Colloquium: "Effect of Geometry of 2D-Dumbbells on the Structure of Random Jammed Packing"


Friday, May 6, 2016 - 11:00am


ESB 1001


Prof. Mahn Won Kim, KAIST & GIST


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 packing structure at an air-water interface under short-range attractions, varying the area fraction j of particles. We observe that the short-range attraction between particles due to capillary interaction does not affect the local structure at maximally random jammed (MRJ) packing fraction, although the systems at low j exhibit characteristic structure of attractive particle systems. 
We investigate the influence of a rigid bond on the packing structure by comparing 2D-dumbbell systems with binary-disk systems and the effects of the asymmetry by controlling the diameter ratio (g ) of the small and large disks of a dumbbell. First, we find that the existence of a bond restricts local segregations between similar kinds of disks, so the phase-separated glass states are forbidden contrary to binary-disk systems. Second, we observe that varying g causes a structural order-disorder-order change at high j. While crystalline structures of disks (g=0) and symmetric dimers (g=1) are similar in local contacting and ordering behaviors despite the shape difference, amorphous structures of asymmetric dimers (g=0.3, 0.5, and 0.7) exhibit distinct features depending on g .


Chair Professor, GIST College, GIST
Emeritus Professor , Department of Physics, Korea Advanced Institute of Science and Technology
Adjunct Professor, Department of Materials ,University of California, Santa Barbara
Ph.D. (Physics):  1975 University of California, Santa Barbara under Prof. D. S. Cannell
President, Asia-Oceania Neutron Scattering Association
President, Korea Institute for Advanced Study
Senior Staff Physicist, Exxon Research and Engineering Co.
Korean Academy of Science and Technology (KAST)
American Physical Society (Fellow)

Hosted by Ram Seshadri.    Light refreshments served.    Download event flyer.