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

[Bálint Aradi]

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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-- 
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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