[Pw_forum] problems with converge of geometric optimization

[Stefano de Gironcoli]

This happens when the energy landscape become noisy compared with the 
expected energy decrease in the relaxation steps.
This can happen when you are very close to the  minimum.
How large are your forces ? How tight is your force/energy threshold ?
stefano

Stephan Rix wrote:
> I am trying to calculate an H-center in CaF2, and I am having trouble with
> the geometry optimization.
> I have tried adjusting various parameters such as ion dynamics, trust
> radius, convergence tresholds, but it seems that convergence cannot be
> improved.
>
> Using bfgs I always get the following error:
>
> %%%%%%%%%%%%%%%%%%%%%%%%%%
>      from bfgs : error #         1
>      bfgs history already reset at previous step
>  %%%%%%%%%%%%%%%%%%%%%%%%%%
>
> Alternatively the electonic convergence gets extremely slow.
>
> In addition, no matter what parameters I adjust the total forces in the
> system never converge, e.g.
>      Total force =     0.026394     Total SCF correction =     0.000314
>      Total force =     0.018379     Total SCF correction =     0.000282
>      Total force =     0.018824     Total SCF correction =     0.000120
>      Total force =     0.018857     Total SCF correction =     0.000155
>      Total force =     0.020215     Total SCF correction =     0.000193
>      Total force =     0.058765     Total SCF correction =     0.000241
>      Total force =     0.016998     Total SCF correction =     0.000205
>      Total force =     0.042967     Total SCF correction =     0.000238
>      Total force =     0.106226     Total SCF correction =     0.000073
>      Total force =     0.137142     Total SCF correction =     0.000071
>      Total force =     0.109549     Total SCF correction =     0.000108
>      Total force =     0.068723     Total SCF correction =     0.000103
>      Total force =     0.076599     Total SCF correction =     0.000168
>      Total force =     0.033233     Total SCF correction =     0.000342
>      Total force =     0.026883     Total SCF correction =     0.000248
>      Total force =     0.025846     Total SCF correction =     0.000378
>      Total force =     0.025596     Total SCF correction =     0.000225
>      Total force =     0.025482     Total SCF correction =     0.000275
>      Total force =     0.025508     Total SCF correction =     0.000128
>
> I am thankful for any suggestions.
>
> Stephan Rix
> Institute for Inorganic und Analytical Chemistry
> Johannes Gutenberg-University Mainz, Germany
>
>   
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