Nsites for magnetic structures

[SVB]

For AFM NiO, https://materialsproject.org/materials/mp-19009/
the material explorer shows Nsites=2 as it does for other rocksalt structures, however it shows the volume of the magnetic supercell (twice the primitive rocksalt cell). Am I missing something, is it a bug or a feature? How can I screen by volume-per-atom for all materials, including those with non-trivial magnetic order?

[SVB]

Just realized this was reported already:

Volume/Nsites not correct for at least mp-1783

mp-1783 (MnS) is listed as Volume = 84.62 A^3 and Nsites = 2. This leads to a large and unrealistic atomic density of ~42 A^3/atom. However, checking the POSCAR, there are actually 8 sites and the volume is 166.375 A^3 leading to a true atomic density of ~20 A^3/atom, which is reasonable. It’s difficult to say how pervasive this issue is, but it’s worth looking into as quantities like atomic density are often used for screening, data analysis, etc. and these quantities seem easy enough to pull …

Error in 'nsites' metadata for a structure?

Hello! For MgNi: the first entry mp1185908 has about the same about gravimetric density as the others but not the same Volume / Nsites. [image] I downloaded the cif to confirm there are four atoms in the unit cell (4 also listed on webpage) so Nsites should be 4? Thanks, Matt

In the latter case, the positions themselves are not equivalent, presumably too large a tolerance was used in the symmetrization routine (and different tolerance for volume and Nsites determination).

However, the former case, just as the one in the OP (mp-19009), is AFM, so a correction to Nsites is non-trivial and due to the true (magnetic) unit cell being twice the unit cell of the atomic structure… Sorry if I’m saying something obvious, just wanted to draw your attention to this potential complication in fixing the problem.