Adsorption of Cations on Aragonite Surface

Crystal growth at CaCO3 interfaces underpins processes from biomineralization to industrial scale control. Although most prior work has focused on calcite, aragonite is a common metastable polymorph whose interfacial chemistry can influence growth pathways and morphology. A key open question is how cations interact with aragonite surfaces that are nominally neutral. Understanding these ion-surface interactions is essential for explaining growth regulation and impurity incorporation in real systems. We address this question using molecular dynamics simulations to compare monovalent and divalent cations interactions with aragonite under aqueous conditions. We find that cations adsorb strongly even on the nominally neutral aragonite surface. We further quantify interfacial structure through ion density profiles normal to the surface and construct the adsorption isotherms for both monovalent and divalent ions.