Bollinger Jonathan A, Jain Avni, Truskett Thomas M
McKetta Department of Chemical Engineering, University of Texas at Austin , Austin, Texas 78712, United States.
Langmuir. 2014 Jul 22;30(28):8247-52. doi: 10.1021/la5017005. Epub 2014 Jul 8.
Molecular dynamics simulations and a stochastic method based on the Fokker-Planck equation are used to explore the consequences of inhomogeneous density profiles on the thermodynamic and dynamic properties of the hard-sphere fluid and supercooled liquid water. Effects of the inhomogeneity length scale are systematically considered via the imposition of sinusoidal density profiles of various wavelengths. For long-wavelength density profiles, bulk-like relationships between local structure, thermodynamics, and diffusivity are observed as expected. However, for both systems, a crossover in behavior occurs as a function of wavelength, with qualitatively different correlations between the local static and dynamic quantities emerging as density variations approach the scale of a particle diameter. Irrespective of the density variation wavelength, average diffusivities of hard-sphere fluids in the inhomogeneous and homogeneous directions are coupled and approximately correlate with the volume available for insertion of another particle. Unfortunately, a quantitatively reliable static predictor of position-dependent dynamics has yet to be identified for even the simplest of inhomogeneous fluids.
分子动力学模拟和基于福克-普朗克方程的随机方法被用于探究非均匀密度分布对硬球流体和过冷液态水的热力学及动力学性质的影响。通过施加各种波长的正弦密度分布，系统地考虑了非均匀性长度尺度的影响。对于长波长密度分布，正如预期的那样，观察到局部结构、热力学和扩散率之间呈现出类似体相的关系。然而，对于这两个系统，行为会随着波长发生转变，当密度变化接近粒子直径尺度时，局部静态和动态量之间会出现性质不同的相关性。无论密度变化波长如何，硬球流体在非均匀和均匀方向上的平均扩散率是相互关联的，并且大致与可供另一个粒子插入的体积相关。遗憾的是，即使对于最简单的非均匀流体，尚未找到一个在定量上可靠的位置相关动力学的静态预测指标。
