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Journal Articles

Ion solvation under gigapascal pressure

Jing, Z.*; Yamaguchi, Toshio*; Machida, Shinichi*; Hattori, Takanori; Zhou, Y.*

Journal of Chemical Physics, 163(19), p.194505_1 - 194505_12, 2025/11

https://doi.org/10.1063/5.0304419

Times Cited Count：0 Percentile：0.00(Chemistry, Physical)

Ion solvation in a range of gigapascal pressure is of great significance for high-pressure chemical synthesis and the circulation of matter within the Earth's interior. We perform neutron scattering (NS) experiments and molecular dynamics simulations of deuterated aqueous solutions of MCl (M = Li, Na, K, Rb, and Cs) at 0.1 MPa and 0.7 GPa/298 K. An empirical potential structure refinement method analyzes the NS data. Upon compression to 0.7 GPa, the outer-shell water molecules enter the nearest neighbor of ions, and the solvated ion clusters become denser. The hydration factor $f_{h}$ and static hydration number $n_{hyd}^{stat}$ based on the orientation distribution of the water dipole in the first solvation shell, show that the compression weakens the hydration ability of the ions. Compression suppresses the diffusion of ions, particularly of the structure-breaking ions. The ionic diffusion coefficient residence time of water molecules $tau_{i}$ and dynamic hydration number $n_{hyd}^{dyn}$ indicate that Rb and Cs exhibit characteristics of structure-making ions under compression. The dynamic properties are more pressure-sensitive than the static structure.

Journal Articles

Highly sensitive detection of sodium in aqueous solutions using laser-induced breakdown spectroscopy with liquid sheet jets

Nakanishi, Ryuzo; Oba, Hironori; Saeki, Morihisa; Wakaida, Ikuo; Tanabe, Rie*; Ito, Yoshiro*

Optics Express (Internet), 29(4), p.5205 - 5212, 2021/02

https://doi.org/10.1364/OE.415308

Times Cited Count：35 Percentile：89.07(Optics)

Laser-induced breakdown spectroscopy (LIBS) combined with liquid jets was applied to the detection of trace sodium (Na) in aqueous solutions. The sensitivities of two types of liquid jets were compared: a liquid cylindrical jet with a diameter of 500 m and a liquid sheet jet with a thickness of 20 m. Compared with the cylindrical jet, the liquid sheet jet effectively reduced the splash from the laser-irradiated surface and produced long-lived luminous plasma. The limit of detection (LOD) of Na was determined to be 0.57 g/L for the sheet jet and 10.5 g/L for the cylindrical jet. The LOD obtained for the sheet jet was comparable to those obtained for commercially available inductively coupled plasma emission spectrometers.

Journal Articles

Role of the hydroxo group in the coordination of citric acid to trivalent americium

Tamain, C.*; Bonato, L.*; Aupiais, J.*; Dumas, T.*; Guillaumont, D.*; Barkleit, A.*; Berthon, C.*; Solari, P. L.*; Ikeda, Atsushi; Guilbard, P.*; et al.

European Journal of Inorganic Chemistry, 2020(14), p.1331 - 1344, 2020/04

https://doi.org/10.1002/ejic.202000124

Times Cited Count：4 Percentile：19.80(Chemistry, Inorganic & Nuclear)

The molecular characterization based on multi-technique approach has led to major highlights on revealing the coordination environment of americium (Am) surrounded by citric acid (H $_{3}$ CitH). The structure of the different complexes at pH 1 and 3 are described. These characterizations are made possible by the comparison of the americium-citric acid system with the americium-tricarballylic acid (one analogue of the citric acid without the alpha-hydroxo group).

Journal Articles

Thermal behavior, structure, dynamic properties of aqueous glycine solutions confined in mesoporous silica MCM-41 investigated by X-ray diffraction and quasi-elastic neutron scattering

Yoshida, Koji*; Inoue, Takuya*; Torigoe, Motokatsu*; Yamada, Takeshi*; Shibata, Kaoru; Yamaguchi, Toshio*

Journal of Chemical Physics, 149(12), p.124502_1 - 124502_10, 2018/09

https://doi.org/10.1063/1.5039892

Times Cited Count：5 Percentile：13.20(Chemistry, Physical)

Differential scanning calorimetry, X-ray diffraction, and quasi-elastic neutron scattering (QENS) measurements of aqueous glycine solutions confined in mesoporous silica (MCM-41) were performed at different glycine concentrations, pH, and loading ratio (= mass of glycine solution / mass of dry MCM-41) in the temperature range from 305 to 180 K to discuss the confinement effect on the thermal behavior, the structure, and the dynamic properties of the solutions.

Journal Articles

Formation and release of molecular iodine in aqueous phase chemistry during severe accident with seawater injection

Kido, Kentaro; Hata, Kuniki; Maruyama, Yu; Nishiyama, Yutaka; Hoshi, Harutaka*

NEA/CSNI/R(2016)5 (Internet), p.204 - 212, 2016/05

https://www.oecd-nea.org/nsd/docs/2016/csni-r2016-5.pdf

Journal Articles

Role of van der Waals corrections in first principles simulations of alkali metal ions in aqueous solutions

Ikeda, Takashi; Boero, M.*

Journal of Chemical Physics, 143(19), p.194510_1 - 194510_7, 2015/11

https://doi.org/10.1063/1.4935932

Times Cited Count：34 Percentile：76.82(Chemistry, Physical)

By resorting to a novel implementation of the first-principles-based van der Waals correction based on maximally localized Wannier functions, we inspect its performance and assess its reliability for aqueous solutions of alkali metal ions. We find that van der Waals interactions, when added to the widely used revPBE gradient corrected functional, influence substantially both structural and dynamical properties of water molecules, with particular emphasis on the hydration shell of the alkali cations. These effects are more evident for strong structure-making and -breaking cationic species. Moreover, self-diffusion coefficients and reorientation correlation times of solvating water molecules change systematically, showing a trend in better agreement with experiments with respect to simulations neglecting the long-range dispersion contributions.

Journal Articles

Dissolution of montmorillonite in compacted bentonite by highly alkaline aqueous solutions and diffusivity of hydroxide ions

Nakayama, Shinichi; Sakamoto, Yoshifumi; Yamaguchi, Tetsuji; Akai, Masanobu; Tanaka, Tadao; Sato, Tsutomu*; Iida, Yoshihisa

Applied Clay Science, 27(1-2), p.53 - 65, 2004/10

https://doi.org/10.1016/j.clay.2003.12.023

Times Cited Count：98 Percentile：90.70(Chemistry, Physical)

Alkaline environments induced by cement in radioactive waste repositories are likely to alter montmorillonite, the main constituent of bentonite buffer materials. Over long time periods, the alteration may cause the physical and/or chemical properties of the buffer to deteriorate. For the purpose of acquiring numerical data to quantify the effect of alteration on permeability of bentonite buffer, dissolution rates of montmorillonite and diffusivity of hydroxide ions in compacted sand-bentonite mixture specimens have been measured under highly alkaline, simulated groundwater conditions. The dissolution rate of montmorillonite was given by the linear dependence on time under the employed experimental conditions of pH 13 to 14 and temperatures of 90 to 170 $^{circ}$ C. The diffusivity of hydroxide ions was obtained in through-diffusion experiments combined with a pore diffusion model. The experiments were performed under relatively low temperatures of 10 to 50 $^{circ}$ C to minimize the effect of alteration of bentonite. The effective diffusivity was on the order of 10 $^{-10}$ to 10 $^{-11}$ m $^{2}$ /s.