Fig. 9: Ground state structures of different models as a function of pressure.

Enthalpy of several thermodynamically relevant carbon crystal structures, calculated as a function of pressure using the GAP-20 potential (top), GAP-20U potential (middle), and DFT (bottom). In each case, energies are compared to the cubic diamond structure at the same pressure, and shaded areas highlight the pressure region when a structure is the ground state. The simple cubic and simple hexagonal structures are marked with sc and sh, respectively, in the bottom panel.