Session D40 - Poster Session I.
POSTER session, Monday afternoon, March 12
Exhibit Hall, Washington State Convention Center
The role of local icosahedral symmetry of bond orientations in the random dense packings of monodispersive spheres has been discussed for several decades. The two key features of this topic are, first, the strong tendency for local tetrahedral packings, and second, the geometrical frustration inherent in clusters of tetrahedral packings. We investigate reducing the geometric frustration by using spheres of two different sizes, where the diameter of the smaller sphere is approximately 0.9 times the diameter of the larger sphere. At this ratio, a frustration-free icosahedron can be formed by tightly packing twelve of the larger spheres around a single smaller sphere. Starting with various relative compositions and with random initial conditions, we have measured the subsequent compaction on vertical shaking of these bidispersive granular beds. We will discuss these results in terms of the decrease in complexity of the energy landscape caused by the possibility of frustration-free local icosahedral packing, and comparison will be made with simulations.