How short-range attractions impact the structural order, self-diffusivity, and viscosity of a fluid
How short-range attractions impact the structural order, self-diffusivity, and viscosity of a fluid
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DOI：
10.1063/1.2753154
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发表时间：
2007-07-28
影响因子：
4.4
通讯作者：
Truskett, Thomas M.
中科院分区：
文献类型：
--
作者：
Krekelberg, William P.;Mittal, Jeetain;Truskett, Thomas M.
我们给出了粘度、自扩散率和(i)硬球流体和（ii）具有短程吸引力的方井流体的局部结构有序的分子模拟数据。后一种流体在其相图中显示出一个动态异常区域，在等时冷却时其流动性增加，这是一个更大的结构异常区域的一个子集，在等时加热时其对相关性增强。这种“异常级联”在性质上类似于最近对液态水的模拟。硬球和方井系统的结果还表明，当粘度和自扩散率与液体的成对结构有序程度发生不同的耦合时，过冷时Stokes-Einstein关系会发生破坏。我们将讨论这些耦合如何反映动态异质性。最后，我们注意到，模拟数据表明，排斥玻璃和吸引玻璃通常可以用两种不同水平的短程结构秩序来表征。(c) 2007年美国物理学会。
We present molecular simulation data for viscosity, self-diffusivity, and the local structural ordering of (i) a hard-sphere fluid and (ii) a square-well fluid with short-range attractions. The latter fluid exhibits a region of dynamic anomalies in its phase diagram, where its mobility increases upon isochoric cooling, which is found to be a subset of a larger region of structural anomalies, in which its pair correlations strengthen upon isochoric heating. This "cascade of anomalies" qualitatively resembles that found in recent simulations of liquid water. The results for the hard-sphere and square-well systems also show that the breakdown of the Stokes-Einstein relation upon supercooling occurs for conditions where viscosity and self-diffusivity develop different couplings to the degree of pairwise structural ordering of the liquid. We discuss how these couplings reflect dynamic heterogeneities. Finally, we note that the simulation data suggest how repulsive and attractive glasses may generally be characterized by two distinct levels of short-range structural order. (c) 2007 American Institute of Physics.