[Pw_forum] phonon modes for transition state

[elbuesta at icqmail.com]

 From my experience with phonons (that is not big), yes it can and very well. I performed a few phonon calculations on noble metals on transition states generated from NEB optimizations, like you did, and the results obtained were good, one negative frequency corresponding to the exchange path and the all the others positive.

All I can say is what is mostly written on the manuals and examples, you have to be really carefull with the thresholds. The energy cutoff must be significant, the charge cutoff very big specially if there is vacuum, a good number of k points are required if the cell is small, the convergence for sel-consistency must be really strict (I would say conv_thr=10-12) and the phonon convergence also (tr2_ph<10-16). I hope it helps.

 
Fabio Negreiros Ribeiro
Departamento de Fisica, Universidade Federal de Minas Gerais, Belo Horizonte, Brazil



-----Original Message-----
From: Stephan Rix <srix at princeton.edu>
To: pw_forum at pwscf.org
Sent: Wed, May 19, 2010 7:10 pm
Subject: [Pw_forum] phonon modes for transition state

   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  
     _______________________________________________ Pw_forum mailing list Pw_forum at pwscf.org http://www.democritos.it/mailman/listinfo/pw_forum  
  

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.quantum-espresso.org/pipermail/users/attachments/20100520/902c7866/attachment.html>