[CP2K-user] [CP2K:21595] Clarification of R_CUTOFF in VDW_POTENTIAL

[emerson p l]

Many thanks for the clarifications, Jürg Hutter! 

Thanks for your time.

Best,

Emerson

Em sexta-feira, 27 de junho de 2025 às 06:01:40 UTC-3, Jürg Hutter escreveu:

> Hi
>
> CP2K does not use MIC for vdW corrections. You can specify any cutoff 
> radius.
> Atoms within 2*R_CUTOFF will interact. You can check the convergence of 
> the vdW
> energy by increasing the cutoff .
>
> regards
> JH
>
> ________________________________________
> From: cp... at googlegroups.com <cp... at googlegroups.com> on behalf of 
> emerson p l <emers... at gmail.com>
> Sent: Thursday, June 26, 2025 9:41 PM
> To: cp2k
> Subject: [CP2K:21590] Clarification of R_CUTOFF in VDW_POTENTIAL
>
> Dear cp2k community, I hope you’re all doing well.
>
> I’m writing to ask for clarification on the choice of the cutoff radius 
> R_CUTOFF​ parameter when using periodic boundary conditions in 
> VDW_POTENTIAL in AIMD and geometry/cell optimizations:
>
> &VDW_POTENTIAL
> POTENTIAL_TYPE PAIR_POTENTIAL
> &PAIR_POTENTIAL
> PARAMETER_FILE_NAME dftd3.dat
> TYPE DFTD3
> REFERENCE_FUNCTIONAL PBE
> R_CUTOFF [angstrom] 10
> &END
> &END VDW_POTENTIAL
>
> Suppose I have a cubic simulation box with side length L = 5 angstrom, and 
> I (mistakenly) set R_CUTOFF​ = 10 angstrom. Would setting RCUTOFF​ = 10 
> angstrom in a 5 angstrom cubic box cause the cutoff sphere to extend beyond 
> the primary cell and overlap with periodic images, resulting in unphysical, 
> multiply-counted interactions?
>
> My understanding from classical MD is that we must obey the minimum-image 
> convention, which requires R_CUTOFF​ ≤ 2 Lmin​​. I don't know if R_CUTOFF 
> has this physical meaning of classical MD.
>
> Thank you very much for your time and insights.
>
> Best,
>
> Emerson
>
>
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