The first step in symmetry generation from ACC involves the formation of Ca 2+ sheets with CO 3 2lying in the interlayer, primarily resulting in the monoclinic crystalline systems categorized as group A in Fig. . This structural change appeared at the initial stage of the WTMetaD simulations, around 500 ns, as shown in Table in the interlayer spaces of Ca 2+ sheets, producing orthorhombic systems. These structures can be identified as precursors to vaterite with C2/c SG.