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Okubo, Takahiro*; Takei, Akihiro*; Tachi, Yukio; Fukatsu, Yuta; Deguchi, Kenzo*; Oki, Shinobu*; Shimizu, Tadashi*
Journal of Physical Chemistry A, 127(4), p.973 - 986, 2023/02
Times Cited Count:1 Percentile:44.88(Chemistry, Physical)The identification of adsorption sites of Cs on clay minerals has been studied in the fields of environmental chemistry. The nuclear magnetic resonance (NMR) experiments allow direct observations of the local structures of adsorbed Cs. The NMR parameters of Cs, derived from solid-state NMR experiments, are sensitive to the local neighboring structures of adsorbed Cs. However, determining the Cs positions from NMR data alone is difficult. This paper describes an approach for identifying the expected atomic positions of Cs adsorbed on clay minerals by combining machine learning (ML) with experimentally observed chemical shifts. A linear ridge regression model for ML is constructed from the smooth overlap of atomic positions descriptor and gauge-including projector augmented wave (GIPAW) ab initio data. The Cs chemical shifts can be instantaneously calculated from the Cs positions on any clay layers using ML. The inverse analysis from the ML model can derive the atomic positions from experimentally observed chemical shifts.
Okubo, Takahiro*; Okamoto, Takuya*; Kawamura, Katsuyuki*; Gugan, R.*; Deguchi, Kenzo*; Oki, Shinobu*; Shimizu, Tadashi*; Tachi, Yukio; Iwadate, Yasuhiko*
Journal of Physical Chemistry A, 122(48), p.9326 - 9337, 2018/12
Times Cited Count:14 Percentile:59.58(Chemistry, Physical)The structures of Cs adsorption on montmorillonite were investigated by the nuclear magnetic resonance (NMR) spectroscopy. The NMR spectra of Cs adsorbed on montmorillonite samples were measured under different Cs contents and relative humidity levels. NMR parameters were evaluated by the first principle calculations in order to identify the relationship between adsorbed Cs structures and NMR parameters. The comparisons between experimental and theoretical NMR spectra revealed that Cs is preferentially adsorbed at sites near Al for low Cs substituted montmorillonites, and that non-hydrated Cs present in partially Cs substituted samples, even after being hydrated under high relative humidity.
Okamoto, Takuya*; Okubo, Takahiro*; Iwadate, Yasuhiko*; Deguchi, Kenzo*; Shimizu, Tadashi*; Oki, Shinobu*; Tachi, Yukio
no journal, ,
The structures of Cs adsorption on montmorillonite were investigated by the nuclear magnetic resonance (NMR) spectroscopy. The NMR spectra of Cs adsorbed montmorillonite samples with different Cs contents were collected by Cs Magic Angle Spinning (MAS) NMR and Cs Triple Quantum (3Q) MAS NMR. The adsorbed Cs structures were evaluated based on the correlations between the structural characteristics and the values of the NMR parameters predicted by the first principal calculations.
Okamoto, Takuya*; Okubo, Takahiro*; Iwadate, Yasuhiko*; Deguchi, Kenzo*; Shimizu, Tadashi*; Oki, Shinobu*; Tachi, Yukio
no journal, ,
The structures of Cs adsorbed on montmorillonite were investigated by Cs Magic Angle Spinning (MAS) NMR spectroscopy. The NMR spectra of Cs adsorbed on montmorillonite samples were measured under different relative humidity levels and were analyzed to evaluate the change in the structure of hydrated Cs sorbed on montmorillonite.