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Jing, Z.*; Yamaguchi, Toshio*; Hattori, Takanori; Yamada, Takeshi*; Tamatsukuri, Hiromu; Matsuura, Masato*; Zhou, Y.*
Journal of Physical Chemistry Letters (Internet), 17(29), p.8419 - 8428, 2026/07
Times Cited Count：0 Percentile：0.00(Chemistry, Physical)We conducted high-pressure neutron diffraction and quasielastic neutron scattering on a series of aqueous alkaline chloride solutions and clarified that the pressure- and ion-induced modifications to the water structure and diffusion originate from distinct physical mechanisms. Applying gigapascal pressure transforms the tetrahedral hydrogen-bonded network structure of water into a dense random packing, due to the collapse of the second and third coordination shells and an increase in the number of interstitial water molecules, regardless of the ion species. On the contrary, dissolved ions disturb the second shell but preserve the inherent tetrahedral network structure of water at ambient pressure. The anomalous trend of water diffusion from Li
to Cs under the ambient conditions disappears under the gigapascal pressure, and all the ions show a behavior of structure-making ions.
Jing, Z.*; Yamaguchi, Toshio*; Machida, Shinichi*; Hattori, Takanori; Zhou, Y.*
Journal of Chemical Physics, 163(19), p.194505_1 - 194505_12, 2025/11
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 
and static hydration number 
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 
and dynamic hydration number 
indicate that Rb and Cs exhibit characteristics of structure-making ions under compression. The dynamic properties are more pressure-sensitive than the static structure.
