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Incorporation of Incompatible Strontium and Barium Ions into Calcite (CaCO3) through Amorphous Calcium Carbonate
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Title: | Incorporation of Incompatible Strontium and Barium Ions into Calcite (CaCO3) through Amorphous Calcium Carbonate |
Authors: | Saito, Ayaka Browse this author | Kagi, Hiroyuki Browse this author | Marugata, Shiho Browse this author | Komatsu, Kazuki Browse this author | Enomoto, Daisuke Browse this author | Maruyama, Koji Browse this author | Kawano, Jun Browse this author →KAKEN DB |
Keywords: | calcite | amorphous calcium carbonate | disorder | MD simulation |
Issue Date: | Mar-2020 |
Publisher: | MDPI |
Journal Title: | Minerals |
Volume: | 10 |
Issue: | 3 |
Start Page: | 270 |
Publisher DOI: | 10.3390/min10030270 |
Abstract: | Calcite is a ubiquitous mineral in nature. Heavy alkaline-earth elements with large ionic radii such as Sr2+ and Ba2+ are highly incompatible to calcite. Our previous study clarified that incompatible Sr2+ ions can be structurally incorporated into calcite through crystallization from amorphous calcium carbonate (ACC). In this study, we synthesized Sr-doped calcite with Sr/(Sr + Ca) up to 30.7 +/- 0.6 mol% and Ba-doped calcite with Ba/(Ba + Ca) up to 68.6 +/- 1.8 mol%. The obtained Ba-doped calcite samples with Ba concentration higher than Ca can be interpreted as Ca-containing barium carbonates with the calcite structure which have not existed so far because barium carbonate takes the aragonite structure. X-ray diffraction (XRD) patterns of the Sr-doped and Ba-doped calcite samples obtained at room temperature showed that reflection 113 gradually weakened with increasing Sr/(Sr + Ca) or Ba/(Ba + Ca) ratios. The reflection 113 disappeared at Ba/(Ba + Ca) higher than 26.8 +/- 1.6 mol%. Extinction of reflection 113 was reported for pure calcite at temperatures higher than 1240 K, which was attributed to the rotational (dynamic) disorder of CO32- in calcite. Our Molecular Dynamics (MD) simulation on Ba-doped calcite clarified that the CO32- ions in Ba-doped calcites are in the static disorder at room temperature. The CO32- ions are notable tilted and displaced from the equilibrium position of pure calcite. |
Rights: | https://creativecommons.org/licenses/by/4.0/ |
Type: | article |
URI: | http://hdl.handle.net/2115/78674 |
Appears in Collections: | 理学院・理学研究院 (Graduate School of Science / Faculty of Science) > 雑誌発表論文等 (Peer-reviewed Journal Articles, etc)
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