Publishing type：Research paper (scientific journal)   Publisher：American Physical Society (APS)  

DOI： 10.1103/physrevb.110.054115

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Other Link： https://link.aps.org/article/10.1103/PhysRevB.110.054115

Authorship：Lead author   Publishing type：Research paper (scientific journal)   Publisher：Mineralogical Society of America  

Abstract

Knowledge of the structural behavior of silicate melts and/or glasses at high pressures provides fundamental information for discussing the nature and properties of silicate magmas in the Earth’s interior. The behavior of Si-O structures under high-pressure conditions has been widely studied, while the effect of cation atoms on the high-pressure structural behavior of silicate melts or glasses has not been well investigated. In this study, we investigated the structures of MgSiO3 and CaSiO3 glasses up to 5.4 GPa by in situ X-ray pair distribution function measurements to understand the effect of different cations (Mg2+ and Ca2+) on high-pressure structural behavior of silicate glasses. We found that the structural behavior of MgSiO3 and CaSiO3 glasses are different at high pressures. The structure of MgSiO3 glass changes by shrinking of Si-O-Si angle with increasing pressures, which is consistent with previous studies for SiO2 and MgSiO3 glasses. On the other hand, CaSiO3 glass shows almost no change in Si-Si distance at high pressures, while the intensities of two peaks at ~3.0 and ~3.5 Å change with increasing pressure. The structural change in CaSiO3 glass at high pressure is interpreted as the change in the fraction of the edge-shared and corner-shared CaO6-SiO4 structures. The different high-pressure structural behavior observed in MgSiO3 and CaSiO3 glasses may be the origin of differences in properties, such as viscosity between MgSiO3 and CaSiO3 melts at high pressures. This signifies the importance of different structural behaviors due to different cations in investigations of the nature and properties of silicate magmas in Earth’s interior.

DOI： 10.2138/am-2023-9060

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Publishing type：Research paper (scientific journal)   Publisher：AIP Publishing  

Understanding the pressure-induced structural changes in liquids and amorphous materials is fundamental in a wide range of scientific fields. However, experimental investigation of the structure of liquid and amorphous material under in situ high-pressure conditions is still limited due to the experimental difficulties. In particular, the range of the momentum transfer (Q) in the structure factor [S(Q)] measurement under high-pressure conditions has been limited at relatively low Q, which makes it difficult to conduct detailed structural analysis of liquid and amorphous material. Here, we show the in situ high-pressure pair distribution function measurement of liquid and glass by using the 100 keV pink beam. Structures of liquids and glasses are measured under in situ high-pressure conditions in the Paris–Edinburgh press by high-energy x-ray diffraction measurement using a double-slit collimation setup with a point detector. The experiment enables us to measure S(Q) of GeO2 and SiO2 glasses and liquid Ge at a wide range of Q up to 20–29 Å−1 under in situ high-pressure and high-temperature conditions, which is almost two times larger than that of the conventional high-pressure angle-dispersive x-ray diffraction measurement. The high-pressure experimental S(Q) precisely determined at a wide range of Q opens the way to investigate detailed structural features of liquids and amorphous materials under in situ high-pressure and high-temperature conditions, as well as ambient pressure study.

DOI： 10.1063/5.0176975

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Authorship：Lead author   Publishing type：Research paper (scientific journal)   Publisher：Japan Association of Mineralogical Sciences  

DOI： 10.2465/jmps.240220

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Publishing type：Research paper (scientific journal)   Publisher：Elsevier BV  

DOI： 10.1016/j.epsl.2023.118287

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Language：Chinese   Publishing type：Book review, literature introduction, etc.   Publisher：Japan Society of High Pressure Science and Technology  

We conducted isotopic model calculations and high-pressure melting experiments in order to estimate the major element composition of the “missing reservoir”, which is a supposed component that should compensate the difference in 142Nd/144Nd ratio between the bulk silicate Earth and carbonaceous chondrite, from which the Earth is assumed to have formed. Our estimation demonstrated that the missing reservoir should have picritic to komatiitic composition, and that it was likely to have been lost from the Earth's surface by a giant impact event at the last stage of the Earth formation.

DOI： 10.4131/jshpreview.27.256

Scopus

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Event date： 2021.5.30 - 2021.6.6

Presentation type：Oral presentation (general)  

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Event date： 2017.8.13 - 2017.8.18

Language：English   Presentation type：Oral presentation (general)  

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Event date： 2017.7.30 - 2017.8.1

Language：English   Presentation type：Symposium, workshop panel (public)  

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Event date： 2017.1.9 - 2017.1.12

Language：English   Presentation type：Oral presentation (general)  

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Event date： 2016.8.27 - 2016.9.4

Language：English   Presentation type：Oral presentation (general)  

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