Bidisperse disk packing — contact network & force chains
A jammed packing of bidisperse disks near the jamming transition (φ_J ≈ 0.84 for 2D). Particles interact via harmonic repulsion: F = k·max(0,1−r/σ_{ij})·r̂. Geometric frustration arises from polydispersity — no crystalline order satisfies all contact constraints simultaneously. Force chains (thick lines) carry stress across the network.