Relation between sound velocity and density for liquid iron alloys under Earth's core pressures

• Project/Area Number: 16K05541
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Research Field: Solid earth and planetary physics
• Research Institution: Osaka University
• Principal Investigator: Sakaiya Tatsuhiro 大阪大学, 理学研究科, 助教 (60452421)
• Project Period (FY): 2016-04-01 – 2019-03-31
• Project Status: Completed (Fiscal Year 2018)
• Budget Amount: ¥4,680,000 (Direct Cost: ¥3,600,000、Indirect Cost: ¥1,080,000); Fiscal Year 2018: ¥1,040,000 (Direct Cost: ¥800,000、Indirect Cost: ¥240,000); Fiscal Year 2017: ¥1,950,000 (Direct Cost: ¥1,500,000、Indirect Cost: ¥450,000); Fiscal Year 2016: ¥1,690,000 (Direct Cost: ¥1,300,000、Indirect Cost: ¥390,000)
• Keywords: 鉄合金 / 音速 / 地球核 / スーパーアース / バーチ則 / 衝撃圧縮 / レーザー / 予備加熱 / ニッケル / シリコン / 磁硫鉄鉱 / 地球・惑星内部構造

Outline of Final Research Achievements

We conducted shock-compression experiments using a high-power laser. The sound velocity and density for liquid iron alloys and metal at pressures up to 1000 GPa were measured by x-ray radiography. At same pressure, the addition of silicon increases the sound velocity of iron and the addition of nickel and sulfur decreases it. It was suggested that there is a linear sound velocity-density relation (Birch's law) in liquid iron alloys and metal. The outer core composition was estimated by using Birch's law. It was suggested that Birch's law has universal relation on material science.

Academic Significance and Societal Importance of the Research Achievements

地球核だけでなくスーパーアースのような巨大地球型惑星の核の圧力条件での音速と密度の関係を評価しており、そのような惑星の中心核組成に制約条件を与えることが可能であり大変重要である。溶融状態の鉄合金や金属物質において音速と密度の間に線形関係（バーチ則）があることを示し、バーチ則の固体-液体間の関係が地球惑星の中心核物質だけでなく、他の金属物質に対しても普遍的である結果を示したことで、地球惑星科学だけでなく物質科学にも影響を与えうることは大変意義があったと考えられる。

Research Products

• [Presentation] Sound velocity and density of liquid iron alloys under Earth’s core pressures by laser-shock compression (2017)
  • Author(s): Tatsuhiro Sakaiya
  • Organizer: JpGU-AGU Joint Meeting 2017
  • Int'l Joint Research