[Pw_forum] Lowdin charge interpretation

[Konrad Gruszka]

Hello

I have question regarding the output of projwfc (the Lowdin charge 
part). I've computed some case where iron is involved. For this I've 
used pseudopotential (pp) file with semicore states in valence:

from UPF file:

Valence configuration:
     nl pn  l   occ       Rcut    Rcut US       E pseu
     3S  1  0  2.00      1.100      1.300    -6.910119
     4S  2  0  2.00      0.800      1.400    -0.388933
     3P  2  1  6.00      1.000      1.300    -4.413015
     4P  3  1  0.00      1.000      1.600    -0.097407
     3D  3  2  6.00      1.400      2.000    -0.551558
  Generation configuration:
     3S  1  0  2.00      1.100      1.300    -6.910160
     4S  2  0  2.00      0.800      1.400    -0.388938
     3P  2  1  6.00      1.000      1.300    -4.413054
     4P  3  1  0.00      1.000      1.600    -0.097411
     3D  3  2  6.00      1.400      2.000    -0.551588
     3D  3  2  0.00      1.400      2.000    -0.400000

so the valence configuration is 3s2 3p6 3d6 4s2 4p0 and the number of 
valence electrons is 16.

The output of Lowdin charge is

   Atom #   Fe: total charge =  16.3479, s =  2.2797, p =  7.1296, d =  
6.9386,
                  spin up      =   8.2041, s =  1.1314,
                  spin up      =   8.2041, p =  3.5414, pz= 1.1805, px=  
1.1805, py=  1.1805,
                  spin up      =   8.2041, d =  3.5313, dz2= 0.7002, 
dxz=  0.7103, dyz=  0.7103, dx2-y2=  0.7002, dxy=  0.7103,
                  spin down    =   8.1438, s =  1.1484,
                  spin down    =   8.1438, p =  3.5882, pz= 1.1961, px=  
1.1961, py=  1.1961,
                  spin down    =   8.1438, d =  3.4073, dz2= 0.5199, 
dxz=  0.7892, dyz=  0.7892, dx2-y2=  0.5199, dxy=  0.7892,
                  polarization =   0.0603, s = -0.0170, p = -0.0467, d 
=  0.1240,


The questions are:

1. Why p shell is filled by 7 electrons? Is the output summing both p 
shells found in pseudopotential file (so total charge is the sum of 3p 
and 4p)?

2. Why therefore the s shell is not summed also? (3s2 + 4s2 should give 
total s =4). Am I missing something?

3. Or in more general way: is the Lowdin output of projwfc giving sums 
over each shell of the same type (if more present in PP file)?

The total charge for Fe in this case is also little bit strange (it 
looks like iron gained electron in 4p despite the loss of 4s ones?)


Well, I know that Lowdin charge analysis is not too precise, but I'm 
hoping to get some qualitative understanding of the above output.

Also, I believe that my calculation is well prepared and converged cause 
results are repeatable.


Thanks in advance!

Konrad  Gruszka

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