[CP2K-user] [CP2K:11824] free energy calculation in pimd

[Christoph Schran]

Dear Webb Foo,

centroid constraints/restraints have been implemented recently and will be 
available in the upcoming new CP2K release v7.1.

The input is very similar to normal MD simulations. I would recommend using 
the exact integrator in combination with the PILE thermostat.
Example inputs (which need to be adapted carefully) can be found under 
tests/Pimd/regtest-1 and regtest-2: h2o_pint_constraints_exact.inp for the 
constraints and w512_pint_pile.inp for the PILE thermostat.
Note that regtests are usually optimized to trigger as many parts of the 
code as possible and are not always best simulation practice. 

Best, Christoph

On Sunday, June 2, 2019 at 3:21:00 AM UTC+2, Webb Foo wrote:
>
> Hi Thomas,
> Thanks for your reply. And I'll have a try.
>
> Cheers,
> Webb
>
> 在 2019年5月31日星期五 UTC+8上午4:52:40，tkuehne写道：
>>
>> Dear Webb Foo, 
>>
>> using constrained MD the free energy profile can be computed in terms of 
>> the potential of mean force by means of the ensemble 
>> average of the Lagrange multipliers to constrain your reaction 
>> coordinate. You will find a particular good description in the SI of
>> the following paper: https://www.pnas.org/content/104/8/2626.short
>> However, when using PIMD, in my opinion the constraint has to be enforced 
>> on the ring-polymer centroid, which most likely 
>> requires a little bit of coding. 
>>
>> Best, 
>> Thomas Kühne
>>
>> Am 30.05.2019 um 10:16 schrieb Webb Foo <l... at gmail.com>:
>>
>> Hello everyone,
>>
>> Can you explain me how to estimate the free energy profile from a pimd 
>> simulation, like constrained MD?
>>
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>> ==============================
>> Thomas D. Kühne
>> Dynamics of Condensed Matter
>> Chair of Theoretical Chemistry
>> University of Paderborn
>> Warburger Str. 100
>> D-33098 Paderborn
>> Germany
>> td... at mail.upb.de
>> +49/(0)5251/60-5726
>>
>>
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