[DFTB-Plus-User] Integration of DFTB+ with pyProcar

[Bálint Aradi]

Dear Francisco,

I am happy to read, that you managed to interface pyprocar with DFTB+.
It is a nice extension to our current functionality.

Our tight binding basis is composed of |atom, Yt_lm> basis functions of 
the form R(r) * Yt_lm(theta, phi), so I am not sure, where the problem 
lies. The only complication might be, that we use real-tesserals Yt 
instead of complex spherical harmonics Y. The Cartesian form of the real 
tesserals can be found in the waveplot tool:

https://github.com/dftbplus/dftbplus/blob/eb660605b2ae059dcc1e7e85581ef0bf391b4f13/app/waveplot/slater.F90#L96

while the conversion between the "normal" spherical harmonics and the 
real tesserals is quite trivial, and done in Maple as

Yt := proc(l, mm, theta, phi)
   if (mm = 0) then Y(l, mm, theta, phi);
   else
     if (mm > 0) then
       sqrt(2) * (-1)^mm* Re(Y(l, mm, theta, phi));
     else
       sqrt(2) * (-1)^mm * Im(Y(l, -mm, theta, phi));
     fi;
   fi;
   simplify(%, radical);
end;

as shown in this Maple worksheet:

https://github.com/dftbplus/dftbplus/blob/main/doc/waveplot/tesserals.mws

Does this give you the right information?

Best regards,

Bálint


On 23.03.23 12:44, Francisco Munoz S. wrote:
> Dear DFTB+ developers,
> 
> I am Francisco Munoz, one of the developers of pyProcar 
> (https://romerogroup.github.io/pyprocar/tutorials.html 
> <https://romerogroup.github.io/pyprocar/tutorials.html>) a code for the 
> postprocessing of electronic structure data, with some features not 
> often found in most codes (e.g. bands unfolding, 2D fermi surfaces, etc).
> 
> The core of our analysis is on projections of the wavefunctions on atoms 
> and orbitals (spherical harmonics), such as PROCAR-file from VASP (we 
> also have support for Elk, Quantum Espresso, Ab init, Lobster).
> 
> As a user of DFTB+, I have written a small code to get the projections 
> pyProcar uses from the DFTB+ wave function. It works nicely (at least 
> for the graphene-like systems I have tried).
> 
> However, to offer this functionality to the wider community, we have a 
> design problem. The projections we obtain are relative to the 
> tight-binding basis, instead of the typical |atom, Y_lm> basis we use. 
> While this could be ok in principle, it could lead to physical mistakes 
> from the users.
> 
> Do you think it would be possible to obtain a file with the atomic and 
> spherical harmonic (+phase factors?) projections of the wave functions 
> from DFTB+? Maybe one of the codes already calculates these projections, 
> but without writing them as an output file?
> 
> Best regards,
> Francisco
> 
> PD: I got a delivery error from info at dftbplus.org <http://dftbplus.org>
> 
> -- 
> Francisco Munoz
> Associate Professor
> Faculty of Sciences,
> Department of Physics
> University of Chile
> +562 29787414
> 
> _______________________________________________
> DFTB-Plus-User mailing list
> DFTB-Plus-User at mailman.zfn.uni-bremen.de
> https://mailman.zfn.uni-bremen.de/cgi-bin/mailman/listinfo/dftb-plus-user

-- 
Dr. Bálint Aradi
Bremen Center for Computational Materials Science, University of Bremen
http://www.bccms.uni-bremen.de/cms/people/b-aradi/


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