[Wien] proper k-points for Nd
Laurence Marks
L-marks at northwestern.edu
Mon Jan 21 14:15:15 CET 2019
"Honest disagreement is often a good sign of progress" -- Mahatma Ghandi
I am not offended that Peter does not agree with my view about noise.....😀
_____
Professor Laurence Marks
"Research is to see what everybody else has seen, and to think what nobody
else has thought", Albert Szent-Gyorgi
www.numis.northwestern.edu
On Sun, Jan 20, 2019, 12:01 Peter Blaha <pblaha at theochem.tuwien.ac.at wrote:
> I disagree with Lauries point: Eventually I want to do even an
> "unphysical" calculation, of course it might be you have to pay a price
> for it, because this unphysical model as eg. a spike in the DOS at EF.
> And mixer should lead to convergence, but sometimes has problems
> (Lauries mixer is still one of the big advantages of WIEN2k. I know
> other codes, which would not be able to converge a 5f system at all).
>
> In any case, put a HDLO (5f) and increase LVNS=6 first.
>
> Most importantly: why are you starting from scratch when doing the
> k-mesh tests. This is very error prone and in particular burns cpu-hours
> completely unnecessarily.
>
> One of my main "advises" is always: do an init_lapw only ONCE ! (except
> you have to change spheres).
>
> You will get much better internal convergence when you continue using
> the previous calculation:
>
> loop:
> runsp ....
> save XXX-k-points
> x kgen (increase the mesh always at least by a factor of 2 (maybe even 4).
> goto loop
>
> I'm not so much surprised about the k-mesh for a magnetic 5d-element
> calculation. I start with 10000 k-points for every metallic spd-element
> and test it with 50000 k. You may need 100 000 or even more. (optics for
> fcc Al is not fully converged with 1 000 000 k-points !). It does not
> cost much cpu, since you should start with a nearly converged calculation.
>
> Your :DIS is still quite large, try to bring it below 0.0001
>
> You can try TEMPS 0.002 as Laurence advised. This will most likely
> improve convergence, but most likely also reduce MMT a little bit, which
> is ok when you compare with room temp experiments, but not for 4k
> measurements ...
>
>
>
> Am 20.01.2019 um 17:50 schrieb Laurence Marks:
> > Sorry Fabien, I am dubious that k-points is the issue, I suspect a bad
> > model.
> >
> > Let me explain, repeating some things I have said before or are in the
> > mixer notes albeit perhaps buried.
> >
> > An "easy" assumption that many people make is that dft problems are well
> > posed, so have "simple" fixed-point solutions. In fact this is not true.
> > In reality dft problems have stacks of numerical issues which leads to
> > "noise". You can think about this in terms of finding the minimum of
> > "F(x) = x*x + Constant*Noise(x)" where Noise(x) is some randomly
> > generated noise. The larger Constant is, the larger the deviation is
> > from x=0 of the apparent minimum. Averaging over more k-points may
> > reduce Constant, but often in my experience does relatively little.
> >
> > A symptom of noise is poor convergence -- which is clearly what is
> > occurring here.
> >
> > If you improve the convergence rate you will reduce the noise. Some
> > suggestions:
> >
> > 1) Use HDLO and reduce RMT
> > 2) Reduce RMT and use HDLO
> > 3) Larger LM (e.g. 8)
> > 4) Larger gmax in case.in2 (e.g. 16)
> > 5) Use TEMPS 0.0018 (room temperature)
> > 6) Peter's suggestions
> >
> > On Sun, Jan 20, 2019 at 10:27 AM tran at theochem.tuwien.ac.at
> > <mailto:tran at theochem.tuwien.ac.at> <tran at theochem.tuwien.ac.at
> > <mailto:tran at theochem.tuwien.ac.at>> wrote:
> >
> > Hi,
> >
> > If not too expensive, you could try more k-points (20000 and 25000)
> > to see if the fluctuations persist.
> >
> > Questions: how many atoms in the unit cell? Are you optimizing the
> > position of atoms?
> >
> > F. Tran
> >
> > On Sunday 2019-01-20 17:17, Victor Zenou wrote:
> >
> > >Date: Sun, 20 Jan 2019 17:17:55
> > >From: Victor Zenou <zanov at post.bgu.ac.il
> > <mailto:zanov at post.bgu.ac.il>>
> > >Reply-To: A Mailing list for WIEN2k users
> > <wien at zeus.theochem.tuwien.ac.at
> > <mailto:wien at zeus.theochem.tuwien.ac.at>>
> > >To: A Mailing list for WIEN2k users
> > <wien at zeus.theochem.tuwien.ac.at
> > <mailto:wien at zeus.theochem.tuwien.ac.at>>
> > >Subject: Re: [Wien] proper k-points for Nd
> > >
> > >Dear Peter, LDM and wien2k users
> > >I did some more calculation with energy and CHARGE convergence
> > criteria
> > >equal to 10^-4 Ryd and 10^-3, respectively. The energy usually
> > converged to
> > >1*10-5 or even 1*10^-6. Still I get energy fluctuation up to
> > 4*10-2 Ryd
> > >(please see below)
> > >I didn't check AFM yet, but this is not the point. The point is to
> get
> > >"stable" calculation for optimal k-points.
> > >I have to say that for each calculation I totally aresed all file
> > except
> > >case.struc.
> > >Also I used all defaults as well as gmax=12, also
> > rmt(min)*kmax=8.5, for all
> > >calculations.
> > >I can repeat all calculation with smaller RMT, such as 2.5, or to
> > check
> > >HDLO.
> > >I think I will start with smaller RMT. Any comments / suggestions?
> > >Victor
> > >
> > >K-pointsIBZ E [Ryd], 10-4 CHARGE convergence CHARGE DISTANCE MMTOT
> > >3000 208 -77040.50516761 -.000504 0.000825 16.00318
> > >5000 280 -77040.48748499 -.000544 0.000758 16.68523
> > >7500 455 -77040.51668342 -.000862 0.000183 16.62547
> > >10000 540 -77040.48747210 -.000817 0.000499 16.67544
> > >15000 840 -77040.46976815 -.000216 0.001362 16.64536
> > >
> > >
> > >
> >
> >
> >
> > --
> > Professor Laurence Marks
> > "Research is to see what everybody else has seen, and to think what
> > nobody else has thought", Albert Szent-Gyorgi
> > http://www.numis.northwestern.edu <http://www.numis.northwestern.edu> ;
> > Corrosion in 4D: MURI4D.numis.northwestern.edu
> > <http://MURI4D.numis.northwestern.edu>
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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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