Deciphering anomalous dielectric traits of nanoconfined water and its roles in modeling crystalline swelling of bentonite

IF 5.6 1区工程技术 Q1 ENGINEERING, GEOLOGICAL

Acta Geotechnica Pub Date : 2024-12-02 DOI:10.1007/s11440-024-02474-x

Wen-jie Dai, Yong-gui Chen, Yu-cheng Li, Wei-min Ye, Qiong Wang, Dong-bei Wu

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引用次数: 0

Abstract

The physicochemical properties of Na-montmorillonite (Na-Mt) determine the intrinsic behaviors of bentonite, which are of great significance for its application in high-level radioactive waste disposal. The dielectric behavior of water under nanoconfinement has been the subject of numerous conjectures due to the difficulties associated with experimental investigation. Na-Mt is modeled via molecular dynamics (MD) simulations at the nanoscale, and the dielectric responses as a function of the basal spacing and water density are studied. The results showed a heterogeneous dielectric profile of interlayer water and an unexpected local dielectric enhancement closed to Mt surface. The morphological characteristics of dielectric constant (\(\upvarepsilon\)) was consistent with the layered structure of interlayer water. The hydrogen bonding network was strengthened near the interface, resulting in a local density augmentation and dipolar mobility decline of interlayer water. This anomalous dielectric behavior was mainly derived from the interfacial effect, rather than the physical field in Na-Mt interlayer. Introducing the MD simulations results into crystalline swelling model, and a significant improvement in accuracy was observed. These results provide a clear insight into the dielectric behavior of interlayer water in Na-Mt.

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纳米密闭水异常介电特性解析及其在膨润土结晶膨胀中的作用

钠蒙脱土（Na-Mt）的理化性质决定了膨润土的内在行为，对其在高放废物处理中的应用具有重要意义。由于实验研究的困难，水在纳米约束下的介电行为一直是许多猜想的主题。通过分子动力学（MD）在纳米尺度上模拟Na-Mt，并研究了介电响应作为基间距和水密度的函数。结果表明，层间水的介电分布呈非均匀分布，在Mt表面附近出现了意想不到的局部介电增强。介电常数（\(\upvarepsilon\)）的形态特征与层间水的层状结构一致。界面附近氢键网络增强，导致层间水局部密度增大，偶极迁移率下降。这种异常介电行为主要是由界面效应引起的，而不是由Na-Mt间层的物理场引起的。将MD模拟结果引入晶体膨胀模型，精度得到显著提高。这些结果对Na-Mt中层间水的介电行为提供了一个清晰的认识。

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来源期刊

Acta Geotechnica ENGINEERING, GEOLOGICAL-

CiteScore

9.90

自引率

17.50%

发文量

297

审稿时长

4 months

期刊介绍： Acta Geotechnica is an international journal devoted to the publication and dissemination of basic and applied research in geoengineering – an interdisciplinary field dealing with geomaterials such as soils and rocks. Coverage emphasizes the interplay between geomechanical models and their engineering applications. The journal presents original research papers on fundamental concepts in geomechanics and their novel applications in geoengineering based on experimental, analytical and/or numerical approaches. The main purpose of the journal is to foster understanding of the fundamental mechanisms behind the phenomena and processes in geomaterials, from kilometer-scale problems as they occur in geoscience, and down to the nano-scale, with their potential impact on geoengineering. The journal strives to report and archive progress in the field in a timely manner, presenting research papers, review articles, short notes and letters to the editors.