平衡分子动力学中内禀不变性的本质简单和复杂流体剪切粘度的估算
Nature of Intrinsic Uncertainties in Equilibrium Molecular Dynamics Estimation of Shear Viscosity for Simple and Complex Fluids
摘要：
我们研究了两种类型的内在不确定性，统计误差和系统尺寸效应，在估计剪切粘度通过平衡分子动力学模拟，并比较它们与相应的不确定性在评估自扩散系数。在剪切应力服从高斯过程的假设下，得到了剪切应力自相关函数和剪切粘度统计误差的不确定性量化公式。简单和复杂流体的模拟结果的分析表明，高斯性是更明显的剪切应力过程（相关的剪切粘度估计）相比，一个单独的分子的速度过程（相关的自扩散系数）。在对应于液态的相对高的密度下，我们观察到剪切粘度表现出复杂的尺寸依赖性行为，除非系统大于一定的长度尺度，否则可以获得可靠的剪切粘度值，而不会出现相对于系统尺寸的任何明显的缩放行为。我们验证了这种尺寸依赖的行为是构型和相关的特征长度尺度的剪切应力相关长度。
英文摘要：
We study two types of intrinsic uncertainties, statistical errors and system size effects, in estimating shear viscosity via equilibrium molecular dynamics simulations and compare them with the corresponding uncertainties in evaluating the self-diffusion coefficient. Uncertainty quantification formulas for the statistical errors in the shear-stress autocorrelation function and shear viscosity are obtained under the assumption that shear stress follows a Gaussian process. Analyses of simulation results for simple and complex fluids reveal that the Gaussianity is more pronounced in the shear-stress process (related to shear viscosity estimation) compared with the velocity process of an individual molecule (related to self-diffusion coefficient). At relatively high densities corresponding to a liquid state, we observe that the shear viscosity exhibits complex size-dependent behavior unless the system is larger than a certain length scale, beyond which reliable shear viscosity values are obtained without any noticeable scaling behavior with respect to the system size. We verify that this size-dependent behavior is configurational and relate the characteristic length scale to the shear-stress correlation length.
机构、总结、中文摘要均由AI分析而来，可能存在错误，请以论文正文为准。
