[Wien] hyperfine field question in ORB package for the aluminum

[Peter Blaha]

The hyperfine field for a metal is coming mainly from the contact term 
due to the induced spin-polarization by the magnetic field.

You should notice, that a field of 9 T is (for theoretical calculations) 
an extremely small field, causing a very small spin-splitting of the 
states near EF, which causes the HFF.
I suppose all you see is numerical noise.

Since only the states at EF are of interest (the field can only reoccupy 
states within a few mRy (or less) around EF), you need to converge your 
calculation with respect to:

a) the k-mesh   (test MUCH larger meshes (10000, 50000 100000 k or more)
b) the magnetic field (increase it and test fields up to 1000 T), You 
are not interested in the absolute number, but in ppm, i.e. the relative 
induced field.

c) The angular momentum component of the hFF introduced by 
case.vorbup/dn is NOT correct. I would even suggest that you put l=0 to
minimize the effect (or use    -orbc  with case.vorbup/dn , where all 
elements are set to zero.)

d) In principle the orbital contribution should be obtainable from the 
NMR-module of wien2k_13. However, also there we observed for metals that 
it is very hard to converge with respect to k-mesh and the final results 
(sum of spin and orbital contribution) does not seem right, while 
spin-only has the correct magnitude (within 10% of the experiment). This 
is an unresolved issue for us so far.


Am 07.10.2013 04:01, schrieb Jing-Han Chen:
> Dear WIEN2k users and authors
>
>    We are currently working on the hyperfine field calculation by using
> ORB package. In fcc aluminum case, we got 0.154 (KGAUSS) when the
> following case.inorb and case.indm are used
>
> case.inorb
> 3 1 0        nmod, natorb, ipr
> PRATT, 1.0    mixmod, amix
> 1 1 0          iatom nlorb, lorb
> 9.            Bext in T
> 0. 0. 1.    direction of Bext in terms of lattice vectors
>
> case.indm
> -9.                      Emin cutoff energy
>   1                       number of atoms for which density matrix is
> calculated
>   1  1  0      index of 1st atom, number of L's, L1
>   0 0           r-index, (l,s)index
>
>    In order to confirm how the magnetic field is applied for the
> multiple sites crystal, we made aluminum as a simple cubic with 4
> inequivalent sites and we believe it should be physically identical to
> fcc. The following case.inorb and case.indm are used.
>
> case.inorb
> 3 4 0        nmod, natorb, ipr
> PRATT, 1.0    mixmod, amix
> 1 1 0          iatom nlorb, lorb
> 2 1 0          iatom nlorb, lorb
> 3 1 0          iatom nlorb, lorb
> 4 1 0          iatom nlorb, lorb
> 9.            Bext in T
> 0. 0. 1.    direction of Bext in terms of lattice vectors
>
> case.indm
> -9.                      Emin cutoff energy
>   4                       number of atoms for which density matrix is
> calculated
>   1  1  0      index of 1st atom, number of L's, L1
>   2  1  0      index of 1st atom, number of L's, L1
>   3  1  0      index of 1st atom, number of L's, L1
>   4  1  0      index of 1st atom, number of L's, L1
>   0 0           r-index, (l,s)index
>
>    Both fcc and simple cubic are run by the same way (-orb -cc 0.00001).
> A complete different HFFs are obtained as the following
>
> :HFF001:            0.059           0.000           0.001
> 0.060 (KGAUSS)
> :HFF002:           -1.193           0.000          -0.010
> -1.204 (KGAUSS)
> :HFF003:            1.681           0.000           0.011
> 1.692 (KGAUSS)
> :HFF004:            0.046           0.000           0.001
> 0.047 (KGAUSS)
>
> We got four different HFFs which we thought they are supposed to be the
> same. Also all of them are very far from the fcc result (0.154 KGAUSS).
> Does anyone know why it happens?
>
>    Any suggestion and comment are appreciated.
>
> --
> Jing-Han Chen
> Graduate Student
> Department of Physics
> Texas A&M University
> 4242 TAMU
> College Station TX  77843-4242
> jhchen at tamu.edu <mailto:jhchen at tamu.edu> <jhchen at tamu.edu
> <mailto:jhchen at tamu.edu>> / http://people.physics.tamu.edu/jhchen/
>
>
>
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-- 
Peter Blaha
Inst.Materials Chemistry
TU Vienna
Getreidemarkt 9
A-1060 Vienna
Austria
+43-1-5880115671