[CP2K-user] [CP2K:16537] Re: Prevent Cell Geometry/Vectors From Changing

[ASSIDUO Network]

Hey Fabian, I'm messaging here since I didn't get a response on my other 
question. What about NEB calculations, what do I do there if I don't want 
the fixed atoms to move?

On Tuesday, January 25, 2022 at 1:24:01 PM UTC+2 ASSIDUO Network wrote:

> 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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