受限水NMR弛豫的间歇性分子运动与首达统计
Intermittent molecular motion and first passage statistics for the NMR relaxation of confined water
AI总结：
通过分子动力学模拟和首次返回通过时间计算，将受限流体微观参数与NMR弛豫率R1关联，仅用统计力学概念预测和解释界面分子弛豫。
摘要：
纳米多孔介质中受限流体的结构与动力学不同于体相，这可以通过NMR弛豫测量来探测。我们在此通过对狭缝纳米孔中的水进行原子分子动力学模拟，表明在不同表面相互作用和受限强度下，NMR弛豫率R1的行为可以根据流体分子在吸附表面层与体相区域之间的交换统计来估算，其中分子经历间歇性动力学。我们采用首次返回通过时间计算来量化分子交换统计，从而将受限流体的微观参数（如吸附时间、孔径和扩散系数）与NMR弛豫率联系起来。该方法允许仅利用统计力学概念来预测和解释界面处流体的分子弛豫，并且可以推广到封闭和开放几何结构。
英文摘要：
The structure and dynamics of fluids confined in nanoporous media differ from those in bulk, which can be probed using NMR relaxation measurements. We here show, using atomistic molecular dynamics simulations of water in a slit nanopore, that the behavior of the NMR relaxation rate, R1, with varying surface interaction and confinement strength can be estimated from the exchange statistics of fluid molecules between the adsorbed surface layer and the bulk region, where molecules undergo intermittent dynamics. We employ first return passage time calculations to quantify the molecular exchange statistics, thereby linking microscopic parameters of the confined fluid-such as adsorption time, pore size, and diffusion coefficient-to the NMR relaxation rate. This approach allows to predict and interpret the molecular relaxation of fluids at interfaces using merely concepts of statistical mechanics and can be generalized to closed and open geometries.
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