Diamond Compression: Unexpected Density Shift Resolved After 20 Years

Researchers from the Lawrence Livermore National Laboratory (LLNL) have compressed small diamonds to conditions exceeding those found in the cores of Neptune and Uranus. The study, published in Nature Physics, resolves a two-decade scientific dispute regarding how carbon behaves under extreme pressure. For twenty years, a discrepancy of approximately 20% existed between computer models and laboratory data. This conflict began when John Eggert demonstrated that diamond becomes denser upon melting under colossal pressure—a behavior that contradicts classical expectations. Previous experiments conducted at Sandia National Laboratories' Z machine suggested the existence of an intermediate crystalline structure before the material turned liquid, but these signals could not be confirmed via direct observation. X-ray Diffraction and Melting Mechanics To resolve the uncertainty, the team conducted experiments at the University of Rochester's Laboratory for Laser Energetics. The researchers used lasers to generate powerful shock waves, creating pressures three times higher than those at the center of the Earth. Unlike previous findings, the carbon did not transition through intermediate phases; it maintained its structure until complete melting occurred.