Departamento de Quimica Fisica I, Facultad de Ciencias Quimicas, Universidad Complutense de Madrid, 28040 Madrid, Spain.
Proc Natl Acad Sci U S A. 2014 Jan 7;111(1):75-80. doi: 10.1073/pnas.1308338110. Epub 2013 Dec 4.
By molecular-dynamics simulations, we have studied the devitrification (or crystallization) of aged hard-sphere glasses. First, we find that the dynamics of the particles are intermittent: Quiescent periods, when the particles simply "rattle" in their nearest-neighbor cages, are interrupted by abrupt "avalanches," where a subset of particles undergo large rearrangements. Second, we find that crystallization is associated with these avalanches but that the connection is not straightforward. The amount of crystal in the system increases during an avalanche, but most of the particles that become crystalline are different from those involved in the avalanche. Third, the occurrence of the avalanches is a largely stochastic process. Randomizing the velocities of the particles at any time during the simulation leads to a different subsequent series of avalanches. The spatial distribution of avalanching particles appears random, although correlations are found among avalanche initiation events. By contrast, we find that crystallization tends to take place in regions that already show incipient local order.
通过分子动力学模拟，我们研究了老化硬球玻璃的非晶化（或结晶）。首先，我们发现粒子的动力学是间歇性的：当粒子在最近邻笼中简单地“嘎嘎作响”时，处于静止期，然后被突然的“雪崩”打断，其中一部分粒子会发生大的重排。其次，我们发现结晶与这些雪崩有关，但两者之间的联系并不直接。在雪崩过程中，系统中的晶体数量增加，但变成晶体的大部分粒子与参与雪崩的粒子不同。第三，雪崩的发生在很大程度上是一个随机过程。在模拟过程中的任何时间随机化粒子的速度，会导致后续的雪崩序列不同。雪崩粒子的空间分布看起来是随机的，尽管在雪崩启动事件之间发现了相关性。相比之下，我们发现结晶往往发生在已经显示出初始局部有序的区域。
