To evaluate structural and free energy changes along specific reaction pathways, it is necessary to define collective variables (CVs) as bias potentials. Recent WTMetaD studies investigated CaCO 3 formation pathways using CVs based on atomic distances and revealed multi-step carbonation pathways from CO 2 to CaCO 3 crystalline seeds in aqueous solutions. WTMetaD simulations further explored phase transitions between C2/c and C2