COMPUTER-SIMULATION OF RANDOM PACKINGS OF SPHERES WITH LOG-NORMAL DISTRIBUTIONS

A computer simulation is described which can produce randomly packed lattices consisting of spheres which obey the log-normal distribution with absolute standard deviations in the range 0 to 0.84. The packings are gravitationally stable and range from random loose packing to random close packing. The packing density for both close and loose packed lattices increases with the absolute standard deviation of the distribution. The structure of the lattice is determined by the occupational mechanism for low absolute standard deviations and its position in the packing density/mean co-ordination plane is a function of both bridging and the angular separation between contacting spheres. As the standard deviation increases, there is a transition from the occupational to the filling mechanism. The filling mechanism is characterised by small particles nesting within the voids produced by larger spheres which form an infrastructure inside the lattice. The degree of bridging within these lattices is reduced to a very low level and the position in the packing density/mean co-ordination plane is a function principally of the angular separation of contacting spheres.