where r ij , Q, and R c are the distance between atoms i and j, the magnitude of the scattering vector (= 4π λ sin(2θ/2); λ and θ are 1.5406 Å for the X-ray wavelength of Cu-K α radiation and the Bragg angle), and the upper distance considered for the r ij calculation, respectively. The total I(Q) and the sum of partial I(Q) from C-C, Ca-Ca, and C-Ca pairs were calculated from the crystalline structures of available vaterite crystals and ACC, as shown in Fig. (a) and (b). ACC structures were constructed using the melt-quenching method following a previous study. Five ACC structures, created starting from different initial configurations with 360 atoms (72 CaCO 3 ), were independently prepared to evaluate the statistical error. It was confirmed that the line shape of the FES derived from WTMetaD simulations was independent of the initial ACC structures. Characteristic peaks representing vaterite crystals at 22 • and 33 • (CV1 and CV2 in Fig. ) in partial I(Q) were chosen as the CVs in the WTMetaD simulations. Strong intensities at these peaks are common features of experimentally reported vaterite crystals. The large-scale atomic/molecular massively parallel simulator (LAMMPS) integrated with the Plumed package (version 2.7.5) was used to perform the WTMetaD simulations.