Effect of bond and asymmetry of 2D-dumbbells on their structure in high concentration regime

• Published in: Soft matter 2012-01, Vol.8 (34), p.915-921
• Main Authors: Han, Youngkyu, Kim, Mahn Won
• Format: Article
• Language: English
• ISSN: 1744-683X; 1744-6848
• DOI: 10.1039/c2sm26437d

Particle shape is one of the major parameters governing the structure in hard-particle systems. A 2D-dumbbell, which consists of a pair of binary disks connected to each other, has two geometrical characteristics: the existence of a bond and asymmetry due to a size difference. We investigate the effects of the geometry of 2D-dumbbells on the packing structure at an air-water interface under short-range attractions, varying the area fraction of the particles. We observe that although the systems at low exhibit the characteristic structure of attractive particle systems, the short-range attraction between the particles due to capillary interaction does not affect the local structure at the maximally random jammed (MRJ) packing fraction. We investigate the influence of a rigid bond on the packing structure by comparing 2D-dumbbell systems with binary-disk systems; we also investigate the effects of asymmetry by controlling the diameter ratio ( ) of the small and large disks of the dumbbell. First, we find that the existence of a bond restricts local segregations between similar kinds of disks, so that phase-separated glass states are forbidden, contrary to the case of binary-disk systems. Second, we observe that varying causes a structural order-disorder-order change at high . While the crystalline structures of disks ( = 0) and symmetric dimers ( = 1) are similar in local contacting and ordering behaviors despite their shape differences, the amorphous structures of asymmetric dimers ( = 0.3, 0.5, and 0.7) exhibit distinct features depending on . Through a packing experiment with 2D wax snowmen of various size ratios between the body and head parts, we investigated the effect of snowman shapes on the structural properties.