[DFTB-Plus-User] electron phonon interaction and matrix derivative

[Dirk Ziemann]

thank you for the quick and helpful answer.

this goes in the right direction and I will have a deeper look into your 
program. At a first look, I do not see, how you get the derivative of 
the overlap S and hamilton matrix H. Is it possible to get it from dftb+ 
(SCC or non-SCC) or did you calculated it by yourself?  I think this is 
the most crucial part of the el-ph coupling.
from the papers on the negf transport calculations , I assume that these 
matrices are calculated in the dftb+ mpi-negf code and maybe also the 
el-ph coupling (gamma) on the level of atomic orbitals:

gamma_ab^q   \approx  d H_ab / d_q  -  \sum_mn  d S_am / d_q S^-1_mn 
H_nb - ...
(atomic orbitals a,b; vibration q)

it would be really nice to get these matrices or coupling out of the 
program.

thank you again and best wishes  dirk


On 25/05/18 13:14, Gabriele Penazzi wrote:
> Hi Dirk,
>
> I assume you are speaking about the formulation as used for example 
> for IETS spectra in molecular junctions.
>
> I don't think that is is supported in the current version, even though 
> there may be ongoing work on that.
>
> Some time ago I wanted to calculate the coupling matrices for some 
> molecules, and I did some scripting to help on that.
> It worked only on molecules (or in Gamma, for bulk), and I would guess 
> it won't run without hassle
> with the new versions of DFTB+ because it has been written 3 or 4 
> years ago and never used again, but maybe
> if that's what you need, you can use it as inspiration. It's public 
> domain: https://bitbucket.org/gpenazzi/dftbtools (lok in elcoupl,py).
>
> It has also the ASE package (Atomic Simulation Environment) as a 
> requirement.
>
>
> 2018-05-25 11:27 GMT+02:00 Dirk Ziemann 
> <dirk.ziemann at physik.hu-berlin.de 
> <mailto:dirk.ziemann at physik.hu-berlin.de>>:
>
>     Dear all,
>
>     I am interested in the electron phonon interaction like it is performed
>     in the negf version and described in the corresponding papers.
>
>     Is it possible to get the coupling matrix in dependence on the single
>     particle states and phonon modes out of the negf version? Or is it
>     possible to get the matrix derivative of the overlap/hamiltonian with
>     respect to x/y/z direction? or something similar to simply create the
>     coupling by "hand"?
>
>     Thank you very much and best wishes
>
>     dirk
>
>
>     p.s. I posted this question some time ago, but it was never
>     answered. because I am still interested in this topic I want to
>     ask this again.
>
>     -- 
>     Dirk Ziemann
>     Humboldt Universität zu Berlin, Institut für Physik
>
>
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>
>
>
>
> -- 
> -- 
> Gabriele Penazzi
> mobile: +45 51894907
> skype: gabriele.penazzi
>
>
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-- 
Dirk Ziemann
Humboldt Universität zu Berlin, Institut für Physik
AG Photobiophysik
Newtonstr. 15, D-12489 Berlin
Room	 1'406
Phone	 +49 30 2093 4997
E-mail	 ziemann at physik.hu-berlin.de

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