[DFTB-Plus-User] MD error in dftb+ ( SCC is NOT converged)

[Bálint Aradi]

On 12/07/2012 03:02 AM, 刘雷 wrote:
> Dear all,
> I am a new user in MD by dftb+ and I have difficulties in MD simulations when I simulated SiC.
> There is an error in output:
> "ERROR!
> -> SCC is NOT converged, maximal SCC iterations exceeded“
> 
> 

Not converging SCC can have various reasons. In your case it could be
the following:

* You could have quasi degenerated levels somewhere, but you do not use
any electronic temperature. You could try to set some finite electronic
temperature or use the AdaptFillingTemp option.

* Your structure could be unphysical. You could try to make a few steps
without SCC convergence and hope for the best: Set ConvergentForcesOnly
to No.

* You have a dissociated system in your MD and charge oscillations occur
between those systems due to the respective positions of their empty
states: That is really hard to cure, sometimes raising the electronic
temperature helps.

 Try to analyse the geometry and the electronic strucutre of your system
in detail, in order to understand the reason for the failure.

  Best regards,

  Bálint

-- 
Dr. Bálint Aradi
Bremen Center for Computational Materials Science, University of Bremen
http://www.bccms.uni-bremen.de/cms/people/b_aradi/


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