Nanosecond-scale structural evolution in shocked coesite - Dr. Wenge Yang

New work from a team of scientists led by Drs. Wenge Yang and Toshimori Sekine of HPSTAR, along with Prof. Jian Su of Nanjing University, have unveiled—for the first time—the dynamic phase transition pathway of coesite under extreme shock conditions. Using laser-driven shock compression, ultrafast X-ray diffraction (XRD), and machine-learning-enhanced molecular dynamics simulations, the team tracked the nanosecond-scale structural evolution of coesite, a high-pressure polymorph of silicon dioxide (SiO₂). The results are published  in  Science Advances. 

Silicon dioxide is a major component of Earth and terrestrial planets, and its high-pressure phase transition processes serve as a "black box" recording planetary impact history. Coesite, a special mineral formed under high-pressure conditions of silicon dioxide, is commonly found in meteorite impact craters. However, how its microscopic structure evolves under transient shock pressures reaching hundreds of gigapascals (GPa) has long remained a mystery. Studying the behavior of coesite under shock conditions in a laboratory is of great significance for understanding meteorite impacts and planetary geological evolution.

By coupling laser-driven shock techniques with X-ray free-electron laser (XFEL) observations, the researchers directly observed the complete phase transition sequence of coesite—from supercooled liquid to metastable crystal—on nanosecond timescales. The results revealed that coesite transforms into various transient phases, including a dense amorphous state, semi-disordered d-NiAs-type SiO₂, seifertite, or stishovite, depending on shock pressure. Remarkably, upon decompression, coesite re-emerges instead of converting into quartz, defying thermodynamic expectations.

“This reverse transformation seems paradoxical,” said Dr. Wenge Yang. While quartz or fused silica is expected to form upon pressure release, the persistence of coesite suggests a kinetic mechanism, potentially linked to limited atomic mobility in supercooled liquids. Despite simulations showing the collapse of silicon’s tetrahedral network within picoseconds, some form of "intermediate-range topological ordering" may inhibit full structural reconfiguration during rapid shock events.

The discovery of a metastable d-NiAs-type SiO₂ phase under shock also settles a two-decade debate, highlighting fundamental differences between shock- and statically-induced phase transitions. Additionally, the identification of seifertite under shock supports its presence in meteorites from Mars and the Moon, such as Shergotty and NWA 4734, affirming extreme pressure histories.

Beyond structural insights, the study has broader implications for understanding heat dissipation and mineral–atmosphere interactions during early planetary evolution. The team is now applying this methodology to other planetary minerals like olivine, aiming to test their findings through future deep-space missions.

“Our work captures, for the first time, the microscopic phase transitions that occur during planetary-scale impacts,” said Dr. Toshimori Sekine. “It’s a significant leap in materials science and planetary geology—offering a new window into the early history of Earth and beyond.”

北京高压科学研究中心的杨文革研究员,Toshimori Sekine研究员与南京大学孙建教授研究团队首次通过动态加载实验与理论模拟，揭示了柯石英矿物在极端冲击压力下的动态相变路径。这一发现为了解地球、月球及火星早期遭遇的陨石撞击历史提供了关键线索，并挑战了传统的高压矿物相变理论。相关研究发表于近期的Science Advances。