Researchers at Lawrence Livermore National Laboratory have resolved a 20-year-old puzzle about diamond's behavior under extreme pressure by subjecting the material to conditions exceeding those found inside Neptune and Uranus. The work reconciles conflicting theoretical predictions with experimental observations, opening pathways for fusion energy research and planetary science.
The team compressed diamond to pressures surpassing 5 megabars, conditions that exist in the deep interiors of ice giant planets where scientists suspect diamond rain forms. Previous experiments and simulations disagreed sharply about how diamond's crystal structure transformed at these extreme pressures, creating a fundamental disconnect in the field.
This new research clarifies the phase transitions diamond undergoes as pressure increases, revealing intermediate stages that earlier models missed. The findings align experimental data with refined theoretical frameworks, settling a debate that had lingered since the early 2000s.
The implications extend beyond planetary science. Understanding diamond's behavior at extreme pressures informs inertial confinement fusion research, where similar high-pressure conditions occur inside the fuel capsules that scientists compress to achieve fusion reactions. Better knowledge of material responses at these pressures could help researchers design more efficient fusion targets and boost energy output.
The study also advances understanding of ice giant interiors. Neptune and Uranus contain water and methane ices surrounding rocky cores, with diamond likely forming and raining toward their centers. The crushing pressures and exotic chemistry inside these worlds create conditions fundamentally different from Earth, and this work provides ground-truth data for models of their internal structure.
The researchers used laser-driven shock compression techniques to achieve the necessary pressures, while sophisticated diagnostics tracked how diamond's atomic arrangement changed in real time. This combination allowed them to observe phase transitions that static compression methods had missed.
The findings appeared in a peer-reviewed journal and represent collaborative work spanning multiple institutions. While the immediate applications focus on fusion and planetary science,