[CP2K-user] [CP2K:14853] Re: Severe deformation of structure during geometry optimization

Lenard Carroll lenardc... at gmail.com
Tue Mar 2 15:07:17 UTC 2021


Just to be 100% clear, are you saying that for the &POISSON section which
deals with the electrostatic potential, that I select PERIODIC XY?

On Tue, Mar 2, 2021 at 4:55 PM Lucas Lodeiro <eluni... at gmail.com> wrote:

> 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>)
> escribió:
>
>> 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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