then a perturbation expansion is employed. The expansion allows one to derive hydrodynamic equations with boundary conditions on the surface of a solute. The boundary conditions are calculated from the radial distribution functions of a binary solvent. The hydrodynamic equations with the boundary conditions provide an analytical expression for the friction. The developed theory is applied to a binary hard-sphere system. The present theory shows that the friction in the system has larger values than those predicted by the Stokes law.

DOI： 10.1143/JPSJS.81SA.SA026

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