First-principles phase diagram of carbon at extreme conditions

Recent discovery a plethora of the planets outside of our solar system brought a possibility of existence of carbon exoplanets. Therefore, accurate phase diagram of carbon at extreme temperatures and pressures is of critical importance for developing models of the exoplanet interiors. We address a knowledge gap by performing first-principles quantum molecular dynamics (QMD) simulations of thermodynamic properties of carbon at terapascal pressures and up to 10,000 K temperatures with the goal of constructing an accurate phase diagram of carbon. To address the issue of accuracy and reliability, a relatively large number of atoms is used for calculation of melting transitions (melt curve) as a function of pressure using two-phase method. We discuss a possibility of novel phase transitions and possible recovery of new high pressures phases of carbon.