Choosing parameters in CP2K

[simin pahlavi]

Hello everybody,
I have same the problem, " Is there any rules to set the value of 
R_CUTOFF?"Could we set it to  1/2 (2.5 sigma) in Lenard johns interactions?
Thank you in advance

On Tuesday, October 1, 2013 at 2:43:48 PM UTC+2, hua... at mail.huji.ac.il 
wrote:
>
> Dear All,
> I am a newbie to CP2K. I have a project on benzene-water cluster and I 
> would like to run MD simulation using DFT PBE functional. 
>
> I have some questions on choosing basis set and parameters for MD 
> simulation. However, after I checked the examples or CP2K reference, I did 
> not get any answers.
>
> In the example file of 
> /opt/cp2k/test/QS/regtest-dft-vdw-corr/dftd3_t1.inp, it used two different 
> basis set for one system, like,
>     &KIND H
>       BASIS_SET DZV-GTH
>       POTENTIAL GTH-PBE-q1
>     &END
>     &KIND C
>       BASIS_SET DZVP-GTH
>       POTENTIAL GTH-PBE-q4
>
> Is that OK? I mean if there is an argon atom in my cluster, as basis set 
> not always including all the atoms after the 3rd period, can I choose 
> different basis set for calculation?
>
>
> In the section of  DISPERSION_FUNCTIONAL, I saw another example like,
>       &vdW_POTENTIAL
>          DISPERSION_FUNCTIONAL PAIR_POTENTIAL
>          &PAIR_POTENTIAL
>             TYPE DFTD3
>             PARAMETER_FILE_NAME ../dftd3.dat
>             REFERENCE_FUNCTIONAL PBE
>             CALCULATE_C9_TERM T
>             R_CUTOFF 7.
>          &END PAIR_POTENTIAL
>       &END vdW_POTENTIAL
>
> the R_CUTOFF parameter is set to 7. The description in the CP2K reference 
> is too brief to understand.
> *       R_CUTOFF 24.0*
> *       Range of potential. The cutoff will be 2 times this value  [Edit]*
> *       This optional keyword cannot be repeated and it expects precisely 
> one real.*
> *       Default value: 1.05835442E+01*
> *       Default unit: [angstrom]*
>
> Is there any rules to set the value of R_CUTOFF? Is there any 
> relationships with what kinds of potential I chose?  Or for what kind of 
> system (contained what kinds of atoms), the R_CUTOFF value should be 
> increased or reduced? 
>
>
> Another question is what's the difference between DFTD3 and DFTD2? Which 
> one is more suitable for the weak interaction such like pi-hydrogen bond? I 
> did not find any description in the CP2K input reference.
> *    TYPE DFTD2*
> *   Type of potential:*
> *     DFTD2 → Grimme D2 method*
> *     DFTD3 → Grimme D3 method*
> *   [Edit]*
> *   This optional keyword cannot be repeated and it expects precisely one 
> keyword.*
> *   Default value: DFTD3*
> *   List of valid keywords:*
> *   DFTD2*
> *    Without description, yet.  [Edit]*
> *   DFTD3*
> *    Without description, yet.  [Edit]*
>
> I appreciated it very much for any of you can give me explanations or 
> suggestions on choosing those parameters. Thank you.
>
> Best regards,
> Huan
>
>
>
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