[Wien] [Warning message: Sum of forces not small, possible numerical issues]

[Laurence Marks]

It is more common to somewhat converge using MSR1 first, e.g. -cc 0.1,
before switching to MSR1a. However, I don't see and clear indication that
something is wrong in your output. A large value of :FCHECK is not unusual
in the early stages.

_____
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

On Fri, Apr 6, 2018, 5:49 AM Dr. K. C. Bhamu <kcbhamu85 at gmail.com> wrote:

>  Thank you Prof. Lyudmila for the inlined reply.
>
> I shall mention the optimization process: I am using  run_lapw
> ............ -it -min to relax the structure with TETRA (default), rmt 3,
> kpt 50 (4x4x2), PBE. Organometallic system (Hybrideperovskite).
>
> I am not sure whether my scf is going well or not because I do not see any
> such message.
> My main concern is about too much time (~40 minutes on 16 core) for one
> scf cycle and this warning.
>
>
> Could you please have a look at my further queries:
>
>
> 06.04.2018 10:09, Dr. K. C. Bhamu wrote:
>
>> :WARN
>>> :WARNING Sum of forces not small, possible numerical issues
>>>
>> I'd look attentively around this place in the scf.
>>
>
>
> I do not find anything in scf with this statment or part of this statment.
> Also, as per my excersie, nothing is mentioned in mailing list for such
> warnings.
>
>
>
>>
>> below is constructive output from six scf cycles:
>>>
>> All looks good, though I do not know what is :ADIST. Something connected
>> with MSR1a option.
>>
>>> :ADIST   Largest Distance  1.71E+02 mau for atom  18
>>> :ADIST   Largest Distance  1.67E+02 mau for atom  32
>>> :ADIST   Largest Distance  1.20E+02 mau for atom  32
>>> :ADIST   Largest Distance  5.87E+01 mau for atom  32
>>>
>>
> :ADIST represents the distance between atoms (Pg number 212 UG). Atom 18
> and 32 are H.  in the 12th Cycle :FGL is positive for both and is around
> ~40mRyd/au.
>
>
>>
>> Too large forces appear and movement of the atoms becomes too large.
>>
>>>         TOTAL FORCE WITH RESPECT TO THE GLOBAL COORDINATE SYSTEM:
>>> :FGL018:  18.ATOM              -228.797027515  -110.869626478
>>>
>>
>> I think that mixer is very clever program, so this possibility is taken
>> into account, and it wiil correctly treat this data.
>>
>
> results from :FGL and hence from :FCHECK is varying. In first cycle the
> total forces from :FCHECK was very small and in the 8th Cycle total forces
> are too high. The average totla force on each atom is
>
>
> results from FCHECk and FR are below (in 12th scf cycle):
> FCHECK *.scf
>
> > :FCHECK:   Sum of forces        -69.940627520    74.707201466
> 256.655266254
> > :FCHECK:   Sum of forces        -64.560329574    73.360823345
> 231.480485436
> > :FCHECK:   Sum of forces        -48.034175166    65.104093472
> 166.986223927
> > :FCHECK:   Sum of forces        -35.064695164    59.878383059
> 106.378782186
> > :FCHECK:   Sum of forces          1.658948381    44.163592598
> -28.823131541
> > :FCHECK:   Sum of forces         -1.715900623    54.670180112
> -38.208248369
> > :FCHECK:   Sum of forces        -44.599628242    84.665399276
>  80.309287437
> > :FCHECK:   Sum of forces       -104.389046420   114.231138278
> 298.688183293
> > :FCHECK:   Sum of forces       -146.872184802   138.002715039
> 506.089724144
> > :FCHECK:   Sum of forces       -139.929513824   116.740866115
> 514.542253158
> > :FCHECK:   Sum of forces        -44.458957001    53.512685999
>  90.795768329
> > :FCHECK:   Sum of forces        -21.346540908    53.389897235
>  -190.728160314
>
>
> :FR *.scf
>
> > :FRMSA: (mRyd/au) 684.75( 18)  482.59 RMS (au) 2.11E-03 MAX 3.34E-03
> :F-cond.(mRyd/au)    2.00 F
> > :FRMSA: (mRyd/au) 666.97( 18)  473.06 RMS (au) 6.32E-03 MAX 1.00E-02
> :F-cond.(mRyd/au)    2.00 F
> > :FRMSA: (mRyd/au) 620.05( 18)  446.96 RMS (au) 7.70E-03 MAX 1.22E-02
> :F-cond.(mRyd/au)    2.00 F
> > :FRMSA: (mRyd/au) 564.83( 18)  415.40 RMS (au) 2.26E-02 MAX 3.60E-02
> :F-cond.(mRyd/au)    2.00 F
> > :FRMSA: (mRyd/au) 410.77( 18)  314.76 RMS (au) 3.10E-02 MAX 5.00E-02
> :F-cond.(mRyd/au)    2.00 F
> > :FRMSA: (mRyd/au) 228.80( 18)  169.19 RMS (au) 3.10E-02 MAX 5.00E-02
> :F-cond.(mRyd/au)    2.00 F
> > :FRMSA: (mRyd/au)  65.91( 17)   47.66 RMS (au) 1.16E-02 MAX 2.21E-02
> :F-cond.(mRyd/au)    2.00 F
> > :FRMSA: (mRyd/au)  57.84(  9)   41.34 RMS (au) 9.47E-03 MAX 1.98E-02
> :F-cond.(mRyd/au)    2.00 F
> > :FRMSA: (mRyd/au)  76.92( 35)   55.05 RMS (au) 7.92E-03 MAX 2.08E-02
> :F-cond.(mRyd/au)    2.00 F
> > :FRMSA: (mRyd/au)  68.91( 21)   60.53 RMS (au) 8.58E-03 MAX 1.53E-02
> :F-cond.(mRyd/au)    2.00 F
> > :FRMSA: (mRyd/au)  59.32( 25)   53.55 RMS (au) 7.45E-03 MAX 1.32E-02
> :F-cond.(mRyd/au)    2.00 F
> > :FRMSA: (mRyd/au)  64.13( 13)   54.92 RMS (au) 6.46E-03 MAX 1.04E-02
> :F-cond.(mRyd/au)    2.00 F
>
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