[Pw_forum] What to do when NEB calculation is difficult to converge?

[Xunlei Ding]

Thank you very much for your detailed instruction.
I'll try it.
Best regards,
Lei

Tone Kokalj wrote:

>On Sun, 2006-08-27 at 09:39 +0200, Xunlei Ding wrote:
>  
>
>>Dear all,
>>I am now doing a neb calculation on a surface adsorption system with 
>>pwscf3.0
>>    
>>
>
>  
>
>>It has more than 400 iterations and has not converged. 
>>    
>>
>
>This is a very large number of iterations, and the error on the 3rd,
>4th, and 5th image is still large. It is difficult to guess why it does
>not converge from your data. The time step ds=1.0 seems reasonable (as
>far as my experience go). 
>
>One thing that you may try is to increase the number of images!
>
>How to do that? You need to do a new calculation with larger number of
>images, but you can use the currently calculated path as the initial
>path for this new calculation.
>
>You may either try with the path_int.sh script that is located in
>pwtools/ directory (edit it to suit your needs). This will generate a
>new path file will requested number of images, and in the pw.x input
>file you specify then new number of images and restart_mode='restart'.
>The other possibility is to insert the current path (for example, the
>axsf file the pw.x has produced) into the input file of pw.x (specify
>new number of images and restart_mode='from_scratch'). You need to do
>some hand-editing then:
>
>ATOMIC_POSITIONS angstroms
>first_image
>   (atomic position of image-1)
>intermediate_image
>   (atomic position of image-1)
>intermediate_image
>....
>last_image
>   (atomic positions of last image)
>
>Regards, Tone
>
>
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>