Inconsistent magnetization-DOS-bandstructure

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!