Role of Water Content in CO ₂ –Anorthite Mineralization: Reactive Molecular Dynamics Simulations

Mineralization is a key mechanism for geological CO2 storage, with feldspar emerging as a promising candidate due to its high carbon sequestration potential and long-term storage stability. In this study, anorthite is employed as a representative feldspar because of its abundance in deep saline aquifers, and a reactive molecular dynamics simulation method is used to investigate the reaction mechanisms of the CO2–water–anorthite system in different hydrothermal environments (temperature range of 400–800 K and water densities of 0.25 and 0.5 g/cm3). The results show that increasing the temperature and water density significantly enhance the efficiency of CO2 mineralization. Notably, the enhancement effect induced by the increased water density becomes more pronounced under high-temperature conditions (>700 K). Furthermore, it is indicated that the water environment plays a crucial role in determining the mineralization pathways. Water molecules drive the carbonation reaction and the reconstruction of the solid surface through mechanisms including surface dissociation, proton transfer, intermediate stabilization, and ion migration. Analysis on spatial distribution of OH species within the system reveals that the anorthite surface is the predominant region where water-mediated mineralization reactions occur. In summary, this study elucidates the reaction mechanisms of the CO2–water–anorthite system at the atomic level, providing the theoretical foundation for optimizing the operational conditions and site selection strategies of geological CO2 storage.