[Wien] hyperfine field question in ORB package for the aluminum
Jing-Han Chen
jhchen at tamu.edu
Fri Oct 18 22:48:12 CEST 2013
Dear Prof. Blaha
It works very well after TEMP broadening is turned on. Thanks for your
suggestion.
2013/10/15 Peter Blaha <pblaha at theochem.tuwien.ac.at>
> 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<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<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 <pblaha at theochem.tuwien.ac.at
>> <mailto:pblaha at theochem.**tuwien.ac.at <pblaha at 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
>> jhchen at tamu.edu <mailto:jhchen at tamu.edu> <mailto:jhchen at tamu.edu
>>
>> <mailto:jhchen at tamu.edu>> <jhchen at tamu.edu <mailto:
>> jhchen at tamu.edu>
>> <mailto:jhchen at tamu.edu <mailto:jhchen at tamu.edu>>> /
>> http://people.physics.tamu.__**edu/jhchen/
>> <http://people.physics.tamu.**edu/jhchen/<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 <tel:%2B43-1-5880115671>
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>>
>>
>> --
>> 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/<http://people.physics.tamu.edu/jhchen/>
>>
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> --
>
> P.Blaha
> ------------------------------**------------------------------**
> --------------
> Peter BLAHA, Inst.f. Materials Chemistry, TU Vienna, A-1060 Vienna
> Phone: +43-1-58801-165300 FAX: +43-1-58801-165982
> Email: blaha at theochem.tuwien.ac.at WWW: http://info.tuwien.ac.at/**
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--
Jing-Han Chen
Graduate Student
Department of Physics
Texas A&M University
4242 TAMU
College Station TX 77843-4242
jhchen at tamu.edu <jhchen at tamu.edu> / http://people.physics.tamu.edu/jhchen/
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