Fig. 3.

Directional entropic forces are emergent in systems of particles and, as such, cannot be imaged directly through microscopy. Here we show the location of potential wells by taking slices of the PMFT (computed from the frequency histogram of the relative Cartesian coordinates of pairs of particles in MC simulations of monodisperse hard particles) parallel to the faces of a tetrahedron (A–D), a tetrahedrally faceted sphere (E–H), and a cube (I–L) at various packing fractions $\varphi =0.2,0.3,0.4,0.5$, indicated at the head of the column. As the packing fraction increases from left to right, the potential well becomes stronger and its shape becomes more well-defined.