[CP2K:753] Re: using empirical VDW correction with CP2K

[lmliu]

thanks axel and Teo,

I use the H-H, H-O and O-O parameters for PBE,  taking from the Chem. Phys.
327 (2006) 54.

          ATOMS        H O
          RCUT [angstrom]        10
          RMIN [angstrom]         0.2
          RMAX [angstrom]        11.0
          VARIABLES    R
          PARAMETERS   CSIX      RZERO    D
          VALUES      -2.675     3.947    3
          FUNCTION    (CSIX/(R**6))*((1.0 - EXP(-1.0*D*((R/RZERO)**7)))**4)

          ATOMS        H H
          PARAMETERS   CSIX      RZERO    D
          VALUES      -2.290     3.538    3

          ATOMS        O O
          PARAMETERS   CSIX      RZERO    D
          VALUES       -9.631    4.233    3

Best Regards,
Limin

2008/3/10, Teodoro Laino <teodor... at gmail.com>:
>
> Dear Limin,
> Please read carefully the error/warning  messages:
>
> On 10 Mar 2008, at 01:36, lmliu wrote:
>
> *** 01:34:59 WARNING in force_env_methods:mixed_energy_forces err=-300
> ***
>  *** ASSERTION (cond) failed at line   1151 Error (0.129985E-11) in
> ***
>  *** computing numerical derivatives larger then(0.100000E-11) .
> ***
>
>
> First: this is not an error message but it is a warning (WARNING in
> [..]).
> Second: It clearly says that: Error (0.129985E-11) in computing numerical
> derivatives larger then(0.100000E-11) .
>
> I guess you can cope with this error on the evaluation of the MIXED
> forces.. don't you (look at the magnitude of the numbers)?
> If you are annoyed from seeing this warning message you can tune the
> precision of the evaluation of the numerical derivative
> with the keyword:
>
>
> http://cp2k.berlios.de/input/InputReference~__ROOT__~FORCE_EVAL~MIXED~GENERIC.html#ERROR_LIMIT<http://cp2k.berlios.de/input/InputReference%7E__ROOT__%7EFORCE_EVAL%7EMIXED%7EGENERIC.html#ERROR_LIMIT>
>
> 10^-12 is an extremely safe parameter. I guess 10^-7 will do your work in
> a very good way as well (please compare these numbers
> with the precision achieved in computing the DFT forces).
> Cheers,
> Teo
>
>
> >
>
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