[Wien] DOS for FSM calc - problem

[Peter Blaha]

The 2 different EF can be interpreted as an external magnetic field.

Without such a field, of course the "meaning" of an FSM calculation is 
only that it may help you to stabilize a particular magnetic solution 
(high-spin, low spin, intermediate spin) and eventually helps to find 
out which of those states is the (theoretical) ground state. Of course, 
in such cases one should test the "stability" of your solution by 
continuation with runsp and see if this state survives (and has a 
lower/higher energy than some other).

And I agree with Gerhard, if "PBE" does not work to reproduce 
experiment, one may have to resort to LDA+U or (the more expensive, but 
potentially more ab initio) hybrid-DFT method.

But be warned: PBE0 makes eg. bulk Pt metal ferromagnetic, so it is not 
always the right method.....


On 10/11/2013 12:44 PM, Fecher, Gerhard wrote:
> If you like to have a correct density of states and a magnetic moment of 6 muB as found in the experiment for Co2FeSi
> then you may better use one of the hybrid functionals e.g. PBE0
>
> about b)
> What is the meaning of two different Fermi energies ?
> I know that there was a paper published about Co2FeSi where FSM was used,
> but finally it is seen (fig 6 of that paper) that the density of states calculated by use of FSM is nonsense,
> as the low lying a1 band exhibits a very large exchange splitting (more then 1 eV)
> that is not physical for s states.
> Overall the FSM just shifts the energy scales of the majority and minority densities away from each other
> (to have more majority and less minority states) until the 6 muB are reached, but that does not have a physical reality.
>
> 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
> ________________________________________
> Von: wien-bounces at zeus.theochem.tuwien.ac.at [wien-bounces at zeus.theochem.tuwien.ac.at]" im Auftrag von "Dominik Legut [dominik.legut at vsb.cz]
> Gesendet: Freitag, 11. Oktober 2013 08:19
> An: A Mailing list for WIEN2k users
> Betreff: Re: [Wien] DOS for FSM calc - problem
>
> Thanks Prof. Blaha for comments,
>
> point a) was clear to me already before.
>
> point b) was new.
>
> Now, it it clear.  I want to have a correct DOS w.r.t. Fermi level. for up and
> dn channel. Hence I rewrote manually Fermi energy for up and
> dn channel in case.qtlup case.qtldn (after calling x lapw2 -qtl -up/dn)
>
> It seems that this trick works as I can see that tetra on line 218 is reading
> EFERM from case.qtlup/case.qtldn file.
>
>
> Hopefully this is what you meant by "introducing two Fermi energies".
>
> Best regards,
>
> Dominik Legut
>
>
>> Dne čtvrtek 10 října 2013 09:18:11 jste napsal(a): > Two remarks to the
> problems reported below:
>>
>> a) After a runfsm calculation, you do NOT have valid case.vectorup/dn
>> files (only dn), so you cannot calculate QTLs directly, but need to
>> recalculate   x lapw1 -up
>>
>> b) Of course, in many cases a FSM calculation will give you the desired
>> moment ONLY by introducing 2 different FERMI energies !.
>> This is not considered when you calculate the QTLs and thus the
>> automatic EF-settings in tetra will not be correct!
>>
>>
>>
>>
>>
>> ----------------------------------------------------------------
>> I have a trouble to calculate the DOS for FSM calculation. I have
>> converged FSM=6.0\mu_B for GGA(PBE) of Co2FeSi using Wien2k 12.1. At the
>> end I checked grep :MMTOT and had a 6\mu_B/unit cell. However, where I
>> make a plot according to UG about FSM I am getting a DOS that is similar
>> to that of pure GGA (i.e. M=5.56\mu_B). Difference of integr. of up and
>> down channels gives me 5.56 like in GGA.
>>
>> Where I could make a step aside?
>>
>> Can someone help to identify it?
>>
>> I am attaching a converged calculation, with *.int and outputting
>> *.dos1ev*.
>>
>> Thanks,
>>
>> Best regards,
>>
>> Dominik Legut
>>
>> -------------------------------------------------
>>
>> Dominik Legut, tel. +420-597 329 122
>>
>> Nanotechnology Centre and IT4Innovations
>>
>> VSB University of Technology Ostrava
>>
>> 17 listopadu 15
>>
>> CZ-70833 Ostrava
>>
>> Czech Republic
>>
>> -------------------------------------------------
> --
> S pozdravem
>
> Dominik Legut
>
> -------------------------------------------------
> Dominik Legut, tel. +420-597 329 122
> Nanotechnology Centre and IT4Innovations
> VSB University of Technology Ostrava
> 17 listopadu 15
> CZ-70833 Ostrava
> Czech Republic
> -------------------------------------------------
> _______________________________________________
> Wien mailing list
> Wien at zeus.theochem.tuwien.ac.at
> http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien
> SEARCH the MAILING-LIST at:  http://www.mail-archive.com/wien@zeus.theochem.tuwien.ac.at/index.html
>

-- 

                                       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/theochem/
--------------------------------------------------------------------------