Department of Physics, Emory University, Atlanta, GA, 30322, USA.
Eur Phys J E Soft Matter. 2021 May 10;44(5):65. doi: 10.1140/epje/s10189-021-00049-2.
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.
我们对双分散 Kob-Andersen (KA) 玻璃形成体进行了分子动力学模拟，对其进行了修改以增加额外的多分散性。已知原始 KA 系统表现出动力学异质性。先前的工作定义了倾向，即通过模拟重建所有粒子的初始位置，但随机化速度来对粒子的平均运动进行平均。倾向的存在表明结构和动力学是相互联系的。在本文中，我们研究了模拟胶体玻璃形成体中倾向测量时会遇到的问题的系统，其中粒子是多分散的（它们有轻微的尺寸变化）。我们通过将双分散 KA 系统改变为由比原始双分散系统中的母体颗粒略大或略小的颗粒组成的四重体来模拟多分散性。然后，我们在初始位置的重建中引入错误，模拟胶体实验中可能犯的错误。这些错误会降低倾向测量的精度，在某些情况下几乎完全降低；在任何有用的意义上，都不再有同构配置的集合。我们的结果表明，只要避免重建错误，多分散样品就适合进行倾向测量。
