[Pw_forum] Another SCF convergence problem

Stefano de Gironcoli degironc at sissa.it
Wed Oct 3 10:06:57 CEST 2007

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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