LLNL Resolves 20-Year Diamond Mystery at 1 TPa, Opening Path to 3x Fusion Gain

3 articles · Updated · ScienceDaily · Aug 20

LLNL scientists measured diamond melting at about 1 terapascal—roughly three times Earth’s core pressure—bringing lab results into near-perfect agreement with quantum simulations and ending a two-decade dispute.
Laser-driven shock experiments with X-ray diffraction showed diamond keeps its crystal structure until it melts, rejecting a proposed intermediate phase seen indirectly in earlier Sandia work.
The updated melting point was more than 1,000 degrees different from LLNL’s original measurements, a correction enabled by diagnostics that captured atomic structure during pressure states lasting only about a billionth of a second.
For fusion, the findings suggest National Ignition Facility capsules may fully melt under slower initial shocks, which models say could triple energy gain if other performance losses are controlled.
Because the tests exceeded pressures inside Neptune and Uranus, the data also sharpen models of ice-giant interiors, including how deep carbon may form and sink as 'diamond rain.'