[Pw_forum] ion relaxation

[Giovanni Cantele]

mohaddeseh abbasnejad wrote:
> Dear all,
>  
> After doing ion relaxation for Si, I received such an error and the 
> program stopped:
> "convergence NOT achieved after 100 iterations: stopping"
> Would you please help me?
> Thanks in advance.
>  
> Yours,
> Mohaddeseh
>
> -- 
> ---------------------------------------------------------
>
> Mohaddeseh Abbasnejad,
> Room No. 323, Department of Physics,
> University of Tehran, North Karegar Ave.,
> Tehran, P.O. Box: 14395-547- IRAN
> Tel. No.: +98 21 6111 8634  & Fax No.: +98 21 8800 4781
> Cellphone: +989177317514
> E-Mail:     m.abbasnejad at gmail.com <mailto:m.abbasnejad at gmail.com>
> Website:  http://physics.ut.ac.ir
>
> ---------------------------------------------------------
>
                                                                        
                                                                        
                                                                        
                            By default the relaxation run stops either 
if convergence has been achieved or  if the total number of ionic + 
electronics steps exceeds nstep.

Usually, the default nstep is sufficient to obtain convergence on ion 
relaxation.

What to do?

i) try to increase nstep, just to see if your system needs more steps to 
converge (possibly, you can restart your previous run, so you'll not 
loose what done until now!)

ii) check your starting config., if "too unphysical" or far from the 
final configuration the code might require a very large number of steps 
to converge

iii) more hints in the link below:                                     
                                                               
http://www.quantum-espresso.org/wiki/index.php/Troubleshooting_(PWscf)#structural_optimization_is_slow_or_does_not_converge


Giovanni

-- 



Dr. Giovanni Cantele 
Coherentia CNR-INFM and Dipartimento di Scienze Fisiche
Universita' di Napoli "Federico II"
Complesso Universitario di Monte S. Angelo - Ed. 6
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E-mail: giovanni.cantele at cnr.it
        giovanni.cantele at na.infn.it
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