Hi,
I guess I never suggested B=10000 T, but anyway, what you should check
is if the calculated HFF vary linear with the applied field.
I could imagine that with such calculations where you should have some
"artificial" degeneracy of the 4 Al atoms, the TETRA method makes some
small problem. In any case, it looks already fairly similar.
Have you ever tried TEMP (with a small broadening ??, so that you do not
destroy the magnetic shift).
In addition, I suggest to increase the IFFT factor in case.in0 to 4 or
6, so that aliasing problems are reduced.
Otherwise I would need to check this out myself.
On 10/15/2013 06:25 PM, Jing-Han Chen wrote:
Dear Prof. Blaha and other wien2k users:
(I posted a similar message yesterday, apologies in case this appears as
a repeat; the first message has not appeared on the list, perhaps
reflected due to included images.)
Regarding tests of the hyperfine fields in aluminum metal, we had
thought about the issue of insufficient k-points, however we thought we
had a handle on this issue. In a 9 T field, a rough calculation shows
that the thin spin-polarized shell at Ef represents about 1/3000 of the
BZ volume for fcc-Al. We ran a script gradually increasing the number of
k-points, with a result (shown in
http://people.physics.tamu.edu/jhchen/points.png) that the HFF settles
down within about 20% of the expected value for 10,000 k-points in B=9T,
with fluctuations dying down to the order of 10% and less in the range
30,000 - 80,000 k-points. We also ran a test for linearity in B at a
setting of 10,000 k-points, and the results appeared to be quite linear
up to 100 T (shown in http://people.physics.tamu.edu/jhchen/field.png).
We ran the test treating fcc-Al as simple cubic with 4 sites in order to
be sure we understood how the field is applied in ORB, and expected if
anything better convergence since the expanded cell gives a greater
k-point density. However the results seem strange: with several k-point
settings we found that in general, the HFF approached the expected value
for fcc-Al after a relatively small number of iterations, yet without
quite converging, and finally the HFF values diverged, with one or more
going large and negative. We had not tried as many variations as for fcc
since the results are much slower to obtain converged HFF.
Following the suggestion of Prof. Blaha after our last posting we tried
increasing to very large field and k-point values, and did finally get
convergence (more than 10 last iterations of HFF is the same) for a
setting of 100000 k-points and 10000 T, yielding 4 reasonably close
positive values as in the following:
------
:HFF001: 143.345 0.000 0.572
143.917 (KGAUSS)
:HFF002: 143.344 0.000 0.572
143.916 (KGAUSS)
:HFF003: 144.427 0.000 0.583
145.010 (KGAUSS)
:HFF004: 143.344 0.000 0.572
143.916 (KGAUSS)
------
However we are concerned that the HFF values are still not identical,
whereas at 10,000 T the spin-polarized shell at Ef represents a
significant fraction of the BZ, and the spin energy is quite large. We
expected this to be more than enough k-points for random sampling of the
shell at Ef. For this reason, and in particular in light of the strange
behavior in which the HFF values almost converge before diverging to
widely separated values, is it possible that there might be some other
issue that we are overlooking?
Any suggestions would be appreciated.
2013/10/7 Peter Blaha <pbl...@theochem.tuwien.ac.at
<mailto:pbl...@theochem.tuwien.ac.at>>
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
jhc...@tamu.edu <mailto:jhc...@tamu.edu> <mailto:jhc...@tamu.edu
<mailto:jhc...@tamu.edu>> <jhc...@tamu.edu <mailto:jhc...@tamu.edu>
<mailto:jhc...@tamu.edu <mailto:jhc...@tamu.edu>>> /
http://people.physics.tamu.__edu/jhchen/
<http://people.physics.tamu.edu/jhchen/>
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Jing-Han Chen
Graduate Student
Department of Physics
Texas A&M University
4242 TAMU
College Station TX 77843-4242
jhc...@tamu.edu <mailto:jhc...@tamu.edu> <jhc...@tamu.edu
<mailto:jhc...@tamu.edu>> / http://people.physics.tamu.edu/jhchen/
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