The diffusion of particles in suspension is investigated by a thermostat based on fluctuating hydrodynamics for dynamic simulations of implicit-solvent coarse-grained model which can take into account both hydrodynamic and Brownian effects. Particles with cut-and-shifted Lennard-Jones and Gaussian-core potential are studied. The results show that their diffusion process can be characterized by three regimes: ballistic motion, short-time diffusion and long-time diffusion. We observe that the mean square displacement ( MSD ) of regime I, ballistic motion, is proportional to t 2 . For the other two regimes, its MSD is proportional to t with different slopes. Furthermore, we study the diffusion coefficients of spherical particles from MSD at different volume fractions. For the cut-and-shifted Lennard-Jones potential model, we observe the diffusion coefficients decrease monotonously with the increase of volume fraction (0.02–0.3), consistent with the results of the experiment. However, for the Gauss-core potential model, the curve of long-time self-diffusion coefficient as a function of dimensional density (0.001 to 1) appears to be nonmonotonic. It shows that the long-time self-diffusion coefficient decreases monotonically when the dimensional density is below 0.3, and then increases anomalously when the dimensionless density passes through 0.3.

中文翻译：

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具有硬球和软球模型的纳米级粒子的自扩散

通过基于波动流体动力学的恒温器研究悬浮液中颗粒的扩散，用于隐式溶剂粗粒模型的动态模拟，该模型可以同时考虑流体动力学和布朗效应。研究了具有切移 Lennard-Jones 和高斯核势的粒子。结果表明，它们的扩散过程可以表现为三种状态：弹道运动、短时扩散和长时间扩散。我们观察到，I 区弹道运动的均方位移 (MSD) 与 t 2 成正比。对于其他两种状态，其 MSD 与斜率不同的 t 成正比。此外，我们研究了来自 MSD 的球形颗粒在不同体积分数下的扩散系数。对于切移的 Lennard-Jones 势模型，我们观察到扩散系数随着体积分数的增加（0.02-0.3）而单调减小，与实验结果一致。然而，对于高斯核势模型，长期自扩散系数作为维度密度的函数（0.001 到 1）的曲线似乎是非单调的。表明长期自扩散系数在维密度低于0.3时单调减小，当无量纲密度通过0.3时反常增大。