[Wien] How to do a spin polarized calculation from a non spin spolarized calculation ?

[Laurence Marks]

Rather than removing the Broyden files, an alternative is to inject a Pratt
step. To do this, look at the values of the GREED (i.e. grep :MIX case.scf)
and chose a moderately small number, e.g. 0.025. Then do "echo 0.025 >
.pratt". This injects a single step without losing the memory.

For reference, a reason why convergence can be poor is because the steps
that have been taken are either too large or too small for good Simplex
gradients. Injecting a single step along the residue direction is a gentler
approach than removing the history completely.

On Mon, Nov 18, 2019 at 2:15 PM Peter Blaha <pblaha at theochem.tuwien.ac.at>
wrote:

> I don't know from where you have this recipe, but it does not work. From
> a non-spinpolarized calc. you cannot go to a spin-polarized solution.
>
> For difficult spin-polarized calculations you may need more than the 40
> default iterations. Continue and specify more iterations (-i 80 or more).
>
> Sometimes, if the mixer really gets confused, it might be necessary to
> trick it. If the solutions oscillate, do 1-2 PRATT cycles (rm *.broy*)
> or try MSEC3 instead of MSR1.
>
> Most of the time, a better k-mesh (more points) and/or Temperature
> broadening (TEMP/S with max 0.010) may help. But don't forget at the end
> to reduce the broadening again (0.002 ~ Room temperature)
>
> If you want to "help" mixer to reach convergence in a really difficult
> situation (and come out of a unclear situation) you could use the FSM
> method.  Suppose you do a supercell of 200 Fe atoms (this would probably
> be a "difficult" system), you can estimate the total spin as 200*2.2 and
> do a    runfsm -m 440.
>
>
> Am 18.11.2019 um 18:02 schrieb Abderrahmane Reggad:
> > Hello wien users
> >
> > When we encounter a problem of converge in a spin polarized calculation
> > there is a solution which states that we do a non spin polarized
> > calculation which is known with its faster convergence and using the new
> > densities as starting densities for a new spin polarized calculation.
> >
> > My question is how to do that ?
> >
> > Best regards
> >
> > --
> > Dr. Abderrahmane Reggad
> > Engineering Physics Laboratory
> > Faculty of Material Sciences, Ibn Khaldoun University, Tiaret, 14000,
> > Algeria
> > Tel: +213(0)561861963 - Algeria
> >
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> --
> --------------------------------------------------------------------------
> Peter BLAHA, Inst.f. Materials Chemistry, TU Vienna, A-1060 Vienna
> Phone: +43-1-58801-165300             FAX: +43-1-58801-165982
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-- 
Professor Laurence Marks
Department of Materials Science and Engineering
Northwestern University
www.numis.northwestern.edu
Corrosion in 4D: www.numis.northwestern.edu/MURI
Co-Editor, Acta Cryst A
"Research is to see what everybody else has seen, and to think what nobody
else has thought"
Albert Szent-Gyorgi
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