Slow relaxations and stringlike jump motions in fragile glass-forming liquids: breakdown of the Stokes-Einstein relation.
Slow relaxations and stringlike jump motions in fragile glass-forming liquids: breakdown of the Stokes-Einstein relation.
复制标题
DOI：
10.1103/physreve.87.012312
复制
发表时间：
2012-10
期刊：
影响因子：
--
通讯作者：
T. Kawasaki;A. Onuki
中科院分区：
文献类型：
--
作者：
T. Kawasaki;A. Onuki
本文对具有软核势的玻璃形成液体二元混合物进行了三维分子动力学模拟。我们调查交叉的配置变化所造成的弦跳跃运动。随着温度T的降低，组成弦的粒子的运动在尺寸和位移上变得更大，而弦周围的粒子的运动变得更小。然后，随着T的降低，后者对时间相关函数的贡献趋于长寿命。结果，弛豫时间τ（α）和粘度η在低T下比逆扩散常数D（-1）更陡地增长，导致Stokes-Einstein关系破裂。在低T，扩散发生的激活过程，可以很好地描述由短时间分析罕见的跳跃运动断裂键和大位移。货车霍韦自相关函数的某些特征来自于高势垒的逃逸跃迁。我们还可视化了在很短的时间内弦形成时的粒子运动。
We perform molecular dynamics simulation on a glass-forming liquid binary mixture with the soft-core potential in three dimensions. We investigate crossover of the configuration changes caused by stringlike jump motions. With lowering the temperature T, the motions of the particles composing strings become larger in sizes and displacements, while those of the particles surrounding strings become smaller. Then the contribution of the latter to time-correlation functions tends to be long-lived as T is lowered. As a result, the relaxation time τ(α) and the viscosity η grow more steeply than the inverse diffusion constant D(-1) at low T, leading to breakdown of the Stokes-Einstein relation. At low T, the diffusion occurs as activation processes and may well be described by short-time analysis of rare jump motions with broken bonds and large displacements. Some characteristic features of the Van Hove self-correlation function arise from escape jumps over high potential barriers. We also visualize the particle motions at string formation taking place in a very short time.