Densest vs. jammed packings of 2D bent-core trimers

We identify the maximally dense lattice packings of tangent-disk trimers with fixed bond angles (θ = θ₀) and contrast them to both their nonmaximally-dense-but-strictly-jammed lattice packings as well as the disordered jammed states they form for a range of compression protocols. While only θ₀ = 0, 60°, and 120° trimers can form the triangular lattice, maximally-dense maximally-symmetric packings for all θ₀ fall into just two categories distinguished by their bond topologies: half-elongated-triangular for 0 < θ₀ < 60° and elongated-snub-square for 60° < θ₀ < 120°. The presence of degenerate, lower-symmetry versions of these densest packings combined with several incommensurable families of less-dense-but-strictly-jammed lattice packings act in concert to promote jamming. Systems jam via a two-stage, two-length-scale process. First, randomly-oriented crystalline grains form and grow to a size that increases with decreasing compression rate and depends strongly on θ₀. Since these grains cannot be compressed further, they effectively behave as single nearly-rigid particles as compression continues. Jamming occurs when they can no longer rotate/translate away from one another upon colliding.