Scientists Melt Diamond at 7,300K and 1 TPa, Settling 20-Year Dispute

3 articles · Updated · ZME Science · Aug 17

Nature Physics measurements put diamond’s melting point at about 7,300 kelvin under roughly 1 terapascal, more than 1,000C below an influential earlier estimate and close to modern simulations.
19 shock-compression experiments at Rochester’s Omega Laser Facility showed diamond kept its ordinary cubic lattice until the diffraction signal vanished into liquid, with no substantial BC8 intermediate phase.
Between 750 and 1,000 gigapascals, temperatures hovered near 7,200-7,400 kelvin even as reflectivity jumped, indicating growing metallic liquid carbon that can be denser than solid diamond.
The result suggests single nanosecond shocks leave carbon atoms trapped in diamond’s structure, helping explain why earlier hints of a BC8 transition were not confirmed.
For fusion and planetary models, the revised melting curve could allow weaker first shocks in diamond fuel capsules—potentially lifting energy yield—and sharpen estimates of where diamond stays solid or melts inside Uranus and Neptune.