Institut für Theoretische Physik, Heinrich-Heine-Universität Düsseldorf, D-40225 Düsseldorf, Germany.
J Chem Phys. 2011 Oct 7;135(13):134115. doi: 10.1063/1.3646212.
Crystallization during the sedimentation process of a binary colloidal hard spheres mixture is explored by Brownian dynamics computer simulations. The two species are different in buoyant mass but have the same interaction diameter. Starting from a completely mixed system in a finite container, gravity is suddenly turned on, and the crystallization process in the sample is monitored. If the Peclet numbers of the two species are both not too large, crystalline layers are formed at the bottom of the cell. The composition of lighter particles in the sedimented crystal is non-monotonic in the altitude: it is first increasing, then decreasing, and then increasing again. If one Peclet number is large and the other is small, we observe the occurrence of a doubled heterogeneous crystal nucleation process. First, crystalline layers are formed at the bottom container wall which are separated from an amorphous sediment. At the amorphous-fluid interface, a secondary crystal nucleation of layers is identified. This doubled heterogeneous nucleation can be verified in real-space experiments on colloidal mixtures.
通过布朗动力学计算机模拟研究了二元胶体硬球混合物在沉淀过程中的结晶。两种物质在浮力质量上不同，但具有相同的相互作用直径。从有限容器中完全混合的系统开始，突然施加重力，并监测样品中的结晶过程。如果两种物质的佩克莱数都不是太大，则在细胞底部形成结晶层。沉降晶体中较轻颗粒的组成在高度上是非单调的：它先是增加，然后减少，然后再次增加。如果一个佩克莱数很大，另一个很小，我们会观察到双异质晶体成核过程的发生。首先，在容器底部壁形成结晶层，与非晶沉积物分离。在非晶-流体界面处，确定了层状的二次晶体成核。这种双异质成核可以在胶体混合物的实际空间实验中得到验证。
