[Pw_forum] SCF correction compared to forces is too large.

[Sonu Kumar]

Dear Prof. Guido Fratesi

Thank you very much for your reply.

I also take this opportunity to wish you
all a merry Christmas. !!

Regards,
sonu

==========================================
Sonu Kumar
Phd Student,Physics Department
Indian Institute of Technology ,Delhi-110016, India
https://profiles.google.com/1009ukumar
web:-http://www.iitd.ac.in/
==========================================



On Fri, Dec 23, 2011 at 2:33 PM, Guido Fratesi <fratesi at mater.unimib.it> wrote:
> Dear Sonu Kumar,
>
> in general this warning means that the forces you are computing are not
> very accurate, BUT relatively to their absolute value.
>  Here, the absolute value of the force is very small so even a tiny SCF
> correction appears large, so the warning. You can safely ignore it
> because there's no harm in missing forces by 25% when they are
> negligible. Notice that how large a 'negligible' force depends on you
> and the system under investigation.
>  In my experience this situation is not unfrequent at the end of the
> optimization process. I expect you could get accurate results in terms
> of coordinates and total energy also with a bit larger scf threshold
> (1d-8?).
>
> Guido
>
> Il 12/23/2011 05:47 AM, Sonu Kumar ha scritto:
>> Dear all QE users,
>>
>> During optimization, i got following message:
>>
>>   Total force =     0.000004     Total SCF correction =     0.000001
>>   SCF correction compared to forces is too large, reduce conv_thr
>>
>> Total force is  less than total scf correction. Then why the message
>> is contradicting? I used  conv threshold for scf=1.0d-10.
>>
>> Thank you.
>>
>> regards,
>>
>> ==========================================
>> Sonu Kumar
>> Phd Student,Physics Department
>> Indian Institute of Technology ,Delhi-110016, India
>> web:-http://www.iitd.ac.in/
>> ==========================================
>> _______________________________________________
>> Pw_forum mailing list
>> Pw_forum at pwscf.org
>> http://www.democritos.it/mailman/listinfo/pw_forum
>>
>
> --
> Guido Fratesi
>
> Dipartimento di Scienza dei Materiali
> Universita` degli Studi di Milano-Bicocca
> via Cozzi 53, 20125 Milano, Italy
> _______________________________________________
> Pw_forum mailing list
> Pw_forum at pwscf.org
> http://www.democritos.it/mailman/listinfo/pw_forum