[Pw_forum] fixed magnetization to check stoner criterion

[Rene Wirnata]

Thank you for this hint Dr. Rebaza. You are absolutely right using the
total_magnetization flag for this system.
Neither non-collinear magnetization nor spin-orbit coupling is required
for my calculations, therefore
we can set nspin to 2 and fix only the magnitude of the magnetization,
because without spin orbit,
no direction is preferred.

The &cell and &ions namelists are simply set in my 'master template
file' I use for all calculations on a
system. In case of a simple scf calculation, these cards are ignored
anyways...so I just keep them in the
input file.

Thanks again for the paper, they did exactly what I needed to know :)

In case anyone is interested in more information on that stoner stuff,
this is the book you want to have a look at:
http://link.springer.com/book/10.1007%2F978-3-642-82499-9


Best regards from Germany,

Rene Wirnata

Am 7/24/2014 12:00 AM, schrieb Arles V. Gil Rebaza:
> Hi Rene Wirnata, I think that you must to obtaind the total energy
> (Et) vs total magnetic moment (MT) and fot with a curve of 4to order
> (Ax^4 + Bx^2+C). The coeficient of the  cuadratic term (B) is related
> with the stones parameter. So, to get this curve you must to do scf
> calculations for each MT value using fixed spin calculations (use
> "total_magnetization" in QE).
> Maybe this paper could help
> you: http://journals.aps.org/prb/abstract/10.1103/PhysRevB.74.014416
>
> In your input file, if you are doing SCF calculation, why you use 
>  &cell
>     press_conv_thr = 0.1
> these tag is for vc-relax calculations
>
>  why ...
> &electrons
>     mixing_mode='TF'
> try with the default setting "plain"
>
> nspin       = 4  .... are you performing non-collinear calculations.??
>
> I hope I've helped 
>
> Best.
>
> Dr. Arles V. Gil Rebaza
> Instituto de Física La Plata
> Argentina.
>
>
>
>
>
> 2014-07-23 11:44 GMT-03:00 Rene Wirnata <renewirnata at gmx.de
> <mailto:renewirnata at gmx.de>>:
>
>     Hi @ all!
>
>     Unfortunately I couldn't find anything on this topic with google,
>     so I have to ask here:
>
>     Currently, I try to test the stoner criterion for the Al5Fe2
>     system and therefore I set
>     */"constrained_magnetization = 'total', fixed_magnetization(3) =
>     i, lambda = 1.d0"/*
>     where i = {0.0 .. 2.2}. This setup will first of all tell me in
>     the output file that I have to
>     set *nspin = 4*, setting it to sth. else won't work, I already
>     tested. Now the problem is
>     none of these calculations will converge doing max. 100
>     iterations. Even if I set
>     *lambda =**0.1*, there's no big change as you can see in the
>     output files.
>
>     Further, the documentation tells me:
>     a) for LDA potentials use *tot_magnetization*, --> mine is GGA, so
>     stay with *contrained_mag**...*
>     b) if I used *tot_magnetization* then I shouldn't use
>     *starting_magnetization*, so maybe this
>     could help? But to what number should I set it, because for every
>     atom in my cell it will
>     become different during the iterations.
>
>     Unfortunately, no one in my institut ever did such calculations
>     before and I am
>     myself still a total beginner with pwscf, so pls excuse if the
>     question is stupid :).
>
>     Thanks a lot in advance!
>
>     Best regards from Germany,
>
>     Rene Wirnata
>
>
>     -- 
>     Attachements see here:
>     https://www.dropbox.com/sh/zxr7phpxdngo0zl/AABWJEqMog7eawxvTec9FH7pa
>
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>
>
> -- 
> ###--------->   Arles V.   <---------###
>
>
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