It is also very interesting to note that the most common 2D net topology is unnamed, i.e., it is not featured in the RCSR database. It is, however, relatively simple and displayed in Figure on the example of mp-7007, a layered NbSe 2 structure with this topology, which is known experimentally (it corresponds to ICSD entry 71339). This niobium(IV) selenide topology features 6-coordinated Nb and 3-coordinated Se atoms, with an hexagonal arrange- The next net topologies in the list have a much lower occurrence, with less than 100 representatives in the database: the 3-coordinated fes net, and two sql-derived lattices mixing 3-fold and 4-fold coordination, bex and bey. They are illustrated on Figure . We note in passing that topologies with 5-fold coordination are very rare among 2D materials.