[Pw_forum] Fwd: Noncollinear magnetization and spin orbit coupling problem on Energy convergence and Spin

[Giovani Faccin]

By the way, just correcting one thing: the k-point convergence you should
test on a periodic material sample, not on the isolated dimers. So items 1
and 3 can be tested on any system, periodic or not, while item 2 needs a
bulk or slab to be tested. By doing those tests on toy systems, the idea is
to get a better starting parameter setup, from the convergence point of
view, before testing the big system later. Anyway, since the slab is large,
you probably won't need to go too high on k-point values.

Hope it helps.

Regards,

Giovani


---------- Forwarded message ----------
From: Giovani Faccin <faccin.giovani at gmail.com>
Date: 2014-03-02 18:17 GMT-04:00
Subject: Re: [Pw_forum] Noncollinear magnetization and spin orbit coupling
problem on Energy convergence and Spin
To: PWSCF Forum <pw_forum at pwscf.org>


Dear Xiao,

I'm didn't catch the entire discussion thread, so first of all, sorry if
this might be redundant. Anyway, looking at your input file, three things
came to mind:

1 - Small cutoff radius (30 Ry / 300 Ry)
2 - Small number of k-points. (3 3 1)
3 - Perhaps, a too large degauss value (0.05 Ry).

So, just in case, I should ask: are those values well converged for all
those pseudopotentials you are using?

If unsure, one simple way to test it is to evaluate dimers of each material
(O2, Se2 etc.) and run scf tests varying those 3 parameters, to see how the
total energy behaves. Once you find a setup that works on all the elements
simultaneously, then you can come back to the full system, using this setup
as a starting point for further tests. As a hint, for some  magnetic
phenomena a precision of at least 10^-2 Ry in total energy convergence can
be relevant.

Regards,

-- 
Giovani M. Faccin <https://sites.google.com/site/faccingiovani/>
CPPP / UFMS - Brazil



-- 
Giovani M. Faccin <https://sites.google.com/site/faccingiovani/>
CPPP / UFMS
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