Researchers at Lawrence Livermore National Laboratory have successfully shock-compressed tiny diamond samples to temperatures exceeding the surface of the Sun and pressures surpassing the centers of Uranus and Neptune, according to a new study published in Gizmodo. The experiments recreate the extreme high-pressure, high-temperature conditions theorized to drive the diamond rain that falls deep inside the middle atmospheres of our solar system’s ice giant planets.
Lawrence Livermore Scientists Recreate Extreme Diamond Melting
The research successfully measures atomic structure, temperature, density, and optical reflectivity under terapascal pressures—reaching tens of millions of times ordinary atmospheric pressure. According to Science Daily, the new data resolves two long-standing discrepancies in carbon research, bringing physical laboratory measurements into close agreement with advanced quantum mechanics-based computer simulations.
Resolving Decades of High-Pressure Physics Mysteries
The investigation builds upon foundational high-pressure melting experiments pioneered approximately 20 years ago by LLNL scientist Jon Eggert and his colleagues. Those early tests revealed the unusual property that diamond becomes denser when it melts, meaning solid diamond would actually float in liquid carbon at high pressures. However, that landmark work left significant puzzles in the scientific community.
For years, a roughly 20% discrepancy persisted between experimentally measured melting temperatures and theoretical predictions. Furthermore, experiments at Sandia National Laboratories utilizing the extreme magnetic fields of the Z machine suggested that diamond might undergo an intermediate phase transformation—shifting to an alternate crystalline structure before finally turning to liquid. The LLNL team addressed these questions by conducting laser-driven dynamic compression experiments at the University of Rochester’s Laboratory for Laser Energetics.
Utilizing the Omega Laser Facility, scientists vaporized the outer layer of a microscopic sample to launch a powerful squeezing shockwave through the interior. Because these high-pressure states lasted for only a billionth of a second, researchers had to capture faint X-ray diffraction signals from lightweight carbon atoms within a minuscule timeframe.
Direct Observations and Structural Behavior
The high-speed laser experiments provided clarity on how carbon behaves under extreme stress. Rather than transitioning through an intermediate crystal phase, the carbon remained entirely within a diamond structure right up until the moment it melted. Study first author Marius Millot noted that the sample remains trapped in the diamond structure because it simply does not have enough time to change during a single shock.
The findings demonstrate that material response depends heavily on the exact method used to apply a shock, rather than solely on pressure and temperature variables. While original temperature measurements were found to be off by more than 1,000 degrees, the improved data quality confirmed the original inference of melting directly through X-ray diffraction.
Implications for Inertial Confinement Fusion Power
Beyond shedding light on planetary interiors, the findings offer practical applications for inertial confinement fusion. In these systems, fuel is encased inside a microscopic diamond capsule and imploded by high-energy lasers. Maintaining a uniform fluid state during the implosion is critical for sustaining an ignited fusion reaction.
The research indicates that utilizing slightly slower initial shocks can achieve full melting of the diamond capsule while making the fusion fuel more compressible. According to investigators, this improvement could potentially triple the maximum energy yield obtained from the same amount of laser energy, advancing the ongoing development of fusion power systems.