[Wien] hyperfine field question in ORB package for the aluminum
Peter Blaha
pblaha at theochem.tuwien.ac.at
Tue Oct 15 18:35:32 CEST 2013
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 <pblaha at theochem.tuwien.ac.at
> <mailto: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/>
>
>
>
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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/
>
>
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--
P.Blaha
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