First Steps towards Understanding the Non-Linear Impact of Mg on Calcite Solubility: A Molecular Dynamics Study

Magnesium (Mg2+) is one of the most common impurities in calcite and known to have a non-linear impact on solubility magnesian calcites. Using molecular dynamics (MD), we observed that Mg2+ impacts overall surface energies, local free energy profiles, interfacial water density, structure and, at higher concentrations, it also causes crystal deformation. Low Mg concentrations did not alter structure, but stabilised Ca2+ locally tended increase etch pit nucleation energy. As result, Ca-extraction energies over wide range 39 kJ/mol were observed. Calcite surfaces with an island less stable compared flat surfaces, incorporation destabilised further, increasing calcium extraction energies. In general, islands high concentrations. The variation depends amount distance nearest addition disruption flexibility carbonate ions rotate. result complex interplay these characteristics cause variability dissolution Taken together, results illustrate scale processes behind concentration magnesium-bearing