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arXiv 1107.4996cond-mat.softcond-mat.mtrl-scicond-mat.stat-mech
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多分散性胶体流体中对相关的有效单组分分析的意义

Implications of the effective one-component analysis of pair correlations in colloidal fluids with polydispersity

Mark J. Pond, Jeffrey R. Errington, Thomas M. Truskett

摘要:

具有连续多分散性的胶体悬浮液的部分对关联函数由于不充分的采样而可能具有挑战性地从光学显微镜或计算机模拟数据表征。因此,通常采用忽略粒子类型之间差异的结构的有效单组分描述。不幸的是,这种简化的描述是否保留或平均出对于理解流体的行为重要的信息取决于多分散性的程度,并且可能难以评估,特别是当对相关性的相应多组分描述不可用于比较时。在这里,我们提出了一个计算机模拟研究,探讨采用有效的单组分结构描述的多分散流体的影响。我们研究的方井模型模拟了具有短程聚合物介导吸引力的悬浮胶体实验行为的关键方面。为了表征该体系的部分对关联函数和热力学过剩熵,我们引入了一种适用于含有大量赝组分流体的Monte Carlo采样策略.从我们的模拟在高颗粒浓度的数据,以及精确的理论结果为稀释系统,显示如何从多组分和有效的单组分治疗出现的结构顺序和颗粒吸引力之间的定性不同的趋势,即使系统的特点是适度的多分散性。我们研究这些差异的后果过剩熵为基础的缩放剪切粘度,我们讨论如何使用多组分处理揭示了相应的动态缩放行为的吸引力的胶体和液态水,有效的单组分分析不捕获之间的相似性。

英文摘要:

Partial pair-correlation functions of colloidal suspensions with continuous polydispersity can be challenging to characterize from optical microscopy or computer simulation data due to inadequate sampling. As a result, it is common to adopt an effective one-component description of the structure that ignores the differences between particle types. Unfortunately, whether this kind of simplified description preserves or averages out information important for understanding the behavior of the fluid depends on the degree of polydispersity and can be difficult to assess, especially when the corresponding multicomponent description of the pair correlations is unavailable for comparison. Here, we present a computer simulation study that examines the implications of adopting an effective one-component structural description of a polydisperse fluid. The square-well model that we investigate mimics key aspects of the experimental behavior of suspended colloids with short-range, polymer-mediated attractions. To characterize the partial pair-correlation functions and thermodynamic excess entropy of this system, we introduce a Monte Carlo sampling strategy appropriate for fluids with a large number of pseudo-components. The data from our simulations at high particle concentrations, as well as exact theoretical results for dilute systems, show how qualitatively different trends between structural order and particle attractions emerge from the multicomponent and effective one-component treatments, even with systems characterized by moderate polydispersity. We examine consequences of these differences for excess-entropy based scalings of shear viscosity, and we discuss how use of the multicomponent treatment reveals similarities between the corresponding dynamic scaling behaviors of attractive colloids and liquid water that the effective one-component analysis does not capture.

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