Related Experiment Video
Updated: Nov 27, 2025
07:26
Synthesis and Microdiffraction at Extreme Pressures and Temperatures
Published on: October 7, 2013
11.5K
Crystal Structure and Melting of Fe Shock Compressed to 273 GPa: In Situ X-Ray Diffraction.
Stefan J Turneaure1, Surinder M Sharma1, Y M Gupta1,2
1Institute for Shock Physics, Washington State University, Pullman, Washington 99164, USA.
Physical Review Letters
|December 4, 2020
Summary
Researchers used X-ray diffraction to study iron under extreme pressure, confirming its hexagonal-close-packed structure up to melting point. This provides new insights into Earth's core conditions.
Area of Science:
- Geophysics
- Materials Science
- High-pressure Physics
Background:
- The precise crystal structure and melting point of iron (Fe) at Earth's core conditions remain debated.
- Existing shock wave and static compression data have not reached a consensus.
Purpose of the Study:
- To determine the stable crystal structure of iron under extreme pressures.
- To establish the melting boundary of iron at high-pressure conditions relevant to Earth's core.
Main Methods:
- In situ X-ray diffraction measurements on laser-shock compressed iron samples.
- Analysis of structural stability along the Hugoniot curve through shock melting.
Main Results:
- The hexagonal-close-packed (hcp) structure of iron is confirmed to be stable along the Hugoniot up to shock melting.
- Shock melting of iron occurs between approximately 242 and 247 gigapascals (GPa).
- Estimated melt temperature at 242 GPa is 5560(360) K, aligning with existing Fe melt curves.
Conclusions:
- The hexagonal-close-packed (hcp) phase of iron is stable through shock melting at Earth's core pressures.
- The study provides critical data for understanding the composition and thermal state of Earth's core.
- Extrapolation suggests a melt temperature of ~6400 K at the inner core boundary pressure.
