Allahyarov E, Sandomirski K, Egelhaaf S U, Löwen H
Institute for Theoretical Physics II: Soft Matter, Heinrich Heine University, Universitätsstrasse 1, 40225 Düsseldorf, Germany.
Theoretical Department, Joint Institute for High Temperatures of the Russian Academy of Sciences, Izhorskaya Street, 13 Boulevard 2, Moscow 125412, Russia.
Nat Commun. 2015 May 15;6:7110. doi: 10.1038/ncomms8110.
Crystallization represents the prime example of a disorder-order transition. In realistic situations, however, container walls and impurities are frequently present and hence crystallization is heterogeneously seeded. Rarely the seeds are perfectly compatible with the thermodynamically favoured crystal structure and thus induce elastic distortions, which impede further crystal growth. Here we use a colloidal model system, which not only allows us to quantitatively control the induced distortions but also to visualize and follow heterogeneous crystallization with single-particle resolution. We determine the sequence of intermediate structures by confocal microscopy and computer simulations, and develop a theoretical model that describes our findings. The crystallite first grows on the seed but then, on reaching a critical size, detaches from the seed. The detached and relaxed crystallite continues to grow, except close to the seed, which now prevents crystallization. Hence, crystallization seeds facilitate crystallization only during initial growth and then act as impurities.
结晶是无序-有序转变的典型例子。然而，在实际情况中，容器壁和杂质常常存在，因此结晶是异质成核的。种子很少能与热力学上有利的晶体结构完美兼容，从而引发弹性畸变，阻碍晶体进一步生长。在此，我们使用一种胶体模型系统，它不仅使我们能够定量控制所引发的畸变，还能以单粒子分辨率可视化并跟踪异质结晶过程。我们通过共聚焦显微镜和计算机模拟确定中间结构的序列，并建立了一个描述我们研究结果的理论模型。微晶首先在种子上生长，但在达到临界尺寸后，会从种子上脱离。脱离且松弛的微晶继续生长，但靠近种子的区域除外，此时种子会阻止结晶。因此，结晶种子仅在初始生长阶段促进结晶，随后就会起到杂质的作用。
