Nature of the physicochemical process in water photolysis uncovered by a computer simulation

Kai, Takeshi; Toigawa, Tomohiro; Ukai, Masatoshi*; Fujii, Kentaro*; Watanabe, Ritsuko*; Yokoya, Akinari*

Journal of Chemical Physics, 158(16), p.164103_1 - 164103_8, 2023/04

New insight into water radiolysis and photolysis is indispensable in the dramatic progress of sciences and technologies in various research areas. In the radiation field, reactive hydrated electrons are considerably produced along radiation tracks. Although the formation results from a transient dynamic correlation between ejected electrons and water, the individual mechanisms of electron thermalization, delocalization, and polarization are unknown. Using a dynamic Monte Carlo code, we show herein that the ejected electrons are immediately delocalized by molecular excitations in parallel with phonon polarization and gradually thermalized by momentum transfer with an orientation polarization in a simultaneous manner. Our results show that these mechanisms heavily depend on the intermolecular vibration and rotation modes peculiar to water. We expect our approach to be a powerful technique for connecting physical and chemical processes in various solvents.

X-ray absorption spectra of aqueous cellobiose; Experiment and theory

Akazawa, Daisuke; Sasaki, Takehiko*; Nagasaka, Masanari*; Shiga, Motoyuki

Journal of Chemical Physics, 156(4), p.044202_1 - 044202_7, 2022/01

https://doi.org/10.1063/5.0078963

The hydration structure of cellulose is very important for understanding the hydrolysis of cellulose at the molecular level. In this paper, we report a joint experimental and theoretical study on the X-ray absorption spectroscopy (XAS) of aqueous cellobiose, a disaccharide unit of cellulose. In the experimental part, high resolution measurements of the carbon K-edge XAS spectra were performed. It was found that the peak heights in the spectrum change considerably over the temperature range of 25 C to 60 C, which is a reflection of the number of hydrogen bonds between cellobiose and water. We suggest that this spectral change could be useful information for identifying the hydration of cellulose in various environments.

Focusing and spin polarization of atomic hydrogen beam

Nagaya, Yuki*; Nakatsu, Hiroki*; Ogura, Shohei*; Shimazaki, Kota*; Ueta, Hirokazu; Takeyasu, Kotaro*; Fukutani, Katsuyuki

Journal of Chemical Physics, 155(19), p.194201_1 - 194201_6, 2021/11

https://doi.org/10.1063/5.0068251

Nuclear quantum effects on autoionization of water isotopologs studied by path integral molecular dynamics

Thomsen, B.; Shiga, Motoyuki

Journal of Chemical Physics, 154(8), p.084117_1 - 084117_10, 2021/02

https://doi.org/10.1063/5.0040791

In this study we investigate the nuclear quantum effects on the acidity constant of liquid water isotopologues at the ambient condition by path integral molecular dynamics simulations. This technique not only reproduces the acidity constants of liquid DO experimentally measured but also allows for a theoretical prediction of the acidity constants of liquid TO, aqueous HDO and HTO, which are unknown due to its scarcity. The results indicate that the nuclear quantum effects play an indispensable role in the absolute determination of acidity constants.

Structure refinement of black phosphorus under high pressure

Akahama, Yuichi*; Miyakawa, Masashi*; Taniguchi, Takashi*; Sano, Asami; Machida, Shinichi*; Hattori, Takanori

Journal of Chemical Physics, 153(1), p.014704_1 - 014704_5, 2020/07

https://doi.org/10.1063/5.0012870

The structure refinement of black phosphorus was performed at pressures of up to 3.2 GPa at room temperature by powder neutron diffraction techniques. The bond lengths and bond angles between the phosphorus atoms at pressures were precisely determined and confirmed to be consistent with those of the previous single crystal X-ray analysis [Brown and Randqvist, Acta Cryst. 19, 684 (1965)]. Although lattice parameters exhibited an anisotropic compressibility, the covalent P1-P2 and P1-P3 bond lengths were almost independent of pressure and only the P3-P1-P2 bond angle was reduced significantly. On the basis of our results, the significant discrepancy in the bond length reported by Cartz et al. [J. Chem. Phys. 71, 1718 (1979)] has been solved. Our structural data will contribute to the elucidation of the Dirac semimetal state of black phosphorus under high pressure.

Changes in electronic structure of carbon supports for Pt catalysts induced by vacancy formation due to Ar irradiation

Okazaki, Hiroyuki*; Kakitani, Kenta*; Kimata, Tetsuya*; Idesaki, Akira*; Koshikawa, Hiroshi*; Matsumura, Daiju; Yamamoto, Shunya*; Yamaki, Tetsuya*

Journal of Chemical Physics, 152(12), p.124708_1 - 124708_5, 2020/03

https://doi.org/10.1063/1.5144568

Spectroscopic determination of interconversion rates among three nuclear spin isomers of methane in crystalline II

Sugimoto, Takeru*; Nasu, Hirokazu*; Arakawa, Ichiro*; Yamakawa, Koichiro

Journal of Chemical Physics, 150(18), p.184302_1 - 184302_5, 2019/05

https://doi.org/10.1063/1.5091070

We measured infrared absorption spectra of crystalline II of methane and succeeded in detecting a prominent Q(2) peak by rapid cooling after annealing as well as previously reported rovibrational and librational-vibrational peaks. The integral intensities of the R(0), R(1), and Q(2) peaks were found to show biexponential dependence on time. This clearly demonstrates the interconversion among the three nuclear-spin isomers occupying low-lying rotational levels.

Neutron scattering studies on short- and long-range layer structures and related dynamics in imidazolium-based ionic liquids

Nemoto, Fumiya*; Kofu, Maiko; Nagao, Michihiro*; Oishi, Kazuki*; Takata, Shinichi; Suzuki, Junichi*; Yamada, Takeshi*; Shibata, Kaoru; Ueki, Takeshi*; Kitazawa, Yuzo*; et al.

Journal of Chemical Physics, 149(5), p.054502_1 - 054502_11, 2018/08

https://doi.org/10.1063/1.5037217

Behavior of intermolecular interactions in -glycine under high pressure

Shinozaki, Ayako*; Komatsu, Kazuki*; Kagi, Hiroyuki*; Fujimoto, Chikako*; Machida, Shinichi*; Sano, Asami; Hattori, Takanori

Journal of Chemical Physics, 148(4), p.044507_1 - 044507_8, 2017/01

https://doi.org/10.1063/1.5009980

Pressure-response on the crystal structure of deuterated -glycine was investigated at room temperature, using powder and single-crystal X-ray diffraction, and powder neutron diffraction measurements under high pressure. No phase change was observed up to 8.7 GPa, although anisotropy of the lattice compressibility was found. Neutron diffraction measurements indicated the distance of the intermolecular DO bond along with the -axis increase with compression up to 6.4 GPa. The distance of another DO bond along with the -axis decreased with increasing pressure, and became the shortest intermolecular hydrogen bond above 3 GPa. In contrast, the lengths of the bifurcated N-DO and C-DO hydrogen bonds, which are formed between the layers of the -glycine molecules along the -axis, decreased significantly with increasing pressure. The decrease of the intermolecular distances resulted in the largest compressibility of the -axis, compared to the other two axes. Hirshfeld analysis suggested that the reduction of the void region size, rather than shrinkage of the strong N-DO hydrogen bonds, occurred with compression.

The Structure of molten CuCl; Reverse Monte Carlo modeling with high-energy X-ray diffraction data and molecular dynamics of a polarizable ion model

Alcaraz, O.*; Trulls, J.*; Tahara, Shuta*; Kawakita, Yukinobu; Takeda, Shinichi*

Journal of Chemical Physics, 145(9), p.094503_1 - 094503_7, 2016/09

https://doi.org/10.1063/1.4962181