Influence of Hydration Film on the Frictional Behavior of Montmorillonite: Insights into Microscopic Mechanics of Layered Minerals

Hydration lubrication plays a significant role in reducing sliding friction in various moving systems, from geological faults to molecular materials systems, but the mechanism of lubrication on microscopic friction remains poorly understood. In this study, through molecular dynamics simulation, the dependence of the shear stress on normal stress was investigated across varying water contents to illuminate the influence of hydration lubrication on microscopic friction. Our findings reveal that the adhesive force between mineral layers is jointly governed by hydration film transition and H-bond characteristics, subsequently governing the friction at the microscale. The variation of the microscopic friction coefficient with water content shows two distinct stages, with a critical transition from a 2-layer to 3-layer water structure altering their correlation from positive to negative. These insights provide a substantial contribution to understanding the fundamental mechanism of hydration lubrication, opening new avenues for exploration in the domain of microscopic friction.