- The capital case letters BL stands for the Bravais lattice. The two small case letter abbreviations of the Bravais lattice type in the second column follow the crystallographic standard convention [25], see also Fig. 1 and the “Bravais lattice types in two dimensions” section. The listed Bravais lattice types are those that the images possess per design on the basis of their 2D-periodic motifs and lattice parameters. The ♦ sign in the table headline refers to the primitive sublattice of a rectangular centered Bravais lattice. When there are parentheses around an entry in the columns of the unit cell angles and lattice vector magnitude ratios, the entry within them refers to a primitive sub-unit of a two times larger rectangular centered unit cell in direct space. Such entries exist only for the CrysTBox and CRISP programs since the PUCE program is not designed to give the user any feedback if the extracted unit cell of a more or less 2D-periodic image might be of the rectangular centered Bravais lattice type. The ☼ signs refer to translational pseudo-symmetries of the special kind or a metric specialization by design. The ☺ signs refer to artifacts of combinations of motif-based and translational pseudo-symmetries of the first kind