### Author Topic: Question about the distances in the SlaterKosterTable  (Read 2009 times)

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#### issac7

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##### Question about the distances in the SlaterKosterTable
« on: October 20, 2023, 09:46 »
Dear sir,
I'm doping DFTB calculations based on user specified Slater-Koster matrix according to
https://docs.quantumatk.com/tutorials/slater_koster/slater_koster.html#slater-koster-tight-binding-models-in-atk-se.
Here is my question: what does the distance "d" stands for?
I'm confused because the specified d is actually out of the nearest distance between atoms.
Code
``````# Setup list of distances
epsilon = numpy.linspace(-0.20, 0.20, 41)
distances = [ d_n1*(1.0+x) for x in epsilon ] + [ 0.5*(d_n1+d_n2) ]``````
Looking forward to your replies. Thanks a lot.
« Last Edit: October 21, 2023, 05:27 by issac7 »

#### Anders Blom

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##### Re: Question about the distances in the SlaterKosterTable
« Reply #1 on: October 24, 2023, 01:38 »
I think the code speaks for itself. d_n1 is the first nearest neighbor distance, d_n2 the second.

#### issac7

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##### Re: Question about the distances in the SlaterKosterTable
« Reply #2 on: October 24, 2023, 07:07 »
Thanks for replying. Sorry for the unclear question. The "d" I put earlier means the <distances=...> in the code. I am confused that the distances that determined the offsite hopping matrix fall out of the nearest atomic distance.

#### Anders Blom

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##### Re: Question about the distances in the SlaterKosterTable
« Reply #3 on: October 24, 2023, 19:26 »
The distances variable basically does two things. It creates a range around the nearest distance, where either the interaction will be constant (to catch any small numerical difference in distances) or a (d/d0)^2 fall-off which is common in these models. The final point is to truncate the interactions at some large distance, it is paired with a zero-term in the hopping elements.