Calcite surface structure and reactivity: molecular dynamics simulations and macroscopic surface modelling of the calcite-water interface.
Calcite surface structure and reactivity: molecular dynamics simulations and macroscopic surface modelling of the calcite-water interface.
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DOI：
10.1039/c2cp42290e
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发表时间：
2012-10
期刊：
影响因子：
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通讯作者：
M. Wolthers;M. Wolthers;D. Tommaso;Z. Du;N. D. Leeuw
中科院分区：
文献类型：
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作者：
M. Wolthers;M. Wolthers;D. Tommaso;Z. Du;N. D. Leeuw
方解石-水的相互作用不仅在固碳和全球碳循环中很重要，而且在含方解石的寄主岩石中的污染物行为和许多工业应用中也很重要。在这里，我们量化方解石表面反应性的表面结构的变化的影响。首先，我们采用经典的分子动力学模拟的方解石表面含有一个蚀坑和生长平台，以显示在水中的局部环境周围的结构不同的表面站点是不同的。除了观察到预期在较低配位位点形成更多的钙-水相互作用和氢键外，我们还观察到锐角与钝角周围氢键的细微差异。随后，我们使用这些信息来完善质子化常数的方解石表面网站，根据电荷分布多位点离子络合（CD-MUSIC）的方法。氢键的细微差异转化为显着不同的充电行为与pH值，特别是对锐角与钝角的角落网站。结果表明，方解石表面活性与表面形貌有直接关系。在这项研究中获得的信息不仅是至关重要的改善现有的宏观表面模型的方解石对污染物的反应性，但也提高了我们的原子水平的矿物-水的相互作用的理解。
Calcite-water interactions are important not only in carbon sequestration and the global carbon cycle, but also in contaminant behaviour in calcite-bearing host rock and in many industrial applications. Here we quantify the effect of variations in surface structure on calcite surface reactivity. Firstly, we employ classical Molecular Dynamics simulations of calcite surfaces containing an etch pit and a growth terrace, to show that the local environment in water around structurally different surface sites is distinct. In addition to observing the expected formation of more calcium-water interactions and hydrogen-bonds at lower-coordinated sites, we also observed subtle differences in hydrogen bonding around acute versus obtuse edges and corners. We subsequently used this information to refine the protonation constants for the calcite surface sites, according to the Charge Distribution MUltiSite Ion Complexation (CD-MUSIC) approach. The subtle differences in hydrogen bonding translate into markedly different charging behaviour versus pH, in particular for acute versus obtuse corner sites. The results show quantitatively that calcite surface reactivity is directly related to surface topography. The information obtained in this study is not only crucial for the improvement of existing macroscopic surface models of the reactivity of calcite towards contaminants, but also improves our atomic-level understanding of mineral-water interactions.