Another source of large negative errors is structures which were starting to collapse, when the atoms move closer to other atoms they might bind to other atoms and form a different connectivity. While breathing MOFs is indicated by a narrowing in one side of cell parameter, collapsing structures shows a large negative deviation in all cell parameters. As an example, refcode ACUBAB_clean which begins with a=8.88Å, b=8.88 Å, c=23.78Å and optimized to a=7.43Å, b=7.68Å, c=15.50Å. This happens mostly to structures with linkers that are relatively small compared to the size of metal node (example refcode ACUBAB_clean and C6DT02320G_c6dt02320g2_clean).