Microstructure and dynamic characteristics of electric double layer at montmorillonite-NaCl aqueous interface

The microscopic structure of solid-liquid interface is of widespread interest across the physical science, with electric double layer (EDL) playing a pivotal role in enhancing our understanding of macroscopic properties of liquid flow. In this study, we employ molecular dynamics simulations to analyze the structure and dynamic properties of liquids in montmorillonite-NaCl aqueous systems. Our focus lies on measuring the distributions of ions and hierarchical water clusters within the hydrogen bond network, providing a comprehensive overview of the liquid structure.

Under static conditions, we introduce a definition of the EDL based on ion distribution and water structures to analyze the structural responses of the EDL to the two phases. The interfacial region is classified into three layers, namely, the Binding Interfacial Layer (BIL), the Diffuse Layer (DL), and the Recovery Layer (RL). These layers predominantly respond to the effects of the solid phase, both phases, and the aqueous phase, respectively. On the surface of charged montmorillonite, we observe disruptions in the typical configurations within the hydrogen bond network in both the BIL and DL. Moreover, the RL exhibits a recovery process of ions and water tetrahedrality, ultimately leading to the bulk solution structure.

Under shearing conditions, we conduct a detailed examination of the structural and dynamic characteristics of the hydrogen bond network to reveal the intricate interaction between the EDL and liquid flow at the nanoscale.