Glassy nature of water in an ultraconfining disordered material: the case of calcium-silicate-hydrate.
Glassy nature of water in an ultraconfining disordered material: the case of calcium-silicate-hydrate.
复制标题
DOI：
10.1021/ja107003a
复制
发表时间：
2011-02
影响因子：
15
通讯作者：
M. Youssef;R. Pellenq;B. Yildiz
中科院分区：
文献类型：
--
作者：
M. Youssef;R. Pellenq;B. Yildiz
我们提出的结构和动力学性质的水超限制在准二维纳米孔的高度无序的硅酸钙水合物（C-S-H），水泥中的主要结合相。我们的方法是基于经典的分子模拟。我们表明，C-S-H纳米孔空间是亲水性的，特别是因为非桥接氧原子上的无序的硅酸盐链作为氢键受体网站，定向定向的界面水分子的氢原子朝向硅酸钙层。在这个层间空间中的水采用了独特的多程结构：在2.7埃的短程扭曲的四面体配位，在4.2埃的中程类似于致密流体和过冷相的无序结构，并通过偶极-偶极相互作用持续的空间相关性高达10埃。一个三阶段的动力学管理的均方位移（MSD）的水分子，具有明确的笼阶段的动态特性在过冷液体和玻璃，与它的中程结构一致，在这里确定。在对应于玻璃材料的β-弛豫的中间时间尺度上，与MSD中的笼状阶段一致，非高斯参数指示平移动力学的显著不均匀性。这种动力学的不均匀性主要是由于氢键强度分布的不均匀性引起的。水分子与硅酸钙壁的强吸引力相互作用用于限制它们的运动。我们的研究结果对描述水泥从凝结到老化的粘聚力和力学行为具有重要意义。
We present the structural and dynamic nature of water ultraconfined in the quasi-two-dimensional nanopores of the highly disordered calcium-silicate-hydrate (C-S-H), the major binding phase in cement. Our approach is based on classical molecular simulations. We demonstrate that the C-S-H nanopore space is hydrophilic, particularly because of the nonbridging oxygen atoms on the disordered silicate chains which serve as hydrogen-bond acceptor sites, directionally orienting the hydrogen atoms of the interfacial water molecules toward the calcium-silicate layers. The water in this interlayer space adopts a unique multirange structure: a distorted tetrahedral coordination at short range up to 2.7 Å, a disordered structure similar to that of dense fluids and supercooled phases at intermediate range up to 4.2 Å, and persisting spatial correlations through dipole-dipole interactions up to 10 Å. A three-stage dynamics governs the mean square displacement (MSD) of water molecules, with a clear cage stage characteristic of the dynamics in supercooled liquids and glasses, consistent with its intermediate-range structure identified here. At the intermediate time scales corresponding to the β-relaxation of glassy materials, coincident with the cage stage in MSD, the non-Gaussian parameter indicates a significant heterogeneity in the translational dynamics. This dynamic heterogeneity is induced primarily because of the heterogeneity in the distribution of hydrogen bond strengths. The strongly attractive interactions of water molecules with the calcium silicate walls serve to constrain their motion. Our findings have important implications on describing the cohesion and mechanical behavior of cement from its setting to its aging.