Dear mp-admins: I got the structure of mp-28478 and mp-27466 by Pymatgen using the Materials Project and found that the unit cell and conventional unit cell of mp-28478 ,mp-27466 maybe is wrong.
What do you mean by wrong? Can you elaborate?
Dear shyamd:
I get the different conventional unit cell(mp-27466) by downloading from website and Pymatgen.I think the structure from website is correct.And the unit cell of mp-27466 maybe smaller with two lithium atoms and six tellurium atoms.Mp-28478 has the same question.Thank you for your prompt reply.
@shyamd I have checked the materials of mp-28478 and mp-27466 from ICSD,the structure is same as MP,but I can’t understand the conventional unit cell(mp-27466).I agree with the structure by downloading from website.I hope you can answer my doubts. Thank you very much.
Hi @YuTingLiu33
I’m still not understanding what you’re saying.
Which parts of the unit cell are wrong? Can you post what you expect these values to be?
Hi @shyamd
I get the different conventional unit cell of mp-27466 by downloading from website and Pymatgen(get_structure_by_material_id(id, final=False,conventional_unit_cell=True)).And I want to know which one is right.Can you check it?
The POSCAR of mp-27466 by getting from Pymatgen :
Li12 Te36
1.0
4.357200 -7.546892 0.000000
4.357200 7.546892 0.000000
0.000000 0.000000 21.345200
Li Te
12 36
direct
0.333333 0.666667 0.416700 Li
0.666667 0.333333 0.083300 Li
0.666667 0.333333 0.583300 Li
0.333333 0.666667 0.916700 Li
0.333333 0.666667 0.666700 Li
0.666667 0.333333 0.833300 Li
0.666667 0.333333 0.333300 Li
0.333333 0.666667 0.166700 Li
0.000000 0.000000 0.750000 Li
0.000000 0.000000 0.250000 Li
0.000000 0.000000 0.500000 Li
0.000000 0.000000 0.000000 Li
0.177000 0.333300 0.083300 Te
0.666700 0.843700 0.083300 Te
0.156300 0.823000 0.083300 Te
0.843700 0.666700 0.416700 Te
0.823000 0.156300 0.416700 Te
0.333300 0.177000 0.416700 Te
0.823000 0.666700 0.916700 Te
0.333300 0.156300 0.916700 Te
0.843700 0.177000 0.916700 Te
0.156300 0.333300 0.583300 Te
0.177000 0.843700 0.583300 Te
0.666700 0.823000 0.583300 Te
0.851000 0.666700 0.166700 Te
0.333300 0.184300 0.166700 Te
0.815700 0.149000 0.166700 Te
0.184300 0.333300 0.333300 Te
0.149000 0.815700 0.333300 Te
0.666700 0.851000 0.333300 Te
0.149000 0.333300 0.833300 Te
0.666700 0.815700 0.833300 Te
0.184300 0.851000 0.833300 Te
0.815700 0.666700 0.666700 Te
0.851000 0.184300 0.666700 Te
0.333300 0.149000 0.666700 Te
0.520000 0.520000 0.750000 Te
0.000000 0.480000 0.750000 Te
0.480000 0.000000 0.750000 Te
0.480000 0.480000 0.250000 Te
0.000000 0.520000 0.250000 Te
0.520000 0.000000 0.250000 Te
0.000000 0.500000 0.500000 Te
0.500000 0.500000 0.500000 Te
0.500000 0.000000 0.500000 Te
0.500000 0.500000 0.000000 Te
0.000000 0.500000 0.000000 Te
0.500000 0.000000 0.000000 Te
The conventional unit cell of mp-27466 by getting from pymatgen is slightly distorted, which maybe make the structure more stable. But I calculate that the energy difference between the structure from website and Pymatgen is very small.
If the website one is right, maybe need to fix the conventional unit cell of mp-28478 .
Thank you for your prompt reply.
Hi @YuTingLiu33
Note that conventional_unit_cell=True will modify the structure, which is why you’re seeing two different lattices. We use spglib to symmetrize the structure, so it’s in the conventional setting they define. This specific lattice may have come from a number of locations such as the ICSD, Pauling Files, etc. We take these structures and calculate as is to get the lowest energy structure for a material. There are limits to how much we relax, so it’s possible you’re two calculations are just more relaxed than what we have. Still, both conventions are correct.
Hi @shyamd
I have understood why I see two different lattices, but I still have a problem. Why the lattice I get through pymatgen (conventional unit cell = true) is different from the lattice I downloaded directly from website (lite3-mp-27466-conventional standard.cif)?In my understanding,both conventions should be consistent.
Thank you for your prompt reply.
AH! I see now. There is a definitely a bug somewhere that is converting the cell to the primitive first before building the CIF. Both are still correct. The one you get from pymatgen is the better one to use for your DFT calculations though.
Ah that’s great, thanks so much!
I really appreciate you taking the time to explain it for me @shyamd