Wu Xiaoyue, Skipper Katherine, Yang Yushi, Moore Fergus J, Meldrum Fiona C, Royall C Patrick
School of Chemistry, University of Leeds, Woodhouse Lane, Leeds, LS2 9JT, UK.
H. H. Wills Physics Laboratory, University of Bristol, Bristol BS8 1TL, UK.
Soft Matter. 2025 Apr 9;21(15):2787-2802. doi: 10.1039/d4sm00889h.
Colloidal particles self assemble into a wide range of structures under external AC electric fields due to induced dipolar interactions [Yethiraj and Van Blaaderen, , 2003, , 513]. As a result of these dipolar interactions, at low volume fraction the system is modulated between a hard-sphere like state (in the case of zero applied field) and a "string fluid" upon application of the field. Using both particle-resolved experiments and computer simulations, we investigate the emergence of the string fluid with a variety of structural measures including two-body and higher-order correlations. We probe the higher-order structure using three-body spatial correlation functions and a many-body approach based on minimum energy clusters of a dipolar-Lennard-Jones system. The latter constitutes a series of geometrically distinct minimum energy clusters upon increasing the strength of the dipolar interaction, which are echoed in the higher-order structure of the colloidal fluids we study here. We find good agreement between experiment and simulation at the two-body level. Higher-order correlations exhibit reasonable agreement between experiment and simulation, again with more discrepancy at higher field strength for three-body correlation functions. At higher field strength, the cluster population in our experiments and simulations is dominated by the minimum energy clusters for all sizes 8 ≤ ≤ 12.
由于感应偶极相互作用，在外部交流电场作用下，胶体颗粒会自组装成各种各样的结构[耶西拉伊和范·布拉德伦，2003年，513页]。由于这些偶极相互作用，在低体积分数下，系统会在类似硬球的状态（在零外加电场的情况下）和施加电场时的“弦流体”之间进行调制。通过颗粒分辨实验和计算机模拟，我们用包括两体和高阶关联在内的各种结构测量方法研究了弦流体的出现。我们使用三体空间关联函数和基于偶极 - 伦纳德 - 琼斯系统最小能量团簇的多体方法来探测高阶结构。随着偶极相互作用强度的增加，后者构成了一系列几何形状不同的最小能量团簇，这在我们这里研究的胶体流体的高阶结构中得到了体现。我们发现在两体水平上实验和模拟结果吻合良好。高阶关联在实验和模拟之间表现出合理的一致性，同样在更高场强下三体关联函数的差异更大。在更高场强下，我们实验和模拟中的团簇分布在所有尺寸8≤≤12时都由最小能量团簇主导。
