Figure 1.

(A) Schematic representation of the available orientations for two NN particles that have an aligned pair of patches or faces. For Cases 1–3 in Section 2, patches are much larger than how they are shown here; the smaller patch areas correspond to Case 4 in Section 2, to illustrate the situations where many of the possible orientations are ones in which patches or faces do not point toward the corners of the bcc cell surrounding a central molecule. Arrows are unit normals, shown only for easier visualization of the possible orientations. (B) Enumerated bcc sites around a central (gray) site, to illustrate that tetrahedrally placed pactches on a central molecule can point simultaneously to only one sublattice (sites 1,2,3,4) or the other (sites 5,6,7,8).