[Pw_forum] NEB Convergence Problem

[Tone Kokalj]

Quoting Vic Bermudez <victor.bermudez at nrl.navy.mil>:
> The potential energy
> surface I'm faced with can't really be modeled as a simple IS --> TS  
> --> FS progression. I
> don't think that it would be acceptable to force it to fit such a  
> simple scheme, even if that were possible.

Nothing is forcing you to adopt a too simple scheme. Your reaction may  
appear very simple on the paper, but this does not mean it consists of  
single elementary step. This means you have to decompose it to a  
several elementary steps. If a step is nonactivated (e.g., adsorption)  
than model it with geometry optimization. If a given step is activated  
(e.g. diffusion or elementary chemical reaction) then model it with  
NEB. Hence your overall reaction may consists of, say, an adsorption,  
a few activated processes (surface diffusion, elementary reactions),  
and desorption. Model each of it with a separate calculation.

Hope this clarifies the issue.

Regards, Tone