[Pw_forum] Another SCF convergence problem

[Vidur Parkash]

Dear Eyvaz

Sorry bout that....yes I meant K_POINTS, is there any thumb rule for deciding how many K-points are good for convergence. Is it dependent on the nature of the system, or on the number of atoms or something else

Pardon me for my newbie like questions...

Vidur

Eyvaz Isaev <eyvaz_isaev at yahoo.com> wrote: 
--- Vidur Parkash  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  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
> > http://www.democritos.it/mailman/listinfo/pw_forum
> >   
> 
> 
> 
> 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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Vidur Parkash

Michigan Technological University
716 EERC, 1400 Townsend Drive
Houghton, MI-49931, USA
Tel: 1-906-487-0023
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