Mizuno Hideyuki, Yamamoto Ryoichi
Department of Chemical Engineering, Kyoto University, Kyoto 615-8510, Japan.
Phys Rev E Stat Nonlin Soft Matter Phys. 2010 Sep;82(3 Pt 1):030501. doi: 10.1103/PhysRevE.82.030501. Epub 2010 Sep 13.
We numerically examine dynamical heterogeneity in a highly supercooled three-dimensional liquid via molecular-dynamics simulations. To define the local dynamics, we consider two time intervals: τ(α) and τ(ngp). τ(α) is the α relaxation time, and τ(ngp) is the time at which non-gaussian parameter of the Van Hove self-correlation function is maximized. We determine the lifetimes of the heterogeneous dynamics in these two different time intervals, τ(hetero)(τ(α)) and τ(hetero)(τ(ngp)), by calculating the time correlation function of the particle dynamics, i.e., the four-point correlation function. We find that the difference between τ(hetero)(τ(α)) and τ(hetero)(τ(ngp)) increases with decreasing temperature. At low temperatures, τ(hetero)(τ(α)) is considerably larger than τ(α), while τ(hetero)(τ(ngp)) remains comparable to τ(α). Thus, the lifetime of the heterogeneous dynamics depends strongly on the time interval.
我们通过分子动力学模拟对高度过冷的三维液体中的动力学非均匀性进行了数值研究。为了定义局部动力学,我们考虑两个时间间隔:τ(α) 和 τ(ngp)。τ(α) 是 α 弛豫时间,τ(ngp) 是范霍夫自相关函数的非高斯参数最大化时的时间。我们通过计算粒子动力学的时间相关函数,即四点相关函数,来确定这两个不同时间间隔内非均匀动力学的寿命,即 τ(hetero)(τ(α)) 和 τ(hetero)(τ(ngp))。我们发现,τ(hetero)(τ(α)) 和 τ(hetero)(τ(ngp)) 之间的差异随着温度的降低而增大。在低温下,τ(hetero)(τ(α)) 远大于 τ(α),而 τ(hetero)(τ(ngp)) 仍与 τ(α) 相当。因此,非均匀动力学的寿命强烈依赖于时间间隔。