日本地球惑星科学連合2014年大会

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セッション記号 M (領域外・複数領域) » M-IS ジョイント

[M-IS36_1AM2] 結晶成長における界面・ナノ現象

2014年5月1日(木) 11:00 〜 12:45 314 (3F)

コンビーナ:*木村 勇気(東北大学)、三浦 均(名古屋市立大学大学院システム自然科学研究科)、塚本 勝男(東北大学大学院理学研究科地学専攻)、佐藤 久夫(三菱マテリアル株式会社エネルギー事業センター那珂エネルギー開発研究所)、座長:長嶋 剣(北海道大学低温科学研究所)、佐藤 久夫(三菱マテリアル株式会社エネルギー事業センター那珂エネルギー開発研究所)

12:00 〜 12:15

[MIS36-06] 炭酸カルシウム表面/クラスターにおける2価陽イオンの安定性に関する理論的考察

*川野 潤1佐久間 博2永井 隆哉3 (1.北大創成、2.物材研、3.北大院理)

キーワード:炭酸カルシウム, 不純物, 結晶成長

Formation process of calcium carbonate polymorphs, calcite, aragonite and vaterite has been extensively investigated, and impurity effect has been proposed as controlling phenomena in order to account for the formation of a particular polymorph. For example, it has been reported that an addition of Mg2+ in a solution inhibits calcite formation and promotes aragonite formation, however incorporation mechanism of this kind of impurities is poorly understood.In general, smaller divalent cations than Ca2+, like Mg2+, cannot form solid solution with aragonite. However, the structure of a crystal surface or small cluster forming at an initial stage of crystal growth can be different from the bulk crystal because of its flexibility, and it can act as the site for incorporation of ions which is unstable in the bulk structure. In the present study, the stability of divalent cations, especially Mg2+, (1) on hydrated aragonite surface and (2) in the cluster forming in an early stage of nucleation was investigated by quantum-chemical calculations, and the impurity effects on the formation of polymorphs were discussed.The calculation results show that Mg2+ is easier to be incorporated into a small cluster, while the hydration energy of Mg2+ is higher than that of other divalent cations. This indicates that Mg2+ is difficult to be released from hydration shell, however, once released, it is easy to incorporate into the cluster. Atomic arrangement of these clusters including Mg2+ is different from that of additive-free CaCO3 clusters. Furthermore, Mg2+ on the aragonite surface considerably affects the surface structure and has an influence on the stability of aragonite. Thus, incorporation of Mg2+ into the clusters and surfaces sites should play an important role on the formation of the crystalline nuclei and the consequent crystal growth.