However, there are cases within MP where a less dense k-point mesh yields lower energy for the given structure. An example is Ac 2 CdGe (mp-1183063). There is only one structure optimisation task listed for this material within the GGA exchange-correlation potential, task mp-1183063 in which the 5 × 5 × 5 mesh was applied. A more dilute k-point mesh of 3 × 3 × 3 yields a lower energy for the structure. We performed DFT structure optimisation of this structure at these meshes and found that the total energy at 3 × 3 × 3 is 27 meV lower in energy than the total energy at 5 × 5 × 5. Such difference exceeds the k-point mesh convergence threshold of 0.001 eV per cell. Another issue in the MP formation energy data is layered materials: there are many examples of structures that have obviously not been fully optimised, as is evidenced by large interlayer distances. An example of these structures is MoS 2 (mp-1027525) with E h = 4 meV/atom. After two structural optimisation tasks, the optimal structure has an interlayer distance of 12.13 Å. However, we re-optimised the structure after dropping the initial interlayer distance by 9 Å, and we obtained a new optimal structure with a total energy that is 17 meV lower in energy that the structure of mp-1027525, which has the longer cell. Even though the impact on the total energy per atom is minimal (~ 1 meV difference), the short and the long cell s would be equivalent data points for training an ML model if one stretches the height of the longer cell by any arbitrary length.