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arXiv 0705.0381cond-mat.soft
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短程吸引力如何影响流体的结构顺序、自扩散率和粘度

How short-range attractions impact the structural order, self-diffusivity, and viscosity of a fluid

William P. Krekelberg, Jeetain Mittal, Venkat Ganesan, Thomas M. Truskett

摘要:

我们提出了分子模拟数据的粘度,自扩散率,和局部结构有序的(i)硬球流体和(ii)方井流体与短程吸引力。后者的流体表现出动态异常的相图,其流动性增加后,等容冷却,这被认为是一个更大的区域的结构异常,其中其对相关性加强等容加热的一个子集。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,在过冷时的斯托克斯-爱因斯坦关系的故障发生的条件下,粘度和自扩散发展不同的耦合的程度成对的结构有序的液体。我们讨论这些耦合如何反映动态的异质性。最后,我们注意到,模拟数据表明如何排斥和吸引力的玻璃通常可以由两个不同的水平的短程结构秩序的特点。

英文摘要:

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 suggests how repulsive and attractive glasses may generally be characterized by two distinct levels of short-range structural order.

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