Formation of Hydroxyl Groups at Calcium-Silicate-Hydrate (C-S-H): Coexistence of Ca–OH and Si–OH on Wollastonite(001)
Formation of Hydroxyl Groups at Calcium-Silicate-Hydrate (C-S-H): Coexistence of Ca–OH and Si–OH on Wollastonite(001)
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DOI：
10.1021/jp500170t
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发表时间：
2014-04
影响因子：
3.7
通讯作者：
S. Sanna;W. Schmidt;P. Thissen
中科院分区：
文献类型：
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作者：
S. Sanna;W. Schmidt;P. Thissen
基于密度泛函理论的总能量计算与从头算热力学相结合，以更好地理解pH值依赖的水-硅灰石（001）（CaSiO 3）相互作用。硅灰石（001）的截断被发现导致几乎可以忽略不计的离子弛豫相对于体几何形状。低水覆盖率的热力学基态产生约2 eV的分子吸附能，并且在硅灰石（001）表面具有共存的Si-OH和Ca-OH基团。每分子的吸附能随着覆盖率的增加而降低到1.4 eV。对于超过一个单层的水覆盖率，吸附能接近水在冰上吸附的特征值。然而，比化学计量界面更有利的是富含Si-OH位点的水-硅灰石（001）界面：即使在碱性pH值下，水-硅灰石（001）界面处的金属-质子交换反应也会降低总能量。
Total-energy calculations based on density-functional theory are combined with ab initio thermodynamics to better understand the pH-value-dependent water–wollastonite(001) (CaSiO3) interaction. The truncation of wollastonite(001) is found to lead to nearly negligible ionic relaxation with respect to the bulk geometry. The thermodynamic ground state for low water coverage gives rise to a molecular adsorption energy of about 2 eV and features coexisting Si–OH and Ca–OH groups at the wollastonite(001) surface. The adsorption energy per molecule decreases to 1.4 eV with increasing the coverage to one monolayer. For water coverages in excess of one monolayer, adsorption energies close to the value characteristic for water adsorption on ice are obtained. More favorable than stoichiometric interfaces, however, are water–wollastonite(001) interfaces that are enriched in Si–OH sites: Even at basic pH values, a metal–proton exchange reaction at the water–wollastonite(001) interface lowers the total energy.