[CP2K-user] Severe deformation of structure during geometry optimization

[fa...@gmail.com]

Dear Lenard,

Yes, you have correctly answered your question. For metals you need a quite 
good sampling of the brillouin zone. Therefore a gamma-point calculation of 
a 5x5 angstrom unit cell is expected to yield unreasonable results. 
The fact that you managed to get a good structure with a cutoff of 300 is 
probably due to a coincidental error cancelling. But as soon as you alter 
the configuration by adding a CO the error cancelling does not work anymore 
and the structure becomes unreasonable again.

You should make sure that your quantity of interest is converged w.r.t the 
size of the k-point grid. 3x3x1still seems small to me, but maybe its 
already enough for you.

Cheers,
Fabian
On Tuesday, 2 March 2021 at 06:42:45 UTC+1 ASSIDUO Network wrote:

> Hi there everyone, I am currently trying to geometry optimize a stack of 
> Au (111) 2x2 surfaces, specifically by fixing the bottom 3 surfaces and 
> relaxing the top 3.
>
> Unfortunately, the top surfaces completely mess up and the final structure 
> looks bad. When I turn KPOINTS on  (3x3x1 or 5x5x1), it no longer happens.
> Finally, when I lower the cutoff to 300, but I leave KPOINTS off, I get a 
> good optimized geometry, but when I try to perform a CO adsorption with 
> that optimized structure, it severely deforms as well.
>
> Does anyone have a solution to my problem, particularly one that doesn't 
> change the ELECTRONIC_TEMPERATURE, KPOINTS or CUTOFF. Is it the need for 
> KPOINTS in a small structure like this that messes up the results?
>
> I have attached all my relevant files.
>
> Kind regards,
> Lenard
>
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