We study the effect of size polydispersity on the stress distributions and structural properties of static frictionless packings under isotropic compressions.More than 50 isostatic packings with constant mean stress of 1 kPa are generated for each size polydispersity s with a uniform distribution of diameter between(d_(0-s)/2)and(d_(0+s)/2).In order to vary the degree of positional order,the size polydispersity s ranges from 0 to 0.5.Several typical structural characterizations,(i.e.,the height of the first pair correlation peak,the global and the local order parameters),the probability distribution of the normalized mean stress and the stress-stress correlation are calculated.The result shows that(i)the stress distribution scales as a power law in the limit of small stresses,and the distribution displays a Gaussian tail in the limit of large stresses;(ii)s has no evident influence on the structural and mechanical properties when s>0.2.
