[Wien] different MLD for bcc structure for magnetic equivalent directions M001, M010 and M100
Karel Vyborny
vybornyk at fzu.cz
Sun Nov 26 18:39:33 CET 2017
I suppose that this does not have to do (much) with centering the mesh.
My guess based on other QMO calculations is that some contributions to
mat. els. of e.g. vx*vx from different parts of the BZ don't cancel
(numerically) even if they actually should.
It is instructive to repeat the calculation without SO and see how big the
difference between sig_xx and sig_yy (for any M direction) is then.
Cheers,
Karel
--- x ---
dr. Karel Vyborny
Fyzikalni ustav AV CR, v.v.i.
Cukrovarnicka 10
Praha 6, CZ-16253
tel: +420220318459
On Sun, 26 Nov 2017, Fecher, Gerhard wrote:
> There was a recent discussion on magnetic anisotropy, With a remark by Peter,
> Did you use a Gamma centered k mesh (and enough k points)
>
> Ciao
> Gerhard
>
> DEEP THOUGHT in D. Adams; Hitchhikers Guide to the Galaxy:
> "I think the problem, to be quite honest with you,
> is that you have never actually known what the question is."
>
> ====================================
> Dr. Gerhard H. Fecher
> Institut of Inorganic and Analytical Chemistry
> Johannes Gutenberg - University
> 55099 Mainz
> and
> Max Planck Institute for Chemical Physics of Solids
> 01187 Dresden
> ________________________________________
> Von: Wien [wien-bounces at zeus.theochem.tuwien.ac.at] im Auftrag von Jaroslav Hamrle [hamrle at karlov.mff.cuni.cz]
> Gesendet: Sonntag, 26. November 2017 12:12
> An: wien at zeus.theochem.tuwien.ac.at
> Betreff: Re: [Wien] different MLD for bcc structure for magnetic equivalent directions M001, M010 and M100
>
> Hi Gerhard,
>
> I know that due to SO, the electronic structure calculated for 100, 010
> and 001 magnetization directions are different.
>
> The problem I have is following:
> I have three calculated electronic structures of bcc Fe, with
> magnetizations along 001, 010 and 100.
> Then, for any cubic structure, the permittivity tensor elements (ep_ij)
> with the same relations with respect to the magnetization should be
> equal in all three calculated structures.
>
> For example,
> symmetry clearly states that diagonal permittivity elements parallel to
> magnetization direction must equal
> ep_xx (for M=100) = ep_yy (for M=010) = ep_zz (for M=001).
>
> My problem is, that for calculated bcc Fe they do not equal.
> More specifically, they do not equal solely for bcc structures in
> wien2k, with disagreement upto 1%.
> For simple cubic and fcc structures they do equal, with tiny
> disagreement upto 0.01%
>
> Any help how to overcome this would be very helpful
>
> Thank you and with my best regards
>
> Jaroslav
>
>
>
>
> On 25/11/17 14:13, Fecher, Gerhard wrote:
>> Hi Jaroslav,
>>
>> with SO, 001 is not equivalent to 001 or 010, if the magnetisation is along 001
>> this you see easily from the changed symmetry after initializing SO (symmetso)
>>
>> regards from Dresden
>>
>> Ciao
>> Gerhard
>>
>> DEEP THOUGHT in D. Adams; Hitchhikers Guide to the Galaxy:
>> "I think the problem, to be quite honest with you,
>> is that you have never actually known what the question is."
>>
>> ====================================
>> Dr. Gerhard H. Fecher
>> Institut of Inorganic and Analytical Chemistry
>> Johannes Gutenberg - University
>> 55099 Mainz
>> and
>> Max Planck Institute for Chemical Physics of Solids
>> 01187 Dresden
>> ________________________________________
>> Von: Wien [wien-bounces at zeus.theochem.tuwien.ac.at] im Auftrag von Jaroslav Hamrle [hamrle at karlov.mff.cuni.cz]
>> Gesendet: Freitag, 24. November 2017 16:36
>> An: wien at zeus.theochem.tuwien.ac.at
>> Betreff: [Wien] different MLD for bcc structure for magnetic equivalent directions M001, M010 and M100
>>
>> Dear colleagues,
>>
>>
>> We have found non-physical asymmetry related with equivalent magnetization
>> directions, when calculating electronic structure for bcc Fe:
>>
>> We want to calculate magnetic linear dichroism, MLD, defined as a
>> difference between diagonal permittivity element being parallel,
>> perpendicular to direction of magnetization, respectively.
>>
>> MLD=epzz - (epxx+epyy)/2 for M001
>>
>> MLD=epyy - (epxx+epzz)/2 for M010
>>
>> MLD=epxx - (epyy+epzz)/2 for M100
>>
>>
>> Obviously, MLD calculated for different equivalent magnetization
>> directions should
>> be identical. But they are not, MLD calculated for 001 is different to
>> MLD calculated for 010 and 100 (MLD for 010 and 100 are identical).
>>
>> In most cases, we used k-mesh 30x30x30, exgange LDA (choice 5), with
>> convergence criteria
>>
>> runsp_lapw -so -cc 0.000001 -ec 0.0000001 -s lapw1
>>
>> and the convergence was reached.
>>
>> * We tested this asymmetry also for fcc structures (Ni, Co, Co2MnSi). We
>> also
>> tested simple cubic structure (bcc Fe, defined as a simple cubic
>> structure with two Fe atoms). In all those cases, the asymmetry
>> disappears. On the other hand, it also appeared also in bcc Ni.
>> Hence, the asymmetry seems to be specifically related with
>> bcc structure.
>>
>> * this asymmetry can be observed already in energy levels (files
>> case.energysoup). Hence, we think, the asymmetry is not a feature of
>> optics.
>> Namely, there is a very good agreement for energies for M010 and M100
>> (in example below difference is below 2e-7Ry), but much bigger
>> difference between energies for M001 and (M010,M100) (in example below
>> max. difference is 18e-6 Ry for band 5). Therefore it seems
>> that this problem arises in either lapw0 or lapw1 for bcc structure.
>>
>> To demonstrate the difference, we show energy levels for the first
>> k-point (in vicinity of the Gamma point shifted in 111 direction from
>> the Gamma point):
>>
>> Fe30M001:
>>
>> 0.333333333333E-01 0.333333333333E-01 0.333333333333E-01 1 55
>> 18 8.0
>> 1 -3.4390104377017581
>> 2 -3.4064979309023942
>> 3 -3.3508627657180750
>> 4 -3.2276472567243979
>> 5 -3.1955089683446780
>> 6 -3.1702455400854954
>> 7 -7.1658179115217727E-002
>> 8 -4.3723732810772589E-002
>> 9 0.37296762299903474
>> 10 0.37521967189559313
>>
>> Fe30M010:
>>
>> 0.333333333333E-01 0.333333333333E-01 0.333333333333E-01 1 55
>> 18 8.0
>> 1 -3.4390110394480322
>> 2 -3.4064968725403300
>> 3 -3.3508644682352022
>> 4 -3.2276486274720977
>> 5 -3.1954902103327028
>> 6 -3.1702472318057655
>> 7 -7.1659013996950252E-002
>> 8 -4.3723316415832839E-002
>> 9 0.37296632778787425
>> 10 0.37521816821120640
>> Fe30M100:
>>
>> 0.333333333333E-01 0.333333333333E-01 0.333333333333E-01 1 55
>> 18 8.0
>> 1 -3.4390109925234049
>> 2 -3.4064968346346225
>> 3 -3.3508643700301919
>> 4 -3.2276485335559135
>> 5 -3.1954901707639891
>> 6 -3.1702471600962974
>> 7 -7.1658839213425571E-002
>> 8 -4.3723135315494835E-002
>> 9 0.37296642179994044
>> 10 0.37521826479385562
>>
>> The difference in energy is (in micro-Ry):
>>
>> left column E(001)-E(100), right column E(010)-E(100)
>>
>> 1 0.5548 -0.0469
>> 2 -1.0963 -0.0379
>> 3 1.6043 -0.0982
>> 4 1.2768 -0.0939
>> 5 -18.7976 -0.0396
>> 6 1.6200 -0.0717
>> 7 0.6601 -0.1748
>> 8 -0.5975 -0.1811
>> 9 1.2012 -0.0940
>> 10 1.4071 -0.0966
>>
>> clearly, energies for M001 are different from those for M010 and M100.
>>
>> * We checked also similar calculation by elk code. Here the
>> asymmetry in optical spectra is not present.
>> On the other hand, it is presented and equals in all wien2k versions 14-17.
>> Similar asymmetry is also present when testing equivalent directions of
>> types 110 and 111 directions in bcc Fe.
>>
>> * calculations were done for k-point mesh 30x30x30, but the same
>> symmetry/asymmetry appears from k-mesh 10x10x10 to mesh 40x40x40. With
>> increasing k-mesh density, the asymmetry somewhat decreases. All other
>> parameters to calculate bcc Fe were default parameters.
>>
>> Any help how to remove this equivalent-magnetization-direction asymmetry
>> is very welcome.
>>
>> With my best regards
>>
>> Jaroslav Hamrle
>> Ondřej Stejskal
>>
>>
>> PS: We attach some spectral dependences of MLD on bcc Fe related to
>> previous text:
>>
>> http://alma.karlov.mff.cuni.cz/hamrle/w2kfig/MLD_Fe30.pdf
>> MLD calculated for Fe30 (meaning bcc Fe with k-mesh 30x30x30), showing
>> unphysical optical anisotropy for equivalent magnetization direction.
>> Particularly notice peak around 4.8 eV, which looks artificial and has
>> opposite sign for M001 and (M010, M100).
>>
>> http://alma.karlov.mff.cuni.cz/hamrle/w2kfig/MLD_Fe46.pdf
>> MLD on Fe46 (notice, peak at 4.8eV has smaller amplitude)
>>
>> http://alma.karlov.mff.cuni.cz/hamrle/w2kfig/MLD_Fe30-as_simple_cubic.pdf
>> MLD on Fe30, where bcc Fe is calculated as simple cubic structure
>> containing two Fe
>> atoms. In this case, the asymmetry disappears.
>>
>> http://alma.karlov.mff.cuni.cz/hamrle/w2kfig/MLD_Fe30-elk.pdf
>> To compare, MLD calculated by code elk does not provide previously
>> discussed
>> anisotropy.
>>
>> http://alma.karlov.mff.cuni.cz/hamrle/w2kfig/MLD_Fe_compareall.pdf
>> Figure showing all previously mentioned MLD together.
>>
>> details of calculations can be found:
>> http://alma.karlov.mff.cuni.cz/hamrle/w2kfig/Fe30M001
>> http://alma.karlov.mff.cuni.cz/hamrle/w2kfig/Fe30M100
>>
>>
>> PSS: there is a small bug in script 'x join_vectorfiles -so -up'
>> The script requires file case.in1c, which is not created and not needed for
>> all other calculations.
>> Anyway, 'cp case.in1 case.in1c' solves the problem.
>>
>> --
>> ------------------------------------------------------------------
>> Mgr. Jaroslav Hamrle, Ph.D.
>> Institute of Physics, room F232
>> Faculty of Mathematics and Physics
>> Charles University
>> Ke Karlovu 5
>> 121 16 Prague
>> Czech Republic
>>
>> tel: +420-95155 1340
>> email: hamrle at karlov.mff.cuni.cz
>> ------------------------------------------------------------------
>>
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>
>
> --
> ------------------------------------------------------------------
> Mgr. Jaroslav Hamrle, Ph.D.
> Institute of Physics, room F232
> Faculty of Mathematics and Physics
> Charles University
> Ke Karlovu 5
> 121 16 Prague
> Czech Republic
>
> tel: +420-95155 1340
> email: hamrle at karlov.mff.cuni.cz
> ------------------------------------------------------------------
>
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