[DFTB-Plus-User] A question regarding the wfc file format

[Ljiljana Stojanovic]

Dear Bálint,

Thank you so much for your answer and explanation, it is very helpful! It
is clear now how the functions are written.

Best wishes,
Ljiljana

On Fri, Aug 26, 2022 at 12:09 PM Bálint Aradi <aradi at uni-bremen.de> wrote:

> Dear Ljiljana,
>
> our STO radial basis functions have the form:
>
> R_l(r) = sum_{p=1}^{npow} sum_{i=1}^{nexp} c_{p,i} r^{l + p - 1}
> exp(-alpha_i * r)
>
> where
>
> l = angular momentum of the radial wave function
> npow = nr. of power terms used
> nexp = nr. of exponential terms used
> c_{p,i} = coefficients in the wfc files.
>
> The p index grows faster, when one reads the coefficients from the wfc
> file.
>
> Best regards,
>
> Bálint
>
>
> On 22.08.22 22:41, Ljiljana Stojanovic wrote:
> > Dear DFTB+ developers,
> >
> > I was wondering if I could ask a question regarding the actual AO
> > functions used in the DFTB+. I was trying to use the STO coefficients
> > and exponents from the wfc.3ob-3-1.hsd file. It is not very clear to me
> > what is the actual functional form of an AO?  For example, in the case
> > of the hydrogen atom, 9 values of coefficients and 3 values of exponents
> > are printed. How are they combined? It seems that 3 different values of
> > the coefficients are combined with the same exponent. I was trying to
> > find an actual form of an orbital, but I didn't manage to find the
> > answer. I need this information to be able to print and visualise the
> NTOs.
> > Any help would be much appreciated.
> > Thanks a lot in advance.
> >
> > Best wishes,
> > Ljiljana Stojanovic
> >
> >
> > _______________________________________________
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> > DFTB-Plus-User at mailman.zfn.uni-bremen.de
> >
> https://mailman.zfn.uni-bremen.de/cgi-bin/mailman/listinfo/dftb-plus-user
>
>
> --
> 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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