SCF convergence in NEB calculation

[Marcella Iannuzzi]

Hi Tobias, 

The replicas along the band should not be too distant. The algorithm 
calculates the distant in terms of RMSD, and tries to evenly distribute 
them along the path. Ideally the RMSD should be around 1-2 Å. 

The energy profile that you sent does not look very promising indeed. You 
should try to understand why the extrema are higher in energy.
Is it due to problems in the SCF, or it is true that the structures in the 
middle are lower in energy?
How does the structure change at each step of the NEB?
What happens if you extract from the band some of those structures and you 
start a standard GEO_OPT?

ciao
Marcella


On Tuesday, July 28, 2015 at 12:44:17 PM UTC+2, Tobias Kraemer wrote:
>
> Hi all,
>
>
> I am running CI-NEB calculations in order to locate transition states 
> along a reaction profile involving organometallic species in the solid 
> state. More precisely, this is a hydrogenation reaction of double bonds, 
> i.e. addition of H2 to an alkene. This should be a straightforward task. 
> Anyway, for some cases it seems the SCF encounters problems to converge, or 
> converges to the wrong electronic state. In particular, those replicas are 
> affected which lead to the  transition state. I can see that the electronic 
> structure may be a bit tricky, since in a TS notable rearrangement of the 
> electrons takes place. It goes without saying, that having a wrong 
> electronic structure in the TS leads to unreasonably high barriers. I 
> should add that these type of calculations haven't imposed any problems so 
> far using other codes. What causes some additional puzzlement is the fact 
> that for the same TS search slightly different input  geometries lead to 
> very different behaviour of the SCF. In one case there is reasonable 
> convergence to a decent electronic structure, in the other case the SCF 
> goes completely havoc.  
>
> So my question really is, how can I control the SCF convergence for a 
> particular replica? Can this be done in the main input file?
>
> your comments are appreciated
>
>
> Tobi
>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://lists.cp2k.org/archives/cp2k-user/attachments/20150729/149a40f7/attachment.htm>