[CP2K:7757] BSSE Calculation while using two copper types

[S Ling]

Hi Chris,

This is not a CP2K-specific question. It is about how you would like to
define the BSSE-corrected interaction energy between two "monomers". In the
original counterpoise scheme by Boys and Bernardi, the geometries of the
two "monomers" were fully optimised with the "dimer" basis. In CP2K, you
will have to set up some GHOST atoms manually in order to relax the monomer
geometries with "dimer" basis. One approximation you can make is that you
calculate the interaction energy at fixed monomer geometries in the
"dimer", i.e. you neglect the geometry relaxations of both "monomers" due
to additional basis sets on GHOST atoms, and this is exactly what CP2K is
doing. In some other quantum chemistry codes (e.g. Gaussian), the geometry
relaxations of monomers may be automatically taken into account if you
switch on the counterpoise correction scheme.

BTW: You didn't break the symmetry in the electronic configuration of Cu
ions, and currently you have a closed-shell singlet solution. Are you sure
that's the electronic ground state?

SL



On 16 May 2016 at 13:15, Chris Campbell <chris... at gmail.com> wrote:

> Afternoon SL,
>
> Apologies for the hassle but wondered if I could quickly ask a follow up
> question.
>
> Initially for my system using a PBE functional I optimised my Adsorbent
> and Adsorbate independently and then together, when i found the difference
> I got an interaction energy of ~25kJ/mol.
>
> Following this BSSE fragment Calculation (using the fully optimised
> combination of Adsorbent and Adsorbate together), I get a value in the
> output of BSSE-free interaction energy: ~-20kJ/mol, which seems very
> reasonable (to me).
>
> This energy, however , calculated for the Adsorbate and adsorbent is not
> from the independent optimisation positions so can I use this energy? or do
> I have to work backwards to calculate the BSSE correction and then apply it
> to the original -25kJ/mol?
>
> Apologies if this is not worded very clearly.
>
> Kindest Regards,
> Chris
>
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