Interparticle friction plays a governing role in the mechanics of particulate materials. However, virtually all experimental studies to date rely on measuring macroscopic responses, and as such it remains largely unknown how frictional effects emerge at the microscopic level. This is particularly challenging in systems subject to thermal fluctuations due to the transient nature of interparticle contacts. Here, we directly relate particle-level frictional arrest to local coordination in an attractive colloidal model system. We reveal that the orientational dynamics of particles slows down exponentially with increasing coordination number due to the emergence of frictional interactions, the strength of which can be tuned simply by varying the attraction strength. Using a simple computer simulation model, we uncover how the interparticle interactions govern the formation of frictional contacts between particles. Our results establish quantitative relations between friction, coordination and interparticle interactions. This is a key step towards using interparticle friction to tune the mechanical properties of particulate materials.

中文翻译：

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有吸引力的胶体物质中粒子间摩擦的出现

颗粒间摩擦在颗粒材料的力学中起着主导作用。然而，迄今为止几乎所有的实验研究都依赖于测量宏观反应，因此在很大程度上仍不清楚摩擦效应是如何在微观层面出现的。由于颗粒间接触的瞬态特性，这在受热波动影响的系统中尤其具有挑战性。在这里，我们在一个有吸引力的胶体模型系统中直接将粒子级摩擦停止与局部协调联系起来。我们揭示了由于摩擦相互作用的出现，粒子的取向动力学随着配位数的增加呈指数下降，其强度可以简单地通过改变吸引力强度来调节。使用简单的计算机模拟模型，我们揭示了粒子间相互作用如何控制粒子之间摩擦接触的形成。我们的结果建立了摩擦、协调和粒子间相互作用之间的定量关系。这是使用颗粒间摩擦来调整颗粒材料机械性能的关键一步。