[Wien] proper k-points for Nd
Laurence Marks
L-marks at northwestern.edu
Tue Jan 22 20:51:58 CET 2019
Dear Viktor,
As Fabien says, two different :MMT indicates that you have two minima. The
mixer only finds local minima, in general not the global although you can
be lucky if they are close. You probably have to look at the f density
matrix which I suspect is slightly different for the two cases. Take the
density matrix into something else and look at the eigenvectors [1] -- they
are probably different (different parity or something).
[1] I have some code "somewhere" where I added this to lapw2, and I think
it is a good general diagnostic particularly for f electrons.
On Tue, Jan 22, 2019 at 1:47 PM tran at theochem.tuwien.ac.at <
tran at theochem.tuwien.ac.at> wrote:
> Hi,
>
> Maybe the two different energies with 30000 k-points correspond
> to different local minima.
>
> If not already done, then do the following:
> 1) restore the calculation with 20000 k-points (restore -f ...)
> 2) execute "x kgen" to generate the mesh with 30000 k-points
> 3) start the calculation (runsp_lapw -ec 0.0001 -cc 0.0001)
>
> FT
>
>
> On Tuesday 2019-01-22 20:34, Victor Zenou wrote:
>
> >Date: Tue, 22 Jan 2019 20:34:09
> >From: Victor Zenou <zanov at post.bgu.ac.il>
> >Reply-To: A Mailing list for WIEN2k users <
> wien at zeus.theochem.tuwien.ac.at>
> >To: A Mailing list for WIEN2k users <wien at zeus.theochem.tuwien.ac.at>
> >Subject: Re: [Wien] proper k-points for Nd
> >
> >Thanks Peter and Laurie for your advises. I hope we all stay friends
> after my finding :)
> >The reason I didn't progress with higher k-points (I guess it doesn't
> work backwards, higher k-points to lower) is that I actually tried that few
> times and it
> >worked (at other phase),but sometimes I got error message after the first
> cycle. In order to be systematic I tried to avoid that.
> >According to Peter's advice I tried again and got an error message (I
> can't recall if it was the same as previous) at lapw2 -up of the first
> cycle.
> >uplapw2.error file showed: " 'LAPW2" - semicore band-ranges too large,
> ghostbands ? ". I 've deleted that file and re- run SCF while unmarking the
> "iterative
> >diag" box and for some reason it worked. It worked another time, as I run
> 2 parallel sessions/cases with different k-points (Nd-SP and Nd-SP2).
> >I have good news and bad ones. The good news
> >20,000 k-points gave the same energy as 15,000 (ec 0.0001, cc 0.0001):
> 77040.469768(3) and 77040.469768(2), with same MMTOT (16.645,
> 16.647). :CHARGE
> >convergence -.000216 and -.000422, for 15000 and 20000 k-points!
> >
> >Now for the troubling news:
> >30,000 k-points gave something different -77040.506092(3),
> MMTOT=16.091; CHARGE convergence -.000070.
> >Running the same at different case, as I said I run 2 parallel cases
> using the same case.struc file) I got for the same 30,000
> k-points -77040.4874669(3),
> >MMTOT=16.682; CHARGE convergence -.000070.
> >It seems that using same k-points gave me two different energies. As I
> understand repeating calculation should give the same results. And if these
> two
> >calculations are the same, unless I did something stuoid, should give
> the same result. Also, the different MMTOT may suggest something wrong with
> the spin
> >polarized calculations. Maybe I should do the k-test without spin
> polarization, as I usually do.
> >I used both to try 60,000 points, and later I will follow Laurie's and
> Peter HDLOs.
> >Victor
> >
> >
> >
> >בתאריך יום א׳, 20 בינו׳ 2019 ב-20:01 מאת Peter Blaha <
> pblaha at theochem.tuwien.ac.at>:
> > 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>
> > > Partner of the CFW 100% program for gender equity,
> > >
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> >
> > > Co-Editor, Acta Cryst A
> > >
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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
> > Email: blaha at theochem.tuwien.ac.at WIEN2k:
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--
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 ; Corrosion in 4D: MURI4D.numis.northwestern.edu
Partner of the CFW 100% program for gender equity, www.cfw.org/100-percent
Co-Editor, Acta Cryst A
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