[DFTB-Plus-User] DFTB+ Repulsive energy

Bálint Aradi balint.aradi at bccms.uni-bremen.de
Mon Nov 23 11:56:29 CET 2009

Dear Reinhard Maurer,

  Please in the future, send your queries regarding DFTB+ to the
appropriate mailing list, so that others can also profit from the
information. (I cc-d my answer there.)

> Is the Term "Repulsive Energy" solely the core core interaction?
> Because I recently had some confusing results where the relative
> core-core-energy (relative to the seperated systems) was negative.
> Of course this could also be due to errors in my inputs I haven't
> found yet, but it could also mean that this includes other energy
> terms.

 The repulsive energy reported by DFTB+ is just the term called
'repulsive' in the DFTB literature, so it does not contain the
vdW-interaction. The repulsive energy on it's own is not just core-core
repulsion, but contains also the so called double counting terms.
Nevertheless, ususally it should be positive for all distances, but
there are some weird parametrization cases, where it goes slightly
negative. But I'd suggest to check your input, as normally it shouldn't
be negative.

  Best regards


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

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