Heterogeneous structure of granular aggregates with capillary interactions.

We investigate the spatial structure of cohesive granular matter with spheres floating at an air-liquid interface that form disordered close packings with pores in between. The interface is slowly lowered in a conical container to uniformly compress and study the system as a function of area fraction ϕ. We find that the free area distributions associated with Voronoi cells show significant exponential tails indicating greater heterogeneity compared with random distributions at low ϕ with a crossover towards a Γ distribution as ϕ is increased. Further, we find significant short range order as measured by the radial correlation function and the orientational order parameter even at low and intermediate ϕ, which is absent when particles interact only sterically.