[Pw_forum] phonon modes for transition state

[lfhuang]

Dear Stephan Rix:
    Apart from some convergence problems sometimes when the structure is far away from equilibrium, PWSCF can calculate the phonons for any structure in principle. 
    Are you sure you have the very transition-state structure in your calculation of phonons?
    Are you sure there is a transition state in the reaction path specified by you?
Transition state is also a saddle-point state, in which there is an imaginary vibrational mode along the migration coordinate with other modes being real. Thus, there should be an imaginary mode if the structure is in/close to the transition state.  

Best Wishes!

Yours Sincerely
L. F. Huang
 
> From: Stephan Rix 
> Subject: [Pw_forum] phonon modes for transition state
> To: pw_forum at pwscf.org
> Message-ID:
> 	
> Content-Type: text/plain; charset="iso-8859-1"
> 
> Dear all,
> 
> I am trying to calculate the phonon modes for a transition state using ph.x.
> 
> I am expecting to find one negative/imaginary mode, but all resulting phonon
> modes are positive.
> 
> The transition state was optimized using pw.x with nudged elastic band and
> climbing image.
> Before running ph.x for the transition state I tested it with respect to
> necessary thresholds on a fully relaxed equilibrium state and the results
> were fine.
> 
> Question: Is ph.x in principle capable of calculating transition state
> phonon modes, i.e. returning negative/imaginary modes?
> If so, I would appreciate any ideas or advice on how to obtain the desired
> negative phonon mode.
> 
> Thanks for your help.
> Stephan
> 
> 
> Stephan Rix
> Dept. of Chemistry
> Princeton University
> Princeton, NJ 08540


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L.F.Huang(黄良锋) DFT and phonon physics
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Add: Research Laboratory for Computational Materials Sciences,
Instutue of Solid State Physics,the Chinese Academy of Sciences,
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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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