Incorporation of Mg2+ in surface Ca2+ sites of aragonite: an ab initio study

• Kawano, Jun

• Sakuma, Hiroshi

• Nagai, Takaya

Abstract

First-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.

Journal

• Progress in earth and planetary science

  Progress in earth and planetary science 2 7-, 2015-12

  Springer

Keywords

• Aragonite
• Impurity
• Surface structure
• First-principles calculation

Details

• CRID: 1050001339019328768
• NII Article ID: 120005677757
• DOI: 10.1186/s40645-015-0039-4
• HANDLE: 2115/60343
• ISSN: 21974284
• Web Site: http://link.springer.com/content/pdf/10.1186/s40645-015-0039-4.pdf
• Web Site: http://link.springer.com/article/10.1186/s40645-015-0039-4/fulltext.html
• Web Site: http://link.springer.com/content/pdf/10.1186/s40645-015-0039-4
• Text Lang: en
• Article Type: journal article
• Data Source:
  • IRDB
  • Crossref
  • CiNii Articles
  • KAKEN