Jin Jaehyeok, Voth Gregory A
Department of Chemistry, Chicago Center for Theoretical Chemistry, Institute for Biophysical Dynamics, and James Franck Institute, The University of Chicago, Chicago, Illinois 60637, USA.
Department of Chemistry, Columbia University, New York, New York 10027, USA.
J Chem Phys. 2024 Jul 21;161(3). doi: 10.1063/5.0212973.
Applying an excess entropy scaling formalism to the coarse-grained (CG) dynamics of liquids, we discovered that missing rotational motions during the CG process are responsible for artificially accelerated CG dynamics. In the context of the dynamic representability between the fine-grained (FG) and CG dynamics, this work introduces the well-known Stokes-Einstein and Stokes-Einstein-Debye relations to unravel the rotational dynamics underlying FG trajectories, thereby allowing for an indirect evaluation of the effective rotations based only on the translational information at the reduced CG resolution. Since the representability issue in CG modeling limits a direct evaluation of the shear stress appearing in the Stokes-Einstein and Stokes-Einstein-Debye relations, we introduce a translational relaxation time as a proxy to employ these relations, and we demonstrate that these relations hold for the ambient conditions studied in our series of work. Additional theoretical links to our previous work are also established. First, we demonstrate that the effective hard sphere radius determined by the classical perturbation theory can approximate the complex hydrodynamic radius value reasonably well. Furthermore, we present a simple derivation of an excess entropy scaling relationship for viscosity by estimating the elliptical integral of molecules. In turn, since the translational and rotational motions at the FG level are correlated to each other, we conclude that the "entropy-free" CG diffusion only depends on the shape of the reference molecule. Our results and analyses impart an alternative way of recovering the FG diffusion from the CG description by coupling the translational and rotational motions at the hydrodynamic level.
将过量熵标度形式应用于液体的粗粒化（CG）动力学，我们发现CG过程中缺失的旋转运动是导致CG动力学人为加速的原因。在细粒化（FG）和CG动力学之间的动力学可表示性背景下，这项工作引入了著名的斯托克斯 - 爱因斯坦和斯托克斯 - 爱因斯坦 - 德拜关系，以揭示FG轨迹背后的旋转动力学，从而仅基于降低的CG分辨率下的平移信息间接评估有效旋转。由于CG建模中的可表示性问题限制了对斯托克斯 - 爱因斯坦和斯托克斯 - 爱因斯坦 - 德拜关系中出现的剪切应力的直接评估，我们引入平移弛豫时间作为代理来应用这些关系，并证明这些关系适用于我们系列工作中研究的环境条件。还建立了与我们之前工作的其他理论联系。首先，我们证明由经典微扰理论确定的有效硬球半径可以相当好地近似复杂的流体动力学半径值。此外，我们通过估计分子的椭圆积分给出了粘度过量熵标度关系的简单推导。反过来，由于FG水平的平移和旋转运动相互关联，我们得出“无熵”的CG扩散仅取决于参考分子的形状。我们的结果和分析提供了一种通过在流体动力学水平上耦合平移和旋转运动从CG描述中恢复FG扩散的替代方法。
