  Recently, Sten Haastrup, Mikkel Strange, Mohnish Pandey, Thorsten Deilmann,
Per S Schmidt, Nicki F Hinsche, Morten N Gjerding, Daniele Torelli, Peter M
Larsen, Anders C Riis-Jensen, Jakob Gath, Karsten W Jacobsen, Jens Jrgen
Mortensen, Thomas Olsen and Kristian S Thygesen [2D Mater. 5 (2018) 042002]
introduced the Computational 2D Materials Database (C2DB), which organises a
variety of structural, thermodynamic, elastic, electronic, magnetic, and
optical properties of around 1500 two-dimensional materials distributed over
more than 30 different crystal structures. Unfortunately, the work contains
serious and fundamental flaws in the field of elasticity and mechanical
stability tests what makes it unreliable.
