[CP2K-user] [CP2K:14850] Re: Severe deformation of structure during geometry optimization

Lucas Lodeiro eluni... at gmail.com
Tue Mar 2 14:55:11 UTC 2021

Just a comment, see your electrostatic potential profile. You are using a
periodical slab picture, then when you add a polar molecule, there is not a
flat potential into the vacuum, in that case, disable the periodicity in
this direction or add an electrostatic field to correct it.
Also, to check the convergence of your quantities with respect to your
model, you could explore bigger slabs than 6 layers.

Regards - Lucas Lodeiro

El mar, 2 mar 2021 a las 6:37, ASSIDUO Network (<lenardc... at gmail.com>)

> 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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