[DFTB-Plus-User] heteroatomic skf files

Bálint Aradi aradi at uni-bremen.de
Thu Jan 28 09:19:34 CET 2016

Dear Nir,

> I noticed when reading the notes for some of the heteroatomic skf files in
> mio-1-1 (e.g., C-N.skf and N-C.skf) that it appears that different
> confining potentials were used for the basis functions and densities in
> each case. It could be that different basis functions were used altogether
> to construct each file. The result is that there is a difference in each
> file for the Hsp0 and Ssp0 matrix elements. Why is that the case, and why
> weren¹t identical parameters used when computing each file?

I am not sure, if I understand, what you refer to. Looking at C-N.skf,
the documented compression radii are:

Atom1 (C): 7.0 / 2.7 2.7
Atom2 (N): 11.0 / 2.2 2.2

For N-C.skf on the other hand

Atom1 (N): 11.0 / 2.2 2.2
Atom2 (C): 7.0 / 2.7 2.7

So, at least looking at the documentation, the compression radii for a
givens species are in both cases the same.

Now, on the matrix elements: Hsp0 has different meanings in the two
SK-files. In C-N.skf it is < C(s) | H | N(pz) >, while in N-C.skf it
would be < N(s) | H | C(pz) > which does not have to be equivalent, and
similarly for the overlap. So for sure, the respective values won't be

I hope, this helps to reduce the confusion about the SK-format a little bit.

  Best regards,


Dr. Bálint Aradi
Bremen Center for Computational Materials Science, University of Bremen

-------------- next part --------------
A non-text attachment was scrubbed...
Name: signature.asc
Type: application/pgp-signature
Size: 836 bytes
Desc: OpenPGP digital signature
URL: <http://mailman.zfn.uni-bremen.de/pipermail/dftb-plus-user/attachments/20160128/ea73811e/attachment.pgp>

More information about the DFTB-Plus-User mailing list