Kim Kang, Saito Shinji
Institute for Molecular Science, Okazaki 444-8585, Japan.
Phys Rev E Stat Nonlin Soft Matter Phys. 2009 Jun;79(6 Pt 1):060501. doi: 10.1103/PhysRevE.79.060501. Epub 2009 Jun 12.
A multitime probing of density fluctuations is introduced to investigate hidden time scales of heterogeneous dynamics in glass-forming liquids. Molecular-dynamics simulations for simple glass-forming liquids are performed and a three-time correlation function is numerically calculated for general time intervals. It is demonstrated that the three-time correlation function is sensitive to the heterogeneous dynamics and that it reveals couplings of correlated motions over a wide range of time scales. Furthermore, the time scale of the heterogeneous dynamics tauhetero is determined by the change in the second time interval in the three-time correlation function. The present results show that the time scale of the heterogeneous dynamics tauhetero becomes larger than the alpha-relaxation time at low temperatures and large wavelengths. We also find a dynamical scaling relation between the time scale tauhetero and the length scale xi of dynamical heterogeneity as tauhetero approximately xiz with z=3.
引入了对密度涨落的多次探测，以研究玻璃形成液体中非均匀动力学的隐藏时间尺度。对简单玻璃形成液体进行了分子动力学模拟，并针对一般时间间隔数值计算了三次关联函数。结果表明，三次关联函数对非均匀动力学敏感，并且它揭示了在很宽的时间尺度范围内相关运动的耦合。此外，非均匀动力学的时间尺度tauhetero由三次关联函数中第二个时间间隔的变化确定。目前的结果表明，在低温和大波长下，非均匀动力学的时间尺度tauhetero变得大于α弛豫时间。我们还发现了非均匀动力学的时间尺度tauhetero与动力学非均匀性的长度尺度xi之间的动力学标度关系，即tauhetero约为xiz，其中z = 3。
