  The effect of increasing structural disorder on the distribution of contact
forces P(f), inside three dimensional particle assemblies is systematically
studied using computer simulations of model granular packings. Starting from a
face-centred cubic array, where all contact forces are identical, an increasing
number of defects is introduced into the assembly, after which the system is
then allowed to relax into a new mechanically stable state. Three distinct
protocols for imposing disorder are compared. A quantitative measure of the
disorder is obtained from distributions of the coordination number and
three-particle contact angle. The distribution of normal contact forces show
dramatic qualitative changes with increasing disorder. In the regime where the
disorder is relatively weak, the pressure and the lowest normal mode frequency
scale approximately linearly in the coordination number, with distance from the
crystalline state. These results for P(f) are discussed in the context of
jamming phenomena in glassy and granular materials.
