Ji Shuting, Torres Sergio Andres Galindo, Chen Jinfeng, Lei Liang, Li Ling
Department of Environmental Science and Engineering, Fudan University, Shanghai, China.
School of Engineering, Westlake University, Hangzhou, Zhejiang, China.
Sci Rep. 2025 Jan 17;15(1):2343. doi: 10.1038/s41598-025-85975-3.
The film water, with an exceptional capacity to maintain a premelting, liquid-like state even under subzero conditions, provides a potential dynamic conduit for the movement of water in frozen soils. However, the distinctive structural and dynamic characteristics of film water have not been comprehensively elucidated. In this study, molecular dynamics (MD) simulations were conducted to examine the freezing of a system containing ice, water, silica, and gas. The simulations revealed that as the temperature approaches the melting point, the air-water interface tends to possess a thicker layer of unfrozen water, characterized by a higher diffusion coefficient and lower viscosity. In contrast, the film water near the silica-water interface tends to be thinner and remains relatively unaffected by temperature, with only one twentieth of the diffusion coefficient and nearly 20 times the viscosity observed at the air-water interface. These distinct characteristics resulted from the varying interactions between water molecules and their immediate surroundings. Consequently, the film water in proximity of the silica can be assumed to be relatively immobile compared to that of air-water interface. These findings have implications for the study of unsaturated frozen soil systems, in particular, the importance of considering the film water at the air-water interface in the modeling framework.
薄膜水即使在零下条件下也具有非凡的能力来维持预融化的、类似液体的状态，为冻土中水分的运动提供了一个潜在的动态通道。然而，薄膜水独特的结构和动态特性尚未得到全面阐明。在本研究中，进行了分子动力学（MD）模拟，以研究包含冰、水、二氧化硅和气体的系统的冻结情况。模拟结果表明，随着温度接近熔点，气-水界面往往会有一层更厚的未冻水，其特征是扩散系数较高且粘度较低。相比之下，二氧化硅-水界面附近的薄膜水往往较薄，并且相对不受温度影响，其扩散系数仅为气-水界面处的二十分之一，而粘度则是气-水界面处的近20倍。这些不同的特性是由水分子与其周围环境之间不同的相互作用导致的。因此，可以认为二氧化硅附近的薄膜水与气-水界面处的薄膜水相比相对不流动。这些发现对非饱和冻土系统的研究具有启示意义，特别是在建模框架中考虑气-水界面处薄膜水的重要性。
