[CP2K-user] [CP2K:13655] QM/MM Mulitpole Rcut

[may...@gmail.com]

Dear Thomas,

Thanks for your response!

My reasoning for a cutoff much lower than the half box size arises from 
these two papers:

Yonetani, JCP, 2006:  https://doi.org/10.1063/1.2198208
Spoel, Marren, JCTC,  2006: https://doi.org/10.1021/ct0502256

where it is suggested that the larger cutoff does not implies accuracy and 
can create "artifacts" in bulk water simulations, particularly if the force 
field was not parameterized for the larger ranges. I don't have experience 
in simulating larger bulk water box (such as the one I mentioned before), 
but does this reasoning makes sense or is there alternative explanation for 
this? Do you have any particular recommendations in such scenarios? Not 
specifically for QM/MM, but for FIST calculations as well.

Best Regards,
Mayank Dodia


On Thursday, July 23, 2020 at 9:39:11 PM UTC+2 tkuehne wrote:

> Dear Mayank, 
>
> the keyword EWALD_PRECISION in the same section already controls the 
> real-space cutoff, 
> i.e. RCUT is only necessary to explicitly override the override the value 
> and as such only useful 
> when you know what you are doing. 
>
> Best, 
> Thomas
>
> Am 22.07.2020 um 12:41 schrieb may... at gmail.com <may... at gmail.com>:
>
> Hi,
>
> Sorry for reposting, but is there someone who can elaborate on the RCUT 
> parameter in the QM/MM Multipole section?
>
>
> https://manual.cp2k.org/trunk/CP2K_INPUT/FORCE_EVAL/QMMM/PERIODIC/MULTIPOLE.html
>     
>
> Best Regards,
> Mayank Dodia
> On Thursday, July 16, 2020 at 1:35:05 PM UTC+2 may... at gmail.com wrote:
>
>> Hi,
>>
>> Are there any guidelines to set the RCUT parameter in the QM/MM Multipole 
>> section?
>>
>>
>> https://manual.cp2k.org/trunk/CP2K_INPUT/FORCE_EVAL/QMMM/PERIODIC/MULTIPOLE.html
>>   
>>
>> Is the RCUT parameter here is equivalent to the FIST EWALD RCUT? In my 
>> case I have a larger MM box of 50*40*40 angstroms^3 and a smaller centered 
>> QM box of 40*30*30 angstroms^3, so in this case, the Multipole RCUT should 
>> be set to 19 angstroms (<R_min/2) or it is okay to set RCUT as same as FIST 
>> EWALD RCUT (~9-12 angstroms.)?
>>
>> Best Regards,
>> Mayank Dodia
>>
>
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> ==============================
> Thomas D. Kühne
> Dynamics of Condensed Matter
> Chair of Theoretical Chemistry
> University of Paderborn
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