Revealing Transition States during the Hydration of Clay Minerals
Revealing Transition States during the Hydration of Clay Minerals
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DOI：
10.1021/acs.jpclett.9b01565
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发表时间：
2019-07-04
影响因子：
5.7
通讯作者：
Greathouse, Jeffery A.
中科院分区：
文献类型：
--
作者：
Ho, Tuan A.;Criscenti, Louise J.;Greathouse, Jeffery A.
由于X射线衍射（XRD）实验观察到的非常快的逐步膨胀过程，从分子尺度上理解粘土矿物中水化状态之间的转变仍然是一个具有挑战性的问题。XRD剖面建模假设粘土样品中多种水合状态共存，以拟合在潮湿条件下获得的实验XRD图案。虽然XRD剖面建模提供了一个宏观的了解粘土矿物的非均质水化结构，水化状态之间的过渡的微观模型仍然缺失。在这里，我们第一次使用分子动力学模拟研究之间的过渡状态的干燥夹层，一层水合物，和两层水合物。我们发现，在粘土颗粒的边缘形成的氢键的层间水化，特别是初始水化的能量障碍作出了重要贡献。
A molecular-scale understanding of the transition between hydration states in clay minerals remains a challenging problem because of the very fast stepwise swelling process observed from X-ray diffraction (XRD) experiments. XRD profile modeling assumes the coexistence of multiple hydration states in a clay sample to fit the experimental XRD pattern obtained under humid conditions. While XRD profile modeling provides a macroscopic understanding of the heterogeneous hydration structure of clay minerals, a microscopic model of the transition between hydration states is still missing. Here, for the first time, we use molecular dynamics simulation to investigate the transition states between a dry interlayer, one-layer hydrate, and two-layer hydrate. We find that the hydrogen bonds that form across the interlayer at the clay particle edge make an important contribution to the energy barrier to interlayer hydration, especially for initial hydration.