I’d like signal a possible bug for the material mp-18717 SrVO3.
- The web page present a bandstructure of a metal (correct) but the field bandgap is >0.
- if I ask to the MPRester the bandstructure (on symline) I get an error (NonType…).
- the correct bandstructure exist in the internal db at the correct task_id mp-994470.
Thanks for taking care of that.
There is indeed a confusing presentation of information. If you examine the bottom of the detail page for mp-18717, you’ll notice we have done a GGA+U calculation for the structure optimization, but we have not yet run a GGA+U calculation for the band structure.
Because the optimized structure is via a GGA+U calculation, it is a “GGA+U material”, and unless there is a GGA+U band structure calculation, the band gap value displayed is based on the loose k-point mesh of the structure optimization. If there was a GGA+U band structure calculation, the band gap value would be more accurate. The API (e.g. via MPRester) reports no bandstructure because there isn’t a GGA+U one corresponding to the structure optimization. In contrast, the website shows any available bandstructure, even if it isn’t GGA+U. This explains the inconsistency between the displayed bandstructure and the band gap field on the detail page in this case.
The behavior of the website and API should be consistent. I think it is better to not present a GGA bandstructure on the website in this case, i.e. I think the API behavior is correct. The MP team will discuss how best to handle this. Thank you for reporting the issue.
This is a bug in the way we currently build the materials detail page, which is changing. Currently we prefer GGA+U values over GGA values. This includes bandgaps, so the GGA+U structure optimization band gap is presented. In reality, this is not a good value and in the future we plan on presenting Unknown if a bandgap from a bandstructure calculation is not available.
Thanks for the clarification. I guessed it was related to a mixing of GGA+U/GGA data reported.
I think it should have a certain priority to avoid misleading users.
One temporary solution could be to had a warning icon like
that one shown in case of band gap from loose k-grid. In this case
it should warn that a GGA+U gap is reported.
Thanks, good work.
another related question:
why I can get a band structure from MPRester while in the webpage
of the considered mp there is no bandstructure shown?
Example: mp-580925, https://materialsproject.org/materials/mp-580925/