The force field parameters and functionals were adopted from Raiteri et al. This is an extension of their previous study and accurately reproduces thermodynamic properties such as solubility and hydration-free energy. The WTMetaD simulation started from an ACC structure with a 2.649 g/cm 3 density. The simulation temperature was set to 800 K to accelerate the reaction, which is below the melting point of stable calcite (1600 K) and aragonite (1098 K). WTMetaD was performed in an isothermal-isobaric (NPT) ensemble controlled by the Nosé-Hoover method 46 at 1 atm with a 1 fs timestep of up to 10.4 µs.