Two-Dimensional Clusters of Colloidal Spheres: Ground States, Excited States, and Structural Rearrangements.
Two-Dimensional Clusters of Colloidal Spheres: Ground States, Excited States, and Structural Rearrangements.
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二维胶体团簇：基态、激发态和结构重排。
DOI：
10.1103/physrevlett.114.228301
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发表时间：
2014
影响因子：
8.6
通讯作者：
V. Manoharan
中科院分区：
文献类型：
--
作者：
R. Perry;Miranda C. Holmes;M. Brenner;V. Manoharan
我们实验研究什么可以说是最简单的，但不平凡的胶体系统：二维集群的六个球形粒子约束的耗尽相互作用。这些团簇具有多个简并基态，其平衡分布由熵因素，主要是对称性决定。我们观察到基态之间的平衡重排，以及所有的低洼激发态。与基态相比，激发态具有软模和低对称性，它们的占据概率取决于通过内部自由度达到的配置空间的大小，以及封装势的深度和曲率的单个“粘性参数”。使用的几何模型，占软模式的熵和扩散率沿着他们，我们准确地再现测量重排率。这个模型的成功，它不需要拟合参数或测量的潜力，表明胶体系统的自由能景观和动力学，它管理可以理解几何。
We study experimentally what is arguably the simplest yet nontrivial colloidal system: two-dimensional clusters of six spherical particles bound by depletion interactions. These clusters have multiple, degenerate ground states whose equilibrium distribution is determined by entropic factors, principally the symmetry. We observe the equilibrium rearrangements between ground states as well as all of the low-lying excited states. In contrast to the ground states, the excited states have soft modes and low symmetry, and their occupation probabilities depend on the size of the configuration space reached through internal degrees of freedom, as well as a single "sticky parameter" encapsulating the depth and curvature of the potential. Using a geometrical model that accounts for the entropy of the soft modes and the diffusion rates along them, we accurately reproduce the measured rearrangement rates. The success of this model, which requires no fitting parameters or measurements of the potential, shows that the free-energy landscape of colloidal systems and the dynamics it governs can be understood geometrically.