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

[Gabriele Penazzi]

Hi Dirk,

I first calculate all the modes, and then dH/dR_ix, dH/dR_ix where R_ix is
the 'x' component of the normale displacement for the mode 'i'. It can
surely be done better, but it was good enough for me as I was looking at
few modes and performance was a non-issue.

2018-05-25 14:46 GMT+02:00 Dirk Ziemann <dirk.ziemann at physik.hu-berlin.de>:

> 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>
> :
>
>> 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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-- 

-- 
Gabriele Penazzi
mobile: +45 51894907
skype: gabriele.penazzi
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