The problem of :FCHECK has two sides:

If it is big for a well converged calculation, it means that the RMTs are not well chosen.

If it gets too big during MSR1a, it means that the minimization might advance badly since the forces are too wrong, or it could also mean that minimization moves on very fast and efficiently, but you got off the Born-Oppenheimer surface a bit. So in essence sometimes even big :FCHECK can minimize efficiently.

The difference between 13.1 and 14.2 are due to two reasons, a) a "push", which I added (mixing of 0.2 for a well converged case) and b) a new version of mixer.

While I still think that overall, both, the "push" AND the "new mixer" are better, there are always counter examples and maybe the new scheme is a little bit too greedy for your particular case. If 13.1 works well, it should be ok to use this mixer.

However, you should now check if the final forces with 13.1 are really small (so that it was "justified" that the mixer switched from MSR1a to MSR1 and stopped optimizing the positions (you probably need a few more normal scf iterations to get a lower :DIS and better converged forces to get a convincing answer) - otherwise 13.1 stopped to early and was "stagnating";

or if eventually due to this push there will be some further movement of atoms and therefore convergence will take longer.

On the other hand, if you are saying that 14.2 does not converge after 100s of cycles, but 13.1 does ...?

Then stay for the moment with 13.1

Peter

On 11/30/2015 04:40 PM, Laurence Marks wrote:
Yes....and no.

In 14.2 Peter added a "Push" for the 1st iteration if :DIS is small,
some lines starting with
#check :dis of first cycle and rerun mixer with increased mixing
after the execution of mixer

This was added to avoid stagnation where it just takes a few small steps
and stops.

In your case this "disturbed" 14.2 and it is adjusting the greed down to
try and stabilize. In 13.1 this push is missing, so it starts with a
small greed and finds what it thinks might be a solution.

The next version does not have this push (it is done inside mixer), but
still needs work.

Unfortunately both cases are really bad -- :FCheck should be close to
1.0 or less, and your values indicate something really wrong. For
reasons I don't understand MSR1a does not behave well with non-centro
symmetric structures. I don't know why this is.

N.B., MSR1a is not perfect, and there are cases where it does not want
to behave well. Whenever the model is susceptible to ghostbands it is
not ideal. I am currently trying a few things, but.....

N.N.B., Peter's explanation of why :FCHECK can be large is that the
linearization of different atoms is unbalanced. Maybe he has ideas about
how to cure this, it is beyond me.


On Mon, Nov 30, 2015 at 9:00 AM, Elias Assmann <elias.assm...@gmail.com
<mailto:elias.assm...@gmail.com>> wrote:

    Hi List,

    I reply to this thread
    
<http://www.mail-archive.com/wien%40zeus.theochem.tuwien.ac.at/msg13276.html>.
    This is still about the same set of oxide calculations.

    Laurence Marks alerted me that :FCHECK (sum of forces) was large (see
    below).  This is the same over a set of similar calculations (somewhat
    different structures, GGA+U vs. plain GGA), and does not seem to get
    better even after hundreds of calculations.

    I have been using the latest Wien2k (14.2), but I did similar things
    before with 13.1 and I did not remember having this problem, at least
    to this extent.  So I compiled 13.1 (same options as 14.2) and
    switched one of my calculations to it for 10 iterations.

    Indeed, it seems that 13.1 is more “well-behaved” in this case than
    14.2 — in any case they are different.  Below, I include some output
    of the two versions, starting from the same charge density in both
    cases.

    As you can see, the two versions are the more or less the same in the
    first iteration, but diverge from there; and 13.1 seems to converge,
    in contrast to 14.2.  Also, 13.1 seems to be already satisfied with
    the structure (it switches MSR1a off), while 14.2 continues
    minimizing.  The greed (on whose smallness Prof. Marks also commented)
    is pretty similar.

    To me, that suggests that I should go on with these calculations using
    the older Wien.  Is there any reason that doing so might be “unsafe”?


             Elias


    14.2 :FCHECK:     11.008001043    12.164812176   -14.416571844
          :FCHECK:    249.814119002   264.664202568  -694.164686632
          :FCHECK:     97.292437031   103.207655853  -256.561081883
          :FCHECK:    126.184534662   136.666423509   -39.224005265
          :FCHECK:    176.349427337   188.815368048    36.914398561
          :FCHECK:     50.400659984    67.046955772    76.978472788
          :FCHECK:    -74.640170442    25.157628216   121.498217602
          :FCHECK:    -82.337983720    28.388321933   121.952351989
          :FCHECK:   -130.382154150    24.859863620   204.399962720
          :FCHECK:    -39.381668995   -31.379111345    91.507308943

    13.1 :FCHECK:     11.009473749    12.153718710   -14.482142314
          :FCHECK:     10.707248409    11.500977675   -16.514184574
          :FCHECK:     10.289877753    10.742969135   -10.026151044
          :FCHECK:      7.566779454     6.128096382    -3.725471547
          :FCHECK:      3.572302068     1.087140350     6.011501945
          :FCHECK:     -4.275691705    -7.052038873    31.588782325
          :FCHECK:     -6.385420320    -8.403344519    33.874614737
          :FCHECK:     -6.106651082    -8.096761064    35.566398852
          :FCHECK:     -5.627436387    -7.565248768    32.843232377
          :FCHECK:     -3.074299958    -4.674255384    27.987425362

    14.2 :ENE  : *WARNING** TOTAL ENERGY      -222784.46215529
          :ENE  : *WARNING** TOTAL ENERGY      -222784.46926026
          :ENE  : *WARNING** TOTAL ENERGY      -222784.46462435
          :ENE  : *WARNING** TOTAL ENERGY      -222784.46263442
          :ENE  : *WARNING** TOTAL ENERGY      -222784.46223935
          :ENE  : *WARNING** TOTAL ENERGY      -222784.46214440
          :ENE  : *WARNING** TOTAL ENERGY      -222784.46218336
          :ENE  : *WARNING** TOTAL ENERGY      -222784.46213858
          :ENE  : *WARNING** TOTAL ENERGY      -222784.46236760
          :ENE  : *WARNING** TOTAL ENERGY      -222784.46181283

    13.1 :ENE  : ********** TOTAL ENERGY      -222784.46212826
          :ENE  : ********** TOTAL ENERGY      -222784.46212374
          :ENE  : ********** TOTAL ENERGY      -222784.46212843
          :ENE  : ********** TOTAL ENERGY      -222784.46207306
          :ENE  : ********** TOTAL ENERGY      -222784.46209495
          :ENE  : ********** TOTAL ENERGY      -222784.46204241
          :ENE  : ********** TOTAL ENERGY      -222784.46199458
          :ENE  : ********** TOTAL ENERGY      -222784.46200681
          :ENE  : ********** TOTAL ENERGY      -222784.46200118
          :ENE  : ********** TOTAL ENERGY      -222784.46201120

    (It appears that the warnings come from the forces.  As mentioned
    before there is not :WAR tag.)

    14.2 :DIS  :  ( 0.0048283 for atom    7 spin 1)      0.0015628
          :DIS  :  ( 0.1175699 for atom    5 spin 1)      0.0137938
          :DIS  :  ( 0.0692919 for atom    5 spin 1)      0.0083222
          :DIS  :  ( 0.0098508 for atom    7 spin 1)      0.0017036
          :DIS  :  ( 0.0167530 for atom    5 spin 1)      0.0022822
          :DIS  :  ( 0.0278296 for atom    7 spin 1)      0.0038446
          :DIS  :  ( 0.0366785 for atom    5 spin 1)      0.0048138
          :DIS  :  ( 0.0371346 for atom    5 spin 1)      0.0047958
          :DIS  :  ( 0.0559135 for atom    5 spin 1)      0.0068198
          :DIS  :  ( 0.0157960 for atom    5 spin 1)      0.0035943

    13.1 :DIS  :  ( 0.0048362 for atom    7 spin 1)      0.0015593
          :DIS  :  ( 0.0022134 for atom   12 spin 2)      0.0012247
          :DIS  :  ( 0.0052633 for atom    5 spin 1)      0.0014252
          :DIS  :  ( 0.0015732 for atom    5 spin 1)      0.0007705
          :DIS  :  ( 0.0046946 for atom    7 spin 1)      0.0010640
          :DIS  :  ( 0.0018880 for atom    8 spin 2)      0.0011590
          :DIS  :  ( 0.0017283 for atom    5 spin 1)      0.0008169
          :DIS  :  ( 0.0009736 for atom    8 spin 2)      0.0006944
          :DIS  :  ( 0.0018888 for atom    5 spin 1)      0.0007013
          :DIS  :  ( 0.0009991 for atom    7 spin 1)      0.0003925

    14.2 :MIX  :   PRATT  REG: 1.00E-06  GREED: 0.200
          :MIX  :   PRATT  REG: 1.00E-06  GREED: 0.200  Reduce 0.25  0.20
          :MIX  :   MSE1a  REG: 1.88E-06  GREED: 0.120  Newton 1.00  0.01
          :MIX  :   MSE1a  REG: 2.17E-06  GREED: 0.083  Newton 1.00  0.01
          :MIX  :   MSE1a  REG: 3.19E-06  GREED: 0.050  Newton 1.00  0.01
          :MIX  :   MSE1a  REG: 4.08E-06  GREED: 0.034  Newton 1.00  0.03
          :MIX  :   MSE1a  REG: 5.17E-06  GREED: 0.022  Newton 1.00  0.00
          :MIX  :   MSE1a  REG: 5.20E-06  GREED: 0.021  Newton 1.00  0.06
          :MIX  :   MSE1a  REG: 7.51E-06  GREED: 0.018  Newton 1.00  0.14
          :MIX  :   MSE1a  REG: 4.52E-06  GREED: 0.017  Newton 1.00  0.10

    13.1 :MIX  :   PRATT  REG: 1.00E-06  GREED: 0.025
          :MIX  :   MSR1a  REG: 1.00E-06  GREED: 0.030  Newton 1.00  0.03
          :MIX  :   MSE1a  REG: 1.59E-06  GREED: 0.030  Newton 1.00  0.18
          :MIX  :   MSE1a  REG: 2.61E-06  GREED: 0.042  Newton 1.00  0.29
          :MIX  :   MSE1a  REG: 3.72E-06  GREED: 0.057  Newton 1.00  0.54
          :MIX  :   MSE1a  REG: 3.58E-06  GREED: 0.093  Newton 1.00  0.46
          :MIX  :   PRATT  REG: 1.00E-06  GREED: 0.025
          :MIX  :   MSR1   REG: 1.00E-06  GREED: 0.050  Newton 1.00  0.05
          :MIX  :   MSE1   REG: 1.60E-06  GREED: 0.050  Newton 1.00  0.22
          :MIX  :   MSE1   REG: 2.41E-06  GREED: 0.055  Newton 1.00  0.40

    On 11/03/2015 02:47 PM, Laurence Marks wrote:
     > I am not sure exactly what the problem(s) were, but from you
    case.scf it
     > was "right" that there were Warnings
     >
     > a) :FCHECK (bottom of case.scf) was large. This is the sum of all the
     > forces, and should be small. Particularly for cells without inversion
     > one can get bad, highly asymmetric densities in which case MSR1a can
     > have problems.
     >
     > b) The greed is small. Too small a value can be as bad as too
    large. I
     > have struggled with this for years and failed to find a strong ansatz
     > for this, although I believe the next release of the mixer will
    be better.



    --
    Elias Assmann
    Institute of Theoretical and Computational Physics
    TU Graz                   ⟨https://itp.tugraz.at/⟩





--
Professor Laurence Marks
Department of Materials Science and Engineering
Northwestern University
www.numis.northwestern.edu <http://www.numis.northwestern.edu>
Corrosion in 4D: MURI4D.numis.northwestern.edu
<http://MURI4D.numis.northwestern.edu>
Co-Editor, Acta Cryst A
"Research is to see what everybody else has seen, and to think what
nobody else has thought"
Albert Szent-Gyorgi


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