[CP2K-user] [CP2K:14854] Re: Severe deformation of structure during geometry optimization

[Matt W]

I normally use WAVELET poisson solver - then you need Y as the non-periodic 
direction (so PERIODIC XZ), the system must be in the centre of the cell 
and you need ~5 A vacuum each side to get converged results.

The ANALYTIC psolver is also usable for 2D poisson, but it requires a much 
bigger cell to converge (~2x), to my knowledge. 

Do check that you are converged with cell size if you go these routes. 
There is also a dipole correction method available somewhere (I've not 
used).

Matt

On Tuesday, March 2, 2021 at 4:04:03 PM UTC Lucas Lodeiro wrote:

> Yes, and in &CELL too, to avoid interaction between slab replicas and 
> their electrostatic fields.
>
> El mar, 2 mar 2021 a las 12:07, Lenard Carroll (<len... at gmail.com>) 
> escribió:
>
>> 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 <el... 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 (<len... 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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