2024-03-29T01:34:33Zhttps://eprints.lib.hokudai.ac.jp/dspace-oai/requestoai:eprints.lib.hokudai.ac.jp:2115/603432022-11-17T02:08:08Zhdl_2115_20074hdl_2115_161Incorporation of Mg2+ in surface Ca2+ sites of aragonite: an ab initio studyKawano, JunSakuma, HiroshiNagai, TakayaAragoniteImpuritySurface structureFirst-principles calculation450First-principles calculations of Mg2+-containing aragonite surfaces are important because Mg2+ can affect the growth of calcium carbonate polymorphs. New calculations that incorporate Mg2+ substitution for Ca2+ in the aragonite {001} and {110} surfaces clarify the stability of Mg2+ near the aragonite surface and the structure of the Mg2+-containing aragonite surface. The results suggest that the Mg2+ substitution energy for Ca2+ at surface sites is lower than that in the bulk structure and that Mg2+ can be easily incorporated into the surface sites; however, when Mg2+ is substituted for Ca2+ in sites deeper than the second Ca2+ layer, the substitution energy approaches the value of the bulk structure. Furthermore, Mg2+ at the aragonite surface has a significant effect on the surface structure. In particular, CO3 groups rotate to achieve six-coordinate geometry when Mg2+ is substituted for Ca2+ in the top layer of the {001} surface or even in the deeper layers of the {110} surface. The rotation may relax the atomic structure around Mg2+ and reduces the substitution energy. The structural rearrangements observed in this study of the aragonite surface induced by Mg2+ likely change the stability of aragonite and affect the polymorph selection of CaCO3.SpringerJournal Articleapplication/pdfhttp://hdl.handle.net/2115/60343https://eprints.lib.hokudai.ac.jp/dspace/bitstream/2115/60343/1/art_10.1186_s40645-015-0039-4.pdf2197-4284Progress in earth and planetary science272015-12enginfo:doi/10.1186/s40645-015-0039-4http://creativecommons.org/licenses/by/4.0publisher