NSF Award
2421938
The Earth's core is the source of the magnetic field and is composed mainly of iron with a smaller amount of light elements. Despite the core’s significance, the extreme pressure and temperature conditions in the region make it challenging to study the constituent materials under relevant conditions. This research project, a collaboration among scientists from Arizona State University, Carnegie Institution, and University of South Florida, will investigate the properties of iron-sulfur (Fe-S) alloys under the pressure-temperature conditions of the core for their crystal structures, melting, and crystallization processes. The team will perform dynamic compression experiments to the necessary pressures and temperatures, paired with molecular dynamics simulations to aid in the interpretation of the results. One of the fundamental questions this project seeks to answer is how sulfur, an important light element in the Earth's iron core, influences the melting behavior and crystal structures of iron alloys at extreme conditions. This information is vital for understanding the complex structures observed in the Earth's core and could reveal the origins of its heterogeneities. Beyond its scientific goals, this project has significant educational and societal impacts. It provides interdisciplinary training for early career researchers and offers hands-on research opportunities for undergraduate students, particularly those underrepresented in the geosciences. The project's findings will be integrated into educational materials, enhancing science education through accessible, high-quality resources.<br/><br/>In this two-year collaborative research project, the team will perform dynamic-compression experiments and molecular dynamics simulations to study the crystal structure, melting, and crystallization of iron-sulfur (Fe-S) alloys at the pressure-temperature (P-T) conditions of the Earth’s core. This work aims to provide essential data for understanding the temperature and structure of the Earth’s core. The Earth's metallic core, generating a magnetic field, presents complex structures revealed by recent seismic studies. However, the extreme P-T conditions pose significant challenges for experimental investigations of core constituents. These dynamic compression experiments will be enabled by sample synthesis in ASU’s FORCE facility. Using large laser facilities, the project will access a range of compression pathways, enabling in-situ X-ray diffraction for monitoring the phase changes in the iron-sulfur alloy system. More specifically, shock-ramp experiments enable an initial shock melts the sample, followed by isentropic compression to re-solidify the sample at high P-T, directly observing the crystallization of Fe-S liquid into stable alloy phases. Complementary machine learning molecular dynamics simulations will model Fe-S behavior under dynamic compression, providing insights into phase transitions and crystal structures. This research addresses key questions: What crystal structures are stabilized in the Fe-S system at core conditions? How does sulfur influence Fe melting? Can Fe-S crystallization explain inner core heterogeneities? The project supports three PIs’ collaborative mentoring of three early career researchers (two postdocs and one Ph.D. student), offering interdisciplinary training in dynamic compression, static compression, and molecular dynamics. Data analysis and simulation codes developed will be included in Jupyter notebook teaching modules, shared for educational and research purposes. Outreach will involve public presentations at ASU and Carnegie Institution, highlighting the Earth's core's significance. This project is co-funded by the Geophysics and Petrology and Geochemistry Programs in the Division of Earth Sciences.<br/><br/>This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.
