[CP2K:2742] units in GENPOT section

Teodoro Laino teodor... at gmail.com
Wed Jun 2 15:27:33 UTC 2010

Hi Noam,

cp2k_internal units are atomic units.

That functional form is extremely flexible: basically you can use it in 
the way you like it more (even device your personal correction potential).
Just for your information, in CP2K it is available Grimme as a 
correction in the  XC section (in this case you don't have to worry 
about parameters since they are already coded).


Noam Bernstein wrote:
> Hi all - I'm trying to set up a DFT calculation with vdW corrections,
> i n the form of a non-bonded potential.  I've been looking at the
> example in tests/QS/regtest-dft-vdw-corr, where I found the
> following section.
>        &GENPOT
>          ATOMS        C  C
>          RCUT [angstrom]        14.9
>          RMIN [angstrom]        0.2
>          RMAX [angstrom]        15.0
>          VARIABLES    R
>          PARAMETERS   CSIX      RZERO    D
>          VALUES      -216.9850 6.57936 2.9688
>          FUNCTION    (CSIX/(R**6))*((1.0 - EXP(-1.0*D*((R/RZERO)**7)))**4)
>        &END
> I think I understand what it's doing, and the functional form is consistent
> with what's in, for example, Williams and Malhotra (Chem Phys v 327).
> However, I haven't been able to figure out what are the units.  The
> PARAMETERS must implicit have units (CSIX must be in units of
> energy*length^6, e.g.), but the documentation says that PARAMETERS are
> in cp2k_internal units, and I couldn't find those defined on the units page of
> the documentation.  Is my guess that  they're Hartree and Bohr correct?
>         thanks,
>         Noam
> P.S. Is there another good source of parameters that I should know about,
> in addition to that Williams and Malhotra paper?

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