Probing metastability of carbon at extreme conditions

In spite of extensive experimental and theoretical efforts, the behavior of carbon at extreme conditions is not completely understood. Previous studies demonstrated the stability of diamond and the absence of other phases of carbon at high pressures up to 1 TPa. However, new metastable phases might appear upon uniaxial compression generated by shock waves. We explore new metastable phases of carbon under both hydrostatic and uniaxial compressions up to 5 TPa using first-principles crystal structure prediction method. Several new metastable phases appear to survive upon decompression to ambient conditions. The experimental validation of these predictions will open up a new avenue in synthesizing new metastable phases of carbon.