[DFTB-Plus-User] Question about SK files for pair of elements

[Ben Hourahine]

Hello Reinaldo,

In the special case of interactions with hydrogen
there is a symmetry between the X-H and H-X cases
due to the spherical symmetry of the H 1s state.
This symmetry doesn't hold for interactions between
atoms where both contain orbitals of higher than s
angular momenta, as only some of the interactions in the
two files are related by symmetry.

Regards

Ben


On 09/08/10 18:06, Reinaldo Pis Diez wrote:
> Dear Bálint and folks,
>
> Due to a recent error when trying to run dftb+ with a very simple
> example, I've verified that in some SK sets some atoms pairs are
> described by exactly the same set, whereas others are not. To be
> clearer, the chalc-0-1 set has the following SK files
>
> As-As-skf
> As-H.skf
> As-S.skf
> S-As.skf
> H-As.skf ->  As-H.skf
>
> in which one can note that H-As and As-H share the same SK file
> through a symbolic link, but As-S and S-As are different files
> (there is a lot of different numbers if you make a diff on them).
> The same happens in pbc-0-2, for example.
> My question is, Why are they different? Shouldn't be the same file
> as X-Y should interact the same way as Y-X? Am I missing something?
> Thanks in advance.
> Regards,
>
> Reinaldo
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>    


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      Dr. B. Hourahine, SUPA, Department of Physics,
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