[DFTB-Plus-User] [Fwd: Re: (no subject)]]

Balint Aradi balint.aradi at bccms.uni-bremen.de
Wed Mar 19 16:39:04 CET 2008

Dear Mathieu,

> As a regular user of DFTB+, I am currently working on calculating the
> Green's function of a graphene nano-ribbon. In order to limit the
> calcultion time, I try to calculate these Green's function by a
> recursive method. This means that I only need to calculate the Green's
> function for the periodic part of the ribbon (which I get with DFTB) and
> then, by a Dyson's equation, I can get the whole Green's function. The
> problem is that I need to know the tight binding hopping terms. I think
> I can get these from the SKF files, but I don't know how to read them. I
> would be very grateful if somebody could help with this issue. I thank
> you in advance.

   please find below the answer of Alessandro Pecchia.

-------- Original Message --------
Usually we compute H and S for two unit cells and obtain the interactions
between cells directly as a matrix sub-block.
For instance we use this strategy to compute the contact Green' functions
using Guinea's decimation algoritm (PRB 28, 4397, 1983).
Or to compute complex - bandstructures.

Probably you need to ask the developers to store the Hamiltonian and the
overlap on some file, if this is not done already.
It is very cumbersome to work directly with the SK files, since there you
have only symmetry-adapted interatomic interaction, not the actual


Best regards


Dr. Bálint Aradi
Bremen Center for Computational Materials Science, University of Bremen
TAB A/3.10, Am Fallturm 1, 28359 Bremen, Germany, Tel.: +49 421 2187421

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