Phase separation kinetics of a symmetric binary mixture of glass-forming liquids
Phase separation kinetics of a symmetric binary mixture of glass-forming liquids
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玻璃形成液体的对称二元混合物的相分离动力学
DOI：
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发表时间：
2020
期刊：
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通讯作者：
A. Ikeda
中科院分区：
文献类型：
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作者：
Yuri Oku;Kyohei Takae;A. Ikeda
玻璃形成流体的混合物有时在低温下表现出玻璃-玻璃相分离。在这里，我们使用分子动力学模拟来研究玻璃-玻璃相分离的最简单的例子之一。本文考虑由A型粒子和B型粒子组成的混合粒子，其中A-A和B-B相互作用是相同的Lennard-Jones相互作用，而A-B相互作用仅是排斥的。为了避免结晶，我们还引入了每种组分粒度的多分散性。我们研究了该模型在不同温度下的50：50浓度下的相分离动力学。我们发现，流体动力粗化发生时，温度高于玻璃态动力学的起始温度。在较低的温度下，在很长的时间内观察到扩散粗化，并且在较短的时间内出现进一步较慢的粗化。低于玻璃化转变温度时，畴的生长不会停止，而是变得对数缓慢甚至比对数更慢。通过分析两个时间的相关函数，我们表明，这些缓慢的粗化过程伴随着减缓的微观动力学，这与没有相分离的老化动力学有定性的相似之处。基于这些结果，我们讨论了玻璃-玻璃相分离过程中的缓慢粗化和类老化微观减慢之间的可能联系。
Mixtures of glass-forming fluids sometimes exhibit glass-glass phase separation at low temperatures. Here, we use a molecular dynamics simulation to study one of the simplest examples of the glass-glass phase separation. We consider a mixture composed of type A and B particles, in which the A-A and B-B interactions are the identical Lennard-Jones interactions and the A-B interaction is repulsive only. To avoid crystallization, we also introduce the polydispersity in the particle sizes for each component. We study the phase separation kinetics of this model at a 50:50 concentration at various temperatures. We find that hydrodynamic coarsening takes place when the temperature is higher than the onset temperature of the glassy dynamics. At lower temperatures, diffusive coarsening is observed over a long duration, and a further slower coarsening appears within a shorter time. Below the glass transition temperature, the domain growth does not stop but becomes logarithmically slow or even slower than logarithmic. By analyzing two-time correlation functions, we show that these slow coarsening processes are accompanied by a slowing down of the microscopic dynamics, which has qualitative similarities with the aging dynamics without phase separation. Based on the results, we discuss a possible link between the slow coarsening and the aging-like microscopic slowing down in the glass-glass phase separation.