[Wien] Mixer surprise when using PBE0 hybrid on-site functional
Xavier Rocquefelte
xavier.rocquefelte at univ-rennes1.fr
Sat Jan 21 08:28:47 CET 2017
Dear Laurence
Thank you so much for your detailled replies.
I agree that something curious happens here. In particular, my surprise
is why the convergency is fast and leads to a ferromagnetic solution in
GGA+U and not in PBE0 on-site hybrid. These two schemes must be quite
similar in the way they correct the GGA eigenvalues. I will continue to
test the different options of mixer. Just one question, I didn't know
the :MV keyword. Where should I find it?
Best Regards
Xavier
Le 20/01/2017 à 22:16, Laurence Marks a écrit :
> I can provide some partial responses, although there are also some
> things that I don't understand. Some of this (maybe most) is not the
> mixer but in other parts of Wien2k.
>
> First, the old (2008) version is there if you use MSEC1, but I have
> not tested it and it may fail. Better is to use MSEC3 which is almost
> the old version. For some classes of problems this is more stable than
> MSR1, and works better. If you are talking about the pre-multisecant
> version (BROYD) that vanished some time ago.
>
> Second, there is a nasty "feature" particularly for +U (eece) cases,
> which is partially discussed in the mixer Readme. There is no
> guarantee that a solution exists -- the KS theorem is for densities
> but U is an orbital term. It is very possible to have cases where
> there is no fixed-point solution. The older MSEC1 (maybe BROYD) could
> find a fake solution where the density was consistent but the orbital
> potential was not. The latest version is much better in avoiding them
> and going for "real" solutions rather than being trapped. For orbital
> potentials it is very important to look at :MV to check that one
> really has a self-consistent orbital potential.
>
> Third, there are cases where PBE (and all the GGA's in Wien2k that I
> have tested) give unphysical results when applied to isolated d or f
> electrons as done for -eece. I guess that the GGA functionals were not
> designed for the densities of just high L orbitals. This leads to very
> bad behavior of the mixing. I know of no way to solve this in the
> mixer, it is a structural problem. It goes away if LDA is used as the
> form for VXC in -eece.
>
> Fourth, larger problem with low symmetry (P1 in particular) can
> certainly behave badly. Part of this might be "somewhere" in Wien2k
> coding, part of it is generic to a low symmetry problem. In many cases
> these have small eigenvalues in the mixing Jacobian which are removed
> when symmetry is imposed. All one can do is use MSEC3 or some of the
> additional flags (see the mixer README) such as "SLOW".
>
> Fifth...probably exists, but I can't think of it immediately.
>
> On Fri, Jan 20, 2017 at 2:03 PM, Xavier Rocquefelte
> <xavier.rocquefelte at univ-rennes1.fr
> <mailto:xavier.rocquefelte at univ-rennes1.fr>> wrote:
>
> Dear Colleagues
>
> I did recently a calculation which has been published long time ago
> using a old WIEN2k version (in 2008).
>
> It corresponds to a spin-polarized calculation for the compound
> CuO. The
> symmetry is removed and the idea is to estimate the total energies for
> different magnetic orders to extract magnetic couplings from a mapping
> analysis. Such calculations were converging fastly without any trouble
> in 2008.
>
> Here I have started from the scratch with a case.cif file to generate
> the case.struct file and initializing the calculation in a
> standard manner.
>
> Then I wanted to have the energy related to a ferromagnetic situation
> (not the more stable). I have 8 copper sites in the unit cell I am
> using.
>
> When this calculation is done using PBE+U everything goes fine.
> However
> when PBE0 hybrid on-site functional is used we observed
> oscillations and
> the magnetic moment disappear, which is definitely not correct. It
> should be mentionned that the convergency is really bad. If we do a
> similar calculation on the cristallographic unit cell (2 copper sites
> only) the calculations converge both in PBE+U and PBE0.
>
> The convergency problems only arises for low-symmetry and high
> number of
> magnetic elements. I didn't have such problems before and I wonder
> if we
> could still use old mixer scheme in such situations. Looking at the
> userguide, it seems that the mixer does not allow to do as before and
> PRATT mixer is too slow.
>
> Did you encounter similar difficulties (which were not in older WIEN2k
> versions)?
>
> Best Regards
>
> Xavier
>
> Here is the case.struct:
>
> blebleble
> P LATTICE,NONEQUIV.ATOMS: 16 1_P1
> MODE OF CALC=RELA unit=bohr
> 14.167163 6.467777 11.993298 90.000000 95.267000 90.000000
> ATOM -1: X=0.87500000 Y=0.75000000 Z=0.87500000
> MULT= 1 ISPLIT= 8
> Cu NPT= 781 R0=0.00005000 RMT= 1.9700 Z: 29.0
> LOCAL ROT MATRIX: 1.0000000 0.0000000 0.0000000
> 0.0000000 1.0000000 0.0000000
> 0.0000000 0.0000000 1.0000000
> ATOM -2: X=0.12500000 Y=0.25000000 Z=0.62500000
> MULT= 1 ISPLIT= 8
> Cu NPT= 781 R0=0.00005000 RMT= 1.9700 Z: 29.0
> LOCAL ROT MATRIX: 1.0000000 0.0000000 0.0000000
> 0.0000000 1.0000000 0.0000000
> 0.0000000 0.0000000 1.0000000
> ATOM -3: X=0.12500000 Y=0.25000000 Z=0.12500000
> MULT= 1 ISPLIT= 8
> Cu NPT= 781 R0=0.00005000 RMT= 1.9700 Z: 29.0
> LOCAL ROT MATRIX: 1.0000000 0.0000000 0.0000000
> 0.0000000 1.0000000 0.0000000
> 0.0000000 0.0000000 1.0000000
> ATOM -4: X=0.87500000 Y=0.75000000 Z=0.37500000
> MULT= 1 ISPLIT= 8
> Cu NPT= 781 R0=0.00005000 RMT= 1.9700 Z: 29.0
> LOCAL ROT MATRIX: 1.0000000 0.0000000 0.0000000
> 0.0000000 1.0000000 0.0000000
> 0.0000000 0.0000000 1.0000000
> ATOM -5: X=0.62500000 Y=0.25000000 Z=0.62500000
> MULT= 1 ISPLIT= 8
> Cu NPT= 781 R0=0.00005000 RMT= 1.9700 Z: 29.0
> LOCAL ROT MATRIX: 1.0000000 0.0000000 0.0000000
> 0.0000000 1.0000000 0.0000000
> 0.0000000 0.0000000 1.0000000
> ATOM -6: X=0.37500000 Y=0.75000000 Z=0.87500000
> MULT= 1 ISPLIT= 8
> Cu NPT= 781 R0=0.00005000 RMT= 1.9700 Z: 29.0
> LOCAL ROT MATRIX: 1.0000000 0.0000000 0.0000000
> 0.0000000 1.0000000 0.0000000
> 0.0000000 0.0000000 1.0000000
> ATOM -7: X=0.37500000 Y=0.75000000 Z=0.37500000
> MULT= 1 ISPLIT= 8
> Cu NPT= 781 R0=0.00005000 RMT= 1.9700 Z: 29.0
> LOCAL ROT MATRIX: 1.0000000 0.0000000 0.0000000
> 0.0000000 1.0000000 0.0000000
> 0.0000000 0.0000000 1.0000000
> ATOM -8: X=0.62500000 Y=0.25000000 Z=0.12500000
> MULT= 1 ISPLIT= 8
> Cu NPT= 781 R0=0.00005000 RMT= 1.9700 Z: 29.0
> LOCAL ROT MATRIX: 1.0000000 0.0000000 0.0000000
> 0.0000000 1.0000000 0.0000000
> 0.0000000 0.0000000 1.0000000
> ATOM -9: X=0.87500000 Y=0.41840000 Z=0.62500000
> MULT= 1 ISPLIT= 8
> O NPT= 781 R0=0.00010000 RMT= 1.6900 Z: 8.0
> LOCAL ROT MATRIX: 1.0000000 0.0000000 0.0000000
> 0.0000000 1.0000000 0.0000000
> 0.0000000 0.0000000 1.0000000
> ATOM -10: X=0.12500000 Y=0.91840000 Z=0.87500000
> MULT= 1 ISPLIT= 8
> O NPT= 781 R0=0.00010000 RMT= 1.6900 Z: 8.0
> LOCAL ROT MATRIX: 1.0000000 0.0000000 0.0000000
> 0.0000000 1.0000000 0.0000000
> 0.0000000 0.0000000 1.0000000
> ATOM -11: X=0.12500000 Y=0.58160000 Z=0.37500000
> MULT= 1 ISPLIT= 8
> O NPT= 781 R0=0.00010000 RMT= 1.6900 Z: 8.0
> LOCAL ROT MATRIX: 1.0000000 0.0000000 0.0000000
> 0.0000000 1.0000000 0.0000000
> 0.0000000 0.0000000 1.0000000
> ATOM -12: X=0.87500000 Y=0.08160000 Z=0.12500000
> MULT= 1 ISPLIT= 8
> O NPT= 781 R0=0.00010000 RMT= 1.6900 Z: 8.0
> LOCAL ROT MATRIX: 1.0000000 0.0000000 0.0000000
> 0.0000000 1.0000000 0.0000000
> 0.0000000 0.0000000 1.0000000
> ATOM -13: X=0.62500000 Y=0.58160000 Z=0.87500000
> MULT= 1 ISPLIT= 8
> O NPT= 781 R0=0.00010000 RMT= 1.6900 Z: 8.0
> LOCAL ROT MATRIX: 1.0000000 0.0000000 0.0000000
> 0.0000000 1.0000000 0.0000000
> 0.0000000 0.0000000 1.0000000
> ATOM -14: X=0.37500000 Y=0.08160000 Z=0.62500000
> MULT= 1 ISPLIT= 8
> O NPT= 781 R0=0.00010000 RMT= 1.6900 Z: 8.0
> LOCAL ROT MATRIX: 1.0000000 0.0000000 0.0000000
> 0.0000000 1.0000000 0.0000000
> 0.0000000 0.0000000 1.0000000
> ATOM -15: X=0.37500000 Y=0.41840000 Z=0.12500000
> MULT= 1 ISPLIT= 8
> O NPT= 781 R0=0.00010000 RMT= 1.6900 Z: 8.0
> LOCAL ROT MATRIX: 1.0000000 0.0000000 0.0000000
> 0.0000000 1.0000000 0.0000000
> 0.0000000 0.0000000 1.0000000
> ATOM -16: X=0.62500000 Y=0.91840000 Z=0.37500000
> MULT= 1 ISPLIT= 8
> O NPT= 781 R0=0.00010000 RMT= 1.6900 Z: 8.0
> LOCAL ROT MATRIX: 1.0000000 0.0000000 0.0000000
> 0.0000000 1.0000000 0.0000000
> 0.0000000 0.0000000 1.0000000
> 1 NUMBER OF SYMMETRY OPERATIONS
> 1 0 0 0.00000000
> 0 1 0 0.00000000
> 0 0 1 0.00000000
> 1
>
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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 <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,
> www.cfw.org/100-percent <http://www.cfw.org/100-percent>
> Co-Editor, Acta Cryst A
>
>
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