论文标题

分子动力学模拟二元球混合物

Molecular Dynamics Simulations of Binary Sphere Mixtures

论文作者

Monti, Joseph M., Grest, Gary S.

论文摘要

对高度分散粒子的流体混合物的明确模拟受到与识别配对邻居相关的数值挑战的限制。最近的算法发展已在一定程度上改善了这些困难,从而更有效地模拟了许多大小分散大小的大小颗粒。我们利用这些功能来对二进制球体混合物进行分子动力学模拟,其弹性刚性颗粒接近硬球极限和粒径比为50,接近胶体极限。该系统被认为由500个大颗粒组成,总颗粒体积分数高达0.51,最多360万个小颗粒。我们的模拟证实了先前在分析上获得的大颗粒与采用有效耗竭相互作用的模拟之间的相关性的定性预测,但也揭示了对小粒子溶剂的明确处理产生的近接触结构的更多见解。在模拟过程中未观察到自发的晶体成核,这表明流体 - 固体共存区域中的成核速率太小,无法观察可行的模拟系统大小和时间表的晶体成核。

Explicit simulations of fluid mixtures of highly size-dispersed particles are constrained by numerical challenges associated with identifying pair-interaction neighbors. Recent algorithmic developments have ameliorated these difficulties to an extent, permitting more efficient simulations of systems with many large and small particles of disperse sizes. We leverage these capabilities to perform molecular dynamics simulations of binary sphere mixtures with elastically stiff particles approaching the hard sphere limit and particle size ratios of up to 50, approaching the colloidal limit. The systems considered consist of 500 large particles and up to nearly 3.6 million small particles with total particle volume fractions up to 0.51. Our simulations confirm qualitative predictions for correlations between large particles previously obtained analytically and for simulations employing effective depletion interactions, but also reveal additional insights into the near-contact structure that result from the explicit treatment of the small particle solvent. No spontaneous crystal nucleation was observed during the simulations, suggesting that nucleation rates in the fluid-solid coexistence region are too small to observe crystal nucleation for feasible simulation system sizes and timescales.

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