[Wien] Mixer surprise when using PBE0 hybrid on-site functional
Xavier Rocquefelte
xavier.rocquefelte at univ-rennes1.fr
Mon Jan 23 08:08:11 CET 2017
Thank you Peter for your reply. I had no doubt that it was possible to
converge the calculation using such strategy. My point was that such
calculation was easy to converge starting from the scratch, directly
using PBE0 and without constraining the total magnetic moment of the
unit cell. At this moment I do not know if the problem is related to the
mixer or to the PBE0 on-site. Indeed, I can imagine that not only mixer
has changed but also PBE0 onsite compared to the WIEN2k version I was
using in 2008. I plan to do the test Fabien has proposed.
Best wishes
Xavier
Le 23/01/2017 à 07:00, Peter Blaha a écrit :
> Sorry, but I cannot reproduce this.
>
> Starting from a converged GGA+U calculation, -eece converges smoothly,
> keeps the :mmt at 8 uB and a reasonable gap of 1.6 eV and :MV goes to
> 10-4.
>
> (quick test with few k-points and rkmax only 6.5)
>
> Am 20.01.2017 um 22:16 schrieb Laurence Marks:
>> 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
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>>
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