[Pw_forum] Another SCF convergence problem

Vidur Parkash vparkash at mtu.edu
Wed Oct 3 17:44:00 CEST 2007

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?  


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 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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Vidur Parkash

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