Diamond melting breakthrough could deliver 3x energy gain in laser-driven nuclear fusion

A new study has improved understanding of diamond melting, which might also be relevant for achieving higher energy gain in laser-driven nuclear fusion. Researchers at Lawrence Livermore National Laboratory (LLNL) document how diamond melts under pressures three times greater than the conditions at the Earth’s core.“We were able to take tiny diamond samples and shock compress them to temperatures hotter than the surface of the sun and to pressures higher than the center of Neptune and Uranus — and still measure atomic structure, temperature, density and optical reflectivity,” said author and LLNL scientist Marius Millot. Applying findings to inertial confinement fusion could triple energy gain The study resolves two long-standing discrepancies in the field, finally matching experimental results to simulations based on quantum mechanics. Applying the findings to inertial confinement fusion could triple energy gain, and the new understanding of diamond’s high-pressure phases could reshape models of planetary interiors, according to a press release.Researchers also highlighted that diamond is more than a dazzling gem — the extremely hard form of carbon makes up the pellet that encases fuel for inertial confinement fusion, and scientists believe it rains down deep inside ice giant planets like Neptune and Uranus. In both cases, the material experiences enormous pressures. Until now, experiments and simulations have disagreed about how it actually behaves under those conditions.The team also pointed out that LLNL has been studying diamond’s extreme behavior for decades. Lab scientist Jon Eggert and colleagues pioneered high-pressure melting experiments about 20 years ago, when they observed that diamond’s density increased when melting.“While this is rather unusual among most materials, we all know an example of such behavior,” said LLNL scientist Marius Millot. “Liquid water is denser than ice, which makes ice cubes float. Jon’s finding means that diamond would float in liquid carbon at high pressures.”While that work was a landmark in the field, it led to more questions. One in particular stumped the research community: there was a roughly 20% difference between the observed and predicted melting temperatures of diamond.“No matter what the theorists did — even with the most advanced computer simulation techniques — they could not reproduce the experiments,” said Millot.Published in Nature, the study resolves the discrepancy between experiments and theoretical simulations of the melting temperature of diamond and show that the diamond structure persists up to 1 TPa. This contradicts a previous report of a transition to the BC8 phase, which density functional theory predicts to be the thermodynamically stable phase of carbon above pressures around 1 TPa. Results provide evidence for shock-induced melting The study’s results provide evidence for shock-induced melting with a slight decrease in melting temperature with increasing pressure near 7,300 K. “Our work delivers atomic-scale benchmarks for quantum simulations of condensed matter at extreme conditions, with implications for planetary interiors. Our improved understanding of diamond melting might also be relevant for achieving higher energy gain in laser-driven nuclear fusion,” said researchers. Get the latest in engineering, tech, space & science - delivered daily to your inbox.Prabhat, an alumnus of the Indian Institute of Mass Communication, is a tech and defense journalist. While he enjoys writing on modern weapons and emerging tech, he has also reported on global politics and business. He has been previously associated with well-known media houses, including the International Business Times (Singapore Edition) and ANI.