High-pressure in-situ fluorescent XAFS and XRD measurements: Chemical state of Xe in magma under high pressure

2023 Fiscal Year Final Research Report

• Project/Area Number: 20K14584
• Research Category: Grant-in-Aid for Early-Career Scientists
• Allocation Type: Multi-year Fund
• Review Section: Basic Section 17040:Solid earth sciences-related
• Research Institution: High Energy Accelerator Research Organization
• Principal Investigator: Wakabayashi Daisuke 大学共同利用機関法人高エネルギー加速器研究機構, 物質構造科学研究所, 助教 (20759964)
• Project Period (FY): 2020-04-01 – 2024-03-31
• Keywords: キセノン / マグマ / シリカメルト / 分子動力学シミュレーション / 高密度化 / 相転移カイネティクス

Outline of Final Research Achievements

In this study, new insights were obtained into the behavior of Xe in silica melt under high pressure. It was found that Xe, which moves between the voids of the network structure consisting of SiO4 tetrahedra in the lower pressure region, is trapped in the voids above 6 GPa. There is no strong bonding between Xe and other atoms, and the trapping is likely due to a decrease in void size resulting from the changes in the network structure (densification). In addition, we have proposed a kinetic model for phase transitions in amorphous materials such as silica melt, and developed an X-ray microscope and a large-scale molecular-dynamics simulation method to observe inhomogeneities in the densification process.

Free Research Field

高圧地球科学

Academic Significance and Societal Importance of the Research Achievements

高圧下におけるシリカメルト中のXeの振る舞いに関する研究成果は、ケイ酸塩メルト（マグマ）のネットワーク構造の変化によってXeが構造中に固定される可能性を示している。地球化学分野において長年の謎とされてきた”missing Xe”問題に示唆を与えるものである。また、本課題の過程で得られた大規模計算手法やX線顕微鏡、非晶質物質の相転移カイネティクスモデルの応用範囲は広く、今後、様々な研究に発展していくことが期待される。