[CP2K-user] [CP2K:16499] Re: Prevent Cell Geometry/Vectors From Changing

[ASSIDUO Network]

Great, thanks for letting me know. 

On Monday, January 24, 2022 at 3:24:58 PM UTC+2 fabia... at gmail.com wrote:

> No, for MD the ensemble type determines if the cell dimensions are fixed 
> or not: 
> https://manual.cp2k.org/cp2k-9_1-branch/CP2K_INPUT/MOTION/MD.html#ENSEMBLE
> The cell only changes if you choose NPT, otherwise it is fixed.
>
> Fabian
>
> On Monday, 24 January 2022 at 08:46:45 UTC+1 lenardc... at gmail.com wrote:
>
>> Thanks for feedback Fabian, I appreciate it. Does the above also apply to 
>> AIMD simulations where you have the
>> &MOTION
>>   &GEO_OPT
>>   &END
>> &END
>> section still included?
>> On Thursday, January 20, 2022 at 2:20:26 PM UTC+2 fabia... at gmail.com 
>> wrote:
>>
>>> Hi Lenard,
>>>
>>> in cp2k there are two types of optimizations, GEO_OPT and CELL_OPT. In 
>>> GEO_OPT the lattice vectors are fixed and only the atomic positions are 
>>> optimized. In a CELL_OPT both the lattice vactors and the atomic positions 
>>> can be relaxed simultaneously.
>>>
>>> So if you don't want the box to change you need 
>>> RUN_TYPE GEO_OPT 
>>> and  the
>>> &MOTION
>>>   &GEO_OPT
>>>   &END
>>> &END
>>> section.
>>>
>>> If the SCF does not converge the forces (and pressure) are probably very 
>>> bad and thus the optimizer (e.g. BFGS) takes unreasonable steps. If the SCF 
>>> does not converge you should probably stop the simulation and improve SCF 
>>> stability.
>>>
>>> Cheers,
>>> Fabian
>>> On Thursday, 20 January 2022 at 05:50:59 UTC+1 lenardc... at gmail.com 
>>> wrote:
>>>
>>>> Hi there. So, I've been doing a few geometry optimizations and I have 
>>>> seen that for some of them, the cell vectors change, sometimes a bit other 
>>>> times a lot. This especially happens when the SCF run is not converged 
>>>> multiple times in a row. The thing is, I don't want the cell vectors to 
>>>> change, I don't want the atoms to go outside of the box, yet it still 
>>>> happens. Can you give me any tips/ideas on how to do a geometry 
>>>> optimizations where atomic positions can only change and the cell geometry 
>>>> cannot, or is this not feasible?
>>>>
>>>> Kind regards,
>>>> Lenard
>>>>
>>>

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