[Pw_forum] Another SCF convergence problem

[Eyvaz Isaev]

--- Vidur Parkash <vparkash at mtu.edu> wrote:

> Thank you everybody for finding a very critical bug
> in my setup, yes The distances are actually double
> of what they're supposed to be
> 
> Will try to fix that!...another thing ....how does
> changing the number of gamma points help the system
> to converge?...and is there any thumb rule for
> choosing the number of gamma points?  

Can you please explain what do you mean "gamma
points"?
If you mean K_POINTS, then their number will not help
if atomic positions are wrong (usually poor
convergency).

Bests,
Eyvaz. 
 

> 
> Vidur
> 
> 
> 
> 
> Stefano de Gironcoli <degironc at sissa.it> wrote: This
> may not be totally relevant but ... have you checked
> that the 
> configuration you are using makes sense ?
> By visualizing it with xcrysden it appear that the
> carbon-carbon 
> distances are all  larger than 3 angstrom ... so
> your system is a 
> collection of weakly interacting atoms, probably
> with very narrow bands. 
> Technically this may be the origin of the
> instability, but ...is this 
> the system you want to study  ?
> Hpe it helps
> stefano
> Stefano de Gironcoli - SISSA and DEMOCRITOS
> 
> 
> 
> Vidur Parkash wrote:
> > Hi
> >  
> > I'm trying to perform a SCf calculation on a
> carbon nanotube cluster
> > (metallic system), and no matter what i do the
> results do not
> > converge.
> > I've tried changing the mixing factor, add a
> smearing, tried a
> > different type of charge mixing, change number of
> k points etc.
> >
> > The input file I've attached is the closest it
> ever reached towards
> > convergence with accuracy better than 0.1 Ry...but
> ultimately failing
> > to converge. 
> >  
> >   
> > Can you please suggest some solutions. The input
> file is attached
> > this time.
> >  
> > Thanks
> >  
> > Vidur Parkash
> >
> > Michigan Tech University
> > 716 EERC, 1400 Townsend Drive
> > Houghton MI-49931, USA
> > Tel: 1-906-487-0023
> >
> >
>
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> >
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> > Pw_forum at pwscf.org
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> >   
> 
> 
> 
> Vidur Parkash
> 
> Michigan Technological University
> 716 EERC, 1400 Townsend Drive
> Houghton, MI-49931, USA
> Tel: 1-906-487-0023
> > _______________________________________________
> Pw_forum mailing list
> Pw_forum at pwscf.org
> http://www.democritos.it/mailman/listinfo/pw_forum
> 


-------------------------------------------------------------------
Prof. Eyvaz Isaev, 
Theoretical Physics Department, Moscow State Institute of Steel & Alloys, Russia, and 
Condensed Matter Theory Group, Uppsala University, Sweden Eyvaz.Isaev at fysik.uu.se, eyvaz_isaev at yahoo.com


       
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