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Your search keyword '"Okada, Junpei T."' showing total 6 results
Start Over Author "Okada, Junpei T." Publisher american chemical society
6 results on '"Okada, Junpei T."'

2. High-Density Liquid Water at a Water-Ice Interface

Author

Niinomi, Hiromasa, Yamazaki, Tomoya, Nada, Hiroki, Hama, Tetsuya, Kouchi, Akira, Okada, Junpei T., Nozawa, Jun, Uda, Satoshi, and Kimura, Yuki

Abstract

Because ice surfaces catalyze various key chemical reactions impacting nature and human life, the structure and dynamics of interfacial layers between water vapor and ice have been extensively debated with attention to the quasi-liquid layer. Other interfaces between liquid water and ice remain relatively underexplored, despite their importance and abundance on the Earth and icy extraterrestrial bodies. By in situ optical microscopy, we found that a high-density liquid layer, distinguishable from bulk water, formed at the interface between water and high-pressure ice III or VI, when they were grown or melted in a sapphire anvil cell. The liquid layer showed a bicontinuous pattern, indicating that immiscible waters with distinct structures were separated on the interfaces in a similar manner to liquid-liquid phase separation through spinodal decomposition. Our observations not only provide a novel opportunity to explore ice surfaces but also give insight into the two kinds of structured water.

Published
2020

6. Atomic and Electronic Structure in MgO-SiO 2 .

Author

Shuseki Y, Kohara S, Kaneko T, Sodeyama K, Onodera Y, Koyama C, Masuno A, Sasaki S, Hatano S, Shiga M, Obayashi I, Hiraoka Y, Okada JT, Mizuno A, Watanabe Y, Nakata Y, Ohara K, Murakami M, Tucker MG, McDonnell MT, Oda H, and Ishikawa T

Abstract

Understanding disordered structure is difficult due to insufficient information in experimental data. Here, we overcome this issue by using a combination of diffraction and simulation to investigate oxygen packing and network topology in glassy ( g -) and liquid ( l -) MgO-SiO 2 based on a comparison with the crystalline topology. We find that packing of oxygen atoms in Mg 2 SiO 4 is larger than that in MgSiO 3 , and that of the glasses is larger than that of the liquids. Moreover, topological analysis suggests that topological similarity between crystalline ( c )- and g -( l -) Mg 2 SiO 4 is the signature of low glass-forming ability (GFA), and high GFA g -( l- ) MgSiO 3 shows a unique glass topology, which is different from c- MgSiO 3 . We also find that the lowest unoccupied molecular orbital (LUMO) is a free electron-like state at a void site of magnesium atom arising from decreased oxygen coordination, which is far away from crystalline oxides in which LUMO is occupied by oxygen's 3 s orbital state in g - and l -MgO-SiO 2 , suggesting that electronic structure does not play an important role to determine GFA. We finally concluded the GFA of MgO-SiO 2 binary is dominated by the atomic structure in terms of network topology.

Published
2024
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