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

[ASSIDUO Network]

Thank you for the quick response.

I understand what you are saying and it makes total sense to me. Thank you 
for clarifying.

The 3x3x1 was just to test how my final adsorption energy changes when I 
change various settings, including alpha, beta, kpoints and cutoff. I got 
similar results to the the 5x5x1 case, however the 5x5x1 result was more 
accurate compared to the ltierature.

On Tuesday, March 2, 2021 at 11:33:40 AM UTC+2 fa... at gmail.com wrote:

> 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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