[CP2K-user] [CP2K:16614] Re: half-harmonic potential for constraint

Emma Rossi emma.rossi.1 at studenti.unipd.it
Fri Feb 18 10:10:35 UTC 2022

Dear Marcella,
thank you for your suggestions and sorry for my late response.

I considered your last proposal, but actually my simulation is already a 
metadynamics (sorry I did not specified in the previous message)on a 
different CV.
I tried (uselessly) to define a new METADYN/METAVAR/WALL section for the 
unbiased CV in FREE_ENERGY, imposing DO_HILLS .FALSE., but I cannot repeat 
METADYN section. 
Is there a way to impose WW equal to 0.0 only for one of CVs included in  
FREE_ENERGY section, so to bias just one of them?

Thank you for your kind support and availability.
Best regards,
Emma Rossi

Il giorno giovedì 10 febbraio 2022 alle 09:55:31 UTC+1 Marcella Iannuzzi ha 

> Dear Emma, 
> The restraint on the distance is not going to help you in this case.
> I see a few other possibilities: 
> You could use a mix force-environment, where you  define a proper 
> potential (non bonded type) for the parameter you want to control.
> You use the restraint on a coordination number, rather than on a distance.
> You activate a sort of fake-metadynamics run, where you apply no 
> metadynamics potential, but a wall potential on the distance CV. 
> Regards
> Marcella
> On Wednesday, February 9, 2022 at 12:33:36 PM UTC+1 
> emma.r... at studenti.unipd.it wrote:
>> Dear CP2K community,
>> I am running a molecular dynamics simulation for a system containing an 
>> ion and triphosphate.
>> I need to avoid the center of mass of triphosphate to go further than 6.5 
>> A away from the ion, but I need to sample lower intermolecular distances. 
>> I would apply an half-harmonic potential centered around 6 A and growing 
>> for larger distances. Unfortunately, I have found only harmonic potentials 
>> for constraining collective variables ( 
>> https://manual.cp2k.org/trunk/CP2K_INPUT/MOTION/CONSTRAINT/COLLECTIVE/RESTRAINT.html
>> )
>> , which would prevent sampling of distances lower than 6 A.
>> I would be very grateful if you could suggest me any solutions for my 
>> problem.
>> Thank you in advance.
>> Best regards,
>> Emma Rossi

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