Chair of Building Physics, Department of Mechanical and Process Engineering, ETH Zurich, Rämistrasse 101, 8092 Zürich, Switzerland.
Université Grenoble Alpes, CNRS, LIPhy, 38000 Grenoble, France.
ACS Nano. 2023 Mar 14;17(5):4507-4514. doi: 10.1021/acsnano.2c10384. Epub 2023 Feb 27.
Diffusion of molecules in porous media is a critical process that is fundamental to numerous chemical, physical, and biological applications. The prevailing theoretical frameworks are challenged when explaining the complex dynamics resulting from the highly tortuous host structure and strong guest-host interactions, especially when the pore size approximates the size of diffusing molecule. This study, using molecular dynamics, formulates a semiempirical model based on theoretical considerations and factorization that offer an alternative view of diffusion and its link with the structure and behavior (sorption and deformation) of material. By analyzing the intermittent dynamics of water, microscopic self-diffusion coefficients are predicted. The apparent tortuosity, defined as the ratio of the bulk to the confined self-diffusion coefficients, is found to depend quantitatively on a limited set of material parameters: heat of adsorption, elastic modulus, and percolation probability, all of which are experimentally accessible. The proposed sorption-deformation-percolation model provides guidance on the understanding and fine-tuning of diffusion.
分子在多孔介质中的扩散是一个关键过程，它是许多化学、物理和生物学应用的基础。当解释由于高度曲折的主体结构和强烈的客体-主体相互作用而导致的复杂动力学时，现有的理论框架受到了挑战，特别是当孔径接近扩散分子的大小时。本研究使用分子动力学，基于理论考虑和因子分解，构建了一个半经验模型，为扩散及其与材料结构和行为（吸附和变形）的关系提供了一种替代观点。通过分析水的间歇动力学，预测了微观自扩散系数。发现表观迂曲度（定义为体相自扩散系数与受限自扩散系数的比值）定量地取决于有限数量的材料参数：吸附热、弹性模量和逾渗概率，所有这些参数都是可以通过实验获得的。所提出的吸附-变形-逾渗模型为理解和微调扩散提供了指导。
