Abstract

We conduct molecular dynamics simulations of a bidisperse Kob–Andersen (KA) glass former, modified to add in additional polydispersity. The original KA system is known to exhibit dynamical heterogeneity. Prior work defined propensity, the mean motion of a particle averaged over simulations reconstructing the initial positions of all particles but with randomized velocities. The existence of propensity shows that structure and dynamics are connected. In this paper, we study systems which mimic problems that would be encountered in measuring propensity in a colloidal glass former, where particles are polydisperse (they have slight size variations). We mimic polydispersity by altering the bidisperse KA system into a quartet consisting of particles both slightly larger and slightly smaller than the parent particles in the original bidisperse system. We then introduce errors into the reconstruction of the initial positions that mimic mistakes one might make in a colloidal experiment. The mistakes degrade the propensity measurement, in some cases nearly completely; one no longer has an iso-configurational ensemble in any useful sense. Our results show that a polydisperse sample is suitable for propensity measurements provided one avoids reconstruction mistakes.

Graphic Abstract

中文翻译：

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忽略多分散性会降低过冷液体中的倾向性测量

摘要

我们对Kob-Andersen（KA）双分散玻璃成型器进行了分子动力学模拟，对它进行了改进以增加其多分散性。已知原始KA系统表现出动态异质性。先前的工作定义了倾向性，即粒子的平均运动在模拟过程中平均，该模拟重建了所有粒子的初始位置，但具有随机速度。倾向的存在表明结构和动力学是联系在一起的。在本文中，我们研究了一些系统，这些系统模拟了在粒子分散的胶态玻璃成形器（尺寸略有变化）中测量倾向性时会遇到的问题。我们通过将双分散KA系统更改为四元组来模拟多分散性，该四元组包含比原始双分散系统中的母粒稍大和稍小的母粒。然后，我们将错误引入到初始位置的重建中，以模仿人们在胶体实验中可能犯的错误。在某些情况下，这些错误使倾向性测量几乎完全消失。在任何有用的意义上，人们都不再具有同构型合奏。我们的结果表明，多分散样品适合于倾向性测量，前提是可以避免重建错误。

图形摘要