Messina René, Löwen Hartmut
Institut für Theoretische Physik II, Heinrich-Heine-Universität Düsseldorf, Universitätsstrasse 1, D-40225 Düsseldorf, Germany.
Phys Rev E Stat Nonlin Soft Matter Phys. 2006 Jan;73(1 Pt 1):011405. doi: 10.1103/PhysRevE.73.011405. Epub 2006 Jan 18.
Crystalline bilayers of charged colloidal suspensions which are confined between two parallel plates and sheared via a relative motion of the two plates are studied by extensive Brownian dynamics computer simulations. The charge-stabilized suspension is modeled by a Yukawa pair potential. The unsheared equilibrium configuration is two crystalline layers with a nested quadratic in-plane structure. For increasing shear rates (.)gamma, we find the following steady states: First, up to a threshold of the shear rate, there is a static solid which is elastically sheared. Above the threshold, there are two crystalline layers sliding on top of each other with a registration procedure. Higher shear rates melt the crystalline bilayers and even higher shear rates lead to a reentrant solid stratified in the shear direction. This qualitative scenario is similar to that found in previous bulk simulations. We have then studied the relaxation of the sheared steady state back to equilibrium after an instantaneous cessation of shear and found a nonmonotonic behavior of the typical relaxation time as a function of the shear rate (.)gamma. In particular, application of high shear rates accelerates the relaxation back to equilibrium since shear-ordering facilitates the growth of the equilibrium crystal. This mechanism can be used to grow defect-free colloidal crystals from strongly sheared suspensions. Our theoretical predictions can be verified in real-space experiments of strongly confined charged suspensions.
通过广泛的布朗动力学计算机模拟研究了夹在两个平行板之间并通过两板的相对运动进行剪切的带电胶体悬浮液的晶体双层。电荷稳定的悬浮液由 Yukawa 对势建模。未剪切的平衡构型是具有嵌套二次平面内结构的两个晶体层。对于增加的剪切速率（γ），我们发现以下稳态：首先，直到剪切速率的阈值，存在弹性剪切的静态固体。高于阈值时，有两个晶体层通过配准过程相互滑动。更高的剪切速率会使晶体双层熔化，甚至更高的剪切速率会导致在剪切方向上分层的再入固体。这种定性情况与先前的体模拟中发现的情况相似。然后，我们研究了在剪切瞬时停止后，剪切稳态回到平衡的弛豫过程，发现典型弛豫时间作为剪切速率（γ）的函数具有非单调行为。特别是，高剪切速率的应用加速了回到平衡的弛豫，因为剪切排序促进了平衡晶体的生长。这种机制可用于从强剪切悬浮液中生长无缺陷的胶体晶体。我们的理论预测可以在强约束带电悬浮液的实空间实验中得到验证。
