Stacking fault energy of the Earth's inner core

2021 Fiscal Year Final Research Report

• Project/Area Number: 20K22365
• Research Category: Grant-in-Aid for Research Activity Start-up
• Allocation Type: Multi-year Fund
• Review Section: 0204:Astronomy, earth and planetary science, and related fields
• Research Institution: Tokyo Institute of Technology
• Principal Investigator: Gomi Hitoshi 東京工業大学, 地球生命研究所, 特任助教 (10876171)
• Project Period (FY): 2020-09-11 – 2022-03-31
• Keywords: 内核 / 積層欠陥エネルギー / KKR-CPA

Outline of Final Research Achievements

In this study, we have performed first-principles calculations using the KKR-CPA method to study the followings. (1) Estimate the order-disorder transition temperatures of B2 FeSi at the Earth's inner core pressure, (2) the relationship between magnetism and the equation of state for hydrogen-saturated fcc FeH (face-centered cubic iron hydride), and (3) the relationship between magnetism and the equation of state for fcc FeHx (0 < x < 1), which is not saturated with hydrogen.
The following conclusions were obtained. (1) The ordered-disordered transition temperature of B2 FeSi is very high, and no disorder transition occurs in the inner core. (2) The calculation of fcc FeH with ferromagnetism reproduces the ambient-temperature experiment well. (3) The calculation of fcc FeHx with paramagnetism reproduces the high-temperature experiment well.

Free Research Field

高圧地球科学

Academic Significance and Societal Importance of the Research Achievements

地球の中心部分は、360万気圧以上の高圧力がかかっているのみならず、5000℃程度の高温状態になっている。このような高温条件では、物質は化学的・構造的・磁気的に不規則な状態が熱力学的に安定になる可能性がある。本研究では、こういった不規則の効果が、地球や惑星の深部条件でどのような影響をもたらすのかを明らかにした。