Bonding Properties and Immiscibility of Liquid Fe-Light-Element Mixtures under High Pressures: ab initio Molecular Dynamics Simulations

2023 Fiscal Year Final Research Report

• Project/Area Number: 21K03705
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Review Section: Basic Section 17040:Solid earth sciences-related
• Research Institution: Hiroshima Institute of Technology
• Principal Investigator: Ohmura Satoshi 広島工業大学, 工学部, 准教授 (90729352)
• Project Period (FY): 2021-04-01 – 2024-03-31
• Keywords: 地球外核 / 不混和 / 液体鉄混合系 / 第一原理分子動力学法 / 結合状態 / 機械学習型ポテンシャル

Outline of Final Research Achievements

The structural and bonding properties of liquid iron-light-element ternary systems such as Fe-H-O, Fe-C-O, Fe-Si-O, and Fe-S-O under high pressure are studied by ab initio molecular dynamics simulations. For the interactions between light elements, Si-O show covalent-like interactions even under high-pressure condition. The Si-O covalent bond causes a shift in the ionic charge of Si to more positive. The shift of atomic charge due to the Si-O covalent bond is possibly related to the gathering of oxygen atoms with negative charges around Si, leading to the separation of Fe-Si-O and Fe-Si domains in liquid Fe-Si-O. Atomic configurations in our simulation also seem to be suggestive of the phase separation though the actual immiscibility region might exist at some lower temperatures. In addition, we created a stable machine-learning interatomic potential and succeeded in performing relatively Large-scale MD simulation.

Free Research Field

理論物性物理学

Academic Significance and Societal Importance of the Research Achievements

本研究では、原子間の化学結合という観点から液体鉄ー軽元素混合系の電子的、構造的性質を明らかにした。この結果は、軽元素同士の相互作用によって電荷の揺らぎが生まれ、原子の存在分布にも偏りが生じることを示唆しており、地球外核の混和・不混和問題に重要な知見を与えるものである。また液体のような乱れた系、かつ組成が非常に偏った系においても機械学習を用いることで計算の大規模化ができる可能性を示している。