[CP2K:5817] Removing DFTB interaction between particular atoms?

[Ralph Koitz]

Hi,

I think it should be feasible to do this without changes to the code. In
your DFTB calculation, find the Slater-Koster parameter file for Carbon,
should be something like 'cc.spl', make three copies of that file 'cx.spl',
'xc.spl', 'xx.spl'. Then edit the file that assigns parameters to atoms ('
scc_parameter' ?), it contains a list of what spl file to use for which
interaction. Add the following lines:
  C   X  cx.spl
  X   C  xc.spl
  X   X  xx.spl
(the C C interaction should already be there).

You can then replace your two desired carbons in graphene by atoms of type
X, and tune their interaction by modifying the xx.spl file. In the simplest
case, set all columns to zero to turn off all interactions. You can also
scale the interaction, or turn off orbital-specific components.
X atoms will still behave like C atoms to other C atoms.

See my slides from the cp2k tutorial for details on setting up a dftb
calculation and on the format of the .spl files.
    http://ralph.koitz.info/doc/dftb_cp2k.pdf

Hope that helps,
Ralph

On Wed, Nov 5, 2014 at 4:35 PM, Rafael Soler-Crespo <rasole... at gmail.com
> wrote:

> Hi all,
>
> I'm trying to perform a calculation to replicate a MD paper on CP2K using
> DFTB to see if the findings still hold (out of curiosity). In this paper, a
> crack is imposed on graphene by removing explicitly atoms from the
> material. I want to do this a little differently by turning off
> interactions between two neighboring carbon atoms. My system has around
> 7000 carbon atoms, and I want to forcefully zero any interactions between
> two adjacent C atoms. I searched around the documentation, but I couldn't
> find a great way to do this. Is it possible for someone to let me know if
> this is possible in CP2K, and if it is not, if it could be coded in
> principle?
>
> Thanks,
> Rafael
>
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