Department of Physics, Emory University, 400 Dowman Drive, Atlanta, Georgia 30322, USA.
Glass and Time, IMFUFA, Department of Science and Environment, Roskilde University, P.O. Box 260, 4000 Roskilde, Denmark.
Phys Rev E. 2019 Nov;100(5-1):053005. doi: 10.1103/PhysRevE.100.053005.
We study hidden scale invariance in the glassy phase of the Kob-Andersen binary Lennard-Jones system. After cooling below the glass transition, we generate a so-called isomorph from the fluctuations of potential energy and virial in the NVT ensemble: a set of density, temperature pairs for which structure and dynamics are identical when expressed in appropriate reduced units. To access dynamical features, we shear the system using the SLLOD algorithm coupled with Lees-Edwards boundary conditions and study the statistics of stress fluctuations and the particle displacements transverse to the shearing direction. We find good collapse of the statistical data, showing that isomorph theory works well in this regime. The analysis of stress fluctuations, in particular the distribution of stress changes over a given strain interval, allows us to identify a clear signature of avalanche behavior in the form of an exponential tail on the negative side. This feature is also isomorph invariant. The implications of isomorphs for theories of plasticity are discussed briefly.
我们研究了 Kob-Andersen 双 Lennard-Jones 系统玻璃相中的隐藏标度不变性。在冷却到玻璃化转变以下后,我们从 NVT 系综中的势能和比热涨落中生成了所谓的等构象:一组密度、温度对,当用适当的约化单位表示时,它们的结构和动力学是相同的。为了研究动力学特征,我们使用 SLLOD 算法和 Lees-Edwards 边界条件对系统进行剪切,并研究应力涨落和垂直于剪切方向的粒子位移的统计数据。我们发现统计数据的良好崩溃,表明等构象理论在该体系中很好地工作。应力涨落的分析,特别是在给定应变间隔内的应力变化分布,使我们能够以负侧的指数尾部的形式识别出雪崩行为的明显特征。这个特征也是等构象不变的。简要讨论了等构象对塑性理论的意义。