Faculty Profiles - YAMAGUCHI, Tsuyoshi

Molecular Dynamics Simulation Study on Heterogeneous Structure, Rheology, and Dynamic Correlation of Concentrated Aqueous Solutions of a Lithium Salt Reviewed

Yamaguchi, T

JOURNAL OF PHYSICAL CHEMISTRY B Vol. 129 ( 3 ) page： 1026 - 1035 2025.1

Authorship：Lead author,　Last author,　Corresponding author Language：English Publishing type：Research paper (scientific journal) Publisher：Journal of Physical Chemistry B

Molecular dynamics simulation of an aqueous solution of lithium bis(trifluoromethanesulfonyl)amide, LiTFSA, was performed at various concentrations to relate its liquid structure with frequency-dependent shear viscosity. The structure factor exhibited a low-q peak that represents a heterogeneous structure composed of water and anion domains, and the lithium ion existed in the water domain due to its strong hydration. The frequency-dependent shear viscosity showed bimodal relaxation, and the relative contribution of the slower mode increased with an increase in the salt concentration. The cross-correlation between the shear stress and the two-body density revealed that the slower viscoelastic mode is assigned to the dynamics of the heterogeneous structure, and the assignment was also confirmed by the comparison between the viscoelastic and structural relaxations. The collective translational motions of the cation and the anion showed a strong negative correlation in a concentrated solution, reflecting the heterogeneous domain structure.

DOI： 10.1021/acs.jpcb.4c07942

Coexistence of two coacervate phases of polyglycine in water suggested by polymer reference interaction site model theory Reviewed

Yamaguchi, T; Chong, SH; Yoshida, N

JOURNAL OF CHEMICAL PHYSICS Vol. 159 ( 24 ) 2023.12

Authorship：Lead author,　Corresponding author Language：English Publishing type：Research paper (scientific journal) Publisher：Journal of Chemical Physics

Mixing Gibbs energy and phase equilibria of aqueous solutions of polyglycine were studied theoretically by means of polymer reference interaction site model integral equation theory combined with the Gibbs-Duhem method. In addition to the ordinary liquid-liquid phase separation between dilute and concentrated solutions, the theoretical calculation predicted the coexistence of two coacervate phases, namely, the lower- and higher-density coacervates. The relative thermodynamic stabilities of these two phases change with the polymerization degree of polyglycine. The higher-density coacervate phase was rapidly stabilized by increasing the polymer length, and the lower-density phase became metastable at large polymers. The hydrogen bonds between the peptide chains were strengthened, and water was thermodynamically destabilized in the higher-density coacervate. A possible relation with the formation of amyloid fibril within a liquid droplet is also discussed.

DOI： 10.1063/5.0185157

Non-Newtonian Dynamics in Water-in-Salt Electrolytes Reviewed International coauthorship

Yamaguchi, T; Dukhin, A; Ryu, YJ; Zhang, DZ; Borodin, O; González, MA; Yamamuro, O; Price, DL; Saboungi, ML

JOURNAL OF PHYSICAL CHEMISTRY LETTERS Vol. 15 ( 1 ) page： 76 - 80 2023.12

Authorship：Lead author Language：English Publishing type：Research paper (scientific journal) Publisher：Journal of Physical Chemistry Letters

Water-in-salt electrolytes have attracted considerable interest in the past decade for advanced lithium-ion batteries, possessing important advantages over the non-aqueous electrolytes currently in use. A battery with a LiTFSI-water electrolyte was demonstrated in which an operating window of 3 V is made possible by a solid-electrolyte interface. Viscosity is an important property for such electrolytes, because high viscosity is normally associated with low ionic conductivity. Here, we investigate shear and longitudinal viscosities using shear stress and compressional longitudinal stress measurements as functions of frequency and concentration. We find that both viscosities are frequency-dependent and exhibit almost identical frequency and concentration dependences in the high-concentration region. A comparison to quasielastic neutron scattering experiments suggests that both are governed by structural relaxation of the TFSI- network. Thus, LiFTSI-water electrolytes appear to be an unusual case of a non-Newtonian fluid, where shear and longitudinal viscosities are determined by the same relaxation mechanism.

DOI： 10.1021/acs.jpclett.3c03145

Effects of intramolecular chain conformation on the hydration and miscibility of polyethylene glycol in water studied by means of polymer reference interaction site model theory Reviewed

Yamaguchi Tsuyoshi, Chong Song-Ho, Yoshida Norio

JOURNAL OF CHEMICAL PHYSICS Vol. 159 ( 4 ) 2023.7

Authorship：Lead author,　Corresponding author Language：English Publishing type：Research paper (scientific journal) Publisher：Journal of Chemical Physics

To examine the conventional idea that the gauche conformation of the OCCO dihedral angle promotes the dissolution of polyethylene glycol (PEG) in water through strong hydration, the thermodynamic properties of liquid mixtures of PEG and water were studied by means of polymer reference interaction site model (PRISM) theory. The intramolecular correlation functions required as input for PRISM theory were calculated by the generator matrix method, accompanied by changes in the distribution of dihedral angles. In the infinite dilution limit, the increased probability of gauche conformation of the OCCO dihedral angles stabilizes the hydration of PEG through enhanced hydrogen bonding between the ether oxygen of PEG and water. The mixing Gibbs energies of the liquid mixtures were also calculated in the whole concentration range based on the Gibbs-Duhem equation, as per our recent proposal. A liquid-liquid phase separation was observed when all the dihedral angles of PEG were in the trans conformation; for the liquid mixture to be miscible in the whole concentration range, the introduction of the OCCO gauche conformation was found to be indispensable. The above theoretical results support the conventional idea that the OCCO gauche conformation is important for the high miscibility of PEG and water.

DOI： 10.1063/5.0159130

Phase equilibrium of three-component liquid systems composed of water, alcohol, and sodium chloride studied by the reference interaction-site model integral equation theory Reviewed

Yamaguchi T., Chong S.H., Yoshida N.

Journal of Chemical Physics Vol. 158 ( 8 ) page： 084502 2023.2

Authorship：Lead author,　Corresponding author Language：English Publishing type：Research paper (scientific journal) Publisher：Journal of Chemical Physics

A theoretical method for calculating the thermodynamic properties and phase equilibria of a binary liquid mixture using the reference interaction-site model (RISM) integral equation theory, which we had proposed recently, was extended to ternary liquid systems containing salt. A novel dielectric correction of the RISM theory for a mixture of solvents was also proposed. The theory was applied to mixtures composed of water, alcohol, and NaCl, where the alcohol was either methanol or ethanol. The decrease in NaCl solubility with increasing alcohol molar fractions in the solvent was calculated. In the ethanol system, the theory yielded salt-induced liquid-liquid phase separation, which was observed experimentally in a ternary mixture of water, 1-propanol, and NaCl. The phase diagram of the ternary system was determined theoretically.

DOI： 10.1063/5.0142256

Study of phase equilibria and thermodynamic properties of liquid mixtures using the integral equation theory: Application to water and alcohol mixtures Reviewed

Yamaguchi Tsuyoshi, Chong Song-Ho, Yoshida Norio

JOURNAL OF CHEMICAL PHYSICS Vol. 157 ( 23 ) page： 234502 2022.12

Authorship：Lead author,　Corresponding author Language：English Publishing type：Research paper (scientific journal) Publisher：Journal of Chemical Physics

A theoretical method for calculating the thermodynamic properties and phase equilibria of liquid-liquid mixtures using the integral equation theory is proposed. The solvation chemical potentials of the two components are evaluated by the integral equation theory and the isothermal-isobaric variation of the total density with composition is determined to satisfy the Gibbs-Duhem relation. Given the density of a pure component, the method can calculate the densities of the mixture at any composition. Furthermore, it can treat the phase equilibrium without thermodynamic inconsistency with respect to the Gibbs-Duhem relation. This method was combined with the reference interaction-site model integral equation theory and applied to mixtures of water + 1-alcohol by changing the alcohol from methanol to 1-butanol. The destabilization of the mixing Gibbs energy by increasing the hydrophobicity of the alcohol and demixing of the water-butanol mixture were reproduced. However, quantitative agreement with experiments is not satisfactory, and further improvements of the integral equation theory and the molecular models are required.

DOI： 10.1063/5.0131475

Measurement of complex shear viscosity up to 3 GHz using an electrodeless AT-cut quartz transducer Reviewed

Effects of molecular shape and flexibility on fast sound of organic liquids Reviewed

Tsuyoshi Yamaguchi, Koji Yoshida, Shinya Hosokawa, Daisuke Ishikawa, Alfred Q. R. Baron

The Journal of Chemical Physics Vol. 157 ( 15 ) page： 154504 2022.9

Yamaguchi Tsuyoshi, Matsuoka Tatsuro

JAPANESE JOURNAL OF APPLIED PHYSICS Vol. 61 ( SG ) 2022.7

Authorship：Lead author,　Corresponding author Language：English Publishing type：Research paper (scientific journal) Publisher：Japanese Journal of Applied Physics

An experimental method is proposed to determine the frequency-dependent complex shear viscosity of liquids based on the quartz crystal microbalance with dissipation method. An AT-cut quartz transducer without metal electrodes is immersed in a sample liquid and the transducer is electrically coupled to the circuit through the dielectric response of the sample itself. After correcting for the apparent change in the resonance properties due to the dielectric coupling of the sample, our method is able to determine the viscosity of liquids of high polarity and low viscosity at frequencies as high as 3 GHz. The method was then applied to ethylene glycol and the viscoelastic relaxation in the GHz regime was observed. Furthermore, it was also applied to room-temperature ionic liquids to show that the dielectric correction of the resonance properties is valid for conductive liquids.

DOI： 10.35848/1347-4065/ac4141

Comparison between longitudinal viscoelastic relaxation and sound dispersion of molecular liquids on the molecular scale Reviewed

Yamaguchi T.

Journal of Chemical Physics Vol. 156 ( 24 ) page： 244505 2022.6

Authorship：Lead author,　Corresponding author Language：English Publishing type：Research paper (scientific journal) Publisher：Journal of Chemical Physics

Molecular dynamics simulation on some molecular liquids was performed to study sound dispersion on the molecular scale. The sound velocity was determined from the intermediate scattering function, and the relation between the longitudinal modulus and frequency was compared with the frequency-dependent longitudinal modulus in the q = 0 limit evaluated by the Kubo-Green theory. The sound dispersion of a monoatomic liquid up to qσ ≅ 2 was almost quantitatively explained by the viscoelasticity in the q = 0 limit when the wavenumber dependence of the heat capacity ratio was taken into account. The situation was similar for a polyatomic molecular liquid for which the intramolecular degrees of freedom were fixed. For a polyatomic liquid with intramolecular degrees of freedom, the sound dispersion on the molecular scale was connected to the high-frequency limit of the ultrasonic relaxation mode assigned to the vibrational energy relaxation. After subtracting the contribution of the vibrational energy relaxation, both the longitudinal viscoelasticity and the sound dispersion depended little on the presence of intramolecular degrees of freedom.

DOI： 10.1063/5.0098098

Implementation of solvent polarization in three-dimensional reference interaction-site model self-consistent field theory Reviewed

Yoshida N., Yamaguchi T., Nakano H.

Chemical Physics Letters Vol. 797 2022.6

Language：English Publishing type：Research paper (scientific journal) Publisher：Chemical Physics Letters

The three-dimensional reference interaction-site model self-consistent field (3D-RISM-SCF) theory is an electronic structure theory of solvated molecules, which can handle the electronic polarization of the solute molecule induced by the interaction with the solvent, whereas the electronic polarization of solvent molecules is ignored. Here, the solvent-polarizable model is implemented to take into account the electronic polarization of solvent molecules. It is applied to the water molecule in an aqueous solution and the p-nitroaniline molecule in an aqueous solution, and the effects of the solvent polarization on the properties of these solutes are demonstrated.

DOI： 10.1016/j.cplett.2022.139579

Volume viscosity and ultrasonic relaxation of ethanol-water mixtures studied by molecular dynamics simulations Reviewed

Yamaguchi Tsuyoshi

PHYSICAL CHEMISTRY CHEMICAL PHYSICS Vol. 24 ( 20 ) page： 12311 - 12318 2022.5

Authorship：Lead author,　Last author,　Corresponding author Language：English Publishing type：Research paper (scientific journal) Publisher：Physical Chemistry Chemical Physics

The volume viscosity of ethanol-water mixtures at various compositions was calculated by means of equilibrium molecular dynamics simulations, and the results were compared with acoustic experiments. The volume viscosity exhibited a strong maximum around the ethanol mole fraction of 0.27, which is in agreement with experiments. The relaxation in the 100 ps regime, which had been revealed by ultrasonic spectroscopy, was also reproduced. Analysis of the two-body density and the adiabatic pressure fluctuation demonstrated that the large volume viscosity of the mixture originates from the long-range concentration fluctuation.

DOI： 10.1039/d2cp00856d

Coupling between Translational Diffusion of a Solute and Dynamicsof the Heterogeneous Structure: Higher Alcohols and Ionic Liquids Reviewed

Yamaguchi Tsuyoshi

JOURNAL OF PHYSICAL CHEMISTRY B Vol. 126 ( 16 ) page： 3125 - 3134 2022.4

Authorship：Lead author,　Last author,　Corresponding author Language：English Publishing type：Research paper (scientific journal) Publisher：Journal of Physical Chemistry B

Translational diffusion of nonpolar monoatomic solutes in a room-temperature ionic liquid and 1-octanol was studied by molecular dynamics simulation. The diffusion coefficient was evaluated in two different ways: (1) from the mean-square displacement of a freely diffusing solute and (2) from the time correlation function of force acting on a fixed solute. The diffusion of the free solute is much greater than the prediction of the Stokes-Einstein (SE) relation when the size of the solute is small, as has been reported by many experimental works. In contrast, the friction on fixed small solutes follows the SE relation. The mechanism of the solute diffusion in both solvents was then analyzed based on the coupling between the translational motion of the solute and the collective dynamics of the heterogeneous intermediate-range structure characteristic to these solvents. Analysis revealed that the coupling is present in all systems, but the relaxation is fast in the cases of free and small solutes. This suggests that the coupling can relax through the motion of the solute when the solute is free and small, while the relaxation of the heterogeneous structure itself is required for large or fixed solutes. The difference in the relaxation dynamics of the friction on the solute and the shear viscosity is explained as the coupling with different dynamic modes of the solvent. Therefore, the validity of the SE relation may not be a good criterion to judge whether the mechanisms of the diffusion and the viscosity are the same or not.

DOI： 10.1021/acs.jpcb.2c01053

Decoupling between Solvent Viscosity and Diffusion of a Small Solute Induced by Self-Motion Reviewed

Yamaguchi Tsuyoshi

JOURNAL OF PHYSICAL CHEMISTRY LETTERS Vol. 12 ( 32 ) page： 7696 - 7700 2021.8

Authorship：Lead author,　Last author,　Corresponding author Language：English Publishing type：Research paper (scientific journal) Publisher：Journal of Physical Chemistry Letters

The self-diffusion of a monatomic solute in liquid 1-octanol and n-tetradecane was investigated by means of a molecular dynamics simulation. The diffusion coefficient of a solute as small as argon is much greater than that obtained from the hydrodynamic-based Stokes-Einstein (SE) relation, as was reported experimentally. A relaxation of the memory function of a freely diffusing solute is much faster than that of the autocorrelation function of a shear stress. However, the SE behavior is recovered when the solute is spatially fixed, and the diffusion coefficient is calculated from the force-force autocorrelation function. A relaxation of the autocorrelation function of the force also follows that of shear stress. The fast diffusion of a small solute is thus ascribed to the decoupling between the structural relaxation of solvent and the solute diffusion induced by the self-motion of the solute.

DOI： 10.1021/acs.jpclett.1c02219

Molecular dynamics simulation study on the isomerization reaction in a solvent with slow structural relaxation Reviewed

CHEMICAL PHYSICS Vol. 542 page： 111056 2021.2

Solvation dynamics in electronically polarizable solvents: Theoretical treatment using solvent-polarizable three-dimensional reference interaction-site model theory combined with time-dependent density functional theory Reviewed

Yamaguchi Tsuyoshi, Yoshida Norio

JOURNAL OF CHEMICAL PHYSICS Vol. 154 ( 4 ) page： 044504 2021.1

Energy analysis of CO<inf>2</inf> separation process with low energy consumption using phase separation solvent

Maeda N., Nakanishi K., Kishimoto A., Machida H., Yamaguchi T., Norinaga K.

15th Greenhouse Gas Control Technologies Conference 2021, GHGT 2021 2021

Publisher：15th Greenhouse Gas Control Technologies Conference 2021, GHGT 2021

We calculated the energy required for regeneration when the phase separation solvent solvent is applied to the treatment of exhaust gas from coal-fired power plants. This solvent is characterized by regeneration at a low temperature of less than 100°C. As a result, it was clarified that under ideal conditions with no pressure drop and no heat loss, the required energy could be suppressed to 1.5 GJ/ton-CO2 by satisfying the following conditions; i) pinch point of the heat exchanger between rich-amine and lean-amine: 1 °C, ii) water concentration of the solvent: kept at 10 wt%, iii) COP of the heat pump: 5.5. However, increase of the pinch point, increase of the water concentration, and decrease of the COP will all result in a significant increase in the required energy. Therefore, in order to realize a process with low energy consumption, it is essential to meet these design constraints.

Durability and fire-hazardous-risk evaluation of unique phase separation solvent using high-boiling amine and ether

Maeda N., Kishimoto A., Machida H., Yamaguchi T., Yanase K., Norinaga K.

15th Greenhouse Gas Control Technologies Conference 2021, GHGT 2021 2021

Publisher：15th Greenhouse Gas Control Technologies Conference 2021, GHGT 2021

Durability and fire hazard risk evaluation were conducted to determine the process feasibility on the unique phase separation solvent with low regeneration temperature (90 °C), consisting of amine, ether, and small amount of water. The results we obtained are as follows; I) The amine degradation rate of the phase separation solvent would be less than 1/10 of that of monoethanolamine (MEA), which was contributed by its high oxidative resistant nature and low regeneration temperature. II) The gas composition formed in the absorber was completely out of combustible range and almost no accumulations of explosive compounds such as peroxides were observed when in contact with 6 % oxygen containing gas (dry base). Therefore, we believe that the phase separation solvent is applicable to the treatment of exhaust gas from coal-fired thermal power plants.

Coupling between Structural and Dielectric Relaxations of Methanol and Ethanol Studied by Molecular Dynamics Simulation Reviewed

JOURNAL OF PHYSICAL CHEMISTRY B Vol. 124 ( 32 ) page： 7027 - 7036 2020.8

Nonequilibrium free-energy profile of charge-transfer reaction in polarizable solvent studied using solvent-polarizable three-dimensional reference interaction-site model theory Reviewed

JOURNAL OF CHEMICAL PHYSICS Vol. 153 ( 3 ) page： 034502 2020.7

Energy-Saving CO2 Capture by H-2 Gas Stripping for Integrating CO2 Separation and Conversion Processes Reviewed

ACS SUSTAINABLE CHEMISTRY & ENGINEERING Vol. 8 ( 23 ) page： 8732 - 8740 2020.6

Development of a solvent-polarizable three-dimensional reference interaction-site model theory (vol 152, 114108, 2020) Reviewed

Yoshida Norio, Yamaguchi Tsuyoshi

JOURNAL OF CHEMICAL PHYSICS Vol. 152 ( 18 ) page： 189904 2020.5

Development of a solvent-polarizable three-dimensional reference interaction-site model theory Reviewed

Norio Yoshida, Tsuyoshi Yamaguchi

Journal of Chemical Physics Vol. 152 ( 11 ) page： 114108 2020.3

Carbon Dioxide Absorption Heat in Liquid-Liquid and Solid-Liquid Phase-Change Solvents Using Continuous Calorimetry Reviewed

Tran Khuyen V. B., Ando Ryuya, Yamaguchi Tsuyoshi, Machida Hiroshi, Norinaga Koyo

INDUSTRIAL & ENGINEERING CHEMISTRY RESEARCH Vol. 59 ( 8 ) page： 3475 - 3484 2020.2

Dynamic Chelate Effect on the Li+-Ion Conduction in Solvate Ionic Liquids Reviewed

Arai Nana, Watanabe Hikari, Yamaguchi Tsuyoshi, Seki Shiro, Ueno Kazuhide, Dokko Kaoru, Watanabe Masayoshi, Kameda Yasuo, Buchner Richard, Umebayashi Yasuhiro

JOURNAL OF PHYSICAL CHEMISTRY C Vol. 123 ( 50 ) page： 30228 - 30233 2019.12

Modelling of CO2 solubility in phase separation solvent composed of amine/ether/water system for CO2 capture Reviewed

Machida Hiroshi, Ando Ryuya, Esaki Takehiro, Yamaguchi Tsuyoshi, Norinaga Koyo

JOURNAL OF MOLECULAR LIQUIDS Vol. 292 2019.10

Composition Dependence of Translation-Orientation Coupling Constant in the Mixture of n-pentane and 2,2-dimethylpropane Studied by Molecular Dynamics Simulation Reviewed

Matsuoka Tatsuro, Yatsuya Masaki, Yamaguchi Tsuyoshi

JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN Vol. 88 ( 9 ) 2019.9

Effect of Molecular Orientational Correlations on Solvation Free Energy Computed by Reference Interaction Site Model Theory Reviewed

Tanimoto Shoichi, Yoshida Norio, Yamaguchi Tsuyoshi, Ten-no Seiichiro L., Nakano Haruyuki

JOURNAL OF CHEMICAL INFORMATION AND MODELING Vol. 59 ( 9 ) page： 3770 - 3781 2019.9

Relation between Anharmonicity of Free-Energy Profile and Spectroscopy in Solvation Dynamics: Differences in Spectral Broadening and Peak Shift in Transient Hole-Burning Spectroscopy Studied by Equilibrium Molecular Dynamics Simulation Reviewed

Yamaguchi Tsuyoshi, Yoshida Norio, Nishiyama Katsura

JOURNAL OF PHYSICAL CHEMISTRY B Vol. 123 ( 32 ) page： 7036 - 7042 2019.8

Shear Thinning and Nonlinear Structural Deformation of Ionic Liquids with Long Alkyl Chains Studied by Molecular Dynamics Simulation Reviewed

Yamaguchi Tsuyoshi

JOURNAL OF PHYSICAL CHEMISTRY B Vol. 123 ( 29 ) page： 6260 - 6265 2019.7

High-frequency shear viscosity and ionic mobility of solutions of polyethylene glycol in ionic liquids

Yamaguchi Tsuyoshi, Kikuzawa Takujiro

JOURNAL OF MOLECULAR LIQUIDS Vol. 284 page： 252 - 257 2019.6

Collective Mesoscale Dynamics of Liquid 1-Dodecanol Studied by Neutron Spin-Echo Spectroscopy with Isotopic Substitution and Molecular Dynamics Simulation Reviewed International coauthorship

Yamaguchi Tsuyoshi, Faraone Antonio, Nagao Michihiro

JOURNAL OF PHYSICAL CHEMISTRY B Vol. 123 ( 1 ) page： 239 - 246 2019.1

Degradation Test for Energy-Saving CO<inf>2</inf> Absorbent based on Phase Separation Type Solvent by Aqueous (Amine + Ether) Solution

Maeda N., Kishimoto A., Machida H., Yamaguchi T.

GHGT 2018 - 14th International Conference on Greenhouse Gas Control Technologies 2018

Publisher：GHGT 2018 - 14th International Conference on Greenhouse Gas Control Technologies

The unique phase separation type amine/ether absorbent is expected to realize the CO2 separation process with low-energy consumption (1.5GJ/ton-CO2). In this study, a degradation test of the absorbent under thermal load of liquid regeneration was conducted in order to clarify 1) the behavior of its performance declination for CO2 capture and 2) the behavior of amine loss mainly caused by generation of by-product. The regeneration condition was chosen based on two assumptions that a) most likely to damage to the solution, which means high-oxidation atmosphere containing oxygen and sulfur oxide, and b) adopting actual operating temperature when absorbing or desorbing. As a result, only a small amount of the CO2 capture capability was lost through 48 hours cyclic thermal load of 50-90 °C. Consequently, it was found that the phase separation type solvent could be durable enough for the practical use. Besides, the running cost associated with make-up amine might be drastically reduced.

Energy-saving CO<inf>2</inf> Capture Process Using Phase Separation Type Solvent by Aqueous (amine + ether) Solution

Machida H., Takehiro E., Yamaguchi T., Norinaga K., Kishimoto A., Akiyama K., Nishimura M.

GHGT 2018 - 14th International Conference on Greenhouse Gas Control Technologies 2018

Publisher：GHGT 2018 - 14th International Conference on Greenhouse Gas Control Technologies

We have developed the phase separation solvent for CO2 capture. Our developed solvent consists amine, organic solvent and water and shows single liquid phase before CO2 absorption though it shows two liquid phases after CO2 absorption. Feature of phase separation solvent is reducing temperature difference between absorber and stripper. We apply the heat pump system for CO2 separation and evaluate the energy consumption. Low temperature swing process saves energy requirement for CO2 capture process with highly-effective reaction-heat recovering. To evaluate the CO2 capture system with our solvent, screening test for amine and organic solvent combination and CO2 solubility measurement were examined. In the phase separation test, three types of solvents were obtained by combining amine and ether, that is, no phase separation with CO2 scrubbing, phase separation with CO2 scrubbing, and thoroughly immiscible. The phase behaviour depends on the hydrophobicity of amines or organic solvents, and the types of solvents were classified using the hydrophobic parameter.

Development of phase separation solvent for CO2 capture by aqueous (amine plus ether) solution

Machida Hiroshi, Oba Kazuki, Tomikawa Takashi, Esaki Takehiro, Yamaguchi Tsuyoshi, Horizoe Hirotoshi

JOURNAL OF CHEMICAL THERMODYNAMICS Vol. 113 page： 64 - 70 2017.10

A method for protein structure sampling under three-dimensional reference interaction site model solvation based on hybrid Monte Carlo framework Reviewed

Norio Yoshida, Tsuyoshi Yamaguchi

Journal of Molecular Liquids Vol. 385 2023.9

Effects of angular momentum and thermostat on molecular dynamics simulation of single-chain conformation in an implicit solvent Reviewed

Tsuyoshi Yamaguchi, Song-Ho Chong, Norio Yoshida

JOURNAL OF MOLECULAR LIQUIDS Vol. 385 2023.9

Authorship：Lead author,　Corresponding author Language：English Publishing type：Research paper (scientific journal) Publisher：ELSEVIER

The effect of angular momentum on single-chain conformation in an implicit solvent model was investigated by molecular dynamics simulation. The distribution of the end-to-end distance depends on whether the angular momentum of the entire molecule is fixed or thermalized, and these two distributions can be transformed from the one to the other through the reweighting method. In addition, depending on the thermostat, the thermalization of the angular momentum becomes insufficient even if no constraint is imposed on the angular momentum, resulting in the distortion of the distribution of chain conformation. These results suggest the importance of the choice of thermostat that enables the thermalization of the angular momentum.

DOI： 10.1016/j.molliq.2023.122311

Durability and fire-hazardous-risk evaluation of unique phase separation solvent using high-boiling-point amine and ether Reviewed

Maeda N., Kishimoto A., Machida H., Yamaguchi T., Yanase K., Norinaga K.

International Journal of Greenhouse Gas Control Vol. 114 2022.2

Language：English Publishing type：Research paper (scientific journal) Publisher：International Journal of Greenhouse Gas Control

Durability and fire hazard risk evaluations were conducted to determine the process feasibility of a unique phase separation solvent with a low regeneration temperature (90 °C) consisting of an amine, ether, and a small amount of water. The results are as follows. I) The amine degradation rate of the phase separation solvent was determined to be less than 1/10 of that of monoethanolamine, which was attributed to the high oxidative resistance and low regeneration temperature of the former. II) The composition of the gas that formed in the absorber was completely out of the combustible range during the treatment of 6% oxygen-containing gas on a dry basis. Therefore, we believe that this phase separation solvent is applicable to the treatment of exhaust gas from coal-fired thermal power plants and can realize stable operation with a small amount of amine required for replenishment.

DOI： 10.1016/j.ijggc.2021.103532

Fluctuation in diethylene glycol diethyl ether/water mixtures near the lower critical solution temperature studied by small- and wide-angle x-ray scattering and thermodynamic calculation Reviewed

Yanase K., Tran K.V.B., Yamaguchi T., Machida H., Norinaga K.

Journal of Molecular Liquids Vol. 346 2022.1

Language：English Publishing type：Research paper (scientific journal) Publisher：Journal of Molecular Liquids

We studied local structure of diethylene glycol diethyl ether (DEGDEE)-water mixtures near the lower critical solution temperature (LCST) by means of simultaneous small- and wide-angle x-ray scattering measurement and thermodynamic calculation based on the activity coefficient model. Long-wavelength limits of structure factors SNN(0), SCC(0), and SNC(0), which respectively represent mean square fluctuations in the particle number, the concentration, and their cross correlation, are determined from scattering intensity extrapolated to the zero scattering vector and thermodynamic quantities according to the Bhatia and Thornton formula. SNN(0) and SCC(0) exhibit maxima near critical concentration. We found that difference between partial molar volumes of water and DEGDEE essentially results in SNN(0) values being one order of magnitude larger than SCC(0) values. Further, we determined Kirkwood-Buff (KB) integrals to clarify a mixing state of the solution from a mesoscopic point of view. The KB integrals also exhibit extrema near critical concentration. These results demonstrate self-segregations of both DEGDEE and water in a nanometer length scale even at homogeneous solution states, which can be regarded as a precursor of the macroscopic phase separation. Concentration dependence of the wide-angle scattering curve suggests that the short-range structure, whose length scale is sub-nanometer, moderately changes between the intrinsic bulk structures of DEGDEE and water. Comparison of the KB integrals with those determined by the activity coefficient model using non-random two-liquid equation is presented and effects of the fluctuation on the phase behavior are discussed.

DOI： 10.1016/j.molliq.2021.117830

Momentum removal to obtain the position-dependent diffusion constant in constrained molecular dynamics simulation Reviewed

Fujimoto Kazushi, Nagai Tetsuro, Yamaguchi Tsuyoshi

JOURNAL OF COMPUTATIONAL CHEMISTRY Vol. 42 ( 30 ) page： 2136 - 2144 2021.8

Authorship：Corresponding author Language：English Publishing type：Research paper (scientific journal) Publisher：Journal of Computational Chemistry

The position-dependent diffusion coefficient along with free energy profile are important parameters needed to study mass transport in heterogeneous systems such as biological and polymer membranes, and molecular dynamics (MD) calculation is a popular tool to obtain them. Among many methodologies, the Marrink–Berendsen (MB) method is often employed to calculate the position-dependent diffusion coefficient, in which the autocorrelation function of the force on a fixed molecule is related to the friction on the molecule. However, the diffusion coefficient is shown to be affected by the period of the removal of the center-of-mass velocity, (Formula presented.), which is necessary when performing MD calculations using the Ewald method for Coulombic interaction. We have clarified theoretically in this study how this operation affects the diffusion coefficient calculated by the MB method, and the theoretical predictions are proven by MD calculations. Therefore, we succeeded in providing guidance on how to select an appropriate (Formula presented.) value in estimating the position-dependent diffusion coefficient by the MB method. This guideline is applicable also to the Woolf–Roux method.

DOI： 10.1002/jcc.26742

Density and Viscosity Calculation of a Quaternary System of Amine Absorbents before and after Carbon Dioxide Absorption Reviewed

Khuyen Viet Bao Tran, Sato Miho, Yanase Keiichi, Yamaguchi Tsuyoshi, Machida Hiroshi, Norinaga Koyo

JOURNAL OF CHEMICAL AND ENGINEERING DATA Vol. 66 ( 8 ) page： 3057 - 3071 2021.8

Language：English Publishing type：Research paper (scientific journal) Publisher：Journal of Chemical and Engineering Data

Viscosity and density of amine absorbents affect directly their flow, which is involved in the process design and simulation of carbon dioxide capture. A mixture of 2-(ethyl amino) ethanol (EAE), diethylene glycol diethyl ether (DEGDEE), and water changes its phase from homogeneous to two-liquid ones on CO2 absorption. It is difficult to calculate the viscosity and density of this phase separation solution, especially those of quaternary-component phases. In this research, models to calculate the density and viscosity of the quaternary-component system of EAE/DEGDEE/water/carbamate were suggested based on nonrandom two-liquid (NRTL)-DVOL and NRTL-DVIS models. Given the component concentrations, these models can replicate well the viscosity and density of the solutions. A good calculation result with a few numbers of parameters makes the models simple and easy to use.

DOI： 10.1021/acs.jced.1c00195

Low temperature swing process for CO2 absorption-desorption using phase separation CO2 capture solvent Reviewed

Online composition analysis of phase separation solvent for carbon dioxide capture using ATR‐FT‐IR Reviewed

Miho Sato, Khuyen Viet Bao Tran, Tsuyoshi Yamaguchi, Hiroshi Machida, Koyo Norinaga

Journal of Advanced Manufacturing and Processing 2020.10

Online composition analysis of phase separation solvent for carbon dioxide capture using ATR‐FT‐IR Reviewed

Miho Sato, Khuyen Viet Bao Tran, Tsuyoshi Yamaguchi, Hiroshi Machida, Koyo Norinaga

Journal of Advanced Manufacturing and Processing Vol. 2 ( 4 ) page： e10067 2020.7

Translation-orientation coupling and Cox-Merz rule of liquid hexane Reviewed

Yamaguchi Tsuyoshi, Matsuoka Tatsuro

The Journal of Chemical Physics Vol. 149 ( 20 ) page： 204502 2018.11

Hiroshi Machida, Ryuya Ando, Takehiro Esaki, Tsuyoshi Yamaguchi, Hirotoshi Horizoe, Akira Kishimoto, Katsuya Akiyama, Makoto Nishimura

International Journal of Greenhouse Gas Control Vol. 75 page： 1 - 7 2018.8

Language：English Publishing type：Research paper (scientific journal) Publisher：Elsevier Ltd

We have developed a phase separation solvent which transforms into two liquid phases after CO2 absorption, in order to establish an energy-saving CO2 capture process. The CO2 loading changes strongly with temperature increase during the phase separation, which enables us to reduce the temperature difference between absorber and desorber. The low temperature swing process economizes the energy requirement for the CO2 capture process with highly-effective reaction-heat recovery. We evaluated the energy consumption of the CO2 capture process with our novel phase separation solvent based on the CO2 solubility. The energy requirement was estimated to be as low as 1.6 GJ/ton-CO2.

DOI： 10.1016/j.ijggc.2018.05.010

Re-investigation of translational–orientational coupling behavior of nematogen in isotropic phase with non-nematogenic additives Reviewed

Wataru Hanai, Tsuyoshi Yamaguchi, Tatsuro Matsuoka

Japanese Journal of Applied Physics Vol. 57 ( 7 ) page： 07LB05 2018.7

Stress-structure coupling and nonlinear rheology of Lennard-Jones liquid Reviewed

Tsuyoshi Yamaguchi

The Journal of Chemical Physics Vol. 148 ( 23 ) page： 234507 2018.6

Coupling between mesoscopic dynamics and shear stress of room-temperature ionic liquid Reviewed

Tsuyoshi Yamaguchi

Physical Chemistry Chemical Physics 2018.6

Shear Viscosity and Heterogeneous Structure of Alkylaminoethanol-Based CO2 Absorbents Reviewed

Tsuyoshi Yamaguchi, Ryuya Ando, Koji Yoshida, Toshio Yamaguchi, Hiroshi Machida

Journal of Physical Chemistry B Vol. 122 ( 14 ) page： 4045 - 4050 2018.4

Language：English Publishing type：Research paper (scientific journal) Publisher：American Chemical Society

Shear viscosity of concentrated aqueous solutions of alkylaminoethanols was determined with changing the length of the alkyl chain and the concentration of dissolved CO2. The viscosity increased with increasing the CO2 loading, reflecting the strengthening of the intermolecular electrostatic interaction. The dependence of the viscosity on both temperature and CO2 loading was described by a modified version of Vogel-Fulchar-Tammann equation. Compared at the same volume concentration of CO2, the viscosity increased with increasing the alkyl chain lengths, and the dependence on the alkyl chain length increased with the CO2 loading. At the same time, small-angle X-ray scattering profiles exhibited the presence of a prepeak when the alkyl chain was long, and the prepeak grew with the CO2 loading. It suggests that the presence of the heterogeneous structure increases the shear viscosity of the CO2 absorbents when the alkyl chain is long.

DOI： 10.1021/acs.jpcb.8b00946

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

Yuka Nakamura, Akira Yoshimori, Ryo Akiyama, Tsuyoshi Yamaguchi

JOURNAL OF CHEMICAL PHYSICS Vol. 148 ( 12 ) page： 124502 2018.3

Language：English Publishing type：Research paper (scientific journal) Publisher：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

Effects of mesoscopic domain structure on shear viscosity of ionic liquids

Yamaguchi Tsuyoshi

ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY Vol. 255 page： . 2018.3

Structural Origin of Shear Viscosity of Liquid Water Reviewed

Tsuyoshi Yamaguchi

Journal of Physical Chemistry B Vol. 122 ( 3 ) page： 1255 - 1260 2018.1

Language：English Publishing type：Research paper (scientific journal) Publisher：American Chemical Society

The relation between the microscopic structure and shear viscosity of liquid water was analyzed by calculating the cross-correlation between the shear stress and the two-body density using the molecular dynamics simulation. The slow viscoelastic relaxation that dominates the steady-state shear viscosity was ascribed to the destruction of the hydrogen-bonding network structure along the compression axis of the shear distortion, which resembles the structural change under isotropic hydrostatic compression. It means that the shear viscosity of liquid water reflects the anisotropic destruction-formation dynamics of the hydrogen-bonding network.

DOI： 10.1021/acs.jpcb.7b10893

Structural Relaxation and Viscoelasticity of a Higher Alcohol with Mesoscopic Structure Reviewed

Tsuyoshi Yamaguchi, Makina Saito, Koji Yoshida, Toshio Yamaguchi, Yoshitaka Yoda, Makoto Seto

Journal of Physical Chemistry Letters Vol. 9 ( 2 ) page： 298 - 301 2018.1

Language：English Publishing type：Research paper (scientific journal) Publisher：American Chemical Society

This work studied the slow dynamics of liquids with mesoscopic structure and its relation to shear viscosity. Quasielastic scattering measurements were made on a liquid higher alcohol, 3,7-dimethyl-1-octanol, using γ-ray time-domain interferometry at a synchrotron radiation facility, SPring-8. The quasielastic scattering spectra were measured to determine the structural relaxation at two wavenumbers of the prepeak and the main peak of the static structure factor. It was found that relaxation at the prepeak is more than 10 times slower than that at the main peak. Compared with the viscoelastic spectrum, which exhibits bimodal relaxation, the relaxations at the prepeak and the main peak were shown to correspond to the slower and faster modes of the viscoelastic relaxation, respectively. This indicates that the dynamics of the mesoscopic structure represented as the prepeak contributes to the shear viscosity through the slowest mode of the viscoelastic relaxation.

DOI： 10.1021/acs.jpclett.7b02907

Development of phase separation solvent for CO2 capture by aqueous (amine plus ether) solution Reviewed

Hiroshi Machida, Kazuki Oba, Takashi Tomikawa, Takehiro Esaki, Tsuyoshi Yamaguchi, Hirotoshi Horizoe

JOURNAL OF CHEMICAL THERMODYNAMICS Vol. 113 page： 64 - 70 2017.10

Language：English Publishing type：Research paper (scientific journal) Publisher：ACADEMIC PRESS LTD- ELSEVIER SCIENCE LTD

Phase separation solvents for CO2 absorption have been designed which transform into two liquid phases after CO2 absorption. We studied seven types of amines and one type of ether-mixed solvents and observed that there are three types of phase phenomena, namely, no phase separation, phase separation with CO2 scrubbing, and initially immiscible. We also observed that these types can be classified using the hydrophobicity of the amine. The solubility of CO2 was measured in the phase separation solvent. In the lower-pressure region, the solvent formed a single liquid phase. When the amount of CO2 in solution reached a separation point, the solvent separated into two liquid phases. (C) 2017 Elsevier Ltd.

DOI： 10.1016/j.jct2017.05.043

Decoupling between the Temperature-Dependent Structural Relaxation and Shear Viscosity of Concentrated Lithium Electrolyte Reviewed

Tsuyoshi Yamaguchi, Koji Yoshida, Toshio Yamaguchi, Michihiro Nagao, Antonio Faraone, Shiro Seki

JOURNAL OF PHYSICAL CHEMISTRY B Vol. 121 ( 37 ) page： 8767 - 8773 2017.9

Language：English Publishing type：Research paper (scientific journal) Publisher：AMER CHEMICAL SOC

The intermediate scattering functions of concentrated solutions of LiPF6 in propylene carbonate (PC) were measured at various temperatures, two different wavenumbers, and three different concentrations using neutron spin echo (NSE) spectroscopy. The temperature dependence of the relaxation time was larger than that of the steady-state shear viscosity in all cases. The shear relaxation spectra were also determined at different temperatures. The normalized spectra reduced to a master curve when the frequency was multiplied by the steady-state shear-viscosity, indicating that the temperature dependence of the steady-state shear viscosity can be explained by that of the relaxation time of the shear stress. It is thus suggested that the dynamics of the shear stress is decoupled from the structural dynamics on the molecular scale.

DOI： 10.1021/acs.jpcb.7b04633

Analysis of shear viscosity and viscoelastic relaxation of liquid methanol based on molecular dynamics simulation and mode-coupling theory International coauthorship

Tsuyoshi Yamaguchi, Antonio Faraone

JOURNAL OF CHEMICAL PHYSICS Vol. 146 ( 24 ) page： 244506 2017.6

Language：English Publishing type：Research paper (scientific journal) Publisher：AMER INST PHYSICS

The role of the prepeak structure of liquid methanol in determining its shear viscosity was studied by means of molecular dynamics (MD) simulation and mode-coupling theory (MCT). The autocorrelation function of the shear stress and the intermediate scattering functions at both the prepeak and the main peak were calculated from the MD trajectories. Their comparison based on MCT suggests that the viscoelastic relaxation in the ps regime is affected by the slow structural dynamics at the prepeak. On the other hand, the MCT for molecular liquids based on the interaction-site model (site-site MCT) fails to describe the coupling between the prepeak dynamics and shear stress. The direct evaluation of the coupling between the two-body density and the shear stress reveals that the viscoelastic relaxation is actually affected by the prepeak dynamics, although the coupling is not captured by the site-site MCT. The site-site MCT works well for a model methanol without partial charges, suggesting that the failure of the site-site MCT originates from the existence of a hydrogen-bonding network structure. Published by AIP Publishing.

DOI： 10.1063/1.4990408

Analysis of Prepeak Structure of Concentrated Organic Lithium Electrolyte by Means of Neutron Diffraction with Isotopic Substitution and Molecular Dynamics Simulation Reviewed

Tsuyoshi Yamaguchi, Koji Yoshida, Toshio Yamaguchi, Yasuo Kameda, Kazutaka Ikeda, Toshiya Otomo

JOURNAL OF PHYSICAL CHEMISTRY B Vol. 121 ( 21 ) page： 5355 - 5362 2017.6

Language：English Publishing type：Research paper (scientific journal) Publisher：AMER CHEMICAL SOC

The prepeak structure of a 3 mol/kg solution,of LiCIC)(4) in propylene carlitinate (PC) was studied by both neutron diffraction with isotopic substitution (NDIS) and molecular dynamics (MD) simulation. The NDIS data showed that the intensity of the prepeak decreases experimentally with an increase in the scattering length of the lithium atom from Li-7 to Li-6 in PC-d(6). On the other hand, although the prepeak was observed in solutions of both PC-d(6) and PC-h(6), it disappears when the 1:1 mixture of PC-d(6) and PC-h(6) was used as the solvent. The prepeak structure and its variation with the isotope substitution were reproduced well by MD simulation, and they were explained in terms of the contrast of the scattering length densities of the ionic and nonpolar domains.

DOI： 10.1021/acs.jpcb.7b00686