Hi all!
It might just be me being an idiot, but I found some entries that confused me, for example, mp-777960 and mp-641117. Both have finite magnetic moments, but looking at the DOS it doesn’t look to me like they should. Plus, DOS seems a bit weird in comparison to the bandstructure - no states in DOS where the bands are…
Hi @AlenaV, welcome to the forum!
This is a good question. For each material, Materials Project will run multiple calculations, for example one to determine the structure and total energy, and some more calculations to determine the band structure and densities of states.
Sometimes, it’s possible for the magnetic moments to be different in different calculations, and this can cause inconsistencies. We try to be careful with the data we report, but the database now has over a million calculations, and if using the database for scientific research we always recommend verifying the specific calculation details. This can be done via the API or the task detail pages.
To take mp-777960 as an example, if we retrieve the structure via the API we get:
Full Formula (Li32 Mn11 Cr5 O48)
Reduced Formula: Li32Mn11Cr5O48
abc : 5.002918 5.011905 38.418513
angles: 91.134350 90.979735 119.784200
pbc : True True True
Sites (96)
# SP a b c magmom
--- ---- -------- -------- -------- --------
0 Li 0.906041 0.083357 0.249932 0
1 Li 0.500759 0.000426 0.999968 0.001
2 Li 0.563854 0.060772 0.187491 0.002
3 Li 0.625599 0.124982 0.37503 0.001
4 Li 0.691592 0.190085 0.562511 0.002
5 Li 0.750386 0.252636 0.749953 0.001
6 Li 0.812374 0.312538 0.937496 0.003
7 Li 0.211736 0.036349 0.124791 0.001
8 Li 0.875699 0.374918 0.124915 0
9 Li 0.3393 0.166488 0.50003 0.001
10 Li 0.461979 0.287768 0.874975 0.001
11 Li 0.936667 0.438278 0.312523 0.001
12 Li 0.998778 0.497561 0.499922 0.001
13 Li 0.593795 0.417699 0.250139 0
14 Li 0.712661 0.536626 0.624943 0.001
15 Li 0.037569 0.21605 0.625255 0.001
16 Li 0.162405 0.339254 0.999886 0.001
17 Li 0.836134 0.660638 4.1e-05 0.001
18 Li 0.959657 0.783697 0.374916 0
19 Li 0.289915 0.465914 0.375197 0.001
20 Li 0.410751 0.587352 0.749867 0
21 Li 0.062306 0.562459 0.687505 0.003
22 Li 0.536869 0.714606 0.125011 0
23 Li 0.661258 0.835501 0.499815 0.001
24 Li 0.126589 0.627576 0.875086 0.001
25 Li 0.786975 0.96024 0.875204 0.001
26 Li 0.188869 0.685132 0.062472 0.002
27 Li 0.250338 0.749268 0.250045 0.001
28 Li 0.312351 0.812609 0.437483 0.003
29 Li 0.374553 0.871766 0.625066 0.001
30 Li 0.43428 0.934156 0.8125 0.002
31 Li 0.089003 0.910787 0.749992 0.001
32 Mn 0.979565 0.145193 0.437495 3.163
33 Mn 0.395549 0.22939 0.687486 3.109
34 Mn 0.520153 0.354728 0.06248 3.102
35 Mn 0.645547 0.479516 0.43749 3.162
36 Mn 0.770641 0.604101 0.812502 3.103
37 Mn 0.895446 0.72948 0.187514 3.12
38 Mn 0.354155 0.52113 0.562498 3.105
39 Mn 0.479499 0.645169 0.937503 3.128
40 Mn 0.604438 0.770566 0.3125 3.109
41 Mn 0.729541 0.89531 0.687497 3.109
42 Mn 0.145533 0.979527 0.937499 3.127
43 Cr 0.856986 0.017088 0.062512 2.102
44 Cr 0.26769 0.107655 0.31248 2.121
45 Cr 0.09984 0.265443 0.812458 2.092
46 Cr 0.232076 0.391526 0.187529 2.132
47 Cr 0.025386 0.859805 0.562552 2.079
48 O 0.946728 0.086805 0.340517 -0.075
49 O 0.90646 0.047766 0.159175 -0.035
50 O 0.570481 0.069379 0.283991 -0.035
51 O 0.695256 0.194729 0.658918 -0.04
52 O 0.554997 0.056163 0.09096 -0.044
53 O 0.67857 0.178912 0.465991 -0.055
54 O 0.809639 0.307537 0.840919 -0.035
55 O 0.819518 0.320398 0.033949 -0.039
56 O 0.94608 0.445437 0.409052 -0.06
57 O 0.211704 0.07264 0.215504 -0.072
58 O 0.930678 0.431183 0.215999 -0.036
59 O 0.33672 0.195452 0.59047 -0.062
60 O 0.463518 0.320757 0.965446 -0.053
61 O 0.1771 0.038524 0.034504 -0.029
62 O 0.30428 0.161459 0.409499 -0.068
63 O 0.428391 0.289421 0.784505 -0.041
64 O 0.070612 0.212397 0.715489 -0.051
65 O 0.037303 0.18444 0.53427 -0.029
66 O 0.161123 0.303724 0.909525 -0.056
67 O 0.593328 0.451517 0.340775 -0.029
68 O 0.712698 0.570938 0.715367 -0.051
69 O 0.552642 0.413727 0.159557 -0.077
70 O 0.676637 0.535085 0.534391 -0.029
71 O 0.804331 0.660866 0.909605 -0.054
72 O 0.201943 0.344067 0.090838 -0.045
73 O 0.320806 0.464017 0.465468 -0.059
74 O 0.448846 0.590704 0.840638 -0.043
75 O 0.288515 0.427821 0.284559 -0.071
76 O 0.411864 0.553647 0.659511 -0.045
77 O 0.836867 0.697615 0.09037 -0.021
78 O 0.963945 0.821046 0.465512 -0.061
79 O 0.924311 0.782094 0.284315 -0.021
80 O 0.576717 0.7189 0.215792 -0.026
81 O 0.696015 0.835758 0.590492 -0.042
82 O 0.820804 0.963583 0.965558 -0.054
83 O 0.530843 0.673005 0.034202 -0.064
84 O 0.661516 0.803935 0.409586 -0.067
85 O 0.069859 0.575361 0.78358 -0.036
86 O 0.787443 0.92927 0.784548 -0.04
87 O 0.054775 0.549354 0.591413 -0.017
88 O 0.178951 0.679397 0.966008 -0.048
89 O 0.194464 0.695333 0.158948 -0.038
90 O 0.315706 0.818171 0.534103 -0.061
91 O 0.446464 0.945887 0.909063 -0.05
92 O 0.305278 0.804867 0.341061 -0.038
93 O 0.430008 0.930293 0.715975 -0.045
94 O 0.087745 0.941432 0.840722 -0.05
95 O 0.054431 0.912072 0.659416 -0.045
So, this is reported as a ferromagnetic material with magnetic moments on the Mn and Cr atoms. The band structure clearly shows a difference between spin-up and spin-down bands (see the dotted orange line vs the blue line). I am, however, concerned about the density of states reported for this material: there is density reported in the gap that is not present in the band structure, suggesting some issue or inconsistency with the calculation for the density of states.
If there is an issue here, we will attempt to fix it in a subsequent database release, and add additional logic/rules to ensure that this is less likely to occur in future.
To give a full answer, I would need more time to investigate, but I hope this helps a little bit.
Best,
Matt
Hi @AlenaV,
Looking more closely at this (thanks @munrojm), it looks like the DOS has been shifted relative to the Fermi level, but otherwise both band structure and DOS are correct and consistent: they have the same band gap, and they do show ferromagnetism.
Best,
Matt
Thank you!