Molecular Dynamics Study for the Effect of Additive Ions on Phase Transformation of Amorphous Precursor Phases of CaCO3

Abstract

Calcium carbonate is an earth-abundant material that exists in a variety of natural environments, including soils and sediments. In recent years, amorphous calcium carbonate (ACC) phases has increasingly received scientific attention because their local orders in the short-range can determine the subsequent pathways for phase transformation. However, the fundamental understanding about the structure-property relationship for these amorphous precursor phases is still lacking. As a fundamental work to elucidate this issue, we introduced additive metal ions, which are usually soluble in aqueous solution and can tailor the local orders of ACC with different hydrophilicity. With molecular dynamics simulation, we investigated the effect of additive ions on the phase transformation process of the ACC model system by varying the hydration levels and molar compositions of additive ions (i.e., Mg2+, Fe2+, Ba2+ and Sr2+). Starting from the cluster nucleation in aqueous solution, the hydrated and anhydrous forms of ACC were systematically examined following the dehydration scheme. Our results revealed that additive ions can exert promoting or inhibiting effect depending on their different hydration strengths and ionic radius. These results can provide a valuable information for controlling the structure and stability of amorphous precursor phases, which can shed light on the mineral carbonation processes for CO2 capture.