[DFTB-Plus-User] How to effect a non-scc dftb calculation, it the current SK parameter compatible ?

Peter Yen peter308 at gmail.com
Fri Mar 24 04:42:59 CET 2017

Dear Mr. Balint
Thank you for your information. I will consult further if i have any other
questions on the Rp part.

                                                          With Best Regards

2017-03-24 11:38 GMT+08:00 Bálint Aradi <aradi at uni-bremen.de>:

> Dear Peter,
> > Thank you for your kind reply. You have mention that the repulsive
> > energy (RP) is fitted to bulk system of gold and since crystal gold
> > will not have charge transfer or nearly zero charge transfer, the RP
> > fitted will be similar to the non-scc case. However, in the case of
> > gold clusters, there are in fact non zero charge transfer among
> > atoms. And i believe the Rp in this case will be quite different to
> > the bulk case since  charge transfer now occurs in the former. In
> > these two extreme cases ( bulk gold and gold clusters Au_n, where n
> > is less than 10 ), do you think two separate RPs is necessary ?
> > Because the Rp in Au-Au.skf is actually fitted to system with nearly
> > zero charge transfer, yet in small clusters case, the charge transfer
> > can't be neglected. I was speculating maybe  the Rps will be quite
> > different in these two cases. Would you provide any comments or
> > advice ? Many thanks.
> According to DFTB theory, the repulsive potential is only a functional
> of the reference density, which is the superposition of the compressed
> neutral atom densities. So the difference, between a system with
> considerable charge transfer and a system with almost no charge transfer
> must be described by the scc-part of the Hamiltonian, not by the
> repulsive, as the reference density is similar in both cases. Therefore,
> when done with care, it is usually possible to create repulsive
> potentials, which are good compromises for both cases.
> 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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Postdoctoral fellow, Physics department,
National Central University, Taiwan(R.O.C)
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