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

[Dirk Ziemann]

Dear Gabriele,

thank you. I will do the same.

best wishes  dirk



On 25/05/18 15:31, Gabriele Penazzi wrote:
> 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 
> <mailto: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
>>     <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 <mailto:ziemann at physik.hu-berlin.de>
>
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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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