PDF(Pubmed)
Abstract：
Which phenomenon slows down the dynamics in supercooled liquids and turns them into glasses is a long-standing question of condensed matter. Most popular theories posit that as the temperature decreases, many events must occur in a coordinated fashion on a growing length scale for relaxation to occur. Instead, other approaches consider that local barriers associated with the elementary rearrangement of a few particles or \"excitations\" govern the dynamics. To resolve this conundrum, our central result is to introduce an algorithm, Systematic Excitation ExtRaction, which can systematically extract hundreds of excitations and their energy from any given configuration. We also provide a measurement of the activation energy, characterizing the liquid dynamics, based on fast quenching and reheating. We use these two methods in a popular liquid model of polydisperse particles. Such polydisperse models are known to capture the hallmarks of the glass transition and can be equilibrated efficiently up to millisecond time scales. The analysis reveals that cooperative effects do not control the fragility of such liquids: the change of energy of local barriers determines the change of activation energy. More generally, these methods can now be used to measure the degree of cooperativity of any liquid model.
摘要：
哪种现象会减慢过冷液体的动力学并将其变成玻璃，这是一个长期存在的凝聚态问题。大多数流行的理论认为，随着温度的降低，许多事件必须以协调的方式发生在一个不断增长的长度尺度上，才能发生放松。相反，其他方法认为，与一些粒子或“激发”的基本重排相关的局部屏障控制着动力学。为了解决这个难题，我们的主要结果是引入一种算法，系统激励极限，可以系统地从任何给定的配置中提取数百种激发及其能量。我们还提供活化能的测量，表征液体动力学，基于快速淬火和再加热。我们在多分散颗粒的流行液体模型中使用这两种方法。已知这种多分散模型捕获玻璃化转变的标志,并且可以有效地平衡直至毫秒时间尺度。分析表明，协同作用不能控制此类液体的脆性：局部屏障能量的变化决定了活化能的变化。更一般地说,这些方法现在可以用来测量任何液体模型的协同程度。
