Densest Packings of Binary Frictional Particles*

Using a pressure-controlled discrete element method, implementing a highly efficient neighbor-detection algorithmic scheme, we have generated a large number of binary sphere-packings spanning a wide range in particle size ratio and filling fraction of small particles, over several orders of magnitude in particle friction coefficient. Our results are consistent with a generalized Furnas model [1] that takes into account friction dependence of the global packing fraction φ_J. Our systems approach the theoretical result in the limit of large size ratios (20:1), with packings containing 1-10 million spheres. We provide evidence that the densest mechanically-stable jammed packings of binary frictional particles (circa φ_J ~ 0.82 - 0.85) are produced at a friction-dependent optimal composition of large and small particles.


[1] C. C. Furnas, Ind. Eng. Chem. 23, 1052 (1931)