First principles study of solid iron alloys under ultrahigh pressure and temperature

2023 Fiscal Year Final Research Report

• Project/Area Number: 21K03698
• 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: Tokyo Institute of Technology
• Principal Investigator: Umemoto Koichiro 東京工業大学, 地球生命研究所, 研究員 (60726991)
• Project Period (FY): 2021-04-01 – 2024-03-31
• Keywords: 地球内核 / 超高圧高音条件 / 鉄合金 / 第一原理計算

Outline of Final Research Achievements

The inner core of the Earth consists of solid iron alloy. However, its chemical composition has not been constrained yet. Since pressure and temperature of the inner core are extremely high, it is still difficult to conduct experiments to measure density and sound velocities on these conditions. Therefore we performed highly reliable first principles study to calculate densities of iron alloys. Compared with some previous similar studies, we predicted a stronger dependence of the density of the inner core on the hydrogen concentration. Based on this prediction, with the presence of hydrogen, amounts of silicon and sulfur smaller than those predicted previously may be able to explain the density deficit of the inner core.

Free Research Field

地球科学

Academic Significance and Societal Importance of the Research Achievements

地球の核が主に鉄からできており、それが液体の外核と固体の内核に分かれていること、そしてそれらが純粋な鉄ではなく軽元素との合金であるとは地震波測定からわかっている。地球の核の化学組成は、地球物理学において長年の未解決問題の一つであり、地球の進化の過程、さらには生命の起源を知る上で重要な要素である。先行研究と異なる密度の水素依存性を予言した本研究は、水素の存在によりケイ素、硫黄の存在も大きく束縛されるであろうことも示唆し、内核の化学組成の問題解決に向けて大きな一歩となる。