Ab initio Molecular Dynamics Simulations of the Hydroxylation of Nanoporous Silica
Ab initio Molecular Dynamics Simulations of the Hydroxylation of Nanoporous Silica
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DOI：
10.1111/jace.13731
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发表时间：
2015-12
影响因子：
3.9
通讯作者：
J. Rimsza;Jincheng Du
中科院分区：
文献类型：
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作者：
J. Rimsza;Jincheng Du
水和二氧化硅之间相互作用的准确信息对于理解其性能至关重要，包括应力下的机械强度和二氧化硅和硅酸盐玻璃的长期化学耐久性。在这项研究中，利用密度泛函理论（DFT）为基础的从头算分子动力学（AIMD）模拟，研究了水和纳米多孔非晶二氧化硅之间的相互作用模型，该模型准确地描述了键的断裂和形成以及化学反应。对于含有水和纳米多孔二氧化硅的系统进行了高达30 ps的AIMD模拟，其孔隙率范围很广（31%-67%）。在AIMD运行期间，观察到部分缺陷（如双元环）被去除，而在初始几何优化期间，更多的反应性配位缺陷被去除。有限的二元环移除可归因于受限的水缺陷运动或位于凹表面的环的稳定性增加。两元环去除机制包括形成过配位硅（Si5）中间缺陷。Si5缺陷在整个模拟过程中持续发展，表明热力学驱动的二元环去除受到动力学限制。在羟基化过程中，监测了原子电荷和键长-键角相关函数等电子结构的变化。
Accurate information on the interactions between water and silica is critical to the understanding of its properties including mechanical strength under stress and long-term chemical durability of silica and silicate glasses. In this study, interactions between water and nanoporous amorphous silica models were investigated using density functional theory (DFT) based ab initio molecular dynamics (AIMD) simulations which accurately describe bond breakage and formation as well as chemical reactions. AIMD simulations up to 30 ps were performed for systems containing water and nanoporous silica with a wide range of porosities (31%–67%). Partial removal of defects, such as two-membered rings, was observed during the AIMD runs whereas more reactive coordination defects were removed during the initial geometry optimization. The limited two-membered ring removal can be attributed to restricted water-defect movement or the increased stability of rings located on concave surfaces. Two-membered ring removal mechanisms included the formation of an overcoordinated silicon (Si5) intermediate defect from the dynamic simulations. Si5 defects continued to develop throughout the simulations, indicating a thermodynamic drive for two-membered ring removal which is kinetically limited. Changes in the electronic structures, such as atomic charges, and bond length-bond angle correlation functions were monitored during the hydroxylation process.