Neutron scattering on an aqueous sodium chloride solution in the gigapascal pressure range

Yamaguchi, Toshio*; Yoshida, Koji*; Machida, Shinichi*; Hattori, Takanori

Journal of Molecular Liquids, 365, p.120181_1 - 120181_10, 2022/11

https://doi.org/10.1016/j.molliq.2022.120181

Neutron scattering measurements were performed on an aqueous 3 mol/kg NaCl solution in DO at temperature and pressure conditions of 0.1 MPa/298K, 1 GPa/298K, 1 GPa/523K, and 4 GPa/523K. The empirical potential structure refinement method was applied to the obtained data to extract the pair correlation function, coordination number distribution, angular distribution (orientation correlation), and spatial density function (3-D structure). From those results, pressure and temperature dependence of solvation and association of ions and solvent-water structure were discussed.

Structure of an aqueous RbCl solution in the gigapascal pressure range by neutron diffraction combined with empirical potential structure refinement modeling

Zhang, W. Q.*; Yamaguchi, Toshio*; Fang, C. H.*; Yoshida, Koji*; Zhou, Y. Q.*; Zhu, F. Y.*; Machida, Shinichi*; Hattori, Takanori; Li, W.*

Journal of Molecular Liquids, 348, p.118080_1 - 118080_11, 2022/02

https://doi.org/10.1016/j.molliq.2021.118080

The ion hydration and association and hydrogen-bonded water structure in an aqueous 3 mol/kg RbCl solution were investigated at 298 K/0.1 MPa, 298 K/1 GPa, 523 K/1 GPa, and 523 K/4 GPa by neutron diffraction combined with EPSR methods. The second hydration layer of Rb and Cl becomes evident under elevated pressure and temperature conditions. The average oxygen coordination number of Rb (Cl) in the first hydration layer increases from 6.3 (5.9) ambient pressure to 8.9 (9.1) at 4 GPa, while decreasing coordination distance from 0.290 nm (0.322 nm) to 0.288 nm (0.314 nm). The orientation of the water dipole in the first solvation shell of Rb and a central water molecule is sensitive to pressure, but that in the first solvation shell of Cl does not change very much. The number of contact-ion pairs Rb-Cl decreases with elevated temperature and increases with elevated pressure. Water molecules are closely packed, and the tetrahedral hydrogen-bonded network of water molecules no longer exists in extreme conditions.

Ion hydration and association in an aqueous calcium chloride solution in the GPa range

Yamaguchi, Toshio*; Nishino, Masaaki*; Yoshida, Koji*; Takumi, Masaharu*; Nagata, Kiyofumi*; Hattori, Takanori

European Journal of Inorganic Chemistry, 2019(8), p.1170 - 1177, 2019/02

https://doi.org/10.1002/ejic.201900016

Neutron diffraction measurements of an aqueous 2 mol dm CaCl solutions in DO have been made at 1 GPa, 298 K as well as 0.1 MPa, 298 K. The experimental structure factors are subjected to Empirical Potential Structure Refinement (EPSR) modeling to reveal the ion hydration and association and solvent water at the atomic level. About seven water molecules surround Ca at the Ca-O and Ca-D distances of 2.44 and 3.70 , respectively, at both pressures, suggesting no significant pressure effect on the cation hydration. On the other hand, the Cl ion shows a drastic change in water oxygen coordination from 7 at 0.1 MPa to 14 at 1 GPa, accompanied by shortening of Cl-O distance from 3.18 to 3.15 . However, the number of water hydrogen atoms around Cl does not change significantly as 6.0 6.7 with shortening Cl-D distance from 2.22 to 2.18 on compression. The pressure effect on the solvent water structure is also drastic as an increase in water oxygen atoms of 4.7 at the O-O distance of 2.79 at 0.1 MPa to 10.3 at 2.85 at 1 GPa. The number of water hydrogen atoms, however, does not change as 1.2 at the O-D distance of 1.74 for both pressures, demonstrating the presence of the OD hydrogen bonds which are significantly bent at 1 GPa at 298 K. This change of hydrogen bonds in water with pressure probably causes the drastic increase in water oxygen atoms around Cl.

Impurity effects in the microscopic elastic properties of polycrystalline Mg-Zn-Y alloys with a synchronised long-period stacking ordered phase

Hosokawa, Shinya*; Kimura, Koji*; Yamasaki, Michiaki*; Kawamura, Yoshihito*; Yoshida, Koji*; Inui, Masanori*; Tsutsui, Satoshi*; Baron, A. Q. R.*; Kawakita, Yukinobu; Ito, Shinichi*

Journal of Alloys and Compounds, 695, p.426 - 432, 2017/02

https://doi.org/10.1016/j.jallcom.2016.10.266

Structure of water from ambient to 4 GPa revealed by energy-dispersive X-ray diffraction combined with empirical potential structure refinement modeling

Yamaguchi, Toshio*; Fujimura, Koji*; Uchi, Kazuya*; Yoshida, Koji*; Katayama, Yoshinori

Journal of Molecular Liquids, 176, p.44 - 51, 2012/12

https://doi.org/10.1016/j.molliq.2012.08.021

X-ray diffraction measurements in an energy-dispersive mode have been made on water under various thermodynamic conditions of 298 K/30 MPa, 473 K/30 MPa and 573 K/30 MPa on a laboratory X-ray diffractometer. All the X-ray structure factors as well as those of water already measured at 298 K/1 GPa, 473 K/0.35 GPa and 486 K/4 GPa by using synchrotron X-ray radiation were subjected to empirical potential structure refinement (EPSR) modeling to reveal the detailed hydrogen bonding features in terms of partial pair correlation function, coordination number and three-dimensional spatial density function as a function of temperature and pressure. It has been shown to what extent the tetrahedral hydrogen-bonded network of water is perturbed by pressure and temperature.