The Effect of Crystal Seeds on Calcium Carbonate Ion Pair Formation in Aqueous Solution: A ReaxFF Molecular Dynamics Study

The effect of crystal seeds on calcium carbonate (CaCO3) cluster formation in aqueous solution is of interest in the fields of geochemistry, inorganic chemistry, atmospheric science, biomedicine, biomineralization, and tissue engineering. Due to an instantaneous and microscopic process, it is still experimentally challenging to directly capture the CaCO3 pre-nucleation. This study employed reactive force field (ReaxFF) molecular dynamics simulations to explore the variation among CaCO3 ion pairs in an aqueous solution with or without crystal seeds. The results show that the addition of crystal seeds can improve CaCO3 ion pair formation. We found that the surface of the calcite phase, compared with the metastable vaterite phase, prefers to attach the ion pairs from solution via proton transfer. This work sheds light on the effect of different crystal seeds on CaCO3 ion pair formation as a precursor of pre-nucleation clusters.