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

[Bálint Aradi]

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,

  Bálint

-- 
Dr. Bálint Aradi
Bremen Center for Computational Materials Science, University of Bremen
http://www.bccms.uni-bremen.de/cms/people/b_aradi/


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