SC4: A metallic phase of carbon at terapascal pressures

A metallic phase of carbon, metastable at terapascal pressure, has been discovered by means of first-principles 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. © 1996 The American Physical Society.