Crystallization of non-Brownian Spheres under Horizontal Shaking

Until now, it has been observed that a collective handling of uniform spheres could only lead to a random close packing of 0.64 maximum volume fraction. In this Letter, we show that denser crystalline arrangements can be obtained when beads are poured at low flow rates into a horizontally shaken container. A parallel is suggested between this process and that of colloidal sedimentation which also yields crystalline structure.