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

Laurence Marks L-marks at northwestern.edu
Fri Apr 6 15:28:32 CEST 2018


My opinion.

Use *TEMPS* not *TEMP*. It won't matter much but I consider it more
rigorous. I normally use TEMPS  0.0018 which is room temperature. (I have
rarely seen large values help, I think that is a relic of old mixers.)

:FCHECK can be positive or negative, that does not matter. It should become
small as the forces and charge density converges. (Of course using a
centro-symmetric structure is better if possible.)

On Fri, Apr 6, 2018 at 8:18 AM, Dr. K. C. Bhamu <kcbhamu85 at gmail.com> wrote:

>
> Thanks Prof. Peter,
>
> There are some more queries.
>
> For the present system, ~3-3.5 is best-reported rmt.  Prof. Oleg reported
> 3.5 in his Sci. Rep. paper while in one of my earlier case I used 3 which
> was fine to me. So I kept rmt 3 in the present case.
>
> Yes, I  am using 16 core here.
>
> The strategy told by Prof. Lawrence is similar to yours. So definitely, I
> will run a crude convergence before structure optimization (after getting
> the final conclusion from present scf).
>
> What should I do if :FCHECK are negative? can it be or I should worry? I
> see :FCHECK is oscillating (see below).
>
>  In all test case of the present calculation, should increase LVNS from 4
> to 6 in case.in1(c)? or in final. I never tested it so do not know how it
> will affect the calculation.
>
>
>
> *Can I use TEMP 0.002 instead of TETRA? *
> If I am not wrong, them in case of MSR1a the :FOR will work after final
> 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
> :FCHECK:   Sum of forces        -62.241454337    85.443479855
> -99.767209873
> :FCHECK:   Sum of forces        -33.315408954    60.975140246
> 18.014683106
> :FCHECK:   Sum of forces         22.819602947   -13.223462643
> 257.628716681
> :FCHECK:   Sum of forces        -30.714958092    40.048468655
> 258.360331510
>
>
>
> regards
>
> Bhamu
>
> On Fri, Apr 6, 2018 at 5:01 PM, Peter Blaha <pblaha at theochem.tuwien.ac.at>
> wrote:
>
>> To be efficient you should:
>>
>> Start with an RKmax 0f 2.5 or 3.75 instead of 3 (check later)
>>
>> Reduce k-points to 2x2x1 (check later).
>>
>> run -it -p  -fc 10   # crude convergence before structure optimization !
>>                      # -p because you want to use the 16 cores. You have
>> to define a suitable .machines file ! Are you sure you are using more than
>> 1 core right now ???
>>
>> Once this is converged, check forces (are they so big that you need to
>> relax ? and :FCHECK. If :FCHECK is still large at the end, probalby your
>> spheres are not ok. And in addition you should increase LVNS from 4 to 6 in
>> case.in1(c).
>>
>> save, and only then start a run -p -it -min
>>
>>
>> On 04/06/2018 12:49 PM, Dr. K. C. Bhamu 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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>>>
>> --
>>
>>                                       P.Blaha
>> ------------------------------------------------------------
>> --------------
>> Peter BLAHA, Inst.f. Materials Chemistry, TU Vienna, A-1060 Vienna
>> Phone: +43-1-58801-165300             FAX: +43-1-58801-165982
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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 ; Corrosion in 4D: MURI4D.numis.northwestern.edu
Partner of the CFW 100% program for gender equity, www.cfw.org/100-percent
Co-Editor, Acta Cryst A
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