Molecular origins of anisotropic adhesion at the kaolinite-ice interface : a temperature-dependent MD study

Abstract

Understanding the thermo-mechanical behavior of soil-ice interface is critical for the stability of geotechnical infrastructure in permafrost regions. Kaolinite, a common clay mineral, exhibits intrinsic surface anisotropy, including hydrophilic Al-OH and hydrophobic Si-O surfaces. However, the influence of this surface anisotropy on the micromechanics of soil-ice interface remains poorly understood. Here, the bulk ice-Ih and kaolinite-ice models were established, and an interface strength damage factor (η) was proposed to quantify the reduction in interfacial adhesion relative to the bulk ice and soil systems. The molecular dynamics (MD) simulation method was employed to investigate the structure, unfrozen water evolution, and interfacial adhesion of ice on these two distinct kaolinite surfaces under ultra-low temperatures (i.e., 110∼270 K). The key findings are: (1) The mechanical strength of bulk ice consistently exceeds the interfacial adhesion of clay-ice interface, with both degrading significantly as temperature rises. (2) The hydrophobic Si-O surface facilitates a thicker quasi-liquid water layer with a higher unfrozen water content than the hydrophilic Al-OH surface. (3) The interfacial adhesion strength of kaolinite-ice interface at Al-OH surface is significantly higher than that at Si-O surface. This study provides quantitative molecular-level insights into how the surface anisotropy of kaolinite affects the thermo-mechanical behavior of soil-ice interface.