JOPSS - Search Results

Journal Articles

Pressure-induced elongation of hydrogen-oxygen bond in sodium silicate melts

Ohashi, Tomonori*; Sakamaki, Tatsuya*; Funakoshi, Kenichi*; Steinle-Neumann, G.*; Hattori, Takanori; Yuan, L.*; Suzuki, Akio*

Journal of Mineralogical and Petrological Sciences (Internet), 120(1), p.240926a_1 - 240926a_13, 2025/06

https://doi.org/10.2465/jmps.240926a

We explore the structures of dry and hydrated (HO and DO) NaSiO $_{19}$ melt at 0-6 GPa and 1000-1300 K and glasses recovered from high pressure and temperatures by in-situ neutron and X-ray diffraction. The structures of the melts at 0-10 GPa and 3000 K are also investigated by ab-initio molecular dynamics simulation. In-situ neutron experiments revealed that the D-O distance increases with compression due to the formation of -O-D-O- bridging species, which is reproduced by the molecular dynamics simulations. The pressure-induced -O-D-O- formation reflects a more rigid incorporation of hydrogen, which acts as a mechanism for the experimentally observed higher solubility of water in silicate melts. Together with shrinking modifier domains, this process dominates the compression behavior of hydrous NaSiO $_{19}$ melt, whereas the compression of dry NaSiO $_{19}$ at 0-10 GPa and 3000 K is governed largely by bending of the Si-O-Si angle. The molecular dynamics simulations on hydrous NaSiO $_{19}$ melts further suggest that the sodium ions are scavenged from its network-modifying role via 2( $^{[4]}$ Si-O + Na) $^{[4]}$ Si-(O- $^{[5]}$ Si-O) $^{2-}$ + 2Na and Si-O + Na + Si-OH Si-(O-H-O-Si) + Na with increasing pressure.

Journal Articles

Effect of interlayer cations on montmorillonite swelling; Comparison between molecular dynamic simulations and experiments

Yotsuji, Kenji*; Tachi, Yukio; Sakuma, Hiroshi*; Kawamura, Katsuyuki*

Applied Clay Science, 204, p.106034_1 - 106034_13, 2021/04

https://doi.org/10.1016/j.clay.2021.106034

Times Cited Count：102 Percentile：99.77(Chemistry, Physical)

Journal Articles

Nanoscale relaxation in "Water-in-Salt" and "Water-in-Bisalt" electrolytes

Gonzalz, M. A.*; Borodin, O.*; Kofu, Maiko; Shibata, Kaoru; Yamada, Takeshi*; Yamamuro, Osamu*; Xu, K.*; Price, D. L.*; Saboungi, M.-L.*

Journal of Physical Chemistry Letters (Internet), 11(17), p.7279 - 7284, 2020/09

https://doi.org/10.1021/acs.jpclett.0c01765

Times Cited Count：24 Percentile：80.73(Chemistry, Physical)

Journal Articles

Molecular dynamics simulations of physical properties of water and cations in montmorillonite interlayer; Application to diffusion model

Yotsuji, Kenji*; Tachi, Yukio; Kawamura, Katsuyuki*; Arima, Tatsumi*; Sakuma, Hiroshi*

Nendo Kagaku, 58(1), p.8 - 25, 2019/00

https://doi.org/10.11362/jcssjnendokagaku.58.1_8

Molecular dynamics (MD) simulations were conducted to investigate physical properties of water and cations in montmorillonite interlayer nanopores. The swelling behaviors and hydration states were firstly evaluated as functions of interlayer cations and layer charge. The diffusion coefficients of water and cations in interlayer nanopores were decreased in comparison with those in bulk water and came closer to those in bulk water when basal spacing increased. The viscosity coefficients of interlayer water estimated indicated a significant effect of viscoelectricity at 1- and 2-layer hydration states and higher layer charge of montmorillonite. These trends from MD calculations were confirmed to be consistent with existing measured data and previous MD simulation. In addition, model and parameter related to viscoelectric effect used in the diffusion model was refined based on comparative discussion between MD simulations and measurements. The series of MD calculations could provide atomic level understanding for the developments and improvements of the diffusion model for compacted montmorillonite.

Journal Articles

Diffusion and adsorption of uranyl ion in clays; Molecular dynamics study

Arima, Tatsumi*; Idemitsu, Kazuya*; Inagaki, Yaohiro*; Kawamura, Katsuyuki*; Tachi, Yukio; Yotsuji, Kenji

Progress in Nuclear Energy, 92, p.286 - 297, 2016/09

https://doi.org/10.1016/j.pnucene.2016.03.006

Times Cited Count：15 Percentile：77.12(Nuclear Science & Technology)

Diffusion and adsorption behavior of uranyl (UO $_2^{2+}$ ) species is important for the performance assessment of radioactive waste disposal. The diffusion behaviors of UO $_2^{2+}$ , K $^{+}$ , CO $_3^{2-}$ and Cl $^{-}$ and H $_{2}$ O in the aqueous solutions were evaluated by molecular dynamics (MD) calculations. The diffusion coefficient (De) of UO $_2^{2+}$ is the smallest and is 26% less than the self-diffusion coefficient of H $_{2}$ O. For the aqueous solution with high concentration of carbonate ions, uranyl carbonate complexes: UO $_{2}$ CO $_{3}$ and UO $_{2}$ (CO $_{3}$ ) $^{2-}$ can be observed. For the clay (montmorillonite or illite)-aqueous solution systems, the adsorption and diffusion behaviors of UO $_2^{2+}$ and K $^{+}$ were evaluated by MD calculations. The distribution coefficients (Kd) increase with the layer charge of clay, and Kd of UO $_2^{2+}$ might be smaller than that of K $^{+}$ . Further, their two-dimensional diffusion coefficients were relatively small in the adsorption layer and were extremely small for illite with higher layer charge.

Journal Articles

A Severe artifact in simulation of liquid water using a long cut-off length; Appearance of a strange layer structure

Yonetani, Yoshiteru

Chemical Physics Letters, 406(1-3), p.49 - 53, 2005/04

https://doi.org/10.1016/j.cplett.2005.02.073

Times Cited Count：52 Percentile：83.97(Chemistry, Physical)

We report that a severe artifact appeared in molecular dynamics simulation of bulk water using the long cut-off length 18 AA ; Our result shows that increasing the cut-off length does not always improve the simulation result. Moreover, the use of the long cut-off length can lead to a spurious result. It is suggested that the simulation of solvated biomolecules using such a long cut-off length, which has been often performed, may contain an unexpected artifact.

Journal Articles