Priezjev Nikolai V
Department of Mechanical Engineering, Michigan State University, East Lansing, Michigan 48824, USA.
Phys Rev E Stat Nonlin Soft Matter Phys. 2013 May;87(5):052302. doi: 10.1103/PhysRevE.87.052302. Epub 2013 May 9.
Molecular dynamics simulations are performed to investigate heterogeneous dynamics in amorphous glassy materials under oscillatory shear strain. We consider three-dimensional binary Lennard-Jones mixture well below the glass transition temperature. The structural relaxation and dynamical heterogeneity are quantified by means of the self-overlap order parameter and the dynamic susceptibility. We found that at sufficiently small strain amplitudes, the mean square displacement exhibits a broad subdiffusive plateau and the system undergoes nearly reversible deformation over about 10(4) cycles. Upon increasing strain amplitude, the transition to the diffusive regime occurs at shorter time intervals and the relaxation process involves intermittent bursts of large particle displacements. The detailed analysis of particle hopping dynamics and the dynamic susceptibility indicates that mobile particles aggregate into clusters whose sizes increase at larger strain amplitudes. Finally, the correlation between particle mobilities in consecutive time intervals demonstrates that dynamic facilitation becomes increasingly pronounced at larger strain amplitudes.
进行分子动力学模拟以研究非晶玻璃态材料在振荡剪切应变下的非均匀动力学。我们考虑三维二元 Lennard-Jones 混合物，其温度远低于玻璃化转变温度。通过自重叠序参量和动态磁化率对结构弛豫和动力学非均匀性进行量化。我们发现，在足够小的应变幅度下，均方位移呈现出一个宽广的亚扩散平台，并且系统在大约 10⁴ 个循环内经历近乎可逆的变形。随着应变幅度的增加，向扩散 regime 的转变发生在更短的时间间隔内，并且弛豫过程涉及大粒子位移的间歇性爆发。对粒子跳跃动力学和动态磁化率的详细分析表明，可移动粒子聚集形成团簇，其尺寸在较大应变幅度下增大。最后，连续时间间隔内粒子迁移率之间的相关性表明，动态促进在较大应变幅度下变得越来越明显。
