Yang Entao, Riggleman Robert A
Department of Chemical and Biomolecular Engineering, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA.
Phys Rev Lett. 2022 Mar 4;128(9):097801. doi: 10.1103/PhysRevLett.128.097801.
External stress can accelerate molecular mobility of amorphous solids by several orders of magnitude. The changes in mobility are commonly interpreted through the Eyring model, which invokes an empirical activation volume. Here, we analyze constant-stress molecular dynamics simulations and propose a structure-dependent Eyring model, connecting activation volume to a machine-learned field, softness. We show that stress has a heterogeneous effect on the mobility that depends on local structure through softness. The barrier impeding relaxation reduces more for well-packed particles, which explains the narrower distribution of relaxation time observed under stress.
外部应力可使非晶态固体的分子迁移率加快几个数量级。迁移率的变化通常通过艾林模型来解释，该模型引入了一个经验活化体积。在此，我们分析了恒应力分子动力学模拟，并提出了一个依赖于结构的艾林模型，将活化体积与一个机器学习场——柔软度联系起来。我们表明，应力对迁移率具有非均匀效应，该效应通过柔软度取决于局部结构。对于堆积良好的粒子，阻碍弛豫的势垒降低得更多，这解释了在应力作用下观察到的弛豫时间分布更窄的现象。
