[Pw_forum] where is the end of an unconverged NEB calculation

[lfhuang]

Dear vega lew:
    Have you gone into the ./tmp directory to see the energy convergence of every image? The calculational statuses of all the images can be found there, and I guess your convergence problem may be due to the same reasons as ordinary electronic structrue calculations, which may be modified by change some parameters e.g. k-points numbers, smearing, nband. Or there may be some defects in the pseudopotential and you should better change for another one. May these be helpful.

Best Wishes!
Yours Sincerely
L.F.Huang

> Date: Fri, 6 Nov 2009 11:35:39 +0800
> From: vega lew 
> Subject: [Pw_forum] where is the end of an unconverged NEB calculation
> To: PWSCF Forum 
> Message-ID:
> 	
> Content-Type: text/plain; charset="iso-8859-1"
> 
> Dear all,
> 
> During my NEB calculations, I found there are two possible situation. First,
> the calculation could be converged after about 100 iterations. Second, the
> calculation never converged in more than 300 iterations. And for the second
> case, the energy barrier went down and down to a certain value, and then the
> reported energy barrier went up gradually. For example in my resent job, the
> energy barrier goes to 1.49 eV from the intial 2.99 eV in about 120
> iterations. Then the energy barrier rise to 1.73 eV bit by bit in following
> 40 iterations. And the calculation is still running while this value is
> still going up. How could I deal with this situation?  Could I take the
> lowest value as the energy barrier of the reaction? How could I know whether
> there will be another smaller value in the longer calculation?
> 
> thank you for reading. Ang hints will be deeply appreciated.
> 
> best,
> 
> vega
> 
> -- 
> ==================================================================================
> Vega Lew ( weijia liu)
> Graduate student
> State Key Laboratory of Materials-oriented Chemical Engineering
> College of Chemistry and Chemical Engineering
> Nanjing University of Technology, 210009, Nanjing, Jiangsu, China
> ******************************************************************************************************************
> Email: vegalew at gmail.com
> Office: Room A705, Technical Innovation Building, Xinmofan Road 5#, Nanjing,
> Jiangsu, China
> ******************************************************************************************************************

------
======================================================================
L.F.Huang(黄良锋) ph.D candidate, DFT and phonon physics
======================================================================
Add: Research Laboratory for Computational Materials Sciences,
Instutue of Solid State Physics,the Chinese Academy of Sciences,
P.O.Box 1129, Hefei 230031, P.R.China
Tel: 86-551-5591464-328(office)
Fax: 86-551-5591434
Web: http://theory.issp.ac.cn (website of our theory group)
http://www.issp.ac.cn    (website of our institute)
======================================================================


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