A few weeks ago I looked up a material (CaFe2O4) in the database and found the phase I was looking for with correct space group and lattice parameters. If I do the query now, I can only found different polymorphs with the same chemical formula but different crystal structure. Why is it so?
Can you tell us the spacegroup that has gone missing? Occasionally the “computed cell” that’s shown on a materials details page will change because our task aggregation procedure, but the “primitive cell” and the “conventional cell” that correspond to the structure should remain the same.
The missing phase is that reported by Decker and Kasper https://doi.org/10.1107/S0365110X5700095X with space group Pnma. Currently, there is another structure (ID:mvc-12123) with same space group, two similar lattice parameters and one that is approximately 3 times the original one. What I find most strange though is that this structure appears as FM, while the other is well-known to be AFM.
Thanks for pointing this out @S_Damerio.
I’ll look into why the correct Pnma isn’t showing up.
I wanted to address the AFM vs FM explicitly. Most of Materials Project is calculated either using no magnetic moments or assuming FM magnetic ordering. This gets us close for many properties for most systems. For select highly studied systems, we already have AFM calculations. So its very possible its labeled as FM simply because we haven’t performed an AFM-calc to compare with. Wre’re in the process of deploying a workflow to do that for all materials in MP.