Total magnetization stored in MP

Hi MP founders,

I tried to recompute total magnetization for some materials, e.g. FeO (mp-1178232). All input files and parameters were set by pymatgen in automation. The structure was directly got from MP.

After a few ionic steps, the relaxation was done (not surprised) but the total magnetization I obtained is 8 magneton Bohr/cell instead of 4 like in MP.

I wonder that the total magnetization stored in MP is normalized to the reduced formula or there is something wrong here.

P/s: the same thing observed in Fe3O4_mp-19306

Thank you,
Anh

Hi Anh,

I am only a user of the MP, not a developer, but I strongly suspect that you are right in your observation that this is a issue of unit cells. If you download the VASP input files, it will give you a conventional unit cell with 8 atoms in total. On the other hand the data given on the MP site clearly indicates a smaller unit cell with only 4 atoms and different lattice vectors.

If you use MPRester to get the structure instead of importing it from the POSCAR file, you will get the reduced cell with only 4 atoms.

with MPRester() as mpr:
    struct = mpr.get_structure_by_material_id("mp-1178232")

results in

Structure Summary
Lattice
    abc : 3.1664873178599873 3.1107873647088145 6.192646264665004
 angles : 60.08497835710322 59.24753083625531 59.40592016569469
 volume : 42.71541095355241
      A : -0.0 2.23904465 2.23904466
      B : 2.17624058 0.01627279 2.22277083
      C : 4.32960659 4.42727827 0.05080999
PeriodicSite: Fe (0.0000, 0.0000, 0.0000) [-0.0000, 0.0000, -0.0000]
PeriodicSite: Fe (2.1648, 2.2136, 0.0254) [-0.0000, 0.0000, 0.5000]
PeriodicSite: O (2.0880, 2.2873, 2.1908) [0.5190, 0.4571, 0.2525]
PeriodicSite: O (4.4179, 4.3953, 2.3218) [0.4810, 0.5429, 0.7475]

Cheers, Michael