Local and global relations between the number of contacts and density in monodisperse sphere packs

The topological structure resulting from the network of contacts between grains (contact network) is studied for large samples of monosized spheres with densities (fraction of volume occupied by the spheres) ranging from 0.59 to 0.64. We retrieve the coordinates of each bead in the pack and we calculate the average coordination number by using three different methods. We show that, in the range of density investigated, the coordination number is larger than four and it increases with the packing fraction. At local level we also observe a positive correlation between local packing fraction and number of neighbours. We discover a dependence between the local densities of configurations with few neighbours in contact and the global sample densities. This might indicate that local configurations with small numbers of neighbours are able to deform plastically when the sample is compactifying.