Furukawa Akira, Kim Kang, Saito Shinji, Tanaka Hajime
Institute of Industrial Science, University of Tokyo, Meguro-ku, Tokyo 153-8505, Japan.
Phys Rev Lett. 2009 Jan 9;102(1):016001. doi: 10.1103/PhysRevLett.102.016001.
A supercooled liquid generally exhibits marked shear-thinning behavior, but its detailed mechanism remains elusive. Here we study the dynamics of structural rearrangements in supercooled liquids under shear, using two-dimensional (2D) molecular dynamics simulation. To elucidate the relationship between heterogeneous dynamics and the rheological behavior, we extend the four-point correlation function, which has been used for analyzing "dynamic heterogenity" in a quiescent condition, to a system under steady shear. In the Newtonian regime, the rearrangement dynamics is strongly heterogeneous in space, but remains isotropic. Contrary to this, in the non-Newtonian regime, where marked shear-thinning behavior appears, we find a novel dynamic effect: The mobile region tends to form anisotropic "fluidized bands." This finding suggests a link between nonlinear rheology and inhomogeneization of flow.
过冷液体通常表现出显著的剪切变稀行为，但其详细机制仍不明确。在此，我们使用二维分子动力学模拟研究了过冷液体在剪切作用下结构重排的动力学。为了阐明非均匀动力学与流变行为之间的关系，我们将用于分析静态条件下“动态非均匀性”的四点关联函数扩展到了稳态剪切系统。在牛顿区域，重排动力学在空间上强烈非均匀，但仍保持各向同性。与此相反，在出现显著剪切变稀行为的非牛顿区域，我们发现了一种新的动态效应：可移动区域倾向于形成各向异性的“流化带”。这一发现表明了非线性流变学与流动不均匀化之间的联系。
