[DFTB-Plus-User] Dear dftb+ developer, is a multipole expansion scheme available for the charge fluctuation term ?

Bálint Aradi aradi at uni-bremen.de
Mon Oct 24 09:10:27 CEST 2016

Dear Peter,

> It seems to me that since dftb+ always neglected some terms in DFT,
> the partial charge can't never be the same with DFT. As a matter of
> fact, some papers proposed to use a so called CM3 method to remedy
> such differences in partial charge predicted by DFT and dftb+. I
> would like to know that whether the two factors i listed above will
> affect the global structures predicted by dftb+ ? Thank you
> sinceriously.

I think, your analysis is in general correct. As for the consequences
for global structures: it really depends. As the repulsive is fitted
against ab initio, you should get in many cases the right DFT-like
structure, depsite the difference in the charges. But, as always with
DFTB, you have to be critical and test if first for small systems.

  Best regards,


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

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