Scandolo, S., G. L. Chiarotti, et al. (1996). "SC4: A metallic phase of carbon at terapascal pressures." Physical Review B 53(9): 5051-5054.

A metallic phase of carbon, metastable at terapascal pressure, has been discovered by means of firstprinciples computer simulations. The simulation shows that, upon fast compression, diamond survives in a metastable state up to about 3 TPa, where it collapses into a metallic sixfold coordinated structure, named SC4. Although SC4 is not the lowest-energy phase at these pressures, it is argued that the transition of diamond to other phases at lower or comparable pressure is hindered by large activation barriers.

http://link.aps.org/doi/10.1103/PhysRevB.53.5051