[Pw_forum] BFGS relaxation ignoring forc_conv_thr

Paolo Giannozzi p.giannozzi at gmail.com
Wed Sep 20 14:03:01 CEST 2017


If you look carefully in the output, you will notice this:

WARNING: bfgs curvature condition failed, Theta= 0.815
Message from routine bfgs:
history already reset at previous step: stopping

This kind of problem arises when one is very close to convergence and forces
contain too much numerical noise for the minimization to be effective.
Not sure why it performs a further step.

Paolo



On Wed, Sep 20, 2017 at 9:56 AM, Leonid Kahle <leonid.kahle at epfl.ch> wrote:

> Dear all,
>
> A relaxation of a rather large system (Li21 Si3 P3 S24) is shown as
> converged even though the force convergence threshold is not reached. I
> will paste the final output below, and the full input and output are
> attached. I put a very low threshold 1D-15 to prove my point here, but also
> more sensible thresholds are ignored.
>
> As explained in the documentation, but also in this forum (
> http://qe-forge.org/pipermail/pw_forum/2004-November/076156.html )
> convergence of the relaxation is achieved when all the components of the
> force vector are smaller than forc_conv_thr (and energy criterion is met as
> well). In the example below this is obviously not the case, but bfgs is
> shown as converged without any warning.
>
> Can anyone help me find an explanation for this? I am using the parallel
> version of QE 6.1 compiled with intel compilers on an x86_64 architecture.
>
> Many thanks in advance,
>
>     Leonid Kahle
>
> --
>
> Doctoral Assistant
> EPFL STI IMX THEOS
> ME-D2 1019 (Bâtiment ME)
> Station 9
> CH-1015 Lausanne (Switzerland)
>
>
>      Forces acting on atoms (cartesian axes, Ry/au):
>
>      atom    1 type  1   force =     0.00000940    0.00000005    0.00000759
>      atom    2 type  1   force =     0.00003922   -0.00005066   -0.00003891
>      atom    3 type  1   force =    -0.00000527   -0.00001786   -0.00000047
>      atom    4 type  1   force =     0.00000695   -0.00000525   -0.00000490
>      atom    5 type  1   force =     0.00000837    0.00000136    0.00000695
>      atom    6 type  1   force =    -0.00000139    0.00000800   -0.00000768
>      atom    7 type  1   force =    -0.00000042   -0.00000074   -0.00000888
>      atom    8 type  1   force =    -0.00002354   -0.00001155   -0.00003861
>      atom    9 type  1   force =     0.00001305   -0.00001546    0.00000555
>      atom   10 type  1   force =    -0.00001756    0.00002269   -0.00001184
>      atom   11 type  1   force =    -0.00000255   -0.00001734    0.00001741
>      atom   12 type  1   force =     0.00001174    0.00001759   -0.00001735
>      atom   13 type  1   force =    -0.00000633   -0.00000979    0.00000484
>      atom   14 type  1   force =    -0.00001325    0.00001294   -0.00000493
>      atom   15 type  1   force =     0.00000782   -0.00002956   -0.00000586
>      atom   16 type  1   force =    -0.00000317    0.00001363    0.00000878
>      atom   17 type  1   force =    -0.00002203    0.00000270   -0.00000480
>      atom   18 type  1   force =    -0.00000998    0.00000531    0.00001788
>      atom   19 type  1   force =     0.00000060   -0.00000321   -0.00001756
>      atom   20 type  1   force =    -0.00000688    0.00002017    0.00000404
>      atom   21 type  1   force =    -0.00000129   -0.00000416   -0.00001532
>      atom   22 type  2   force =    -0.00000319   -0.00000167    0.00000395
>      atom   23 type  2   force =     0.00001103    0.00001040    0.00000626
>      atom   24 type  2   force =     0.00000396   -0.00000186    0.00000201
>      atom   25 type  3   force =    -0.00001044    0.00000478   -0.00000086
>      atom   26 type  3   force =    -0.00001291    0.00000415   -0.00000411
>      atom   27 type  3   force =     0.00001756   -0.00000296    0.00000913
>      atom   28 type  4   force =    -0.00001578    0.00000879    0.00000423
>      atom   29 type  4   force =    -0.00001227    0.00000946   -0.00000839
>      atom   30 type  4   force =     0.00001416    0.00001301    0.00001436
>      atom   31 type  4   force =     0.00001660   -0.00000202    0.00000659
>      atom   32 type  4   force =     0.00003452   -0.00001067    0.00001793
>      atom   33 type  4   force =     0.00000938   -0.00001056    0.00000237
>      atom   34 type  4   force =    -0.00001496   -0.00000472    0.00000305
>      atom   35 type  4   force =    -0.00001625   -0.00000739   -0.00000918
>      atom   36 type  4   force =     0.00001063    0.00001606   -0.00000310
>      atom   37 type  4   force =    -0.00000110    0.00000394   -0.00000268
>      atom   38 type  4   force =    -0.00000163    0.00000039    0.00000700
>      atom   39 type  4   force =    -0.00000066   -0.00000016    0.00000132
>      atom   40 type  4   force =    -0.00000813    0.00000603    0.00000016
>      atom   41 type  4   force =    -0.00001613    0.00000196    0.00000515
>      atom   42 type  4   force =    -0.00000014    0.00000820   -0.00000460
>      atom   43 type  4   force =     0.00000091    0.00000952    0.00001063
>      atom   44 type  4   force =     0.00000012   -0.00000246    0.00000554
>      atom   45 type  4   force =     0.00000154    0.00000256    0.00001045
>      atom   46 type  4   force =     0.00000846    0.00000608   -0.00000078
>      atom   47 type  4   force =     0.00000508   -0.00000261    0.00001345
>      atom   48 type  4   force =     0.00000340    0.00000050    0.00000619
>      atom   49 type  4   force =     0.00000354   -0.00000332    0.00000588
>      atom   50 type  4   force =    -0.00000428    0.00000637    0.00000854
>      atom   51 type  4   force =    -0.00000650   -0.00000066   -0.00000641
>
>      Total force =     0.000149     Total SCF correction =     0.000000
>
>      bfgs converged in   4 scf cycles and   3 bfgs steps
>      (criteria: energy <  1.0E-06 Ry, force <  1.0E-15 Ry/Bohr)
>
>      End of BFGS Geometry Optimization
>
>
>
>
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-- 
Paolo Giannozzi, Dip. Scienze Matematiche Informatiche e Fisiche,
Univ. Udine, via delle Scienze 208, 33100 Udine, Italy
Phone +39-0432-558216, fax +39-0432-558222
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