Table 1. The honeycomb variants discussed in this work, defined by the dx, dy shifts in column 0.

The honeycomb features are presented in consecutive columns as follows: (1) a single honeycomb cell; (2) two pairs of cells from the two layers, showing how their bottoms fit together; (3) projection of one upper-layer cell (red) on several lower-layer cells (blue), with the Dirichlet-domain generating points in green (for the lower cells) or black (upper cell), and with auxiliary vectors between those points (green dashed lines) that generate the bottom faces of the red upper cell; the centers of symmetry are marked as small black circles and the black lines mark the reference frame for the coordinates of the vertices of the red cell (x axis horizontal, y vertical); the dx, dy shifts are marked explicitly in rows 3 and 7; (4) projection on the mean plane of a honeycomb fragment with several upper- and lower-layer cells, with all edges and vertices above the mean plane in red and all edges and vertices below that plane in blue; the vertices and edges lying exactly on the mean plane are in green; the symmetry elements of the appropriate layer space group are in black. The shaded areas in column (4) cover one unit cell of the corresponding layer space groups. The relatively small figures in this table are reproduced at a larger scale in the supporting information.

0	1	2	3	4
dx = 1/2, dy = √3/2
dx = 0, dy = √3/2
dx = 1/4, dy = √3/4
dx = 0, dy = 0
dx = 1/4, dy = √3/2
dx = 0, dy = √3/4
dx = 1/5, dy = 2√3/5